Gsm Opt Pres

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GLOBAL SYSTEM FOR

MOBILE COMMUNICATIONS

R

Introduction toPerformance Optimization



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Contents

1. What is Performance Optimization?2. Background and Foundations

3. System Architecture4. RF Propagation5. Antenna Systems

6. Traffic Considerations

7. Call Processing

8. Performance from System Statistics9. Performance from Mobile Field Data10.Common Problems and Solutions11.Managing for Growth

PART I

PART II



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GLOBAL SYSTEM FOR


R

Lesson 1.

Introduction to

Performance Optimization


http://slidepdf.com/reader/full/gsm-opt-pres 4/3961 - 4

What is Performance Optimization?

• “Performance Optimization” means differentthings to different people• identifying and fixing design issues (can’t get a

needed site, coverage holes, interference, etc.)

• “cluster testing” and “cell integration” to ensure newBTS hardware works and call processing is normal• “fine-tuning” system parameters for best call quality• identifying and fixing problem & complaint issues• monitoring and projecting growth; dimensioning

system to stay ahead of blocking and degradation• parallel tasks in the IP network for data performance



What IS Good Voice Performance?

• User has good RF performance

• adequate desired signal• absence of interference

• mobile TX power low, so good battery life

• good RXqual

• User can make/receive calls without blocking• low BTS blocking

• low BSC, MSC, and trunk blocking

• User has good Mobility• proper location updating for call delivery



What IS Good Data Performance?

• All of the Voice Performance Criteria, plus• Good Accessibility• IP session easily and reliably established

• Low Latency• low packet round-trip-delay (<~0.2 sec.)

• Good Throughput

• good data throughput rate• ~20-40 kb/s



What’s Needed for Troubleshooting?

• Knowledge of each part of the overall process• Signal and Interference principals, RF basics

• GSM/GPRS/EDGE air interface and protocols

• channels, steps in call processing, messaging• GSM network elements and functions

• Network Hardware and Administrative Interfaces

• Field test tools and interfaces• IP principles, practice, and techniques



Aeronautical Analogy: Investigation Tools

Control & Parameters Messaging

BTS

1150011500

114.50

118.25

130.75

Aeronautical

Investigations

CDMAInvestigations

Flight Data Recorder Cockpit Voice Recorder

TEMS Data Layer 3 Message Files

To study the cause of an aeronautical accident, we try to recover the

Flight Data Recorder and the Cockpit Voice Recorder.To study GSM call failures, we review field and system data



GLOBAL SYSTEM FOR


R

Lesson 2Technology and Industry

Development

Technology Background for

GSM Performance Optimization



How Did We Get Here?

Days before radio.....

• 1680 Newton first suggestedconcept of spectrum, but for visible light only

• 1831 Faraday demonstratedthat light, electricity, andmagnetism are related

• 1864 Maxwell’s Equations:spectrum includes more thanlight

• 1890’s First successful demosof radio transmission

UN S

LF HF VHF UHF MW IR UV XRAY



Telegraphy: 170 Years Old• Samuel F.B. Morse had the idea of the telegraph on a

sea cruise in the 1833. He studied physics for two years,and In 1835 demonstrated a working prototype, which hepatented in 1837.

• Derivatives of Morse’ binary code are still in use today

• The US Congress funded a demonstration line fromWashington to Baltimore, completed in 1844.

• 1844: the first commercial telegraph circuits were cominginto use. The railroads soon were using them for traindispatching, and the Western Union company resold idle

time on railroad circuits for public telegrams, nationwide

• 1857: first trans-Atlantic submarine cable was installed

Samuel F. B. Morseat the peak of his career

Field Telegraphyduring the US Civil War, 1860’s

Submarine Cable Installationnews sketch from the 1850’s



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Telephony: 135 Years Old

• By the 1870’s, the telegraph was in use all over the world and largelytaken for granted by the public, government, and business.

• In 1876, Alexander Graham Bell patented his telephone, a device for carrying actual voices over wires.

• Initial telephone demonstrations sparked intense public interest and bythe late 1890’s, telephone service was available in most towns and citiesacross the USA

Telephone Line Installation Crew1880’s

Alexander Graham Bell and his phonefrom 1876 demonstration



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Radio: only 110 Years Old• 1888: Heinrich Hertz, German physicist, gives lab demo of

existance of electromagnetic waves at radio frequencies

• 1895: Guglielmo Marconi demonstrates a wireless radiotelegraph over a 3-km path near his home it Italy

• 1897: the British fund Marconi’s development of reliable

radio telegraphy over ranges of 100 kM• 1902: Marconi’s successful trans-Atlantic demonstration

• 1902: Nathan Stubblefield demonstrates voice over radio

• 1906: Lee De Forest invents “audion”, triode vacuum tube• feasible now to make steady carriers, and to amplify signals

• 1914: Radio became valuable military tool in World War I

• 1920s: Radio used for commercial broadcasting

• 1940s: first application of RADAR - English detection of incoming German planes during WW II

• 1950s: first public marriage of radio and telephony - MTS,Mobile Telephone System

• 1961: transistor developed: portable radio now practical

• 1961: IMTS - Improved Mobile Telephone Service

• 1970s: Integrated circuit progress: MSI, LSI, VLSI, ASICs• 1982 first meetings of CEPT GSM working group

Guglielmo Marconiradio pioneer, 1895

Lee De Forestvacuum tube inventor

MTS,IMTS



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Frequencies Used by Wireless Systems

Overview of the Radio Spectrum

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 MHz3,000,000 i.e., 3x106 Hz

AM LORAN Marine

3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 26 28 30 MHz30,000,000 i.e., 3x107 Hz

Short Wave -- International Broadcast -- Amateur CB

30 40 50 60 70 80 90 100 120 140 160 180 200 240 300 MHz300,000,000 i.e., 3x108 Hz

FM VHF TV 7-13VHF LOW Band VHFVHF TV 2-6

0.3 0.4 0.5 0/6 0.7 0.8 0.9 1.0 1.2 1.4 1.6 1.8 2.0 2.4 3.0 GHz3,000,000,000 i.e., 3x109 Hz

UHF TV 14-69UHF GPS

DCS, PCSCellular & GSM

3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 26 28 30 GHz30,000,000,000 i.e., 3x1010 Hz

Broadcasting Land-Mobile Aeronautical Mobile TelephonyTerrestrial Microwave Satellite



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North American Cellular Development

• In the late 1970’s, the FCC (USA Federal Communications Commission)and the Canadian government allocated 40 MHz. of spectrum in the 800MHz. range for public mobile telephony.

• FCC adopted Bell Lab’s AMPS (Advanced

Mobile Phone System) standard, creatingcellular as we know it today

• The USA was divided into 333 MSAs(Metropolitan Service Areas) and over 300 RSAs

(Rural Service Areas)• By 1990, all MSAs and RSAs had competing licenses granted and at

least one system operating. Canadian markets also developed.

• In 1987, the FCC allocated 10 mHz. of expanded spectrum

• In the 1990’s, additional technologies were developed for cellular • TDMA (IS-54,55,56, IS-136) (also, GSM in Europe/worldwide)

• CDMA (IS-95)

• US Operators did not pay for their spectrum, although processing fees

(typically $10,000’s) were charged to cover license administrative cost

333 MSAs300+ RSAs



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North American Cellular Spectrum

Downlink Frequencies(“Forward Path”)

Uplink Frequencies(“Reverse Path”)

Frequency, MHz824 835 845 870 880 894

869

849

846.5825

890

891.5

Paging, ESMR, etc.A B A B

Ownership and

Licensing

Frequencies used by “A” Cellular Operator

Initial ownership by Non-Wireline companies

Frequencies used by “B” Cellular Operator

Initial ownership by Wireline companies

• In each MSA and RSA, eligibility for ownership was restricted

• “A” licenses awarded to non-telephone-company applicants only

• “B” licenses awareded to existing telephone companies only

• subsequent sales are unrestricted after system in actual operation



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North America PCS Development

By 1994, US cellular systems were seriouslyoverloaded and looking for capacity relief

• The FCC allocated 120 MHz. of spectrumaround 1900 MHz. for new wirelesstelephony known as PCS (Personal

Communications Systems), and 20 MHz.for unlicensed services

• allocation was divided into 6 blocks; 10-year licenses were auctioned to highestbidders

51 MTAs

493 BTAs

PCS Licensing and Auction Details• A & B spectrum blocks licensed in 51 MTAs (Major Trading Areas )

• Revenue from auction: $7.2 billion (1995)

• C, D, E, F blocks were licensed in 493 BTAs (Basic Trading Areas)

• C-block auction revenue: $10.2 B, D-E-F block auction: $2+ B (1996)

• Auction winners are free to choose any desired technology

A D B E F Cunlic.data

unlic.voice A D B E F C

1850MHz.

1910MHz.

1990MHz.

1930MHz.

15 15 155 5 5 15 15 155 5 5

PCS SPECTRUM ALLOCATIONS IN NORTH AMERICA



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PCS Spectrum - First Auctions: A & B

1850 Frequency, MHz1910 1930 1990

DA B E F C DA B E F C0 300 400 700 800 900 1200

• The PCS spectrum wasdivided into six “blocks”which were separately

auctioned.• The A and B blocks

were auctioned in each

of 51 Major Trading

Areas (MTAs)• Auction completed

3Q1995

• Total Revenue:$7.2B

Major Trading Areas (MTAs)



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The PCS Spectrum: Blocks C, D, E, F

1850 Frequency, MHz1910 1930 1990

DA B E F C DA B E F C0 300 400 700 800 900 1200

• In 1996, Blocks C, D, E, and Fwere auctioned to companies in

each of 493 Basic Trading Areas (BTAs)

• Total Revenue:

• C: $10.2B

• D & E: ~$2 B

• Most of the C-block biddershad difficulty gettingconstruction financing; a longsaga of litigation

Basic Trading Areas (BTAs)



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What’s Really Happening? The Big Picture

• Commercial telegraphy gave birth to telephony, then died

• Telephony and Land Mobile Radio married, giving IMTS & Cellular

• IP networks developed, their usage and bandwidth are increasing

• 3G is a marriage of IP and Wireless!

1900s 2000s1800s10 20 30 40 50 60 70 80 90 10 20 3050 60 70 80 90

Commercial Telegraphy

Commercial Switched Telephony

Wireless Voice and IP Data

40 50

Digital Switching

IMTS-Cellular-GSM-GPRS-WCDMA

IP NetworksThe Internet Voice over IP

Land Mobile RadioHF, VHF, UHF, Trunked

Extinction!

Extinction?

Extinction?

WiFi 802.11802.16, 802.20



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Major Wireless Players

Primeco

CDMA

The Largest Players, Areas, and Technologies• T-Mobile (GSM)• Union of Western Wireless, OmniPoint, BellSouth,

GTE, Powertel, Pacific Bell, with DeutscheTelekom capital

• Verizon (CDMA, 1xRTT, 1xEV-DO)• Combination of GTE, Bell Atlantic, Vodaphone,

Airtouch, Primeco (1900 & 800 MHz.)

• Cingular (TDMA, GSM, GPRS, EDGE) **• Combination of BellSouth, Southwestern Bell (1900

& 800 MHz.)

• AT&T Wireless Systems (TDMA>GSM, GPRS,EDGE, eventually WCDMA) **

• Combination of new PCS, McCaw Cellular,Primeco (1900 & 800 MHz.)

• Sprint PCS (CDMA, 1xRTT)• 1900 MHz. only

• Leap Wireless/Cricket Communications (CDMA)• Discount provider -- fixed rate, unlimited minutes –

no roaming, no data (1900 MHz. Only)

• Nextel (IDEN)• Proprietary TDMA technology at 800 MHz. only• experimenting with OFDM broadband technology

Sprint PCSCDMA

AT&T WirelessIS-136

WesternWireless

cificll

PowertelBellSouth

OmniPoint

Aerial

GSMPa

Be



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Global Wireless Snapshot 4Q 2003

Worldwide USA

Total Wireless Users

GSM users

CDMA users

TDMA users

IDEN users

Analog users

1,320,000,000 100%

870,000,000 65.9%

224,000,000 17.0%

124,000,000 9.4%

68,000,000 5.2%

34,000,000 2.6%

141,000,000 100%

33,732,506 23.9%

64,503,287 45.7%

26,375,232 18.6%

11,978,382 8.5%

4,510,594 3.2%

• Total Worldwide Wireless customers surpassed total worldwide

landline customers at year-end 2002, with 1,00,080,000 of each.• 2/3 of worldwide wireless customers use the GSM technology• CDMA is second-most-prevalent with 17.0%• In the US, CDMA is the most prevalent technology at 45.7%

• Both CDMA and GSM are growing in the US• most IS-136 TDMA systems are converting to GSM + GPRS + EDGE



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Wireless Users by Technology

GSM

24%

CDMA

46%

TDMA

19%

Analog

3%

IDEN

8%

GSM

66%

CDMA

17%

TDMA

9%

Analog

3%

IDEN

5%

• GSM is by far the dominant global technology• CDMA is dominant in its country of origin, the USA

• The IS-136 TDMA community is rapidly implementing

GSM• primary motivation is to provide GPRS and/or EDGE fast data

US Wireless Operators:



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US Wireless Operators:Technologies and Subscribers

Totals: 64,503,287 33,732,506 26,275,232 11,978,382 4,510,594 Company Subscribers CDMA GSM TDMA IDEN Analog

Verizon 33,166,130 29,849,517 3,316,613

Cingular 22,348,869 11,174,435 11,174,435

AT&T Wireless 21,328,373 10,664,187 10,664,187

Sprint PCS 15,103,346 15,103,346

Nextel 10,817,261 10,817,261

T-Mobile 10,102,914 10,102,914

Alltel 7,755,772 6,980,195 775,577

US Cellular 4,184,035 2,928,824 836,807 418,403

Leap Wireless 1,530,744 1,530,744 Western Wireless 1,224,596 1,224,596

Dobson 1,122,546 1,122,546

Quest 1,020,496 1,020,496

Nextel Partners 895,792 895,792

Triton PCS 847,012 423,506 423,506

Rural Cellular Corp. 736,801 736,801

Alamosa Holdings 634,749 634,749

Airgate PCS 601,518 601,518

US Unwired 552,374 552,374

Centennial 540,863 540,863 Midwest Wireless 288,313 288,313

SourhernLINC 265,329 265,329

Ntelos 256,166 256,166

Horizon PCS 246,858 246,858

Ubiquitel 239,408 239,408

MetroPCS 1,694,024 1,694,024

Cellular South 561,273 280,636 280,636

Commnet PCS 357,174 357,174

NewComm 306,149 306,149

West Coast PCs 295,944 295,944

Meriwether Communications 275,534 275,534

Touch America 224,509 224,509

Airadigm Communications 163,279 163,279

Cellcomn 163,279 163,279

Conestoga Wireless 142,869 142,869

Lewis and Clark 132,665 132,665

Public Service Cellular 112,255 112,255

Entertainment Unlimited 112,255 112,255

NPI Wireless 112,255 112,255

Poplar PCS 102,050 102,050

CorrWireless 102,050 102,050 Iowa Wireless 102,050 102,050

NTCH 81,640 81,640

Edge Wireless 75,006 75,006

Skagit Wireless 73,476 73,476

141,000,000



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Question and Answer

5/19/2004 25

Question and Answer:



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Question and Answer:Wireless Perspective

• Approximately how old is radio technology?

• When did you make your first wireless call?• on what system?

• what technology?

• how was the quality?

• Trace the history of your company

• who were its predecessors?• Name some competitors and their technologies

• What’s the next big thing for your company?



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RF Basics:

Radio Signals, Modulation, andBandwidth



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Characteristics of a Radio Signal

• The purpose of telecommunications is tosend information from one place toanother

• Our civilization exploits the transmissible

nature of radio signals, using them in asense as our “carrier pigeons”

• To convey information, somecharacteristic of the radio signal must be

altered (I.e., ‘modulated’) to represent theinformation

• The sender and receiver must have aconsistent understanding of what the

variations mean to each other • RF signal characteristics which can be

varied for information transmission:

• Amplitude

• Frequency• Phase

SIGNAL CHARACTERISTICS

S (t) = A cos [ ωc

t +ϕ ]

The complete, time-varying radio signal

Amplitude (strength)of the signal

Natural Frequencyof the signal

Phase of the signal

Compare these Signals:

DifferentAmplitudes

DifferentFrequencies

DifferentPhases



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Amplitude Modulation (“AM”)

AM is “linear modulation” -- thespectrum of the baseband signaltranslates directly into sidebands onboth sides of the carrier frequency

Despite its simplicity, AM has definitedrawbacks which complicate its usefor wireless systems:

• Only part of an AM signal’s energyactually carries information(sidebands); the rest is the carrier

• The two identical sidebands wastebandwidth

• AM signals can be faithfully

amplified only by linear amplifiers• AM is highly vulnerable to external

noise during transmission

• AM requires a very high C/I (~30

to 40 dB); otherwise, interferenceis objectionable

TIME-DOMAIN VIEWof AM MODULATOR

x(t) = [1 + amn(t)]cos ωc t

where:

a = modulation index (0 < a <= 1)

mn(t) = modulating waveform

ωc

= 2π f c

, the radian carrier freq.

Σa

1

+

+

x(t)

cos ωc

mn(t)

FREQUENCY-DOMAIN VIEW

V o l t a g e

Frequency0 f c

mn(t)BASEBAND

x(t)

UPPERSIDEBAND

LOWERSIDEBAND

CARRIER



Frequency Modulation (“FM”) Frequency Modulation (FM) is a type of

angle modulation• in FM, the instantaneous frequency

of the signal is varied by themodulating waveform

Advantages of FM

• the amplitude is constant – simple saturated amplifiers can

be used

– the signal is relatively immuneto external noise

– the signal is relatively robust;required C/I values are typically17-18 dB. in wirelessapplications

Disadvantages of FM• relatively complex detectors arerequired

• a large number of sidebands areproduced, requiring even larger

bandwidth than AM

TIME-DOMAIN VIEW

sFM(t) = A cos [ωc t + mω

m(x)dx+ϕ0 ]t

t0

where:

A = signal amplitude (constant)

ωc = radian carrier frequency

mω = frequency deviation index

m(x) = modulating signal

ϕ0 = initial phase


V

o l t a g e

Frequency0 f c

SFM(t)

UPPERSIDEBANDS

LOWERSIDEBANDS

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Phase Modulation (“PM”) Phase Modulation (PM) is a type of angle

modulation, a “sister” of FM• the instantaneous phase of the

signal is varied according to themodulating waveform

Advantages of PM: similar to FM

• the amplitude is constant – simple saturated amplifiers can

be used

– the signal is relatively immuneto external noise

– the signal is relatively robust;required C/I values are typically17-18 dB. in wirelessapplications

Disadvantages of PM• relatively complex detectors arerequired

• a large number of sidebands areproduced, requiring even larger

bandwidth than AM

TIME-DOMAIN VIEW

sPM(t) = A cos [ωc t + mω

m(x) +ϕ0 ]

where:

A = signal amplitude (constant)

ωc = radian carrier frequency

mω = phase deviation index

m(x) = modulating signal

ϕ0 = initial phase


V

o l t a g e

Frequency0 f c

SFM(t)

UPPERSIDEBANDS

LOWERSIDEBANDS

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M d l ti d O i d B d idth



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Modulation and Occupied Bandwidth

Voltage

Time

Time-Domain(as viewed on an

Oscilloscope)

Frequency-Domain(as viewed on a

Spectrum Analyzer)

• The bandwidth of a signal carryinginformation depends on:• bandwidth of information itself • modulation method

• Information to be transmitted,called “input” or “baseband”• bandwidth usually is small, much

lower than frequency of carrier

• Unmodulated carrier • the carrier itself has Zero

bandwidth!!

• AM-modulated carrier • Notice the upper & lower sidebands

• total bandwidth = 2 x baseband• FM-modulated carrier

• Many sidebands! bandwidth is acomplex mathematical function

• PM-modulated carrier • Many sidebands! bandwidth is a

complex mathematical function

Voltage

Frequency0

f c

f c

Lower Sideband

Upper Sideband

f c

f c

Modulation by Digital Information



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Modulation by Digital Information

• Modulation by a digital waveform: Nomore continuous analog variations,

now we’re “shifting” between discretelevels. We call this “shift keying”.

• The user gets to decide what levelsmean “0” and “1” -- there are no

inherent values• Steady Carrier without modulation

• Amplitude Shift Keying

ASK applications: digital microwave

• Frequency Shift KeyingFSK applications: control messages in

AMPS cellular; TDMA cellular

• Phase Shift Keying

PSK applications: TDMA cellular,GSM & PCS-1900

Our previous modulation examples used continuously-variable

analog inputs. If we quantize the inputs, restricting them todigital values, we will produce digital modulation.

Voltage

Time1 0 1 0

1 0 1 0

1 0 1 0

1 0 1 0

S t l Effi i f



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Spectral Efficiency of

Digital Modulation ModulationScheme

Shannon Limit,BitsHz

BPSK 1 b/s/hz

QPSK 2 b/s/hz

8PSK 3 b/s/hz16 QAM 4 b/s/hz

32 QAM 5 b/s/hz

64 QAM 6 b/s/hz

256 QAM 8 b/s/hz

• Each symbol of a digitallymodulated RF signal carriesone or a few bits of information

• how many bits is determined bythe number of degrees of modulation freedom

• More complex modulationschemes can carry more bitsper symbol in a givenbandwidth, but require better signal-to-noise ratios

• The actual number of bits per

second which can be conveyedin a given bandwidth under given signal-to-noise conditionsis described by Shannon’sequations

SHANNON’SCAPACITY EQUATION

C = Bω log2 [ 1 + ]SN

Bω = bandwidth in HertzC = channel capacity in bits/secondS = signal power

N = noise power

Digital Modulation Schemes



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Digital Modulation Schemes

• There are many different digital modulation techniques• Linear Modulation

• BPSK Binary Phase Shift Keying

• DPSK Differential Phase Shift Keying• QPSK Quadrature Phase Shift Keying IS-95 CDMA fwd l ink

• Offset QPSK IS-95 CDMA reverse link

• Pi/4 DQPSK IS-54, IS-136 control and traffic channels

• Constant Envelope Modulation• BFSK Binary Frequency Shift Keying AMPS control chan.

• MSK Minimum Shift Keying• GMSK Gaussian Minimum Shift Keying GSM, CDPD

• Hybrid Combinations• MPSK M-ary Phase Shift Keying• QAM M-ary Quadrature Amplitude Modulation• MFSK M-ary Frequency Shift Keying FLEX paging protocol

Di it l M d l ti f GSM GMSK



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Digital Modulation for GSM: GMSK

• MSK (Minimum frequency Shift Keying)

• peak frequency deviation set to half the bit rate

• still allows orthogonal detection of the two binary states• Advantages:

• constant envelope, spectral efficiency, good BER

performance, self-synchronizing capabilities• GMSK is a derivative of MSK

• message waveform (in NRZ format) is Gaussian-

filtered for pulse shaping before modulation• greatly reduces spectral sidelobes

• introduces slight penalty in BER performance, but no

worse than already imposed by mobile RF channel

Spectrum Occupied by a GSM Signal



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Thanks to Maxim Semiconductor for the emissionmask and to Agilent for the measured spectra.

Measured Spectrum of a GSM Signal



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Frequency Reuse: It’s a Matter of C/I!

AMPS, D-AMPS, N-AMPS

CDMA/WCDMA

30 30 10 kHz Bandwidth

200 kHz

1250 kHz

1 3 1 Users

8 Users

22 Users1

1

11

1

11

11

1

11

1

1

12

34

4

32

56

17

Typical Frequency Reuse N=7



Vulnerability:

C/I ≅ 17 dB

Vulnerability:C/I ≅ ~9 dB

Vulnerability:EbNo ≅ 6 dB

GSM/GPRS/EDGE

Each wireless technologyuses a modulation type

with inherent signalbandwidth and C/Irequirements

Operator’s licensed

spectrum will hold acertain number of signals

C/I requirementsdetermine how closelyfrequencies can bereused – n=7, 4, 1, etc.

Co-Channel Interference



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Co-Channel Interference

• Traditional ‘static’frequency planningassigns channels in acell pattern

• The number of cellsin the pattern ischosen to achieve therequired C/I value

• closer reuse gives

more capacity butpoorer C/I

• farther reuse reducescapacity but givesgood C/I

f2

f3

f4

f5 f6

7

f4

f6

f4

f7 f2

f7

f2

f5

f3

f5

f3

f6

f1

f1

f1

f1

f1

f1

f1

Example: 7-cell clustersN=7

Handover and C/I



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Handover and C/I

An obvious purpose of handover is to keep the call from droppingas the mobile moves out of rangeof individual cells

Another important purpose of handover is to ensure the mobileis using the cell with the bestsignal strength and best C/I at alltimes

Notice in the signal graphs atlower right how the mobile’s C/I ismaintained at a usable level as it

A

B

C

D

goes from cell to cell A B

RSSI,dBm

-120

-50

C DSites

C/I

AMPS

Tech-nology

NAMPS

TDMA

GSMCDMA

Analog FM

ModulationType

Analog FM

DPQSK

GMSKQPSK/OQPSK

30 kHz

ChannelBandwidth

10 kHz

30 kHz

200 kHz1,250 kHz

C/I ≅ 17 dB

NeededC/I, db

C/I ≅ 17 dB

C/I ≅ 17 dB

C/I ≅ 9 dBEb /No ≅ 6dB

Q ti d A



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Question and Answer

5/19/2004 42

Question and Answer:R di Si l M d l ti B d idth



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Radio Signals, Modulation, Bandwidth

• Suppose you have a 9600 bps stream of information totransmit. How much radio spectrum do you need? What

are the tradeoffs?• What is the difference between analog modulation and

digital modulation?

• What is FSK? GMSK?• What is the approximate C/I needed for good GSM

performance?

• How much spectrum does a GSM signal use?• What are two purposes of handoffs?

• What C/I is necessary for good GSM performance?



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Multiple Access Methods

Frequency Reuse




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F r e q u

e n c y

T i m e

Power

TDMA

F r e q u e n c y

T i m e

Power

FDMA

F r e q u e n

c yT i m e

Power

CDMA

C O D E

FDMA: AMPS & NAMPS•Each user occupies a private Frequency,protected from interference through physicalseparation from other users on the same

frequency

TDMA: IS-136, GSM

•Each user occupies a specific frequency but

only during an assigned time slot. Thefrequency is used by other users duringother time slots.

CDMA

•Each user occupies a signal on a particular frequency simultaneously with many other users, but is uniquely distinguishable bycorrelation with a special code used only by

this user

GSM Technology Path to 3G



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GSM Technology Path to 3G

Technology

Generation

SignalBandwidth,

#Users

Features:Incremental

Progress

1G

variousanalog

DataCapabilities

various

various

various

2G

GSM

200 kHz.7.5 avg.

Europe’sfirst Digitalwireless

none

2.5G or 3?

GPRS

200 kHz.Many

Pkt. users

•Packet IP

access•Multipleattached

users

9-160 Kb/s(conditionsdetermine)

3G

EDGE

200 kHz.fast data

many users

Faster data

rates ondedicated200 kHz

data carrier

384 Kb/smobile user

3G

UMTSUTRA

WCDMA3.84 MHz.up to 200+voice users

and data

Integratedvoice and

data

2Mb/sstatic user

TDMA IS 136 Technology Path to 3G



1 - 47

TDMA IS-136 Technology Path to 3G

2G

CDPD

30 kHz.Many

Pkt Usrs

19.2kbps

USPacketDataSvc.

Technology

Generation

SignalBandwidth,

#Users


Progress

DataCapabilities

2G

TDMAIS-54

IS-136

30 kHz.3 users

USA’sfirstDigital

wireless

none

2.5G or 3?

GPRS

200 kHz.Many

Pkt. users

•Packet IP

access•Multipleattached

users

9-160 Kb/s(conditionsdetermine)

3G

EDGE

200 kHz.fast data

many users

Faster data

rates ondedicated200 kHz

data carrier

384 Kb/smobile user

3G

UMTSUTRA

WCDMA3.84 MHz.up to 200+voice users

and data

Integratedvoice and

data

1G

AMPS

30 kHz.1

First

System,Capacity

&Handoffs

None,2.4K bymodem

2Mb/sstatic user

2G

GSM

200 kHz.7.5 avg.

Europe’sfirstDigital

wireless

none

CDMA Technology Path to 3G



1 - 48

CDMA Technology Path to 3G

Technology

Generation

SignalBandwidth,

#Users


Progress

1G

AMPS

DataCapabilities

30 kHz.1

First

System,Capacity

&Handoffs

None,2.4K bymodem

2G

IS-95A/J-Std008

1250 kHz.20-35

First CDMA,Capacity,Quality

14.4K

2G

IS-95B

1250 kHz.25-40

•Improved Access•Smarter Handoffs

64K

2.5G or 3?

IS-2000:1xRTT

1250 kHz.50-80 voice

and data

•Enhanced Access•ChannelStructure

153K307K230K

3G

1xEV-DO1xEV-DV

1250 kHz.Many packet

users

Faster data

rates ondedicated

1x RF datacarrier

2.4 Mb/s(1xEV-DO)5 Mb/s

(1xEV-DV)

3G

IS-2000:3xRTT

F: 3x 1250kR: 3687k

120-210 per 3 carriers

Faster data

rates onshared 3-

carrier bundle

1.0 Mb/s

CDMAone CDMA2000/IS-2000

4G: Broadband Wireless Access



1 - 49

Not BWA; for comparison only

802.16

BPSK to

256QAM

OFDM

54 Mb/s

TDD, FDD

various

2-11 GHz

10-66 GHz

802.20Mobile BWATechnology

ModulationType

Max Raw

Data Rate

Access

Method

FrequencyBand

Infrared

IRDA

various

4 Mb/s

Single User per

Optical Carrier

Optical

802.11b

CCK

11

Mb/s

DSSS

2.4 GHz

802.11a

BPSK, QPSK,

16QAM, or

64QAM

54 Mb/s

DSSS

5 GHz

HIPERLAN

Type 1

FSK or

GMSK

23.5 Mb/s

OFDM

5 GHz

HIPERLAN

Type 2

BPSK, QPSK,

16QAM, or

64QAM

54 Mb/s

various.

5 GHz

Bluetooth

GFSK

FH

1 Mb/s

various

2.4 GHz

BLUETOOTH

802.11A, B,WIFI, WILAN

Infrared IRDA

4G – Evolution or Revolution?



1 - 50

H i g h

- T i e r $ $ $

L o w - T i e

r $

1G: AMPS

• There’s a revolution going on!• 2.5G services are here now, 3G arriving 2004 through 2005• A groundswell of commercial (and even free!) WILAN deployment

• 3G networks and 4G networks have unique advantages• Will 3G and 4G be integrated by wireless operators?

Technology EnvironmentService Provider/

Infrastructure Owner

PSTN IP/VPNs

2G: TDMA, GSM,IS95 CDMA, IDEN

2.5G: GPRS, EDGE

3G: IS2000 1xRTT,1xEV DO, 1xEV DVUMTS WCDMA

4G: Wireless LAN802.11b “Wi-Fi”

802.11a, gHIPERLAN Type 1HIPERLAN Type 2BluetoothInfrared freenetworks.org

Near-Universal Macro-Coverage

Hotspots

2G to 3G Migration Paths



1 - 51

2G to 3G Migration Paths

TechnologyFamily

3G Technology2G Technology

CDMA

GSM

IS-136

TDMA

cdma2000

UMTSWCDMA

UWC-136

3xRTT

FrequencyDivisionDuplex

TimeDivisionDuplex

EDGE and136 HSoutdoor

136 HS

indoor

1xEV DV

1xEV DO

GSM+

GPRSGSM+

EDGE

What’s Your Path for 3G Migration?



1 - 52

3xRTT

1xEV DV

1xEV DO

1900 MHz..800 MHz..

Cingular/SBC/BellSouth22,348,869

Verizon/Vodaphone/BAMS/GTE33,166,130

Alltel7,755,772

Other CDMA Independents12,570,229

Nextel+11,978,382

AT&T Wireless21,328,373

Sprint PCS15,103,346

WCDMAUMTSUTRA

1xRTTcdma2000

T-Mobile

10,102,914

??!

Other TDMA Independents4,436,611 X UWCC

IS-136

GPRSEDGEGSM

X

OFDM

?

Wireless Capacity Examples



1 - 53

Fwd/Rev Spectrum kHz. 12,500 12,500 12,500 15,000 15,000 15,000 5,000 5,000 5,000

Technology AMPS TDMA CDMA TDMA GSM CDMA TDMA GSM CDMA

Req'd C/I or Eb/No, db 17 17 6 17 12 6 17 12 6

Freq Reuse Factor, N 7 7 1 7 4 1 7 4 1

RF Signal BW, kHz 30 30 1250 30 200 1250 30 200 1250

Total # RF Carriers 416 416 9 500 75 11 166 25 3

RF Sigs. per cell @N 59 59 9 71 18 11 23 6 3

# Sectors per cell 3 3 3 3 3 3 3 3 3

#CCH per sector 1 1 0 1 0 0 1 0 0

RF Signals per sector 18 18 9 22 6 11 6 2 3

Voicepaths/RF signal 1 3 22 3 8 22 3 8 22SH average links used 1 1 1.66 1 1 1.66 1 1 1.66

Unique Voicepaths/carrier 1 3 13.253 3 8 13.253 3 8 13.253

Voicepaths/Sector 18 54 198 66 48 242 18 16 66

Unique Voicepaths/Sector 18 54 119 66 48 145 18 16 39

P.02 Erlangs per sector 11.5 44 105.5 55.3 38.4 130.9 11.5 9.83 30.1

P.02 Erlangs per site 34.5 132 316.5 165.9 115.2 392.7 34.5 29.49 90.3

Capacity vs. AMPS800 1 3.8 9.2 4.8 3.3 11.4 1.0 0.9 2.6

800 Cellular (A,B) 1900 PCS (A, B, C) 1900 PCS (D, E, F)

Question and Answer



1 - 54

Question and Answer

5/19/2004 54

Question and Answer:Multiple Access Methods & Frequency Reuse



1 - 55

Multiple Access Methods & Frequency Reuse

• Name three popular Multiple Access Methods

• Which multiple access method does GSM use?

• What major existing technology is beingreplaced rapidly by GSM?

• Name two data technologies compatible withGSM.

• How is EDGE able to give faster data than

GPRS?• What technology is intended to replace EDGE?

• How do GPRS data speeds compare to WiFi?



1 - 56

GSM RF FUNDAMENTALS

Communications Technology Evolution



1 - 57

gy

• Commercial telegraphy gave birth to telephony, then died

• Telephony and Land Mobile Radio married, giving IMTS & Cellular

• IP networks developed, their usage and bandwidth are increasing

• The wedding of IP and Wireless is happening now in 3G!

1900s 2000s1800s 10 20 30 40 50 60 70 80 90 10 20 3050 60 70 80 90

Commercial Telegraphy

Commercial Switched Telephony

Wireless Voice and IP Data

40 50

Digital switching

IMTS-Cellular-GSM-GPRS-WCDMA

IP NetworksThe Internet Voice over IP

Land Mobile RadioHF, VHF, UHF, Trunked

Extinction!

Extinction?

Extinction?

The Beginnings of GSM



1 - 58

g g

• 1980’s: Europe used variety of first generation analog cellular systems: TACS, ETACS, NMT450, NMT900, Netz, etc.

• Operation was limited to various national boundaries

• Poor roaming capabilities, poor economies of scale in mfg.

• In 1982, CEPT the Conference of European Posts and Telegraphscreated a group to study and define a 2G Pan-European system

• Group Spécial Mobile (GSM)

• In 1989, administration of GSM was transferred to the EuropeanTelecommunications Standards Institute (ETSI)

• In 1990, the GSM specification, Phase I, was published

• GSM has become very popular due to many positive factors• Non-proprietary: anyone can manufacture networks/handsets

• Thorough/integrated standard: well-defined RF air interface, networkarchitecture, call delivery and roaming features

GSM Worldwide Acceptance



1 - 59

p

GSM commercial deploymentbegan in 1991

By 1993, there were 36 GSMnetworks in 22 countries

In 2000, there were over 200GSM networks in over 110countries around the world

• Operation in 900 MHz., 1800MHz., and 1900 MHz. bands

The wide acceptance of GSM has provided tremendouseconomies of scale in network, handset, and test equipment

manufacturing and distribution Worldwide in 2001, GSM users have passed the 500 million mark

• One in 12 human beings uses a GSM phone!

The global dominance of GSM provides a large market for the2.5G and 3G enhancements GPRS and UMTS WCDMA

GSM

66%

CDMA

17%

TDMA

9%

Analog

3%

IDEN

5%

GSM vs. North American Standards



Two different approaches to wireless technology development!• Americans: Invent cool new stuff driven by market forces, write

standards if it works and the market aCepts it

• Europeans: Study, Plan, build Standards, build Consensus,

Plan, Review, build more Consensus, finally Deploy The differences are visible in the resulting standards

• American: multiple interim standards necessary to definefunctionality

• Europeans: single integrated standard covers all functionality

Other Features

Air InterfaceRF Architecture

Network Architecture

Intersystem Roaming,Call Delivery, Handoff

The GSM StandardOne coordinated, uniformly

structured family of documents

IS-95/J-Std 008 CDMA

IS-634 A-interface

IS-41C, D, P

IS-637SMS

IS-683OTA

IS-707Data

Etc.

North American CDMA GSM

1 - 60

GSM Terminology



Some commonterms havedifferent meaningswhen used in GSM

or North Americanpractice!

Sector β

Sector α

Sector γ

CELL Cellβ

Cellα

Cellγ

BTS

It’s a Sector! It’s a Cell!

Sector β

Sector γ

Cellβ

Cellγ

That was a Handoff! That was a Handover!

The frequencies used

1 - 61

by each sector are

its channel set.

The frequencies used

by each cell are

its allocation.

Structure of a GSM Signal



1 - 62

GSM carriers are spaced 200 kHz.apart

In the BTS downlink signal,different timeslots belong todifferent users - a mobile listens

only to its recurring timeslots• During unused timeslots, amobile can measure the signalstrength of surrounding BTSsto guide the handover process

The mobile on its uplink transmitsonly during its assigned timeslots

• Mobiles transmit only duringtheir own timeslots

• Mobile transmit timeslots occur

three timeslots after thecorresponding BTS transmittimeslot

• This avoids simultaneousmobile TX/RX and the

need for duplexer at themobile

200 kHz

8 Slots 12

34


RequiredC/I ≅ 9-12 dB

BTS

The Frequencies Used by GSM

Europe and International



1 - 63

GSM Uplink124 ch.

GSM Downlink124 ch.

915 935 960890

u ope a d te at o a

MHz.

824 835 845 880 894869849 890

Paging, ESMR, etc.A B A B

North American 850 MHz. Cellular Band

MHz.

1850 1865 1885 1900 1910 1930 1945 1965 1975 1990

A75 ch.

D25

B75 ch.

E25

F25

C125

C225

C325

A75 ch.

D25

B75 ch.

E25

F25

C125

C225

C325

North American 1900 MHz. PCS Licensed Blocks

MHz.

• GSM operates in a variety of frequency bands worldwide• Spectrum is provided in “blocks”

• Base stations transmit in the upper block• Mobiles transmit in the lower block

• GSM carrier frequencies are assigned in 200 KHz.Increments within operator’s licensed spectrum block

• Each cell’s carriers are called its “allocation”

Multiple GSM Carriers – with no hoppingTime



1 - 64

• A GSM base station transceiver makes a signal ~240 kHz. wide

• The signal is time-divided into a repeating pattern of frames• Each frame is 60/13 = 4.515 ms long, there are ~221.5 frames per second

• Each frame is further subdivided into 8 timeslots, each 15/26 ms = 577µs long

• A timeslot can hold the bits of a channel of information• One user’s voice signal, or a signaling/administrative channel

• One GSM base station can have several transceivers, each oneproducing a GSM signal on a different frequency - six carriers in theexample above• Various repeating patterns of information can use the timeslots to carry

channels of information

TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS8






Frequency 1

Frequency 2

Frequency 3

Frequency 4

Frequency 5

Frequency 6

1 timeslot 577 µs

1 frame 4.515 ms

Multiple GSM CarriersWith Frequency Hopping



1 - 65

Frequency 1

Frequency 2

Frequency 3

Frequency 4

Frequency 5

Frequency 6

1 frame 4.515 ms

Time

Frequency 7

Frequency 8

Frequency 9

Frequency 10

Frequency 11

Frequency 12

Frequency 13

Frequency 14

Frequency 15

Frequency 16

BCCH: no hop

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

hopping freq.

GSM Signal Coding



1 - 66

•

GSM Bit Interleaving over Frames



1 - 67

Channels in GSM: Repeating Patterns

• Channels of information in GSM occupy physical



1 - 68

Channels of information in GSM occupy physical

timeslots of the GSM signal in repeating patterns• Similar to the way that classes and activities of a university

occupy the physical classrooms on a defined schedule

• Some classes meet daily, some only three days a week• Some labs once or twice a week

• Meals daily in the cafeteria, movies on Friday nights

• Graduation ceremonies once each semester

• Dedicated channels (carrying traffic or controlinformation for individual users) occur in a repeating 26-multiframe pattern 120 ms long

• 24 frames are used for traffic, one for SACH, one is unused• Full-rate s occur in each traffic frame

• Half-rate s (if used) occur in alternating traffic frames

• 1/8 rate dedicated channels are defined for special purposes andare called SDCHs (Stand-Alone Dedicated Control Channels)

GSM Traffic Channels:Hyperframes, Superframes, Multiframes, Frames, and Bursts



1 - 69

One Hyperframe3h 28m 53.760s2048 superframes

1 20472046204520442 3 4 50

0 1 2 3 4 5 6 47 48 49 50

0 1 2 3 4 5 6 7 8 91 0

1 1 1 2 1 3

1 4 1 5

1 6

1 7 1 8

1 9

2 0

2 1 2 2 2 3

2 4 2 5

BP 0 BP 1 BP 2 BP 3 BP 4 BP 5 BP 6 BP 7

OneSuperframe

6.120 s51 multiframes of 26 frames each

One 26Multiframe

120 ms26 frames

OneFrame1 frame

T a i l B i t s

T a i l B i t sGuard

Bits

StealingBit

StealingBit

Data BitsTraining

SequenceData Bits

3 57 bits 1 26 bits 1 57 bits 3 8.25 bits15/26 ms

~0.577 ms

One Burst (156.25 bits)

SACHUNUSED

s s

Gross Rate 270.833 kbps

Used for traffic channels andassociated signaling only

60/13 ms ~4.615 ms

GSM Control Channels:Hyperframes, Superframes, Multiframes, Frames, and Bursts

O H f



1 - 70

3h 28m 53.760s2048 superframes

One Hyperframe

0 1 2 3 24 25

0 1 2 3 4 5 6 7 8 91 0

1 1 1 2 1 3

1 4 1 5

1 6

1 7 1 8

1 9

2 0

2 1 2 2 2 3

2 4 2 5

2 6

2 7 2 8

2 9 3 0 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9

4 0

4 1 4 2 4 3

4 4 4 5

4 6

4 7 4 8

4 9 5 0

1 20472046204520442 3 4 50

6.120 s26 multiframes of 51frames each

235.38 ms51 frames

OneSuperframe

BP 0 BP 1 BP 2 BP 3 BP 4 BP 5 BP 6 BP 7OneFrame 60/13 ms ~4.615 ms1 frame

T a i l B i t s

T a i l B i t sGuard

Bits

StealingBit

StealingBit

Data BitsTraining

SequenceData Bits

3 57 bits 1 26 bits 1 57 bits 3 8.25 bits15/26 ms

~0.577 ms

One Burst (156.25 bits)

One 51Multiframe

Gross Rate 270.833 kbps

F C H

S C H

B C H

1

B C H

2

B C H

3

B C H

4

F C H

S C H

F C H

S C H

F C H

S C H

F C H

S C H

n o t u s e d

Used for control channels only

CCH5 or SDCH

CCH5 or SDCH

CCH6 or SACH

CCH7 or SACHCCH 2CCH 1

CCH0 or SYS_INFO

7 & 8CCH3 or SDCH

CCH4 or SDCH

Typical Timeslot Allocation in Multiframe Patternson One GSM RF Carrier

TIME



1 - 71

FCCH

SDCCH0

SCH

BCCH

1

0 1 2 3 4 5 6 7 8 9 10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

TimeSlot

0

TimeSlot

1

Frame

Number

Frame

Number 0 1 2 3 4 5 6 7 8 9 1

011

12

13

14

15

16

17

18

19

20

21

22

23

24

25 0 1 2 3 4 5 6 7 8 9 1

011

12

13

14

15

16

17

18

19

20

21

22

23

24

25

AGCH/PCH

BCCH

2

BCCH

3

BCCH

4

AGCH/PCH

AGCH/PCH

AGCH/PCH

FCCH

SCH

AGCH/PCH

AGCH/PCH

AGCH/PCH

AGCH/PCH

FCCH

SCH

AGCH/PCH

AGCH/PCH

AGCH/PCH

AGCH/PCH

SDCCH

0

SDCCH

0

SDCCH

0

SDCCH

0

SDCCH

1

SDCCH

1

SDCCH

1

SDCCH

1

FCCH

SCH

CBCH

CBCH

CBCH

CBCH

SDCCH

3

FCCH

SCH

SDCCH

3

SDCCH

3

SDCCH

3

S ACCH

0

S ACCH

0

S ACCH

0

S ACCH

0

S ACCH

1

S ACCH

1

S ACCH

1

S ACCH

1

S ACCH3

S ACCH3

S ACCH3

S ACCH3

S ACCH2

S ACCH2

S ACCH2

S ACCH2

I DL E

I DL E

I DL E

S ACCH1

S ACCH1

S ACCH1

S ACCH1

S ACCH0

S ACCH0

S ACCH0

S ACCH0

SDCCH7

SDCCH6

SDCCH5

SDCCH4

SDCCH3

SDCCH2

SDCCH0

SDCCH0

SDCCH0

SDCCH2

SDCCH2

SDCCH2

SDCCH3

SDCCH3

SDCCH3

SDCCH4

SDCCH4

SDCCH4

SDCCH5

SDCCH5

SDCCH5

SDCCH1

SDCCH1

SDCCH1

SDCCH1

SDCCH6

SDCCH6

SDCCH6

SDCCH7

SDCCH7

SDCCH7

I DL E

TCH

TCH

TCH

TimeSlot

2

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

I DL E

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

I DL E

TCH

TCH

TCH

TimeSlot

3

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

I DL E

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

I DL E

TCH

TCH

TCH

TimeSlot

4

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

I DL E

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

I DL E

TCH

TCH

TCH

TimeSlot5

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S

ACCH

I DL E TC

HTCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S

ACCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

I DL E

TCH

TCH

TCH

TimeSlot

6

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

I DL E

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

I DL E

TCH

TCH

TCH

TimeSlot

7

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

I DL E

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

S ACCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

I DL E

51 Multiframe Pattern for Control Channels

26 Multiframe Pattern for Traffic Channels 26 Multiframe Pattern for Traffic Channels

TIME

A GSM Uplink Normal Burst



1 - 72

• GSM is a TDMA system and a mobile’s transmission bursts arecarefully constructed not to overlap with bursts from other mobiles

• Different propagation delays of mobiles near and far mobiles theBTS are compensated by automatically advancing mobile transmit

timing• Special training sequences are included in each uplink burst and

downlink timeslot to facilitate demodulation• During unused timeslots, a mobile measures the strength of

surrounding base stations to guide the handover process (this iscalled MAHO, Mobile Assisted Hand Over)

GSM Bursts on the Uplink: 4 Types



1 - 73

StealingBit

StealingBitNormal Burst

Guard

BitsData Bits Training Bits Data Bits T a i l

T a i l

3 57 bits 1 26 bits 1 57 bits 3 8.25 bits

GuardBits T

a i l

T a i l

Data Bits Training Bits Data Bits

Synchronization Burst

3 39 bits 64 bits 39 bits 3 8.25 bits

GuardBits T

a i l

T a i l

Fixed ‘0’ or Fill-in Bits

Frequency Correction Burst or Dummy Burst

3 142 bits 3 8.25 bits

access Burst

Tail

Bits

Guard

Bits

Training Bits Data Bits T a i l

8 41 bits 36 bits 3 68.25 bits



1 - 74

GSM ChannelsDOWNLINK CHANNELS UPLINK CHANNELS



1 - 75

BCH BTS identity, channel allocation,frequency hopping sequences

FCH RACHProvides frequency referenceSlotted aloha channel used to

request network access

SCHDefines burst period boundaries

and time slot numbering

PCHCarries pages to mobiles,

alerting of incoming calls

SDCHStand Alone Dedicated

Control ChannelAGCH Allocates SDCH to mobile toobtain dedicated channel after

a request on the RACHTraffic Channel

BTS FACHFast Associated Control

Channel

SACHSlow Associated Control

Channel

F-TRAFFIC

SDCH

FACH

0 to many

SACH

Traffic Channel

Fast Associated Control Channel

Slow Associated Control Channel

Stand Alone Dedicated

Control Channel

BTSBTS

Frequency Hopping



1 - 76

f1f2f3f4f5f6f7f8f9f10f11f12f13f14f15f16

time f r e q u e n

c y

• Frequency Hopping (FH) is an optional technique for improvingperformance• Transceivers in the cells are programmed to hop through different

sequences of frequencies• this minimizes and statistically randomizes the occurrences of co-

channel and adjacent-channel interference – better than the staticrelationships which would occur with a fixed frequency plan

• another benefit is anti-fading diversity – if a user happens to stop ina faded location, the fade exists only on a few of the frequencies in

its hopping sequence and bit interleaving overcomes the bit errors

Question and Answer



1 - 775/19/2004 77

Question and Answer:GSM RF Fundamentals



1 - 78

• What is the role of the BCH channel?

• How many frames per second occur in a GSM

signal?• How many timeslots are in a frame?

• What are the typical functions of each timeslot?

• Name the four types of BTS bursts and describetheir functions

• What do “guard bits” do?• What is “timing advance” and why is it needed?

• What are the benefits of frequency hopping?



1 - 79

GPRS RF FUNDAMENTALS

General Packet Radio Service

What’s GPRS All About?

• GSM: Global System for Mobile Communication



1 - 80

y• The world’s most widely used wireless phone technology

• Over 500,000,000 users worldwide!

• TDMA-based radio interface, 200 kHz.-wide signals

• But very limited data capability• 9,600 or 14,400 bps maximum in circuit-switched mode

• WCDMA / UMTS: The Long-Term 3G Data Solution

• Uses spread-spectrum CDMA techniques, 4-MHz.-wide signals• Provides both voice and high speed packet data access

• But not widely deployed and available until late 2004 or later

• GPRS: General Packet Radio Service• A packet-switched IP-capable way of using GSM radioinfrastructure

• Defined in 1996, wide deployment beginning in 2001

• Provides both interim pre-WCDMA and long-term packet access

The GPRS Timeslot Allocation

In conventional GSM, a channel is permanently allocated for a particular



1 - 81

user during the entire call period (whether speaking or silent, whether transmitting data or not)

• In GPRS, the channels are only allocated when data packets aretransmitted or received, and they are released after the transmission

• For bursty traffic this results in much more efficient use of the scarce

radio resources• Multiple users can share one channel

BTS

GPRS allows a single mobile totransmit and/or receive on multipletimeslots of the same frame (this is

called multislot operation)• This provides “bandwidth on

demand” in a very flexiblescheme

• One to eight timeslots per framecan be allocated to a mobile

• Uplink and downlink allocationscan be allocated separately,which efficiently supportsasymmetric data traffic (suitablefor web browsing, for example)

•This GPRS mobile is in “3+1” timeslot mode•3 timeslots assigned on downlink•1 timeslot assigned on uplink

MultiSlot Classes of GPRS TerminalsMultiSlot

Class RX TX Sum

Max # of SlotsTta Ttb Tra Trb

TypeMinimum # of Slots

1 1 2 3 2 4 21 12 1 3 2 3 12 13• A mobile’s multislot class is the



1 - 82

2 2 3 2 3 133 1 4 1 3 142 2 4 1 3 153 2 4 1 3 163 3 4 1 3 174 1 5 1 2 183 2 5 1 2 194 2 5 1 2 110

4 3 5 1 2 1114 4 6 2 1 2 1123 a) 3 a)134 3 a)145 3 a)156 2 a)167 1 3178 0 0 018

3 b) 2 c)19 1320321222223

242526

272829

23446

88888888

888

345678

234

466

n/an/an/an/an/an/a

n/an/an/an/an/an/an/an/a

n/an/an/a

11111111

11222222

1111111

111

33333333

3

n/an/an/an/an/an/a

333

222

2222222

222

b)b)b)b)b)b)b)

b)b)b)

c)c)c)c)c)c)c)

c)c)c)

a)a)a)a)

sum of • Number of simultaneously

supported slots in uplink

• Number of simultaneouslysupported slots in downlink

• DL and UL number of slots canbe different due to

asymmetrical traffic• Class 1 = 1 Rx and 1 Tx slot

• Class 29 = 8 Rx and 8 Tx slots

• As of mid-2001, Class-B

mobiles with multislot class 4(3 DL + 1 UL) were available

a) = 1 with frequency hoppinga) = 0 without frequency hopping

b) = 1 with frequency hopping or change from RX to TXb) = 0 without frequency hopping and no change from RX to TXType 1 mobiles never transmit and receive at the same time

Type 2 mobiles are capable of transmitting and receiving simultaneously c) = 1 with frequency hopping or change from RX to TXc) = 0 without frequency hopping and no change from RX to TX

Allocation of GPRS Channels



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• A GPRS-capable cell may allocate physical channels for GPRS• Such a physical channel is called a Packet Data Channel (PDCH)

• The PDCHs are taken from the common pool of all channels available inthe cell

• The radio resources of a cell are shared by all GPRS and all non-GPRSmobiles in the cell

• The mapping of physical channels to either GPRS or GSM usage canbe performed dynamically, based on:

• Capacity on demand principle

• Depending on the current traffic load, priority of service, and the multislotclass

• A load supervision procedure monitors the PDCHs in the cell• The number of channels allocated to GPRS can be changed

according to current demand• Physical channels not currently in use by conventional GSM can be

allocated as PDCHs to increase the GPRS quality of service• When there is a resource demand for services with higher priority,

PDCHs can be de-allocated

GPRS Services



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• GPRS bearer services provide end-to-end packet-switched datatransfer. There are two kinds:

• PTP Point-to-Point Service, available now, has two modes:• PTP Connectionless Network Service (PTP-CLNS) for IP

• PTP Connection-oriented network Service (PTP-CONS) for X.25• PTM Point-to-Multipoint Service (available in future releases)

• PTM-M Multicast Services broadcasts packets in certain geographicalareas; a group identified indicates whether the packets are intendedfor all users or for a group

• PTM-G Group Call Service addresses packets to a group of users(PTM group) and are sent out in geographical areas where the groupmembers are currently located

• SMS Short Message Services

• Supplemental Call Services:• CFU Call Forwarding Unconditional, CFNRc Call ForwardingSubscriber Not Reachable, CUG Closed User group

• Non-Standard Services may be offered at GPRS service providers• Database access, messaging, e-transactions, monitoring, telemetry

GPRS Initial Release Features



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• All network manufacturers support IP and interworking of both internet and intranet from their first GPRS release• To support this functionality, some form of server functionality

must be provided• Domain Name Server (DNS) is required to translate between

domain names and IP addresses

• Dynamic Host Configuration Protocol (DHCP) is required to allowautomatic reassignment of addresses for mobile hosts

• In early networks, a single SGSN will probably besufficient due to the gradual growth of users and trafficas mobiles become available

• The connection between the GGSN and the MSC/VLR,HLR, and SMSC will require a gateway using SS7/IP or SIG to link the IP backbone with the interfaces to thesenetwork elements

Question and Answer



1 - 865/19/2004 86

Question and Answer:GPRS RF Basics



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• How are packet data and circuit-switched able to coexiston the same GSM transceiver?

• If a cell has more voice and GPRS data traffic than it can

carry, how are the resources assigned?• Can GPRS use frequency hopping?

• What is “multislot” operation?

• What range of data rates are possible on one timeslot?

• How many timeslots can a GPRS user simultaneouslyuse?

• Does a GPRS device need a duplexer?

• What classes of terminals do you have on your network?



1 - 88

EDGE RF BasicsEnhanced Data Rates for

GSM Evolution

“GPRS On Steroids?!”

What is EDGE?

S GSM t t l d l i f l



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• Some GSM operators expect long delays in successfulcommercial deployment of 3G WCDMA UMTS

• There is a need to offer fast data as soon as possible, at

minimum capital cost• to avoid losing market share to the CDMA2000 operators with

their 1xRTT and 1xEV-DO services which are just reaching

commercial popularity• Phase 1 of EDGE (Release’99) supports best effort

packet data at speeds up to about 384 kbps - three

times faster than GPRS• Phase 2 of EDGE (Release’2000) adds Voice over IP

capability

The EDGE Air Interface

E t d GPRS k t d t ith d ti



1 - 90

• Extends GPRS packet data with adaptivemodulation/coding

• 2x spectral efficiency of GPRS for best effort data

• 8-PSK/GMSK at 271 ksps in 200 KHz RF channelssupports 8.2 to 59.2 kbps per time slot• Supports peak rates over 384 kbps• Requires linear amplifiers with < 3 dB peak to average

power ratio using linearized GMSK pulses• Initial deployment with less than 2x 1 MHz using 1/3

reuse with EDGE Compact as a complementary data

service

Anticipated Steps in the EDGE Evolution



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• Best effort IP packet data on EDGE• Voice over IP on EDGE circuit bearers• Voice over IP with statistical radio resource multiplexing• Network based intelligent resource assignment• Smart antennas & adaptive antennas

• Downlink speeds at several Mbps based on widebandOFDM and/or multiple virtual channels

Two EDGEs: Compact and Classic



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• Fundamental difference is the frequency reuse and

minimum startup spectrum: Compact (1/3 and 2x 600kHz) and for Classic (4/12 and 2x 2.4 MHz)• Classic is specified by ETSI SMG2• Compact is specified by the PDFG of the UWC

• Compact achieves 4/12 reuse on control channels bycombining 4/4 time reuse with 1/3 space reuse

• Compact achieves 2x spectral efficiency of Classic ontraffic channels by combining 1/3 reuse with partialloading

EDGE Modulations



1 - 93

Scheme Modulation Maximum

rate [kb/s]

Code Rate Family

MCS-9 59.2 1.0 A

MCS-8 54.4 0.92 A

MCS-7 44.8 0.76 B

MCS-6 29.6 / 27.2 0.49 A

MCS-5

8PSK

22.4 0.37 B

MCS-4 17.6 1.0 C

MCS-3 14.8 / 13.6 0.80 A

MCS-2 11.2 0.66 B

MCS-1

GMSK

8.8 0.53 C

The EDGE Multi-Mode Radio Link



1 - 94

Scheme Modulation Maximum

rate [kb/s]

Code Rate Header Code

Rate

Blocks

per 20 ms

Family

MCS-9 59.2 1.0 0.36 2 A

MCS-8 54.4 0.92 0.36 2 A

MCS-7 44.8 0.76 0.36 2 B

MCS-6 29.6 / 27.2 0.49 1/3 1 AMCS-5

8PSK

22.4 0.37 1/3 1 B

MCS-4 17.6 1.0 0.53 1 C

MCS-3 14.8 / 13.6 0.80 0.53 1 A

MCS-2 11.2 0.66 0.53 1 B

MCS-1

GMSK

8.8 0.53 0.53 1 C

EDGE Payload Format

37 octets 37 octets 37 octets37 octets

MCS-3

MCS 6

Fa mily A



1 - 95

MCS-6

MCS-9

28 octets 28 octets 28 octets28 o ctets

MCS-2

MCS-5

MCS-7

Family B

22 octets22 octets

MCS-1

MCS-4

Family C

34+3 octets34+3 octets

MCS-3

MCS-6Fa mily A

padding

MCS-8

34 octets 34 octets 34 octets34 o ctets

Carriers, Frames,Timeslots & Channelsfor EDGE Classic & EDGE Compact



1 - 96

• A GSM carrier’s time is divided into frames

• A frame is divided into 8 timeslots and each isdesignated a timeslot number, TN0 …TN7

• All timeslots of a carrier’s timeslot number areconsidered a single physical channel

• Control/Traffic logical channels map to parts of

the physical channels

GSM Carriers and TDMA Frames for EDGE Classic and Compact



1 - 97

1/3 Frequency Re-use (EDGE Compact)

• 3 x 200 kHz carrier, reused in every site

• <1MHz x 2 initial deployment



1 - 98

<1MHz x 2 initial deployment

• 3 sectors per site

Time Reuse Scheme for EDGE Compact

T N 0 T N 1 T N 2 T N 3O F F T N 4 T N 5O F F T N 6 T N 7O F F



1 - 99

T N 0 T N 1 T N 2 T N 3O F F T N 4 T N 5O F F T N 6 T N 7O F FT ra ff ic C o n tro l T ra ff ic T ra f f ic T ra f f ic

Base Station Frame Synchronization - so that all base stations can beswitched on/off synchronously to achieve reuse in time

Modified air-interface protocols - to be able to handle the resulting

discontinuous nature of transmissionsse is in space only Reuse for control and reuse for traffic channels are independent of

each other

The actual reuse employed - for traffic or control - is operator

controlled and limited only by the available spectrum Typically, 4/12 is used for control and 1/3 for traffic. However, other

combinations are also possible subject to performance requirements,environment and spectrum availability.

Question and Answer



1 - 1005/19/2004 100

Question and Answer:EDGE RF Basics

• What is the rationale for EDGE? Do you see a



1 - 101

• What is the rationale for EDGE? Do you see aworkable business case for deploying it?

• How does EDGE achieve it’s speed increaseover GPRS, and what is the nominal ratio of EDGE’s best to GPRS’ best rates?

• How many modulation/coding schemes areavailable in EDGE?

• What is EDGE compact? EDGE classic?

• What is your company’s present direction onEDGE, and what is your own recommendation?Why?

GLOBAL SYSTEM FOR


R



1 - 102

Lesson 3:

GSM Architecture

GSM Network Overview



1 - 103

• At a high level, GSM is a mobile telephony network based on thecellular concept. Users can place and receive calls without beingfixed to a specific location or wired to a physical connection.

• To supply this capability, a GSM network consists of three basiccomponents:

• Subscriber Terminal Devices

• Radio Base Station Network

• Network Switching and Services Infrastructure

Architecture of the GSM system

GSM is a PLMN (Public Land Mobile Network):



1 - 104

• GSM components• MS (mobile station)

• BTS (base transceiver station)• BSC (base station controller)• MSC (mobile switching center) and G-MSC• HLR, VLR (location registers)• AuC, EIR

Subsystems• RSS (radio subsystem): covers all radio aspects• NSS (network and switching subsystem): call forwarding, handover,

switching• OSS (operation subsystem): management of the network

Architecture of the GSM Network



1 - 105

• The GSM technical specifications define the different entities that form theGSM network by defining their functions and interface requirements.The GSM network can be divided into four main parts:

• The Mobile Station (MS).

• The Base Station Subsystem (BSS).

• The Network and Switching Subsystem (NSS).

• The Operation and Support Subsystem (OSS). (also known as NMS:network management system)

Example of a PLMN (Public LandMobile Network)

• Each GSM network forms a PLMN or Public Land Mobile Network Usually



1 - 106

• Each GSM network forms a PLMN or Public Land Mobile Network. Usually,in each country there is more than one PLMN.

• Each PLMN consists of two basic parts: The NSS or Network SwitchingSubsystem and the BSS or Base Station Subsystem.

• The NSS consists of the Mobile Services Switching Center (MSC), theVisitor Location Register (VLR), the Equipment Identity Register (EIR /

optional) and the Home Location Register (HLR) with integrated AuC(Authentication Center).

• The BSS consists of one Base Station Controller (BSC) that is connected toa number of Base Transceiver Stations (BTS).

• The Transcoding Rate and Adoption Unit also belongs to the BSS. EachPLMN contains at least one HLR” Each PLMN contains at least one HLR”

Public Land Mobile Network (PLMN)



1 - 107

• A Public Land Mobile Network (PLMN) is established and operatedby an administration or Recognized Private Operating Agency(RPOA) for the specific purpose of providing land mobiletelecommunications service services to the public.

• A PLMN may be regarded as an extension of a network (e.g. ISDN);it is a collection of MSCs areas within a common numbering plan(e.g. same National Destination Code) and a common routing plan.The MSCs are the functional interfaces between the fixed networks

and a PLMN for call set-up.

Public Land Mobile Network (PLMN)



1 - 108

• Functionally the PLMNs may be regarded asindependent telecommunications entities even thoughdifferent PLMNs may be interconnected through the

ISDN/PSTN and PDNs for forwarding of calls or networkinformation.

• A similar type of interconnection may exist for theinteraction between the MSCs of one PLMN.

The Three Subsystems of GSMand Their Interfaces

AAir



1 - 109

NMS

NSSBSS

O&M

MS

GSM Subsystems



1 - 110

A ir A

VLR HLR

VLR

MSC

MSC

O&M

GSM: Elements and Interfaces



1 - 111

The PLMN – GSM Architecture

EIRMSC-Area

AuC

VLR

VLR



1 - 112

HLR

MSC-Area

EIR

MSC-Area

G-MSC

MSC-Area

HLR

G-MSC

MSC-Area

MSC-Area

BSS

BSS

MSC

VLRBTS

BTS

BTS

TRAU

Gateway to

External networks

Gateway toExternal networks

MSC-Area

BSC

VLR

VLR

Subsystems of a GSM PLMN



1 - 113

• The description of the system based on its functional elements, describingboth its function and the interrelation between the elements, give a broad

overall view of the system itself. A higher level of understanding can beachieved if a study is undertaken dividing it into subsystems.

• A subsystem is an entity composed of one or more physical equipment tocarry out a specific task. The union of these specific activities achieves the

intended operation of the GSM PLMN.

The subsystems mentioned above are:• The Base Station System (BSS)• The Switching and Management Subsystem (SMSS) (or NSS)

• The Operation and Maintenance Subsystem (OMSS).

GSM Network Subsystems

Mobile Station (MS) Subscriber Identity Module (SIM)



1 - 114

Base Station Subsystem (BSS) Base Tranceiver Station (BTS) part of BSS Base Station Controller (BSC) part of BSS Transcoding Rate and Adaptation Unit (TRAU) part of BSS

SMSS or Network Switching Subsystem (NSS); Subsystems are connected viaSS7

Mobile Services Switching Center (MSC) part of NSS

Home Location Register (HLR) part of NSS Visitor Location Register (VLR) part of NSS Equipment Identity Register (EIR) part of NSS

OMA&P (Operations, maintenance, administration & Provisioning) includingNetwork Management Systems (NMS) and OSS (Operation Support Systems)

Trouble Ticketing Service Activation Service QoS and SLA Management Fault Localization and Correction Billing

Customer Care

Operation and maintenance subsystem

• The handling of the features related to system security, based on the validation of identitiesof the various Telecommunication entities, are carried out by:• Authentication Centre's) (AUC)



1 - 115

) ( )• This is in charge of providing the authentication key used for authorizing the subscriber

access to the associated GSM PLMN.• Equipment Identity Register's) (EIR)

• This is in charge of handling Mobile Station Equipment Identity included with each MobileStation.• The subsystem is in charge of remote operations and maintenance of the PLMN. Control

functions are monitored and controlled in the Operations and Maintenance Centre (OMC).• To centralize PLMN control, one or more Network Management Centres (NMC) can be

installed.• In relation to operation and maintenance aspects there is the underlying concept of TMN:

Telecommunication Management Network, defined by the ITU-T in Recommendation M.30.• In this context, operations for which the OMC is responsible are defined as all those actions

of a technical and/or administrative nature that may be needed due to changes in externalconditions (demands for services, etc.).

• Following the same line, maintenance is understood as all those technical and/or administrative actions (including supervisory actions) intended to maintain the system

operating correctly of restore normal operation after a breakdown in one of its parts, in theshortest possible time.

The Switching and Management Subsystem(SMSS) or Network Switching Subsystem

(NSS)



1 - 116

• is the subsystem in which are included all the functions required to handle signallingprotocols, by which calls are established, maintained and cleared. It should be notedthat because of the mobile nature of the subscribers, the Switching and ManagementSubsystem must be able to control and handle certain specific functions for themobile environment.

• The main functions of this subsystem are:• - Specific functions related to the mobile nature of subscribers regarding the handling of

calls: e.g. paging.• - Management of radio resources during a call.• - Management of the signalling protocol with the BSS.• - Location registration: interworking with the VLR.• - The hand-over procedure: connection with another BSS in the same or different MSC area

within the same PLMN when a mobile moves during a call.• - Interrogation of the HLR to obtain the MS roaming number an the MS location.

• - Exchange of signalling information with other mobile functional entities (VLR, HLR, GCR or other MSCs).

The Base Station System (BSS)

• The base station system includes the functions of the physical layer according to the Reference Model for the Open Systems Interconnection of



1 - 117

according to the Reference Model for the Open Systems Interconnection of ISO/CCITT, both in the mobile station (MS) and the base station System(BSS).

• The base station system is composed of a number of logical channels. Thestructuring criteria for the logical channels and their access capabilities arecovered in GSM 04.03.

• The base station system has two types of channels:

• Traffic channels (TCH)• Signalling channels• The traffic channels are used to transmit user data or coded speech and are in

turn divided into two channel types, Bm or full rate (TCH/F) and Lm or half-ratechannels (TCH/H). Together the base station system may support trafficchannels as described in GSM 05.03

• The signalling channels are divided in turn in broadcast control channels (BCCH);common control channel (CCCH); stand-alone dedicated control channel(SDCCH) and associated control channel (ACCH). (An associated controlchannel is always associated with each TCH or SDCCH).

Roadmap 1: GSM-Based Network Infrastructure Signaling

Traffic and Signaling

PSTN/ISDNCS-CN



1 - 118

BTS

BTS

HLR

MSC/VLR SS7/MAP

A-Interface

PDA

A-Interface

BSC

BSC

BSC - Base Station Controller BTS - Base transceiver stationCS - Circuit switchedGSM - Global System for Mobile CommunicationsHLR - Home location register MAP - Mobile Application PartMSC - Mobile services switching center PDA - Personal digital assistant

PLMN - Public Land Mobile NetworkPSTN - Public Switched Telephone NetworkSS7 - Signaling System Number 7

G-MSC

MSC/VLR

Roadmap 2: GSM System ArchitectureReview

radio

subsystem

MS MS

network and switching

subsystem

fixed

partner networks



1 - 119

Um

Abis

ABSS

MS MS

BTS

BSCBTS

BTS

BSCBTS

MSC

MSC

IWF

ISDNPSTN

PSPDN

CSPDN

S S 7

EIR

HLR

VLR

ISDNPSTN

Roadmap 3: Simplified GSM NetworkArchitecture

VLR

Um



1 - 120

BTS

BTS

BSC TRAU MSC

PSTNISDN

SS7

HLR EIR AUC

MSC

GMSC

Abis AAsub

BSC

BTS

MS

MS-SIM

Roadmap 4: The PLMN – GSMArchitecture

HLR

MSC-Area

AuC

EIR



1 - 121

MSC-Area

MSC-Area

G-MSC

MSC-Area

HLR

G-MSC

MSC-Area

MSC-Area

BSS

BSS

MSC

VLRBTS

BTS

BTS

TRAU

Gateway to

External networks

Gateway toExternal networks

MSC-Area

BSC



1 - 122



1 - 123



1 - 124

Mobile Station (MS)



1 - 125

• The MS is the mobile handset, it contains the ME and the SIM

• Mobile equipment (ME)

• mobile handset hardware, including RF, GSM modulation etc

• Identified by a unique International Mobile Equipment Identity (IMEI)(different from the phone number)

• Subscriber Identity Module (SIM)• contains subscriber-related information

• Identified by a unique International Mobile Subscriber Identity (IMSI)(different from the phone number)

Base Station Subsystem (BSS)

The BSS consists of BTSs and BSCs



1 - 126

The BSS consists of BTSs and BSCs

Base Tranceiver Station (BTS) – responsible for communication with the MS – responsible for radio transmission and reception – includes antennas, modems, signal processing

Base Station Controller (BSC) – responsible for radio interface management of BTS and MS, i.e.channel management and handovers

– responsible for communication with the NSS

– a single BSC typically manages 10-20 BTSs

Radio Subsystem

• The Radio Subsystem (RSS) comprises the

cellular mobile network up to the switchingcenters



1 - 127

• Components

• Base Station Subsystem (BSS):

• Base Transceiver Station (BTS): radio components includingsender, receiver, antenna - if directed antennas are used one

BTS can cover several cells• Base Station Controller (BSC): switching between BTSs,

controlling BTSs, managing of network resources, mappingof radio channels (Um) onto terrestrial channels (A interface)

• BSS = BSC + sum(BTS) + interconnection

• Mobile Stations (MS) 4.16.1

The Base Station System (BSS)

• The Base Station System (BSS) is the system of



1 - 128

• The Base Station System (BSS) is the system of base station equipments (transceivers,controllers, etc...) which is viewed by the MSCthrough a single A-interface as being the entityresponsible for communicating with MobileStations in a certain area. Similarly, in PLMNssupporting GPRS, the BSS also has an interfaceto an SGSN. The radio equipment of a BSS may

support one or more cells.

The Base Station Subsystem (BSS)

• The BSS connects the Mobile Station and the NSS It is



1 - 129

The BSS connects the Mobile Station and the NSS. It isin charge of the transmission and reception.

• The BSS can be divided into two parts:

• The Base Transceiver Station (BTS) or Base Station.

• The Base Station Controller (BSC).

BSS

A BSS i t f b t ti Wh



1 - 130

• A BSS may consist of one or more base stations. Where

an Abis-interface is implemented.

• The BSS consists of one Base Station Controller (BSC)

and one or more Base Transceiver Station (BTS).

• The functionality is described in GSM 08.02.

Base Station Controller (BSC)

• A Base Station Controller (BSC) is a network



1 - 131

( )component in the PLMN with the functions for

control of one or more BTS.• A Base Transceiver Station (BTS) is a network

component which serves one cell.

• The split of functions between BSS and MSC isdescribed in the 08-series of GSM TechnicalSpecifications.

System Architecture: Radio StationSubsystem (RSS)

• Components

• MS (Mobile Station)

Network and switchingsubsystem

radio stationsubsystem



1 - 132

( )

• BSS (Base Station Subsystem):

consisting of • BTS (Base Transceiver Station):

sender and receiver

• BSC (Base Station Controller):controlling several transceivers

• Interfaces

• Um : radio interface

• Abis : standardized, open interface

with16 kbit/s user channels

• A: standardized, open interfacewith

64 kbit/s user channels

Um

Abis

A

BSS

MS MS

BTS

BSC MSCBTS

BTS

BSCBTS

MSC

Base Transceiver Station and BaseStation Controller

Functions BTS BSCManagement of radio channels X



1 - 133

Management of radio channels XFrequency hopping (FH) X X

Management of terrestrial channels XMapping of terrestrial onto radio channels XChannel coding and decoding XRate adaptation XEncryption and decryption X XPaging X XUplink signal measurements X

Traffic measurement X

Authentication XLocation registry, location update XHandover management X

The Transcoding Rate and Adoption Unit (TRAU)

TRAU Frame



1 - 134

MSC

BTS

BSC

TRAU64 kbit/s16 kbit/s16 kbit/s

MSC

BTS

BSC

TRAU

64 kbit/s64 kbit/s16 kbit/s

TRAU Frame

The Base Station Controller (BSC) DB: DatabaseTCE: Trunk Control ElementTM: TransMisson

DB

TM TCE TM TCE

A b i s-

A-I n



1 - 135

Central Module Central Functions/Clock-Distribution

SwitchTM TCE

TM TCE

TM TCE

TM TCE

-I n t er f a

c e

OMC

n t er f a c

e

The Base Transceiver Station (BTS)

The RF-part of a BTS

Air-Interface



1 - 136

O&M Module Operation & Maintenance Functions/ Clock DistributionO&M Module Operation & Maintenance Functions/ Clock Distribution

A b i s-I n t

er f a c e

TransmissionModules

TransmissionModules

TRXDigital Signal Processing(Low Frequency)

TRXDigital Signal Processing(Low Frequency)

S l ow

F r e q u en c y

H

o p pi n g

RF-Transmit(RF-TX)

RF-Receive(RF-RX)

RF-Transmit(RF-TX)

RF-Receive(RF-RX)Input

Filter

InputFilter

OuputFilter

OuputFilter

Mobile Station (MS)

VoiceDecoding

•Channel Decoding•De-Interleaving•Reformating Deciphering Demodul



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GSM SIMGSM SIM

ID-1 SIM

Voiceencoding

•Channel Encoding•Interleaving•Burst Generation Ciphering Modulation Amplifier

SIM= Subscriber Identity Module

Plug-in SIM

The Mobile Station (MS)

• The mobile station consists of the physical equipment used by a



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• The mobile station consists of the physical equipment used by aPLMN subscriber; it comprises the Mobile Equipment (ME) and theSubscriber Identity Module (SIM).

• The ME comprises the Mobile Termination (MT) which, depending

on the application and services, may support various combinationsof Terminal Adapter (TA) and Terminal Equipment (TE) functionalgroups.

• These functional groups are described in GSM 04.02.

Review: Base Station Subsystem



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• The Base Station Subsystem controls the radiolink with the Mobile Station. It is mainlycomposed of _______ and the ________.

Review: Base Station Subsystem

• The Base Station Subsystem controls the radio link with



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the Mobile Station. It is mainly composed of the BaseTransceiver Station (BTS) and the Base StationController (BSC).

• The BSC-to-BTS link is called the Abis interface which is

cable or an optical fiber interface, and allows operationbetween components made by different suppliers.

• The BTS is made up of the antenna and the radio

transceivers.

Network and Switching Subsystem(NSS)

• NSS contains the switching functions of GSM, as well as

databases for mobility management



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databases for mobility management

• NSS contains – Mobile Switching Centre (MSC)

– Gateway MSC (GMSC)

– Home Location Register (HLR) - co-located with GMSC

– Visitor Location Register (VLR) - co-located with MSC/GMSC• Signaling between MSC, GMSC, HLR, VLR

via SS7 signaling network, using specifically the mobile

application part (MAP) of signaling System No 7 (SS7)

NSS cont’d...

• Mobile Switching Centre (MSC)coordinates setup of calls to and from GSM users



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– coordinates setup of calls to and from GSM users

– controls several BSCs

• Gateway MSC (GMSC)

– gateway to external network – incoming call is routed to GMSC, which then determinesMS location

– GMSC function is often in the same machine as the MSC

NSS cont’d...

• Home Location Register (HLR)

– contains information about subscribers e g subscriber



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contains information about subscribers, e.g. subscriber

profiles, also information on their current location – IMSI, user phone number, address of current VLR etc

• Visitor Location Register (VLR)

– temporarily stores subscription data for subscriberscurrently in the (G)MSC area

– contains more precise location data than does the HLR

– linked to one or more MSCs

The Network and Switching Subsystem(NSS)

• Its main role is to manage the communications betweenthe mobile users and other users such as mobile users



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the mobile users and other users, such as mobile users,

ISDN users, fixed telephony users, etc.

• It also includes data bases needed in order to storeinformation about the subscribers and to manage their

mobility. The different components of the NSS are:

• The Mobile services Switching Center (MSC)

• The Gateway Mobile services Switching Center (GMSC)

Review: Network Switching Subsystem(NSS)

• The NSS includes the:



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• The NSS includes the:

• 1) the Mobile Switching Center(MSC)

• 2) the Home Location Register(HLR)

• 3) the Visitor Location Register(VLR)• 4) the Equipment Identity Register(EIR)

• 5) the Authentication Register(AUC)

Network and switching subsystem

• NSS is the main component of the public mobile network GSM

• switching, mobility management, interconnection to other networks,system control

• Components



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Components

• Mobile Services Switching Center (MSC)controls all connections via a separated network to/from a mobileterminal within the domain of the MSC - several BSC can belong to aMSC

• Databases (important: scalability, high capacity, low delay)• Home Location Register (HLR)central master database containing user data, permanent and semi-permanent data of all subscribers assigned to the HLR (one provider canhave several HLRs)

• Visitor Location Register (VLR)local database for a subset of user data, including data about all user currently in the domain of the VLR

4.20.1

System architecture: Network and SwitchingSubsystem (NSS)

network

subsystem

fixed partner

networks

ISDNPSTN

Components MSC (Mobile Services Switching Center):

IWF (Interworking Functions)



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MSC

MSC

IWF

ISDNPSTN

PSPDNCSPDN

S S

7

EIR

HLR

VLR

PSTN

ISDN (Integrated Services Digital Network) PSTN (Public Switched Telephone Network)

PSPDN (Packet Switched Public Data Net.)

CSPDN (Circuit Switched Public Data Net.)

Databases

HLR (Home Location Register)

VLR (Visitor Location Register)

EIR (Equipment Identity Register)

Question and Answer



1 - 1485/19/2004 148

Review: Network Switching Subsystem(NSS)

The NSS includes the:



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The NSS includes the:

1)

2)

3)4)

5)

Mobile-services Switching Centre (MSC)

• The Mobile-services Switching Centre (MSC) constitutes the interfacebetween the radio system and the fixed networks. The MSC performs allnecessary functions in order to handle the calls to and from the mobilestations.



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stations.

• In order to obtain radio coverage of a given geographical area a number of base stations are normally required; i.e. each MSC would thus have tointerface several base stations. In addition several MSCs may be requiredto cover a country.

• The main difference between a MSC and an exchange in a fixednetwork is that the MSC has to take into account the impact of theallocation of radio resources and the mobile nature of the subscribersand has to perform in addition, at least the following procedures:

• procedures required for the location registration (see GSM 03.12);• procedures required for handover (see GSM 03.09).

Mobile Services Switching Center

• The MSC (mobile switching center) plays a central role in GSM• switching functions

• additional functions for mobility support

• management of network resources



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• management of network resources

• interworking functions via Gateway MSC (GMSC)

• integration of several databases

• Functions of a MSC

• specific functions for paging and call forwarding• termination of SS7 (signaling system no. 7)

• mobility specific signaling

• location registration and forwarding of location information

• provision of new services (fax, data calls)• support of short message service (SMS)

• generation and forwarding of accounting and billing information

MSC Area – VLR Area

• The MSC area is the part of the network covered by anMSC An MSC area may consist of one or several



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MSC. An MSC area may consist of one or several

location areas.

• An MSC area may also consist of one or several BSCareas.

• The VLR area is the part of the network controlled by aVLR. A VLR area may consist of one or several MSC

areas

The Gateway MSC (GMSC)

• If a network, delivering a call to the PLMN cannot interrogate theHLR, the call is routed to an MSC.



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,

• This MSC will interrogate the appropriate HLR and then route thecall to the MSC where the mobile station is located. The MSC whichperforms the routing function to the actual location of the MS iscalled the Gateway MSC (GMSC).

• The acceptance of an interrogation to an HLR is the decision of theoperator.

• The choice of which MSCs can act as Gateway MSCs is for theoperator to decide (i.e. all MSCs or some designated MSCs).

• Source: GSM 03.04.

SMS Related Sub Systems

SMS Gateway MSC (SMS-GMSC)

Th SMS G t MSC (SMS GMSC) t i t f b t



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• The SMS Gateway MSC (SMS-GMSC) acts as an interface betweena Short Message Service Centre an the PLMN, to allow shortmessages to be delivered to mobile stations from the Service Centre(SC).

SMS Interworking MSC

• The SMS Interworking MSC acts as an interface between the PLMNand a Short Message Service Centre (SC) to allow short messagesto be submitted from Mobile Stations to the SC.

The Interworking Function (IWF)

• The Interworking Function (IWF) is a functional entity associatedwith the MSC. The IWF provides the functionality necessary to allowinterworking between a PLMN and the fixed networks (ISDN, PSTN

d PDN )



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and PDNs).

• The functions of the IWF depend on the services and the type of fixed network. The IWF is required to convert the protocols used inthe PLMN to those used in the appropriate fixed network.

• The IWF may have no functionality where the serviceimplementation in the PLMN is directly compatible with that at thefixed network. The interworking functions are described in GSM

Technical Specifications 09.04, 09.05, 09.07 and 09.09.

GSM Location Register

• To enable communication to a mobile station the network must knowwhere this mobile station is located. This information is stored in afunction named location register.



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Home Location Register (HLR)

• The Home Location Register (HLR) is the location register to whicha mobile subscriber is assigned for record purposes such assubscriber information.

Visitor Location Register (VLR)

• The Visitor Location Register (VLR) is the location register, other

than the HLR, used by an MSC to retrieve information for, e.g.handling of calls to or from a roaming mobile station currentlylocated in its area.

GSM Location Register

Authentication Centre (AuC)• The Authentication Centre (AuC) is an entity which stores data for

each mobile subscriber to allow the International Mobile Subscriber Identity (IMSI) to be authenticated and to allow communication over the radio path between the mobile station and the network to beciphered. The AuC transmits the data needed for authentication and



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ciphering via the HLR to the VLR, MSC and SGSN which need toauthenticate a mobile station.• The procedures used for authentication and ciphering are described

more fully in GSM 03.20.

Equipment Identity Register (EIR)• The Equipment Identity Register (EIR) in the GSM system is the

logical entity which is responsible for storing in the network theInternational Mobile Equipment Identities (IMEIs), used in the GSM

system.• The equipment is classified as "white listed", "grey listed", "blacklisted" or it may be unknown as specified in GSM 02.16 andGSM 09.02.

GPRS Location Register (GSM 2+)

Serving GPRS Support Node (SGSN)

The location register function in the SGSN stores subscriptioninformation and location information for each subscriber registered inthe SGSN



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the SGSN.

• The SGSN is needed only in a PLMN which supports GPRS.

Gateway GPRS Support Node (GGSN)

The location register function in the GGSN stores subscriptioninformation and routeing information (needed to tunnel packet datatraffic destined for a GPRS MS to the SGSN where the MS isregistered) for each subscriber for which the GGSN has at least onePDP context active.

• The GGSN is needed only in a PLMN which supports GPRS

The Group Call Register (GCR)

• The Group Call Register (GCR) shall hold for a related MSC area for

each group ID and cell from which Voice Group Call Service (VGCS)or Voice Broadcast Service (VBS) calls can be established bymobile stations the voice group call reference or voice broadcast callreference to be used for a VGCS or VBS call to be established andan indication whether the originating MSC is the MSC responsible



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an indication whether the originating MSC is the MSC responsiblefor that call.

• If the originating MSC is not responsible for that call, the GCR shallhold the routing information identifying the MSC responsible for thatcall.

• A GCR may be in charge of one or several MSC. Each MSCinvolved in a voice group or broadcast call requests its proper voicegroup or broadcast call attributes from its related GCR by use of thevoice group or broadcast call reference.

NMS/OSS

The Operation and Support Subsystem (OSS)



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• The OSS is connected to the differentcomponents of the NSS and to the BSC, in order

to control and monitor the GSM system.

• It is also in charge of controlling the traffic load

of the BSS.

Operation Subsystem

• The OSS (Operation Subsystem) enables centralized operation,management, and maintenance of all GSM subsystems

• Components



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• Authentication Center (AUC)• generates user specific authentication parameters on request of a VLR

• authentication parameters used for authentication of mobile terminals andencryption of user data on the air interface within the GSM system

• Equipment Identity Register (EIR)• registers GSM mobile stations and user rights

• stolen or malfunctioning mobile stations can be locked and sometimes evenlocalized

• Operation and Maintenance Center (OMC)

• different control capabilities for the radio subsystem and the networksubsystem

4.22.1

Operation SubSystem (OSS)or Operation Support Systems

• Network operation and maintenance



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• Subscriber data management

• Call charging

• Mobile equipment management via EquipmentIdentity Register (EIR)

The Home Location Register (HLR)

• This functional entity is a data base in charge of the management of mobile subscribers.



1 - 163

• A PLMN may contain one or several HLRs: it depends on the number of mobile subscribers, on the capacity of the equipment and on theorganisation of the network.

• The following kinds of information are stored there:

• The subscription information;

• Some location information enabling the charging and routing of calls towardsthe MSC where the MS is registered (e.g. the MS Roaming Number, the

VLR Number, the MSC Number, the Local MS Identity).

HLR and GPRS



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If GPRS is supported, also:

• Location information enabling the charging and

routing of messages in the SGSN where the MS iscurrently registered (e.g. the SGSN Number);

HLR and LCS



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If LCS is supported, also• A LCS privacy exception list, which indicates the

privacy class of the MS subscriber;

• A GMLC list,• A MO-LR list.

Configuration of a PLMN supporting LCS

SMLCLMU

Type A

SMLCLp CBC

CBC-

SMLC



1 - 166

MSBTS

(LMUType B)

MSC/VLR

HLR

Gateway

MLC

External

LCS client

Le Lg

Lg

Lh

GatewayMLC

Other PLMN

Um Ls

BSC A Abis

Lb

LMU

Type B

Abis

gsmSCF

Lc

CBC-BSC

GSM Identities in HLR



1 - 167

• Different types of identity are attached to each mobilesubscription and are stored in the HLR. If GPRS is not

supported the following identities are stored:

• the International Mobile Station Identity (IMSI);

• one or more Mobile Station International ISDNnumber (s) (MSISDN);



At Least One Identity

• There is always at least one identity, apart



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from the IMSI, attached to each mobilesubscription and stored in the HLR.

• The IMSI or, the MSISDN may be used as a keyto access the information in the database for a

mobile subscription.

Other Information in HLR

The data base contains other information such as:• Teleservices and bearer services subscription information;• Service restrictions (e.g. roaming limitation);



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• A list of all the group IDs a Service subscriber is entitled to use toestablish voice group or broadcast calls;• Supplementary services; the HLR contains the parameters attached to

these services;

and, if GPRS is supported, also• Information about if a GGSN is allowed to dynamically allocate PDP

addresses for a subscriber.

• NOTE: Supplementary services parameters need not all be stored in the HLR.However, it seems safer to store all subscription parameters in the HLR evenwhen some are stored in a subscriber card.

• The organisation of the subscriber data is outlined in GSM 03.08.

The Visitor Location Register (VLR)

• A mobile station roaming in an MSC area is controlled by the Visitor Location Register in charge of this area. When a Mobile Station



1 - 171

(MS) enters a new location area it starts a registration procedure.

• The MSC in charge of that area notices this registration andtransfers to the Visitor Location Register the identity of the location

area where the MS is situated. If this MS is no yet registered, theVLR and the HLR exchange information to allow the proper handlingof calls involving the MS.

• A VLR may be in charge of one or several MSC areas.

Data Stored in VLR

• The VLR contains also the information needed to handle the calls set-up or received by the MSs registered in its data base (for some supplementaryservices the VLR may have to obtain additional information from the HLR) the

f ll i l t i l d d



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following elements are included:• the International Mobile Subscriber Identity (IMSI);• the Mobile Station International ISDN number (MSISDN);• the Mobile Station Roaming Number (MSRN),• the Temporary Mobile Station Identity (TMSI), if applicable;

• the Local Mobile Station Identity (LMSI), if used;• the location area where the mobile station has been registered.• If GPRS is supported: the identity of the SGSN where the MS has been

registered. Only applicable to PLMNs supporting GPRS and which have a Gsinterface between MSC/VLR and SGSN

• the last known location and the initial location of the MS;

Zones for Regional Subscription

• A PLMN operator may define a number of regional subscriptionareas, each of which is a subset of the service area for anunrestricted mobile subscriber.



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• A regional subscription area may be contained within the servicearea of a single PLMN, or may lie within the service areas of two or

more PLMNs.

• Each regional subscription area consists of one or more zones; eachzone is contained within the service area of a PLMN.

Zones for Regional Subscription

• The definition of a mobile subscriber's regional subscription area isstored within the HLR per National Destination Code(s) (NDC) of aPLMN and is transferred to the VLRs of that PLMN.



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• The VLR evaluates this information to extract the restricted or accessible MSC areas and location areas to which the mobilesubscriber is allowed to roam.

• The VLR and/or SGNS informs the HLR if an entire MSC area isrestricted.

• Zones for Regional Subscription and their handling are defined inGSM 03.03, GSM 03.08 and GSM 09.02.

Service Area

• The service area is defined as an area in which a mobile subscriber can be reached by another (mobile or fixed) subscriber without the



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can be reached by another (mobile or fixed) subscriber without thesubscriber's knowledge of the actual location of the mobile stationwithin the area. A service area may consist of several PLMNs.

• One service area may consist of one country, be a part of a countryor include several countries. The location registration systemassociated with each service area must thus contain a list of allmobile stations located within that service area.

Group Call Area

• The group call area is a predefined area composed of

one or a number of cells to which a particular VoiceG C S ( GCS) S



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one or a number of cells to which a particular VoiceGroup Call Service (VGCS) or Voice Broadcast Service(VBS) call is distributed.

• The composition of a group call area is predefined in thenetwork. The group call area may include cells of morethan one MSC area and cells of more than one PLMN.

Group Call Register (GCR)

• The Group Call Register (GCR) is a register holdinginformation about VGCS or VBS calls, the voice group or

broadcast call attributes respectively



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broadcast call attributes, respectively.

• Voice group or broadcast call attributes are defined for a

specific voice group or broadcast call reference andinclude the data required to configure the conferencebridge for a VGCS or VBS call and other call related

attributes.

Serving Mobile Location Center (SMLC)

• The Serving Mobile Location Centre (SMLC)node is responsible for managing the overall co-ordination and scheduling of resources required



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ordination and scheduling of resources requiredto perform positioning of a mobile, andcalculating the final location estimate and

accuracy.

• There may be more than one SMLC in a PLMN.



Gateway Mobile Location Centre(GMLC)

• The Gateway Mobile Location Centre (GMLC) is

the first node an external Location Application



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the first node an external Location Applicationaccesses in the GSM PLMN.

• The GMLC performs registration authorizationand requests routing information from the HLR.There may be more than one GMLC in a PLMN.

GMLC

• The Gateway Mobile Location Centre containsfunctionality required to support LCS (LoCation

Services)



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Services).

• In one PLMN (Public Land Mobile Network), there may

be more than one GMLC.

• The GMLC is the first node an external LCS client

accesses in a GSM or UMTS network.

Location Measurement Unit (LMU)

• An LMU makes radio measurements to support one or

more positioning methods



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more positioning methods.

Two types of LMU are defined:

Type A LMU: accessed over the normal GSM air interface

Type B LMU: accessed over the Abis interface

Question and Answer



1 - 1835/19/2004 183

Review

• A GSM network is composed of several subsystemswhose functions and interfaces are specified. Theseare the:

1)



1 - 184

1)2)

3)

4)

5)

Review

1) base station subsystem (BSS)

2) bil t ti (MS)



1 - 185

2) mobile station (MS)

3) network and switching subsystem (NSS)

4) operations subsystem (OSS)

5) operations and maintenance Center (OMC)

GPRS



1 - 186

GPRS

Network Elements and

Internal Interfaces

The GSM-GPRS-EDGE-UMTS Architecture

Core Network

Core Network

BSCBase

Station

Controller

BSC

BTSBase

Transceiver

Stations

BTSSIM

Gateway

MSC

VLR

HLR

MSCMobile

SwitchingCenter

Gateway

VLR MSC

MobileSwitching

Internet

ISDN

PLMNPSTN

PLMNPSTN Mobile

SIM

MobileEquipment

MobileStation

2.5G: GSM + GPRS

GSM TODAY



1 - 187

UTRAN

BSCBase

StationController PCU

BTSBase

Transceiver Stations

MobileEquipment

MSC HLR

S tc gCenter

GatewayGPRSSupport

node

ServingGPRSSupport

node

Core Network

Gateway

MSC

VLR

HLR

MSCMobile

Switching

Center

GatewayGPRSSupport

node

ServingGPRSSupport

node

UMTSSIM

MobileEquipment

RNCRadio

NetworkController

RNCRadio

NetworkController

Node B

Node B

Node B

Node B

Internet

ISDN

PSTN MobileStation

Internet

ISDN

PLMNPSTN

User Equipment

3G: UMTS, UTRA

Architecture of a Phase-1 GSM NetworkCore Network

GatewayMSC

VLR

HLR

MSCMobile

switchingCenter

BSCBase

StationController

BTSBase

Transceiver Stations

Internet

ISDN

PLMNPSTN

SIM

MobileEquipment

MobileStation

EIR AuC AbisInterface

AInterface

UmInterface

HLR - Home Location RegisterPLMN - Public Land Mobile NetworkGSM Functional Entities and Network Elements



1 - 188

EIR - Equipment Identity Register

AuC - Authentication Center

HLR - Home Location Register

VLR - Visitor Location Register

BSC - Base Station Controller

BTS - Base Transceiver StationSIM - Subscriber Identity Module

ME - Mobile Equipment

MS - Mobile Station

PLMN - Public Land Mobile Network

PSTN - Public switched Telephone Network

ISDN - Integrated Services Digital Network

GMSC - Gateway Mobile switching Center MSC - Mobile switching Center

• The network elements and interfaces of GSM are standardized• This provides for inter-vendor participation in operators’ networks

• Competition improves quality, provides economies of scale

GSM Network Evolution and History

Core Network

GatewayMSC

VLR

HLR

MSCMobile

switchingCenter

BSC

BaseStation

Controller

BTS

BaseTransceiver Stations

Internet

ISDN

PLMNPSTN

SIM

MobileEquipment

MobileStation

PHASE-I GSM NETWORK



1 - 189

• The present GSM network architecture emerged fromwork of the ETSI in the late 1980s

• The GSM network can be divided into three maindomains

• The Network Switching Subsystem (GMSC, VLR, HLR, MSC)

• The Operations and Support Subsystem (not shown, includesOMC-R)

• The Base Station Subsystem BSS (includes BSCs, BTSs)

GSM Evolution: General Packet Radio Service

• Around 1994, the GSM phase 2 standards were

enhanced to include several new and improved services.These enhancements are known as GSM Phase 2 Plus.• One of the new features proposed in 1994 was a new

true packet radio bearer service, GPRS

• GPRS allows a user with suitable mobile station tooccupy multiple time slots up to all 8 timeslots if



1 - 190

occupy multiple time slots, up to all 8 timeslots if available and the user’s terminal allows• Supported Data rates per timeslot are 9.06, 13.4, 15.6, 21.4 kb/s

• Maximum burst throughput could theoretically reach 8 x 21.4kb/s = 171.2 kb/s, although realistic expectations are around 115kb/s due to BCH and other requirements

• GPRS applications include internet access/web

browsing, video and Road Traffic and TransportInformatics (RTTI), and e-commerce and point-of-saleaccounting

GPRS Network ArchitectureVLR

SMSC

MSC

GGSN SGSN

BSCBase

Station

Controller PCUSN

BTSBase

Transceiver

Station

SIM

Mobile

Eqpm’tPSPDN

PLMNPSTNISDN

MobileStationTCU

Ater

AgprsGbGnG

SGSNof a

differentPLMN Gp

A

EIRHLR

Gd

Gs

Gf Gr Gc

New GPRS elements and in terfaces

Existing GSM Core Network elements

User data & signaling

Signaling only

LEGEND

Abis



1 - 191

UmInterface

gprsbnGi

• The GSM network architecture was modified to add packet services,

through the addition of the new network elements GGSN and SGSN• GGSN Gateway GPRS Support Node• Responsible for routing data packets entering and leaving the radio network; also

as a router for packets within the network

• SGSN Serving GPRS Support Node• responsible for packet delivery to mobiles in its area

• a type of packet swi with capability to interrogate the GSM databases HLR andVLR for location and service profiles of mobiles

• Data is “tunneled” from the GGSN to the SGSN using GTP, GPRSTunneling Protocol, encapsulating packets de-encapsulating ondelivery

Understanding the Backbone NetworksVLR

SMSC

MSC

GGSN SGSN PCUSN

BTSBase

Transceiver

Station

SIM

Mobile

Eqpm’tPSPDN

PLMNPSTNISDN

MobileStationTCU

GbGnG

SGSNof a

differentPLMN Gp

A

EIRHLR

Gd

Gs

Gf Gr Gc

New GPRS elements and in terfaces

Existing GSM Core Network elements

User data & signaling

Signaling only

LEGEND

BSCBase

Station

Controller

Ater

Agprs

Abis



1 - 192

UmInterface

bnGiFRAME RELAY

IP or X.25

gprs

• Gb between SGSN-PCUSN uses Frame Relay protocols• Gn between SGSN-GGSN uses IP routing, GPRS Tunnel Protocol• Gr between SGSN-HLR is an extension of MAP• Gi between GGSN and PDNs uses IP and X.25

• Gd between SGSN-SMSC delivers SMS messages using MAP• Gc between GGSN-HLR is optional, uses MAP• Gs between SGSN-MSC/VLR is optional, uses BSSMAP

GPRS Backbone Networks Two kinds of GPRS

backbones:

• Intra-PLMN amongGSNs of same PLMN(private, IP-based)

• Inter-PLMN amongGSNs of different

PLMNs (roamingagreements)



Gateways between thePLMNs and the externalinter-PLMN backbone are

called Border Gateways• Border Gateways perform security functions to prevent unauthorized

access and attacks The Gn and GP interfaces are also defined between two SGSNs

• This allows exchange of user profiles as mobiles move around The Gf interface allows a SGSN to query the IMEI of a registering mobile The Gi interface connects the PLMN to external public or private PDNs

• Interfaces to IPv4, IPv6, and X.25 networks are supported The Gr interface allows an SGSN to communicate with an HLR

1 - 193

GPRS-GSM Coordination

The MSC/VLR may be

extended with functionsand register entries for

efficient coordination

between GPRS packet

switched and GSM circuit-swi services



1 - 194

s se ces

• Combined GPRS and

non-GPRS location

updates

Paging requests for circuit-switched GSM calls can be performed via theSGSN

• The Gs interface connects the databases of SGSN and MSC/VLR

The Gd interface allows short message exchanges via GPRS

• Gd interconnects the SMS gateway MSC (SMS-GMSC) with the SGSN

Serving GPRS Support Node (SGSN)

Functions

• The Serving GPRS Support Node

(SGSN) is responsible for thefollowing to and from the mobilestations in its service area:• Packet Routing and Transfer • Mobility management (attach/detach

and location management)• Logical Link management



1 - 195

• Authentication and charging functions,encryption

• Compression (optional)

• Location register of SGSN storeslocation (cell, vlr) and user profiles

• A typical PLMN network will start withonly one SGSN

• Each BSC has a PacketCommunications Unit, PCU• Similar hardware provides the

PCUSN function

Several models of theNortel Passport Swi

for SGSN and PCUSN service

Gateway GPRS Support Node (GGSN)

Functions

• The Gateway GPRS Support

Node (GGSN) is the interfacebetween external packet datanetworks and GSM backbonenetwork• Converts GPRS packets from

the SGSN into packet dataprotocol format (IP, X.25) for the

Nortel’s GGSN:Bay Contivity Extranet SwiCES 4500



1 - 196

p ( , )external networks

• Converts PDP addresses of incoming data packets to GSM

address of destination user, andforwards to responsible SGSN• GGSN stores the current SGSN

address of the user and theuser’s profile in its location

register • GGSN performs authentication

and charging functions• Performs tunneling

CES-4500

Initial GPRS traffic in a PLMNnetwork will be low, and a singleGGSN will suffice for first serviceand an appreciable timethereafter

PCU in BTS Advantage: short Round Trip Delay

GSM BTS Changes Required toSupport GPRS• Since GPRS uses new

coding schemes, aChannel Codec Unit (CU)is required• The CU can normally be

implemented within BTS

software• Timeslot allocation for

BTS BSC

SGSNCU

CUPCU

Gb

Interface

Abis

Um

Interface

Three Possible GPRS BSS Configurations



PCU at SGSN Advantage: Leverage -- 1 PCUSN can manage multiple BSCs

PCU in BSC

Timeslot allocation for GPRS is handled by anew Packet Controller

Unit (PCU) which alsoimplements frame relayconnection with theGPRS network

• The PCU function can bephysically implemented inthe BTS, BSC, or at theSGSN, but is conceptuallypart of the BSS

BTS

BSC

SGSNCU

CUPCU

BTS BSC SGSNCU

CUPCU

Gb

Interface

bis

Interface

1 - 197

Channel Coding Implemented at the BTSGPRS Coding Schemes

CodingScheme

Pre-

Cod.USF

Infobits

WithoutUSF

Parity

BitsBC

Tail

Bits

CS-1CS-2CS-3

CS-4

Output

Conv.encoder

Punct

uredBits

Code

Rate

Data

RateKbit/s

366

12

181268312

428

401616

16

444

456588676

456

0132220

1/2~2/3~3/4

1

9.0513.415.6

21.4



1 - 198

• Channel coding is used to protect the transmitted GPRSdata packets against errors• The channel coding in GPRS is very similar to that of GSM

• An outer block coding, an inner block coding, and an interleavingscheme are used

• Four different coding schemes are defined above• Early network manufacturers were only implementing

CS-1 and CS-2

Quality of ServiceReliability

Probability of

Class LostPacket Dupli-catedPacket

Out-of SequencePackets

Corrupt-edPackets

1 109 109 109 109

2 104 105 105 106

3 102 105 105 102

Service Precedence

High

Medium

Low

M bil k t li ti h id f li bilit



1 - 199

• Mobile packet applications have a wide range of reliabilityexpectations -- real-time multimedia, Web browsing, email transfer

• QoS Classes settable per session are a very important feature• Service Precedence

• Priority of a service in relation to other services

• Reliability• Required transmission characteristics (3 classes defined)

• Delay• Maximum values for mean delay and 95-percentile delay

• Throughput• Maximum-Peak bit rate and the mean bit rate

Quality of Service: the Delay Parameter

Delay

128 byte packetClass Mean

Delay95%Delay

MeanDelay

95%Delay

1 <0.5s <1.5s <2s <7s2 <5s <25s <15s <75s

3 <50s <250s <75s <375s

1024 byte packet

4 Best Effort Best Effort Best Effort Best Effort



1 - 200

• Using these QoS Classes, QoS profiles can be

negotiated between the user and the networkfor each session, depending on QoS demandand currently available resources.

• Billing is based on data volume, type of service, andQoS profile

Mobile Classes and Simultaneous Usage• In a GSM network, two classes of service can run

concurrently:

• Circuit-switched Services (speech, data, and SMS)• Packet-switched Services (GPRS)

• Three Classes of Mobile Stations are defined:

• Class A mobiles• Support simultaneous operation of GPRS and conventional GSM



1 - 201

services, but two separate radio chains are required

• Class B mobiles

• Able to register with the network for both GPRS and conventionalGSM services simultaneously, but can only use one of the twoservices at a given moment - voice can pre-empt data

• Class C mobiles

• Able to attach for either conventional GSM or GPRS, manuallyswitched

• Simultaneous registration (and usage) is not possible, except for SMS messages which can be received and sent at any time

Question and Answer



1 - 2025/19/2004 202

Question and Answer:this topic

• What is an SGSN? A GGSN?• What is different about the functions of an SGSN and a

GGSN?

• When a user is browsing the web, who assigns an IPaddress for the session?



1 - 203

address for the session?

• Can a user continue its data session while moving from

BTS to BTS?• Can a user continue its data session while moving from

BTS on one BSC/MSC to a BTS on a different

BSC/MSC?• What is mobile IP?

GLOBAL SYSTEM FOR


R

Lesson 4:



1 - 204

Lesson 4:

RF Propagation

Introduction to Propagation• Propagation is a key process within every radio link. During propagation,

many processes act on the radio signal.

• attenuation• the signal amplitude is reduced by various natural mechanisms; if there is too much

attenuation, the signal will fall below the reliable detection threshold at the receiver. Attenuation is the most important single factor in propagation.

• multipath and group delay distortions• the signal diffracts and reflects off irregularly shaped objects, producing a host of

components which arrive in random timings and random RF phases at the receiver.This blurs pulses and also produces intermittent signal cancellation andreinforcement. These effects are combatted through a variety of special techniques



1 - 205

g y p q

• time variability - signal strength and quality varies with time, often dramatically

• space variability - signal strength and quality varies with location and distance

• frequency variability - signal strength and quality differs on differentfrequencies

• Effective mastery of propagation requires understanding:• Physics: understand the basic propagation processes

• Measurement: obtain data on propagation behavior in area of interest

• Statistics: characterize what is known, extrapolate to predict the unknown• Modelmaking: formalize all the above into useful models

Propagation Effects of Earth’s Atmosphere

• Earth’s unique atmosphere supports life

and also introduces many propagationeffects -- some useful, some troublesome

• Skywave Propagation: reflection from

Ionized Layers• LF and HF frequencies (below roughly 50



1 - 206

MHz.) are routinely reflected off layers of theupper atmosphere, ionized by the sun

• this phenomena produces intermittent world-wide propagation and occasional total outages

• this phenomena is strongly correlated with

frequency, day/night cycles, variations inearth’s magnetic field, 11-year sunspot cycle

• these effects are negligible for wirelesssystems at their much-higher frequencies

More Atmospheric Propagation Effects• Attenuation at Microwave Frequencies

• rain droplets can substantially attenuate RFsignals if wavelengths are comparable to, or smaller than, droplet size

• rain attenuations of 20 dB/km. or more possible

• troublesome mainly above 10 GHz., and intropical areasRefraction

by air layers

“Rain Fades” onMIcrowave Links



1 - 207

• must be considered in reliability calculationsduring path design

• not major factor in wireless systems propagation

• Diffraction, Wave Bending, Ducting• signals 50-2000 MHz. can be bent or reflected at

boundaries of different air density or humidity

• phenomena: very sporadic, intermittent

• can occur in wireless systems

by air layers

Ductingby air layers

>100 mi.

Influence of Wavelength on Propagation

• Radio signals in theatmosphere propagate atalmost speed of light

λ = wavelength

C = distance propagated in 1 second

F = frequency, Hertz

• The wavelength of a radiosignal determines many of its

λ = C / F

for AMPS: F= 870 MHz

λ = 0.345 m = 13.6 inches



1 - 208

g ypropagation characteristics• Antenna elements size are typically in

the order of 1/4 to 1/2 wavelength

• Objects bigger than a wavelength canreflect or obstruct RF energy

• RF energy can penetrate into abuilding or vehicle if they haveapertures a wavelength in size, or larger

λ /2

for PCS-1900: F = 1960 MHz

λ = 0.153 m = 6.0 inches

Dominant Mobile PropagationMost propagation in the mobile

environment is dominated by

these three mechanisms:• Free space

• No reflections, no obstructions

• first Fresnel Zone clear

• Signal spreading is only mechanism

• Signal decays 20 dB/decade

B

A

d

D

Free Space

Reflectionwith partial cancellation



1 - 209

• Reflection

• Reflected wave 180°out of phase• Reflected wave not attenuated much

• Signal decays 30-40 dB/decade

• Knife-edge diffraction

• Direct path is blocked by obstruction• Additional loss is introduced

• Formulae available for simple cases

• We’ll explore each of these further...

Knife-edgeDiffraction

Free-Space Propagation• The simplest propagation mode

• Antenna radiates energy which spreads inspace

• Path Loss, db (between two isotropicantennas) = 36.58+20*Log10(FMHZ)+20Log10(DistMILES )

• Path Loss, db (between two dipoleantennas) = 32.26+20*Log10(FMHZ)+20Log10(DistMILES )

Free Space“Spreading” Lossenergy intercepted

r



1 - 210

20 Log10(FMHZ) 20Log10(DistMILES )• Notice the rate of signal decay:

• 6 db per octave of distance change,which is 20 db per decade of distancechange

• Free-Space propagation is

applicable if:• there is only one signal path (no reflections)• the path is unobstructed (i.e., first Fresnel

zone is not penetrated by obstacles)

First Fresnel Zone =Points P where AP + PB - AB < λ/2 Fresnel Zone radius d = 1/2 (λD)^(1/2)

1st Fresnel Zone

B

A

d

D

by receivingantenna is

proportional to 1/r 2

Reflection With Partial Cancellation• Mobile environment characteristics:

• Small angles of incidence and reflection

• Reflection is unattenuated (reflection coefficient =1)• Reflection causes phase shift of 180 degrees

• Analysis• Physics of the reflection cancellation predicts signal

decay of 40 dB per decade of distance

Heights Exaggeratedfor Clarity

HTFT

HTFT

DMILES

Path Loss [dB ]= 172 + 34 x Log (DMiles )- 20 x Log (Base Ant. HtFeet)



1 - 211

- 10 x Log (Mobile Ant. HtFeet)

SCALE PERSPECTIVE

Comparison of Free-Space and Reflection Propagation Modes Assumptions: Flat earth, TX ERP = 50 dBm, @ 1950 MHz. Base Ht = 200 ft, Mobile Ht = 5 ft.

Received Signal inFree Space, DBM

Received Signal inReflection Mode

DistanceMILES

-52.4

-69.0

1-58.4

-79.2

2-64.4

-89.5

4-67.9

-95.4

6-70.4

-99.7

8-72.4

-103.0

10-75.9

-109.0

15-78.4

-113.2

20

Signal Decay in Various Environments

We’ve seen how the signaldecays with distance in twobasic modes of propagation:

• Free-Space

• 20 dB per decade of distance

• 6 db per octave of distance

Signal Level vs. Distance

-20

-10

0



1 - 212

p

• Reflection Cancellation

• 40 dB per decade of distance

• 12 db per octave of distance

• Real-life wireless propagation

decay rates are typicallysomewhere between 30 and40 dB per decade of distance

-40

-30

Distance, Miles1 3.16 102 5 7 86

One Octaveof distance (2x)

One Decade

of distance (10x)

Knife-Edge Diffraction• Sometimes a single well-defined

obstruction blocks the path, introducing

additional loss. This calculation is fairlyeasy and can be used as a manual toolto estimate the effects of individualobstructions.

• First calculate the diffraction parameter ν from the geometry of the path

H

R1 R2

( += -H2

λ

1 1

R1 R2)



1 - 213

• Next consult the table to obtain theobstruction loss in db

• Add this loss to the otherwise-determined path loss to obtain the totalpath loss.

• Other losses such as free space andreflection cancellation still apply, butcomputed independently for the path asif the obstruction did not exist

ν

attendB

0-5

-10

-15

-20

-25

-4 -3 -2 -1 0 1 2 3-5

1 2

Space Diversity vs. Rayleigh Fading

• Fortunately, Rayleigh fades are short,

lasting a small percentage of the time• Fades received on two antennas

separated by several wavelengths

• “Space Diversity” can be obtained by

using two receiving antennas andswitching instant-by-instant towhichever is best

D



1 - 214

whichever is best

• Required separation D for good

decorrelation is 10-20λ• 12-24 ft. @ 800 MHz.

• 5-10 ft. @ 1900 MHz.

Signal receivedby Antenna 1

Signal receivedby Antenna 2

CombinedSignal

Question and Answer



1 - 2155/19/2004 215

Question and Answer:RF Propagation Basics

• Name three common modes of propagation that often dominate amobile’s environment

• What is the mode of propagation giving the strongest signals (i.e.,smallest path loss)

• Is this a desirable mode? Under what conditions does it occur?• What is the mode most often seen in cluttered cities?

• Why does it have more attenuation?



1 - 216

Why does it have more attenuation?

• How do RF signals manage to reach obstructed locations? Is there

any way to predict how much RF will get through?• RF signals seem “full of tiny holes” in the real world.

• What is the name of this phenomena? What causes it?

• How far are these “holes” typically spaced from one another?

• What causes these holes, and is there any way to avoid them?• What is the wavelength of an FM radio station on 100 MHz.?

Propagation Models



1 - 217

Propagation Models

Propagation Model Types And Their Uses

Simple Analytical• Free space (Friis formula)• Reflection cancellation• Knife-edge diffraction

Area• Okumura-Hata

• Euro/Cost-231• Walfisch-Betroni/Ikegami

Point to Point

Examples of various model types

• Simple Analytical models• Used for understanding and

predicting individual paths andspecific obstruction cases

• General Area models• Primary drivers: statistical

• Used for early systemdimensioning (cell counts, etc.)

• Point-to-Point models



1 - 218

Point-to-Point• Ray Tracing

- Lee’s Method, others• Tech-Note 101• Longley-Rice, Biby-C

Local Variability

• Rayleigh Distribution• Normal Distribution• Joint Probability Techniques

Point to Point models• Primary drivers: analytical

• Used for detailed coverageanalysis and cell planning

• Local Variability models• Primary drivers: statistical

• Characterizes microscopic levelfluctuations in a given locale,confidence-of-service probability

General Principles Of Area Models

• Area models mimic an average

path in a defined area• They’re based on measureddata alone, with noconsideration of individual pathfeatures or physical

mechanisms• Typical inputs used by model:

• Frequency

RSSI,dBm

-120

-110

-100

-90

-80

-70

-60

-50

0 3 6 9 12 15 18 21 24 27 30 33

Distance from Cell Site, km

FieldStrength,dBµV/m

+90

+80

+70

+60

+50

+40

+30

+20



1 - 219

q y• Distance from transmitter to

receiver • Actual or effective base station& mobile heights

• Average terrain elevation• Morphology correction loss

(Urban, Suburban, Rural, etc.)• Results may be quite different

than observed on individualpaths in the area

Green Trace shows actual measured signalstrengths on a drive test radial, as determinedby real-world physics.

Red Trace shows the Okumura-Hataprediction for the same radial. The smooth

curve is a good “fit” for real data. However,the signal strength at a specific location on theradial may be much higher or much lower than the simple prediction.

The Okumura Model: General Concept

M e d i a n A t t e n u a t i o n A ( f , d

) , d B

1

2

5

40

70

80

100

100 3000500Frequency f, MHz

10

50

70Urban Area

d ,

k m

30

850

26

35

100 200 300 500 700 1000 2000 3000

Frequency f, (MHz)

5

10

15

20

25

30

C o r r e c t i o n f a c t o r , G a r e a ( d B )

9 dB

850 MHz

O p e n a r e a

Q u a s i o p

e n a r e a

S u b u

r b a n a

r e a



1 - 220

The Okumura model is based on analysis of measurements made in Tokyo and its

suburbs during the late 1960’s and early 1970’s on numerous VHF, UHF, andmicrowave signal sources in both polarizations and at a wide range of heights.

The data were analyzed with respect to almost every imaginable variable. Thisanalysis was distilled into the curves above, showing a median attenuation

relative to free space loss Amu (f,d) and correlation factor Garea (f,area), for BS antenna height ht = 200 m and MS antenna height hr = 3 m.

Okumura has served as the basis for high-level design of many existingwireless systems, and has spawned a number of newer models adaptedfrom its basic concepts and numerical parameters.

Structure of the Okumura ModelPath Loss [dB] = LFS + Amu(f,d) - G(Hb) - G(Hm) - Garea

Free-Space

Path Loss

Base StationG

Mobile StationHeight Gain

= 10 x Log (Hm /3)

Amu(f,d) AdditionalMedian Loss

fromOkumura’s Curves

B 100

70Urban Area

Morphology Gain0 dense urban5 urban

10 suburban17 rural

35

30

a ( d B )

O p e n a r e a

ea



1 - 221

• The Okumura Model uses a combination of terms from basic

physical mechanisms and arbitrary factors to fit 1960-1970 Tokyodrive test data

• Later researchers (HATA, COST231, others) have expressedOkumura’s curves as formulas and automated the computation

Height Gain= 20 x Log (Hb /200)

M e d i a n A t t e n u a t i o n A ( f , d ) , d B

1

2

5

40

70

80

100

100 3000500

Frequency f, MHz10

50

d ,

k m

30

850

26

100200 300 500 700 1000 2000 3000

Frequency f, (MHz)

5

10

15

20

25

C o r r

e c t i o n f a c t o r , G a r e a

850 MHz

Q u a s i o p

e n a r e a

S u b u r

b a n a r e a

The Hata Model: General Concept• The Hata model is an empirical formula for propagation loss

derived from Okumura’s model, to facilitate automatic calculation.

• The propagation loss in an urban area is presented in a simplegeneral format A + B x log R, where A and B are functions of frequency and antenna height, R is distance between BS and MSantennas

• The model is applicable to frequencies 100 MHz-1500 MHz,distances 1-20 km, BS antenna heights 30-200 m, MS antennaheights 1-10 m



1 - 222

heights 1 10 m

• The model is simplified due to following limitations:

• Isotropic antennas

• Quasi-smooth (not irregular) terrain

• Urban area propagation loss is presented as the standard formula

• Correction equations are used for other areas• Although Hata model does not imply path-specific corrections, it

has significant practical value and provide predictions which arevery closely comparable with Okumura’s model



The EURO COST-231 Model

LCOST (urban) [dB] = 46.3 + 33.9 x log ( f ) + [ 44.9 - 6.55 x log ( hb ) ]

x log ( d ) + Cm -13.82 x log ( hb ) - A ( hm )

The COST-231 model was developed by EuropeanCOoperative for Scientific and TechnicalResearch committee. It extends the HATAmodel to the 1.8-2 GHz. band in anticipation of PCS use.

• COST-231 is applicable for frequencies 1500-



1 - 224

pp q2000 MHz, distances 1-20 km, BS antenna

heights 30-200 m, MS antenna heights 1-10 m• Parameters and variables:

• f is carrier frequency , in MHz• hb and hm are BS and MS antenna heights (m)

• d is BS and MS separation, in km• A(hm) is MS antenna height correction factor (same as in Hata model)

• Cm is city size correction factor: Cm=0 dB for suburbs and Cm=3 dB for metropolitan centers

EnvironmentalFactor C1900

-2 dense urban

-5 urban-10 suburban-26 rural

Examples of Morphological Zones• Suburban: Mix of

residential and businesscommunities. Structuresinclude 1-2 story houses50 feet apart and 2-5story shops and offices.

• Urban: Urbanresidential and officeareas (Typical structures

5 10 t b ildi

Suburban SuburbanSuburban



1 - 225

are 5-10 story buildings,

hotels, hospitals, etc.)• Dense Urban: Dense

business districts withskyscrapers (10-20 stories

and above) and high-riseapartments

UrbanUrbanUrban

Dense Urban Dense UrbanDense Urban

Although zone definitions are arbitrary, the examples and definitions illustrated aboveare typical of practice in North American PCS designs.

Example Morphological Zones• Rural - Highway:

Highways near open

farm land, large openspaces, and sparselypopulated residentialareas. Typicalstructures are 1-2 storyhouses, barns, etc.

• Rural - In-town: Openfarm land, large open

RuralRuralRural

RuralRural -- HighwayHighwayRural - Highway



1 - 226

, g pspaces, and sparsely

populated residentialareas. Typicalstructures are 1-2 storyhouses, barns, etc.

SuburbanSuburbanSuburban

Notice how different zones may abruptly adjoin one another. In the case immediatelyabove, farm land (rural) adjoins built-up subdivisions (suburban) -- same terrain, butdifferent land use, penetration requirements, and anticipated traffic densities.

The MSI Planet General Model

Pr - received power (dBm)Pt - transmit ERP (dBm)Hb - base station effective antenna heightHm - mobile station effective antenna heightDL - diffraction loss (dB)

K1 - intercept K2 - slopeK3 - correction factor for base station antenna height gainK4 - correction factor for diffraction loss (accounts for clutter heights)K5 - Okumura-Hata correction factor for antenna height and distance

Pr = Pt + K1 + k2 log(d) + k3 log(Hb) + K4 DL + K5 log(Hb) log(d)+ K6 log (Hm) + Kc + Ko



1 - 227

5 gK6 - correction factor for mobile station antenna height gain

Kc - correction factor due to clutter at mobile station locationKo - correction factor for street orientation

This is the general model format used in MSI’s popular PlaNETpropagation prediction software for wireless systems. It includes

terms similar to Okumura-Hata and COST-231 models, along withadditional terms to include effects of specific obstructions andclutter on specific paths in the mobile environment.

Typical Model ResultsIncluding Environmental Correction

Tower

Height,m

EIRP(watts) C,dB Range,kmf =1900 MHz.

Dense Urban

Urban

Suburban

Rural

30

30

30

50

200

200

200

200

0

-5

-10

-17

2.52

3.50

4.8

10.3

COST-231/Hata



1 - 228

Tower Height,m

EIRP(watts)

C,dB

Range,kmf = 870 MHz.

Dense Urban

UrbanSuburban

Rural

30

3030

50

200

200200

200

-2

-5-10

-26

4.0

4.96.7

26.8

Okumura/Hata

Propagation at 1900 MHz. vs. 800 MHz.• Propagation at 1900 MHz. is similar to 800 MHz., but all

effects are more pronounced.

• Reflections are more effective

• Shadows from obstructions are deeper

• Foliage absorption is more attenuative

• Penetration into buildings through openings is more effective,but absorbing materials within buildings and their wallsattenuate the signal more severely than at 800 MHz.



1 - 229

• There is more “contrast” of hot and cold signal areasthroughout a 1900 MHz. system, compared to whatwould have been obtained at 800 MHz.

• Overall, coverage radius of a 1900 MHz. BTS is abouttwo-thirds the distance which would be obtained withthe same ERP, same antenna height, at 800 MHz.

Walfisch-Betroni/Walfisch-IkegamiModels

• Ordinary Okumura-type models do work

in this environment, but the Walfischmodels attempt to improve accuracy byexploiting the actual propagationmechanisms involved

Path Loss = LFS + LRT + LMS

LFS = free space path loss (Friis formula)



1 - 230

LRT

= rooftop diffraction loss

LMS = multiscreen reflection loss• Propagation in built-up portions of cities

is dominated by ray diffraction over the

tops of buildings and by ray“channeling” through multiple reflectionsdown the street canyons

-20 dBm

-30 dBm

-40 dBm

-50 dBm

-60 dBm

-70 dBm

-80 dBm

-90 dBm-100 dBm

-110 dBm

-120 dBm

SignalLevel

Legend

Area View

Statistical TechniquesDistribution Statistics Concept

RSSI,dBm

Distance

Signal Strength predictedby area model

Signal Strength Predicted Vs. Observed

ObservedSignal Strength

• An area model predicts signalstrength Vs. distance over an area

• This is the “median” or mostprobable signal strength at every

distance from the cell• The actual signal strength at any

real location is determined by localphysical effects, and will be higher



1 - 231

MedianSignalStrength

σ,

dB

Occurrences

RSSI

NormalDistribution

physical effects, and will be higher or lower

• It is feasible to measure theobserved median signal strength Mand standard deviation σ

• M and σ can be applied to findprobability of receiving an arbitrarysignal level at a given distance

Statistical TechniquesPractical Application Of Distribution Statistics

• General Approach:

• Use a model to predict RSSI

• Compare measurements with model

• obtain median signal strength M

• obtain standard deviation σ

• now apply correction factor to obtainfield strength required for desiredprobability of service

A li ti Gi

RSSI,

dBm

10% of locationsexceed this RSSI

50%

90%

Percentage of locations whereobserved RSSI exceeds predicted

RSSI



1 - 232

• Applications: Given

• A desired outdoor signal level (dbm)

• The observed standard deviation σ

from signal strength measurements

• A desired percentage of locationswhich must receive that signal level

• Compute a “cushion” in dB which willgive us that % coverage confidence

Distance

MedianSignalStrength σ,

dB

Occurrences

RSSI

NormalDistribution

Cell EdgeArea Availability And Probability Of Service

• Overall probability of service is best close to theBTS, and decreases with increasing distance awayfrom BTS

• For overall 90% location probability within cellcoverage area, probability will be 75% at cell edge

• Result derived theoretically, confirmed in modelingwith propagation tools, and observed frommeasurements

• True if path loss variations are log-normally

Statistical View of Cell Coverage

90%

75%



1 - 233

True if path loss variations are log normally

distributed around predicted median values, as inmobile environment

• 90%/75% is a commonly-used wireless numericalcoverage objective

• Recent publications by Nortel’s Dr. Pete Bernardindescribe the relationship between area and edgereliability, and the field measurement techniquesnecessary to demonstrate an arbitrary degree of coverage reliability

90%75%

Area Availability:overall within areaat edge of area

Application Of Distribution Statistics:Example

• Let’s design a cell to deliver at least -95dBm to at least 75% of the locations at

the cell edge(This will provide coverage to 90% of total locations within the cell)

• Assume that measurements you havemade show a 10 dB standard deviation

σ• On the chart:

• To serve 75% of locations at the celledge , we must deliver a median signalstrength which is 675 times stronger

Cumulative Normal Distribution

40%

50%

60%

70%

80%

90%

100%

75%



1 - 234

strength which is .675 times σ stronger

than -95 dBm• Calculate:- 95 dBm + ( .675 x 10 dB )= - 88 dBm

• So, design for a median signal strengthof -88 dBm!

Standard Deviations fromMedian (Average) Signal Strength

0%

10%

20%

30%

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

0.675σ

Statistical Techniques:Normal Distribution Graph & Table For ConvenientReference

Cumulative Normal Distribution

40%

50%

60%

70%

80%

90%

100%

Cumulative

Probability

0.1%

1%

5%

10%

Standard

Deviation

-3.09

-2.32

-1.65

-1.28

-0.84 20%

-0.52 30%

0 50%

0.52 70%



1 - 235

Standard Deviation from Mean Signal Strength

0%

10%

20%

30%

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

0.675 75%

0.84 80%

1.28 90%

1.65 95%

2.35 99%

3.09 99.9%

3.72 99.99%

4.27 99.999%

Building Penetration

Statistical Characterization• Statistical techniques are

effective against situations that

are difficult to characterizeanalytically

• Building coverage is modeled

using existing outdoor path lossplus an additional “building

penetration loss”

Building penetration

Typical Penetration Losses, dBcompared to outdoor street level

Environment Median Std

Vehicle penetration



1 - 236

• Median value estimated/sampled• Statistical distribution determined

• Standard deviation estimated or measured

• Additional margin allowed in linkbudget to offset assumed loss

• Typical values are shown at left

Environment

Type(“morphology”)

Median

Loss,dB

Std.

Dev.σ, dB

Urban Bldg. 15 8

Suburban Bldg. 10 8

Rural Bldg. 10 8

8 4Typical Vehicle

Dense Urban Bldg. 20 8

Composite Probability Of ServiceAdding Multiple Attenuating Mechanisms

σCOMPOSITE = ((σOUTDOOR)2+(σPENETRATION)2)1 /2

LOSSCOMPOSITE = LOSSOUTDOOR+LOSSPENETRATION

Building

Outdoor Loss + Penetration Loss



1 - 237

LOSSCOMPOSITE LOSSOUTDOOR LOSSPENETRATION

• For an in-building user, the actual signal level includes regular outdoor path attenuation plus building penetration loss

• Both outdoor and penetration losses have their own variabilitieswith their own standard deviations

• The user’s overall composite probability of service must includecomposite median and standard deviation factors

Composite Probability of ServiceCalculating Fade Margin For Link Budget

• Example Case: Outdoor attenuation σ is 8 dB., and penetration lossσ is 8 dB. Desired probability of service is 75% at the cell edge

• What is the composite σ? How much fade margin is required?

Composite Probability of Service

σCOMPOSITE = ((σOUTDOOR)2+(σPENETRATION)2)1/2

= ((8)2+(8)2)1/2 =(64+64)1/2 =(128)1/2 = 11.31 dB

On cumulative normal distribution curve, 75%

probability is 0.675 σ above median.Fade Margin required =

(11.31) • (0.675) = 7.63 dB.Cumulative Normal Distribution

90%

100%



1 - 238

Composite Probability of ServiceCalculating Required Fade Margin

EnvironmentType

(“morphology”)MedianLoss,

dB

Std.Dev.σ, dB

Urban Bldg. 15 8Suburban Bldg. 10 8

Rural Bldg. 10 8

8 4Typical Vehicle

Dense Urban Bldg. 20 8

BuildingPenetration

Out-Door

Std.Dev.σ, dB

88

8

8

8

CompositeTotal

AreaAvailabilityTarget, %

90%/75% @edge90%/75% @edge

90%/75% @edge

90%/75% @edge

90%/75% @edge

FadeMargin

dB

7.67.6

7.6

6.0

7.6

Standard Deviations fromMedian (Average) Signal Strength

0%

10%

20%

30%

40%

50%

60%

70%

80%

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

75%

.675

Question and Answer



1 - 2395/19/2004 239



Propagation Measurements



1 - 241



Elements of Typical Measurement Systems

Wireless

Receiver

PC or Collector

GPSReceiver

DeadReckoning

Main Features• Field strength measurement

• Accurate collection in real-time• Multi-channel, averaging capability

• Location Data Collection Methods:

• Global Positioning System (GPS)

• Dead reckoning on digitized mapdatabase using on-board compassand wheel revolutions sensor

• A combination of both methods is



1 - 243

g A combination of both methods is

recommended for the best results• Ideally, a system should be

calibrated in absolute units, not justraw received power level indications

• Record normalized antenna gain,measured line loss

Typical Test Transmitter Operations• Typical Characteristics

• portable, low power needs

• weatherproof or weather resistant

• regulated power output

• frequency-agile: synthesized

• Operational Concerns• spectrum coordination and proper

authorization to radiate test signal



1 - 244

• antenna unobstructed• stable AC power

• SAFETY:

• people/equipment falling due to

wind, or tripping on obstacles

• electric shock

• damage to rooftop

A Typical Mobile Test Receiver • Receivers and decoders are

installed only for the appropriate

technologies and frequency bands• Internal GPS or external GPS may

be used, with or without dead-reckoning capabilities

Internal GPS

Up to 2 handsetsmay be connectedfor GSM or CDMAat 800 or 1900 MHz.

inputs to internal RXs

MainOn/Off

RF toInt. GPS



1 - 245

Internal GPS

Receiver,if used

Up to 4technology-specific

decoder boards: AMPS, TDMA

GSM, CDMAPaging

Up to 4technology and

band-specificreceivers:800 MHz. cellular 150, 450, 800 Paging1900 PCS

Selecting and Tuning Propagation Models

• Parameters of propagation

models must be adjusted for best fit to actual drive-testmeasured data in the areawhere the model is applied

• The figure at right shows drive-test signal strengths obtainedusing a test transmitter at anactual test site



1 - 246

• Tools automate the process of comparing the measured datawith its own predictions, andderiving error statistics

• Prediction model parametersthen can be “tuned” tominimize observed error

Measured Data vs. Model Predictions



1 - 247

• Is the propagation model approximately correct?• Is the data scatter small enough to justify use of a model?• correct slope to match data• correct position up/down on Y-axis?

Analysis of Measured vs. Predicted• Several tools produce histograms showing the distribution of the

differences between measured and predicted values

• The mean of the difference between predicted and measured is avery important quantity. It should be small (on order of a few dB).

• The standard deviation of the difference also should be small. If itis substantially larger than 8 dB., then either:

• the environment is very diverse(perhaps it should be broken intopieces with separate models for



1 - 248

better fit) or • the slope of the model is

significantly different than theobserved slope of the

measurements (review the Sig. vs.Dist. graph)

Displaying Error Distribution by Location

• Suppose a major hill blocked

the signal in one direction, or the antenna pattern had anunexpected minimum in thatdirection

• This would cause the data inthe shadowed region to differ substantially from data in allremaining directions



1 - 249

• Some tools can display theerror values on a map like theone at right, to provide quickvisual evidence for recognizing this type of problem

Question and Answer



1 - 250

5/19/2004 250


Propagation Measurements

• Why does anybody do ‘propagation measurements’?

• When would you do propagation measurements?

• What’s different about propagation measurements anddrive-testing for troubleshooting call problems?

• What’s the most urgently important thing in doing



1 - 251

propagation measurements and drive-testing?• Describe the equipment you use, if any, for propagation

measurements.

• How do you analyze the data?

GLOBAL SYSTEM FOR


R

Typical WirelessOmni Antenna

Lesson 5:

Antennas for Wireless Systems



1 - 252

y

Isotropic Dipole

Understanding Antenna RadiationThe Principle Of Current Moments

• An antenna is just a passive

conductor carrying RF current• RF power causes the current

flow

• Current flowing radiateselectromagnetic fields

• Electromagnetic fields causecurrent in receiving antennas

TX RX

Zero currentat each end

Maximum currentat the middle

Current induced inreceiving antennais vector sum of

contribution of everytiny “slice” of

each tinyimaginary “slice”of the antennadoes its share

of radiating



1 - 253

• The effect of the total antenna isthe sum of what every tiny “slice”of the antenna is doing

• Radiation of a tiny “slice” is

proportional to its length timesthe magnitude of the currentin it, at the phase of thecurrent

Width of banddenotes current

magnitude

radiating antenna

Different Radiation In Different Directions• Each “slice” of the antenna

produces a definite amount of radiation at a specific phase

angle• Strength of signal received

varies, depending on direction of departure from radiating antenna

• In some directions, thecomponents add up in phaseto a strong signal level

• In other directions, due to the

TX

MaximumRadiation:contributions

in phase,reinforce

MinimumRadiation:

contributionsout of phase,cancel



1 - 254

different distances the variouscomponents must travel toreach the receiver, they areout of phase and cancel,

leaving a much weaker signal• An antenna’s directivity is the

same for transmission &reception

MinimumRadiation:

contributionsout of phase,cancel



Antenna Gain• Antennas are passive devices: they do not

produce power

• Can only receive power in one form andpass it on in another, minus incidental losses

• Cannot generate power or “amplify”

• However, an antenna can appear to have “gain”compared against another antenna or condition.This gain can be expressed in dB or as a power ratio. It applies both to radiating and receiving

• A directional antenna, in its direction of maximum radiation, appears to have “gain”

d i t di ti l t

Omni-directionalAntenna



1 - 256

compared against a non-directional antenna• Gain in one direction comes at the expense of

less radiation in other directions

• Antenna Gain is RELATIVE, not ABSOLUTE

• When describing antenna “gain”, thecomparison condition must be stated or implied

DirectionalAntenna

Effective Radiated Power • An antenna radiates all power fed to it from

the transmitter, minus any incidental losses.Every direction gets some amount of power

• Effective Radiated Power (ERP) is theapparent power in a particular direction

• Equal to actual transmitter power times

antenna gain in that direction• Effective Radiated Power is expressed in

comparison to a standard radiator

• ERP: compared with dipole antenna ERP B A (ref)

ReferenceAntenna

TX100 WA

DirectionalAntenna

TX100 W

B



1 - 257

• EIRP: compared with Isotropic antenna A

B

100w275w

Example: Antennas A and B each radiate 100 watts fromtheir own transmitters. Antenna A is our reference.

Antenna B is directional. In its maximum direction, itssignal seems 2.75 stronger than the signal from antenna A. Antenna B’s ERP in this case is 275 watts.

Reference AntennasDefining Gain And Effective Radiated Power

• Isotropic Radiator

• Truly non-directional -- in 3 dimensions• Difficult to build or approximate physically, butmathematically very simple to describe

• A popular reference: 1000 MHz and above• PCS, microwave, etc.

• Dipole Antenna• Non-directional in 2-dimensional plane only• Can be easily constructed, physically practical• A popular reference: below 1000 MHz

• 800 MHz. cellular, land mobile, TV & FM

Isotropic

Dipole



1 - 258

(watts or dBm) ERPEffective Radiated Power Vs. Dipole

Effective Radiated Power Vs. Isotropic

Gain above Dipole reference

Gain above Isotropic radiator

(watts or dBm) EIRP

dBd

dBi

Quantity Units

Notice that a dipolehas 2.15 dB gaincompared to anisotropic antenna.

Antenna Gain And ERP Examples• Many wireless systems at 1900 & 800 MHz use omni

antennas like the one shown in this figure

• These patterns are drawn to scale in E-field radiationunits, based on equal power to each antenna

• Notice the typical wireless omni antenna concentratesmost of its radiation toward the horizon, where users

are, at the expense of sending less radiation sharplyupward or downward

• The wireless antenna’s maximum radiation is 12.1 dBstronger than the isotropic (thus 12.1 dBi gain), and10 dB stronger than the dipole (so 10 dBd gain).

Dipole

Isotropic



1 - 259

Isotropic

Dipole

Omni

12.1 dBi

10dBd

Gain ComparisonTypical WirelessOmni Antenna

Gain 12.1 dBi or 10 dBd

Radiation PatternsKey Features And Terminology

An antenna’s directivity is

expressed as a series of patterns• The Horizontal Plane Pattern graphs

the radiation as a function of azimuth(i.e..,direction N-E-S-W)

• The Vertical Plane Pattern graphs theradiation as a function of elevation (i.e..,up, down, horizontal)

• Antennas are often compared by noting

specific landmark points on their

Typical Example

Horizontal Plane Pattern

0 (N)

90(E)270

0

-10

-20

-30 dB

Notice -3 dB points

10 dBpoints

MainLobe



1 - 260

specific landmark points on their patterns:

• -3 dB (“HPBW”), -6 dB, -10 dBpoints

• Front-to-back ratio• Angles of nulls, minor lobes, etc.

90(E)

180 (S)

270(W)

Front-to-back Ratio

a Minor Lobe

nulls or minima

How Antennas Achieve Their Gain

Quasi-Optical Techniques (reflection, focusing)• Reflectors can be used to concentrate

radiation• technique works best at microwave frequencies, where

reflectors are small

• Examples:• corner reflector used at cellular or higher frequencies

• parabolic reflector used at microwave frequencies• grid or single pipe reflector for cellular

Array techniques (discrete elements)

• Power is fed or coupled to multiple



1 - 261

• Power is fed or coupled to multipleantenna elements; each element radiates

• Elements’ radiation in phase in somedirections

• In other directions, a phase delay for eachelement creates pattern lobes and nulls

In phase

Out of

phase

Types Of Arrays

• Collinear vertical arrays• Essentially omnidirectional in

horizontal plane• Power gain approximately

equal to the number of elements

• Nulls exist in vertical pattern,

unless deliberately filled• Arrays in horizontal plane

• Directional in horizontalplane: useful for

sectorization

RFpower



1 - 262

sectorization• Yagi• one driven element, parasitic

coupling to others

• Log-periodic

• all elements driven• wide bandwidth

• All of these types of antennasare used in wireless

RF

power

Omni AntennasCollinear Vertical Arrays

The family of omni-directional wirelessantennas:

• Number of elements determines• Physical size• Gain• Beamwidth, first null angle

• Models with many elements have verynarrow beamwidths• Require stable mounting and

careful alignment• Watch out: be sure nulls do not

fall in important coverage areas V ti l Pl P tt

Number of Elements

Power Gain

Gain,dB

Angleθ

0.00 n/a3.01 26.57°4.77 18.43°6.02 14.04°6.99 11.31°7.78 9.46°8.45 8.13°9.03 7.13°9.54 6.34°10.00 5.71°10.41 5.19°10.79 4.76°11.14 4.40°

1234567891011121314

1234567891011121314 11.46 4.09°

Typical Collinear Arrays



1 - 263

fall in important coverage areas• Rod and grid reflectors are sometimes

added for mild directivity

Examples: 800 MHz.: dB803, PD10017,BCR-10O, Kathrein 740-198

1900 MHz.: dB-910, ASPP2933

beamwidth

Angleof

firstnull

θ

-3 dB

Vertical Plane Pattern



Example Of Antenna Catalog

Specifications

Frequency Range, MHz.

Gain - dBd/dBiVSWR

Beamwidth (3 dB from maximum)Polarization

Maximum power input - WattsInput Impedance - Ohms

Lightning ProtectionTermination - StandardJumper Cable

Electrical Data Antenna Model ASPP2933 ASPP2936 dB910C-M

1850-1990 1850-1990 1850-1970

3/5.1<1.5:1

32°Vertical

40050

Direct GroundN-Female

Order Sep.

6/8.1<1.5:1

15°Vertical

40050


Order Sep.

10/12.1<1.5:1

5°Vertical

40050


Order Sep.

Mechanical Data Antenna Model

Overall length - in (mm)

ASPP2933

24 (610)

ASPP2936

36 (915)

dB910C-M

77 (1955)



1 - 265

g ( )Radome OD - in (mm)

Wind area - ft2 (m2)Wind load @ 125 mph/201 kph lb-f (n)Maximum wind speed - mph (kph)

Weight - lbs (kg)Shipping Weight - lbs (kg)

Clamps (steel)

( )1.1 (25.4)

.17 (.0155)4 (17)

140 (225)

4 (1.8)11 (4.9)

ASPA320

( )1.0 (25.4)

.25 (.0233)6 (26)

140 (225)

6 (2.7)13 (5.9)

ASPA320

( )1.5 (38)

.54 (.05)14 (61)

125 (201)

5.2 (2.4)9 (4.1)

Integral

Example Of Antenna CatalogRadiation Pattern

• Vertical Plane Pattern

• E-Plane (elevation plane)

• Gain: 10 dBd

• Dipole pattern is superimposed at

scale for comparison (not oftenshown in commercial catalogs)

• Frequency is shown

• Pattern values shown in dBd

Note 1 degree indices through



1 - 266

• Note 1-degree indices throughregion of main lobe for mostaccurate reading

• Notice minor lobe and null detail!

Question and Answer



1 - 2675/19/2004 267


Antenna Basics

• How can an antenna, being just a piece of metal,

actually have “gain”?• What is an isotropic antenna, and what is it good

for?

• What is a dipole antenna, and what is it goodfor?

• Name some of the major specifications of anantenna’s pattern and tell their significance



1 - 268

antenna s pattern, and tell their significance.

• What is the impedance of most GSM antennas?

• What causes an antenna to be directional?



Antenna Systems

• Antenna systems include morethan just antennas

• Transmission Lines

• Necessary to connecttransmitting and receivingequipment

• Other Components necessary toachieve desired system function• Filters, Combiners, Duplexers -

to achieve desired connections• Directional Couplers, wattmeters

- for measurement of

performance• Manufacturer’s system may T r a n s m i s s i o n L i n e

Jumper

Antenna



1 - 270

pManufacturer s system mayinclude some or all of theseitems• Remaining items are added

individually as needed bysystem operator

F R

Dupl

exer

Combiner

BPF

TX

RX

TX

Jumpers

DirectionalCoupler

Types of Transmission LinesTypical coaxial cables

Used as feeders in wireless applicationsPhysical Characteristics

• Type of line• Coaxial, stripline, open-wire

• Balanced, unbalanced

• Physical configuration• Dielectric:• air • foam

• Outside surface

• unjacketed• jacketed



1 - 271

FoamDielectric

Air Dielectric

jacketed

• Size (nominal outer diameter)• 1/4”,1/2”, 7/8”, 1-1/4”, 1-

7/8”, 2-1/4”, 3”

Attenuation, Impedance, Velocity,

Power HandlingElectrical Characteristics• Attenuation

• Varies with frequency, size, dielectriccharacteristics of insulation• Usually specified in dB/100 ft and/or

dB/100 m

• Characteristic impedance Z0 (50 ohmsis the usual standard; 75 ohms issometimes used)• Value set by inner/outer diameter ratio

and dielectric characteristics of insulation

• Connectors must preserve constant

dD

Characteristic Impedance

of a Coaxial LineZo = ( 138 / ( ε 1/2 ) ) Log10 ( D / d )

ε = Dielectric Constant= 1 for vacuum or dry air



1 - 272

pimpedance (see figure at right)

• Velocity factor • Determined by dielectric characteristics

of insulation.• Power-handling capability

• Varies with size, conductor materials,dielectric characteristics

Special Properties of

Quarter-Wave Line Sections

• Transmission lines have

impedance-transforming properties• When terminated with same

impedance as Zo, input to lineappears as impedance Zo

• When terminated withimpedance different from Zo,input to line is a complexfunction of frequency and line

length. Use Smith Chart or

Zo=50Ω ZLOAD=50Ω

ZIN = 50Ω

Matched condition

Zo=50Ω

ZLOAD=

83-j22Ω

ZIN = ?

Mismatched condition

Deliberate mismatch



1 - 273

formulae to compute

• Special Case: ¼-wavelength long

line has convenient propertiesuseful in matching networks

• ZIN = (Zo2)/(ZLOAD)

Zo=50Ω

ZLOAD=

100ΩZIN=25Ω

λ /4

ZIN= ZO2 / ZLOAD

Deliberate mismatchfor impedance transformation

Transmission Lines

Some Practical Considerations• Transmission lines practical

considerations

• Periodicity of inner conductor supporting structure cancause VSWR peaks at somefrequencies, so specify the

frequency band whenordering

• Air dielectric lines• lower loss than foam-dielectric; dry air

is excellent insulator • shipped pressurized; do not accept



1 - 274

• shipped pressurized; do not acceptdelivery if pressure leak

• Foam dielectric lines• simple, low maintenance; despite

slightly higher loss• small pinholes and leaks can allow

water penetration and gradualattenuation increases

Foam

Dielectric

Air Dielectric

Transmission Lines

Important Installation Practices• Respect specified minimum

bending radius!

• Inner conductor must remainconcentric, otherwise Zo

changes

• Dents, kinks in outer conductor change Zo

• Don’t bend large, stiff lines (1-5/8” or larger) to make direct

connection with antennas• Use appropriate jumpers

Observe

MinimumBending



1 - 275

• Use appropriate jumpers,weatherproofed properly.

• Secure jumpers against wind

vibration.

BendingRadius!

Transmission Lines

Important Installation Practices, Continued• During hoisting

• Allow line to support its own

weight only for distancesapproved by manufacturer

• Deformation and stretching mayresult, changing the Zo

• Use hoisting grips, messenger cable

• After mounting

• Support the line with proper

mounting clamps atmanufacturer’s recommended

200 ft~60 mMax.

3-6 ft



1 - 276

manufacturer’s recommendedspacing intervals

• Strong winds will set up

damaging metal-fatigue-inducingvibrations

RF Filters

Types And Applications• Filters are the basic building blocks of

duplexers and more complex devices

• Most manufacturers’ networkequipment includes internalbandpass filters at receiver input andtransmitter output

• Filters are also available for specialapplications

• Number of poles (filter elements) and

other design variables determinefilter’s electrical characteristicsNotice construction: RF inputexcites one quarter-wave

element and electromagnet

Typical RF Bandpass Filter

∼λ /4



1 - 277

• Bandwidth rejection

• Insertion loss

• Slopes

• Ripple, etc.

element and electromagnetfields propagate from elementto element, finally exciting thelast element which is directly

coupled to the output.Each element is individually setand forms a pole in the filter’soverall response curve.

RF Filters

Basic Characteristics And Specifications

• Types of Filters

• Single-pole:• pass

• reject (notch)

• Multi-pole:• band-pass

• band-reject

• Key electrical characteristics

• Insertion loss• Passband ripple

Typical bandpass filters have

insertion loss of 1-3 dB. andpassband ripple of 2-6 dB.

Typical RF bandpass filter

0

A t t e n

u a t i o n , d B

Frequency, megaHertz

passband rippleinsertionloss

-3 dB passbandwidth



1 - 278

Passband ripple

• Passband width• upper, lower cutoff frequencies

• Attenuation slope at band edge

• Ultimate out-of-band attenuation

Bandwidth is typically 1-20% of center frequency, depending onapplication. Attenuation slopeand out-of-band attenuationdepend on # of poles & design

Basics Of Transmitting Combiners

• Allows multiple transmitters tofeed single antenna, providing

• Minimum power loss fromtransmitter to antenna

• Maximum isolation betweentransmitters

• Combiner types• Tuned

• low insertion loss ~1-3 dB• transmitter frequencies must be

significantly separated

• Hybrid

Typical tuned combiner application

TX TX TX TX TX TX TX TX

Antenna

Typical hybrid combiner application

Antenna

~-3 dB



1 - 279

• Hybrid• insertion loss -3 dB per stage• no restriction on transmitter

frequencies• Linear amplifier

• linearity and intermodulation aremajor design and operation issues

TX TX TX TX TX TX TX TX

~-3 dB

~-3 dB

Duplexer Basics

• Duplexer allows simultaneoustransmitting and receiving on oneantenna

• Nortel 1900 MHz BTS RFFEsinclude internal duplexer

• Nortel 800 MHz BTS does notinclude duplexer but commercial

units can be used if desired• Important duplexer specifications

• TX pass-through insertion loss

• RX pass-through insertion loss

• TX-to-RX isolation at TXf (RX i t d l ti

f R f T

RX TX

Antenna

Duplexer

Principle of operation

Duplexer is composed of individual

bandpass filters to isolate TX fromRX while allowing access to antennafor both Filter design determines



1 - 280

frequency (RX intermodulationissue)

• TX-to-RX isolation at RXfrequency (TX noise floor issue)

• Internally-generated IMP limitspecification

for both. Filter design determinesactual isolation between TX and RX,and insertion loss TX-to-Antenna

and RX-to-Antenna.

Directional Couplers

• Couplers are used to measureforward and reflected energy in atransmission line; it has 4 ports:• Input (from TX),

Output (to load)• Forward and Reverse Samples

• Sensing loops probe E& I in line

• Equal sensitivity to E & H fields• Terminations absorb induced

current in one direction, leavingonly sample of other direction

• Typical performance

specifications• Coupling factor ~20 ~30

Principle of operation

ZLOAD=50Ω

Input

Reverse Sample

Forward Sample

RT

RT

Typical directional coupler

Main line’s E & I induce equal signals in



1 - 281

Coupling factor 20, 30,~40 dB., order as appropriatefor application

• Directivity ~30-~40 dB., f($)• defined as relative attenuationof unwanted direction in eachsample

sense loops. E is direction-independent,but I’s polarity depends on direction andcancels sample induced in one direction.

Thus sense loop signals are directional.One end is used, the other terminated.




Other RF Elements of Antenna Systems

• What are the main characteristics of a transmission line?

What’s most important?• Why do we have to use precisely shaped connectors for

transmission lines?

• How is reflected power measured?• What is a multi-pole filter? Why does it have multiple

poles? How is it adjusted?

• How does a transmit combiner work?• What is a duplexer and how does it work?



1 - 283

• What is a duplexer, and how does it work?

• Name some precautions to take when handling installing

transmission lines and antennas at a BTS.

Reflected Power in Antenna Systems

and Typical Test Practices



1 - 284

Testing Communications Feedlines

and Antennas• AC power wiring and voice telephone wiring do not

require extremely critical wiring practices• just make sure the connections and insulation are

good, heat is not allowed to build up, and you’ll havegood results

• AC power frequencies and audio signal frequencieshave wavelengths of many miles

• a few feet of wire won’t radiate much energy

• High frequency RF wiring practice is much morecritical since signal wavelengths are only a fewinches or feet• any bend or protruding bit of wire can serve as an

unintentional antenna, “leaking” energy• even splices and connections can leak energy unlesstheir shape and dimensions are closely controlled



1 - 285

their shape and dimensions are closely controlled• abrupt changes in cable shape “reflect” energy back

down the transmission line, causing many problems

• Precisely shaped cables and connectors, carefulinstallation and accurate testing are required to avoidsignificant antenna system performance problems

Forward and Reflected Energy

Transmission Line

Antenna

Transmitter Forward Power

Virtually no reflected power

50Ω

50Ω

50Ω

• In a perfect antenna system, the transmissionline and the antenna have the same impedance• we say they are “impedance matched”

• All the energy from the transmitter passesthrough and is radiated from the antenna



1 - 286

through and is radiated from the antenna• virtually no energy is reflected back to the

transmitter

Forward and Reflected Energy

Transmission Line

Antenna

Transmitter

Significant Reflected Power

50Ω

42-j17Ω

Forward Power

dent or kink37Ω

• In a damaged antenna system, the impedance match is not good• there could be a dent, kink, or a spot with water in the transmission line

• the different impedance in the line at this spot will cause some of the energy to

be reflected backwards• the antenna could be damaged or dangling, causing it to have an altered

impedance



1 - 287

impedance• the antenna’s different impedance will reflect some of the energy backwards

down the line

• The Site Master ® Distance-To-Fault mode will be helpful in finding thelocation of the damage

How Much Reflection? Four Ways to Say It

• There are four ways of expressing howmuch energy is being reflected• different users like different methods

• Voltage Standing Wave Ratio (VSWR)(used by hobbyists and consumers)• the reflected voltage is in phase with the

incident voltage at some places and outof phase at others

• VSWR is the ratio of Vmax/Vmin• Reflected Power as % of Forward

Power (used by field personnel in someindustries)

• just divide Rev by Fwd, use percent• Return Loss (used by field personnel)• how many db weaker is the reflected

Vmax

Vmin

SWR: Standing Wave Ratio

= Vmax/ Vmin

FORWARD

REFLECTED

Reflected Power (%)

= 100 x

RevPwr

FwdPwr

FORWARD

REFLECTED

Return Loss (db)

= 10 x Log10RevPwr FwdPwr



1 - 288

• how many db weaker is the reflectedenergy than the forward energy

• Reflection Coefficient (academic users)• vector ratio of reflected/incident voltage

or current• usually expressed as a polar vector, with

magnitude and phase

REFLECTED

FORWARD

REFLECTED

Reflection Coeffic ient (vector ratio)

Vreflected

Vincident

=

Comparing Reflection Reports in Different

Forms• Reflection expressed in one form can beconverted and expressed in the other forms

• For example, consider a VSWR of 1.5 : 1

• this is 4% reflected power

• this is a return loss of 14 db

• to calculate the reflection coefficient, the

phase of the reflection is also needed FORWARD

REFLECTED

Reflected Power (%)

= 100 x RevPwr FwdPwr

FORWARD

C

Return Loss (db)

= 10 x Log10

RevPwr

FwdPwr

Vmax

Vmin

SWR: STANDINGW AVER ATIO= Vmax/ Vmin

=

Reflected Power Forward Power

Reflected Power Forward Power

1 +

1 -

VSWR vs. Return Loss

30

40

50



1 - 289

REFLECTED

FORWARD

REFLECTED

Reflection Coeffic ient (vector ratio)Vreflected

Vincident

=

VSWR

0

10

20

1 1.5 2 2.5 3

The Anritsu® /Wiltron Site Master ®• The Site Master ® is one of

the most convenient and

popular “combination”instruments for testingcommunications feedlinesand antennas

• Built Into a Site Master ®are:• sweep signal generator • directional coupler

• signal detector • processing software to

display return loss and

The Site Master ® is a “combination”instrument not much larger than a cigar box.In the field, it provides the functions of a



display return loss anddistance to fault

• Optional: Spectrum Analyzer • Optional: Power Meter • Battery and charging circuit

spectrum analyzer with tracking sweepgenerator, directional coupler, and power meter. In the past, a trunk full of instruments

were required to test communicationsantenna systems. Today, a Site Master ® caneven be carried to the tower top if needed.

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Get Acquainted with the Site Master ® Top

Panel

Port for external RFdetector and attenuator

Optional RF Input portfor optional spectrum

Battery Charging LED

Serial Interface for direct printing and



1 - 291

to make power measuements.

RF input/output port for transmission line tests

(VSWR, return loss, DTF)

for optional spectrumanalyzer capabilities

External Power jack. AcceptsDC input 11-15 VDC, 1.2A max.Note! The inner pin is positive

and the sleve is negative.

Power ON LED

transferring tracesto or from a PC.

Introducing the Site Master ® Front

Panel

Active Function Block

KeypadHard Keys



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Function Hard Keys Soft Keys

Setting the Mode: What Will Be

Displayed • The MODE button selects what willbe displayed by the Site Master ®:• Frequency on the X-Axis, along with

• SWR on the Y-Axis, or • Return Loss on the Y-Axis, or • Cable Loss (one-port) on Y-Axis

• Distance-to-Fault (DTF) on the X-Axis,with

• SWR on the Y-Axis, or • Return Loss on the Y-Axis

• Power Monitor • unit displays power level using optional

Power Monitor and an attenuator • In the Frequency and Distance-to-

Fault (DTF) modes the two top

x

y



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Fault (DTF) modes, the two topsoftkeys allow entry of the upper and

lower frequency limits for the sweepusing the keypad or the up-downcontrol• active function block shows key labels

Setting Freq/Dist: x-Axis Units• In Frequency mode, the FREQ/DIST button

selects the frequency range to be swept.

• Press F1 softkey, select the low-end sweepfrequency, press ENTER

• Press F2 softkey, select the high-end sweepfrequency, press ENTER

• In Distance-to-Fault mode, the FREQ/DISTbutton selects the distance range to betested, and allows entry of necessaryinformation about the line being swept• Press D1 softkey, select starting distance for

sweep, press ENTER• Press D2 softkey, select maximum distancefor sweep, press ENTERP DTF AID ftk f i d t id

x



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• Press DTF AID softkey for a window to guideselection of line or manual entry of line

characteristics, OR• Press MORE softkey to individually enter theloss, velocity, type, and window desired

Setting AMPLITUDE: y-Axis Units

• In Frequency and Distance-to-

Fault modes, the AMPLITUDEbutton allows entry of y-axisscale values:

• Press the top softkey, set thedesired top y-axis value, thenpress ENTER

• you can key in the value or scrollwith the up/down button

y



1 - 295

• Press the second-from-top

softkey, set desired bottom y-axisvalue, ENTER

Setting SWEEP: What Will Be Displayed

• The SWEEP button selects how theSite Master ® will sweep and display

its measurements:• Resolution can be set to 130, 259, or 517 bins on the x-axis

• Single-Sweep will stop the normal

continuous sweeping, and run onesweep each time the RUN/HOLDkeypad button is pressed

• Trace Math can add or subtract theimmediate measurements to the

measurements seen on the previoussweep, thereby showing a running delta• Trace Overlay will display a previously



1 - 296

y p y p ystored trace as an overlay for visualcomparison with the current

measurement• the stored trace must have the same

settings as the presently-measuring trace

Site Master ® AccessoriesPortable Case

DIN-N

Adaptors

• The tough fabric carrying caseprovides travel protection and

is a comfortable holder for theSite Master ® when measuring

• a pouch and zippered foam-lined carrier hold power

supplies, terminations andadaptors

• The extension cable can beused to place the official

reference point at the end of the cable

Between series adaptors can



1 - 297

ExtensionCable

• Between-series adaptors canbe used to connect the native

Type-N connector with anyother family of adapters.

Powering Up and Calibrating Before Use

• To provide reliable readings, Site Master ® should be calibratedimmediately prior to making important measurements

• When first powered up, Site Master ® will show a welcome screen asit completes a self-test.• When prompted, press ENTER to begin normal operation, or wait five

seconds and normal operation will begin automatically

• If the internal battery is low, connect external DC power • If the unit displays “CAL OFF”, recalibration is required before

measuring• Decide which location you wish to use as the “reference point” for

the measurements: the top panel port of the Site Master ®

, or the endof a phase-stable extension cable• Site Master ® must be calibrated using the “OSL” method: a reference

open reference short and reference load connected to the reference



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open, reference short, and reference load connected to the referencepoint during calibration as requested in screen prompts

• Calibration is also required if the temperature varies substantially, if thereference point is changed, or the measurement frequency is changed

Site Master ® Accessories Used In

Calibration• If you will use an extension cable as

the reference point, attach it now

• The most convenient calibrationprocess uses the Anritsu® InstaCalfixture.• This device automatically presents an

open, short, and load in response toautomatic triggers during calibration

• If a recently certified InstaCal is notavailable, the manual calibrationprocess must be used

• Press START CAL and follow theprompts, attaching the referencel d h t d

InstaCal Module

PrecisionShort & Open



loads when requested

• At conclusion, you should see theCAL ON message displayed at thetop of the screen

PrecisionLoad

1 - 299

Return Loss Display



1 - 300

Distance-to-Fault Display



1 - 301

Smith Chart Display



1 - 302

Wiltron SOP

InstaCal Module



1 - 303


PrecisionLoad

Wiltron SOP

InstaCal Module

DIN-N

Adaptors

Extension

Cable



1 - 304


PrecisionLoad



Wiltron SOP



1 - 306

Wiltron SOP



1 - 307

Wiltron SOP



1 - 308

Question and Answer



1 - 3095/19/2004 309


Reflected Power in Antenna Systems• Name at least three ways reflected power

amount can be described.

• What is the worst routinely acceptable reflectedpower amount for an antenna system?

• How can you measure reflected power?• How would you track down the source of

excessive reflected power in an antennasystem?

• Does water in a cable or connector always



1 - 310

Does water in a cable or connector always

cause reflected power?

Some Antenna ApplicationPrinciples



1 - 311

Near-Field/Far-Field Considerations

• Antenna behavior is very different close-in andfar out

• Near-field region: the area within about 10 timesthe spacing between antenna’s internalelements

• Inside this region, the signal behaves as

independent fields from each element of theantenna, with their individual directivity

• Far-field region: the area beyond roughly 10times the spacing between the antenna’sinternal elements

• In this region, the antenna seems to be apoint-source and the contributions of theindividual elements are indistinguishable

Near-field

Far-field



1 - 312

g

• The pattern is the composite of the array

• Obstructions in the near-field can dramaticallyalter the antenna performance

Local Obstruction at a Site

Diffractionover

obstructingedge

Local obstruction example• Obstructions near the site are

sometimes unavoidable• Near-field obstructions can

seriously alter pattern shape

• More distant local obstructionscan cause severe blockage, asfor example roof edge in the

figure at right• Knife-edge diffraction analysiscan help estimate diffraction lossin these situations



1 - 313

in these situations

• Explore other antenna mountingpositions

Estimating Isolation Between Antennas

Often multiple antennas are needed at a siteand interaction is troublesome

• Electrical isolation between antennas

• Coupling loss between isotropic antennasone wavelength apart is 22 dB

• 6 dB additional coupling loss with eachdoubling of separation

• Add gain or loss referenced from horizontalplane patterns• Measure vertical separation between

centers of the antennas• vertical separation usually is very effective

• One antenna should not be mounted in mainlobe and near-field of another • Typically within 10 feet @ 800 MHz

f @



1 - 314

• Typically 5-10 feet @ 1900 MHz



Antenna Downtilt

What’s the goal?Downtilt is commonly used for two reasons

• 1. Reduce Interference• Reduce radiation toward a

distant co-channel cell• Concentrate radiation

within the serving cell

• 2. Prevent “Overshoot”• Improve coverage of

nearby targets far belowthe antenna

• otherwise within “null” of antennapattern

• Are these good

strategies?

Scenario 2

Cell A

Scenario 1

Cell B



1 - 316

strategies?

• How is downtiltapplied?

Consider Vertical Depression Angles

• Basic principle: important to matchvertical pattern against intendedcoverage targets

• Compare the angles toward objectsagainst the antenna vertical pattern-- what’s radiating toward the target?

• Don’t position a null of the antenna

toward an important coveragetarget!• Sketch and formula

• Notice the height and horizontal

distance must be expressed in thesame units before dividing (both in

feet, both in miles, etc.)

Horizontaldistance

Verticaldistance

θ Depression angle



1 - 317

θ = ArcTAN ( Vertical distance / Horizontal distance )

Types Of Downtilt

• Mechanical downtilt

• Physically tilt the antenna

• The pattern in front goesdown, and behind goes up

• Popular for sectorization and

special omni applications• Electrical downtilt

• Incremental phase shift isapplied in the feed network

• The pattern “droops” allaround, like an invertedsaucer



1 - 318

• Common technique whendowntilting omni cells

Reduce Interference

Scenario 1

The Concept:

• Radiate a strong signaltoward everything withinthe serving cell, butsignificantly reduce the

radiation toward the areaof Cell B

The Reality:

• When actuallycalculated, it’s surprisinghow small the differencein angle is between thefar edge of cell A and thenear edge of Cell B• Delta in the example is

Cell AConcept

Cell B

weak

strong

θ1 = ArcTAN ( 150 / ( 4 * 5280 ) )

Reality

12 miles4

heightdifference

150 ft θ21



1 - 319

p

only 0.3 degrees!!• Let’s look at antenna

patterns

( ( ) )= -0.4 degrees

θ2 = ArcTAN ( 150 / ( 12 * 5280 ) )= -0.1 degrees

Reduce Interference

Scenario 1 , Continued

• It’s an attractive idea, but

usually the angle betweenedge of serving cell andnearest edge of distant cellis just too small to exploit• Downtilt or not, can’t get

much difference in antennaradiation between θ1 and θ2

• Even if the pattern were

sharp enough, alignmentaccuracy and wind-flexingwould be problems

• delta θ in this exampleis less than one degree!

• Also, if downtilting -- watchout for excessive RSSI andIM involving mobiles near cell!

-0.4

-0.1

θ1 = -0.4 degrees



1 - 320

cell!

• Tight handoffs and goodpower control are moreimportant

g

θ2 = -0.1 degrees

Avoid Overshoot

Scenario 2• Application concern: too little

radiation toward low, close-incoverage targets

• The solution is common-sense

matching of the antenna verticalpattern to the angles whereradiation is needed

• Calculate vertical angles to targets!!

• Watch the pattern nulls -- where dothey fall on the ground?

• Choose a low-gain antenna with afat vertical pattern if you have a

wide range of vertical angles to “hit”• Downtilt if appropriate

• If needed, investigate special “null-filled” antennas with smooth

Scenario 2



1 - 321

filled antennas with smooth

patterns

Other Antenna Selection ConsiderationsBefore choosing an antenna for widespread deployment, investigate:

• Manufacturer’s measured patterns

• Observe pattern at low end of band, mid-band, and high end of band• Any troublesome back lobes or minor lobes in H or V patterns?

• Watch out for nulls which would fall toward populated areas

• Be suspicious of extremely symmetrical, “clean” measured patterns

• Obtain Intermod Specifications and test results (-130 or better)

• Inspect return loss measurements across the band

• Inspect a sample unit

• Physical integrity? weatherproof?

• Dissimilar metals in contact anywhere?

• Collinear vertical antennas: feed method?

• End (compromise) or center-fed (best)?



1 - 322

• Complete your own return loss measurements, if possible• Ideally, do your own limited pattern verification

• Check with other users for their experiences

Question and Answer



1 - 3235/19/2004 323


Some Antenna Application Principles• What is the “near field” of an antenna?

• How far must you be from an antenna before itspattern seems correctly formed and focused?

• What is downtilt? What are the different types?

• How do you control coverage with downtilt? Is itpossible to plan, or must everything be done byexperiment?

• A BTS antenna is 300 feet above ground. Whatis the depression angle to a shopping center onemile away on level ground? To the edge of an



1 - 324

adjoining cell 4 miles away on level ground?

GLOBAL SYSTEM FOR


R

Lesson 6:

Basic Traffic Concepts

Typical TrafficDistribution

on a Cellular System

60%

70%

80%

90%

100%

SUN

MON

TUE

Efficiency %80%

41



1 - 325

0%

10%

20%

30%40%

50%

Hour

WED

THU

FRI

SAT

# Trunks

Capacity,Erlangs

1 50

A Game of Avoiding Extremes

The traffic planner has to walk a fineline between two problems:

• Overdimensioning• too much cost• insufficient resources to construct• traffic revenue is too low to

support costs• very poor economic efficiency!

• Underdimensioning• blocking• poor technical performance

(interference)• capacity for billable revenue is low• revenue is low due to poor quality• users unhappy, cancel service



1 - 326

• very poor economic efficiency!

Dimensioning the System:

An Interactive, Iterative Process

• Some traffic engineering decisions trigger resource acquisition

• additional blocks of numbers from the localexchange carrier

• additional cards for various functions in theswitch and peripherals

• additional members in PSTN trunk groups;

additional T-1/E-1s to busy sites• Some traffic engineering decisions trigger

more engineering• finding more frequencies to add to blocking

sites• adding additional cells to relieve blocking• finding short-term fixes for unanticipated

problems

• This course is concerned primarily with

DMS-MTX

Cell

PSTNOffice



1 - 327

This course is concerned primarily with

determining the number of voice channelsrequired in cells, with the related siteengineering and frequency or code planning

Basics of Traffic EngineeringTerminology & Concept of a Trunk

• Traffic engineering in telephony is focused on the

voice paths which users occupy. They are called bymany different names:

• trunks

• circuits• radios (AMPS, TDMA), transceivers (“TRXs” in GSM),

channel elements (CDMA)

• Some other common terms are:• trunk group

• a trunk group is several trunks going to the same destination,combined and addressed in switch translations as a unit , for traffic



1 - 328

routing purposes• member

• one of the trunks in a trunk group

Units of Traffic Measurement

Traffic is expressed in units of Circuit Time

General understanding of telephone traffic engineering beganaround 1910. An engineer in the Danish telephone system, A. K.

Erlang, was one of the first to master the science of trunkdimensioning and publish the knowledge for others. In his honor,the basic unit of traffic is named the Erlang.

• An Erlang of traffic is one circuit continuously used during anobservation period one hour long.

Other units have become popular among various users:• CCS (Hundred-Call-Seconds)

• MOU (Minutes Of Use)



1 - 329

• It’s easy to convert between traffic units if the need arises:1 Erlang = 60 MOU = 36 CCS

How Much Traffic Can One Trunk Carry?

• Traffic studies are usually for periods of one hour

• In one hour, one trunk can carry one hour of traffic -- One Erlang

• If nothing else matters, this is the limit!

• If anyone else wants to talk -- sorry!

Absolute Maximum Capacityof One Trunk

One Trunk

One ErlangConstantTalker



1 - 330

We must not plan to keep trunks busy all the time. There must bea reserve to accommodate new talkers! How much reserve? next!

Traffic Engineering And Queuing Theory

• Traffic engineering is an application of a science called queuing theory

• Queuing theory relates user arrival

statistics, number of servers, andvarious queue strategies, with theprobability of a user receiving service

• If waiting is not allowed, and a blocked

call simply goes away, Erlang-Bformula applies (popular in wireless)

• If unlimited waiting is allowed before acall receives service, the Erlang-C

formula applies• If a wait is allowed but is limited in time,

Binomial & Poisson formulae apply

• Engset formulae apply to rapid, packet-

Ticket counter analogy

User population

Queue

Servers

Queues we face in

everyday life1) for telephone calls

2) at the bank

3) at the gas station



1 - 331

like transactions such as pagingchannels

4) at the airline counter

Offered And Carried Traffic

• Offered traffic is what users attempt tooriginate

• Carried traffic is the traffic actuallysuccessfully handled by the system

• Blocked traffic is the traffic that couldnot be handled• Since blocked call attempts never

materialize, blocked traffic must beestimated based on number of blocked

attempts and average duration of successful calls

CarriedTraffic

BTS BTS BTS BTS BTS BTS

OfferedTraffic

BSCMTX

BlockedTraffic

PSTN or other Wireless user

TOff = NCA x TCD

TOff = Offered traffic

Offered Traffic =

Carried Traffic + Blocked Traffic



1 - 332

NCA = Number of call attemptsTCD = Average call duration

• Blocking is inability to get a circuit when one is needed• Probability of Blocking is the likelihood that blocking will

happen

• In principle, blocking can occur anywhere in a wirelesssystem:• not enough radios, the cell is full• not enough paths between cell site and switch

• not enough paths through the switching complex• not enough trunks from switch to PSTN

• Blocking probability is usuallyexpressed as a percentage

using a “shorthand” notation:• P.02 is 2% probability, etc.• Blocking probability sometimes

is called “Grade Of Service”

• Most blocking in cellular systems

Principles of Traffic Engineering

Blocking Probability / Grade of Service

PSTN Office

DMS-MTX

Cell

Cell

Cell

P.02

P.005

Typical Wireless System

Design Blocking Probabilities



1 - 333

occurs at the radio level.• P.02 is a common goal at the

radio level in a systemP.001 P.005

P.02

Number of Trunks

vs. Utilization Efficiency• Imagine a cell site with just one voice channel. At a P.02

Grade of Service, how much traffic could it carry?

• The trunk can only be used 2% of the time, otherwise theblocking will be worse than 2%.

• 98% availability forces 98% idleness. It can only carry .02Erlangs. Efficiency 2%!

• Adding just one trunk relieves things greatly.Now we can use trunk 1 heavily, with trunk 2handling the overflow. Efficiency rises to 11%

The Principle of Trunking Efficiency• For a given grade of service, trunk

utilization efficiency increases as thenumber of trunks in the pool grows larger.

Efficiency %80%

41

Erl Eff%Trks

1

2

0.02

0.22

2%

11%

Erlang-B P.02 GOS



1 - 334

• For trunk groups of several hundred,utilization approaches 100%.

# Trunks

Capacity,Erlangs

1 50

Number of Trunks,

Capacity, and Utilization Efficiency• The graph at left illustrates

the capacity in Erlangs of a

given number of trunks, aswell as the achievableutilization efficiency

• For accurate work, tablesof traffic data are available

• Capacity, Erlangs

• Blocking Probability (GOS)• Number of Trunks

• Notice how capacity and

05

10

15

20

2530

35

40

45

Capacity and Trunk Utilization

Erlang-B for P.02 Grade of Service

Trunks

010

20

30

40

5060

70

80

90

50403020100UtilizationEfficiencyPercent

Capacity,Erlangs



1 - 335

utilization behave for thenumbers of trunks in typicalcell sites

Traffic Engineering & System

DimensioningUsing Erlang-B Tables to determine Number of Circuits Required

Probability

of blocking0.0001 0.002 0.02

7

En

12

2.935

0.2

Capacity

in Erlangs

Number of

availablecircuits



1 - 336

A = f (E,n)300

Erlang-B Traffic Tables

Abbreviated - For P.02 Grade of ServiceOnly

#TrunksErlangs #TrunksErlangs #Trunks #TrunksErlangs #TrunksErlangs #TrunksErlangs #TrunksErlangs #TrunksErlangs1 0.0204 26 18.4 51 41.2 76 64.9 100 88 150 136.8 200 186.2 250 235.8

2 0.223 27 19.3 52 42.1 77 65.8 102 89.9 152 138.8 202 188.1 300 285.7

3 0.602 28 20.2 53 43.1 78 66.8 104 91.9 154 140.7 204 190.1 350 335.7

4 1.09 29 21 54 44 79 67.7 106 93.8 156 142.7 206 192.1 400 385.9

5 1.66 30 21.9 55 44.9 80 68.7 108 95.7 158 144.7 208 194.1 450 436.1

6 2.28 31 22.8 56 45.9 81 69.6 110 97.7 160 146.6 210 196.1 500 486.4

7 2.94 32 23.7 57 46.8 82 70.6 112 99.6 162 148.6 212 198.1 600 587.28 3.63 33 24.6 58 47.8 83 71.6 114 101.6 164 150.6 214 200 700 688.2

9 4.34 34 25.5 59 48.7 84 72.5 116 103.5 166 152.6 216 202 800 789.3

10 5.08 35 26.4 60 49.6 85 73.5 118 105.5 168 154.5 218 204 900 890.6

11 5.84 36 27.3 61 50.6 86 74.5 120 107.4 170 156.5 220 206 1000 999.1

12 6.61 37 28.3 62 51.5 87 75.4 122 109.4 172 158.5 222 208 1100 1093

13 7.4 38 29.2 63 52.5 88 76.4 124 111.3 174 160.4 224 210

14 8.2 39 30.1 64 53.4 89 77.3 126 113.3 176 162.4 226 212

15 9.01 40 31 65 54.4 90 78.3 128 115.2 178 164.4 228 213.9

16 9.83 41 31.9 66 55.3 91 79.3 130 117.2 180 166.4 230 215.9

17 10.7 42 32.8 67 56.3 92 80.2 132 119.1 182 168.3 232 217.9

18 11.5 43 33.8 68 57.2 93 81.2 134 121.1 184 170.3 234 219.9

19 12.3 44 34.7 69 58.2 94 82.2 136 123.1 186 172.4 236 221.9

20 13.2 45 35.6 70 59.1 95 83.1 138 125 188 174.3 238 223.9

21 14 46 36.5 71 60.1 96 84.1 140 127 190 176.3 240 225.9

Er

langs



1 - 337

22 14.9 47 37.5 72 61 97 85.1 142 128.9 192 178.2 242 227.923 15.8 48 38.4 73 62 98 86 144 130.9 194 180.2 244 229.9

24 16.6 49 39.3 74 62.9 99 87 146 132.9 196 182.2 246 231.8

25 17.5 50 40.3 75 63.9 100 88 148 134.8 198 184.2 248 233.8

The Equation behind the Erlang-B TableThe Erlang-B formula is fairly simple to implement on

hand-held programmable calculators, in spreadsheets,

or popular programming languages.

Pn(A) =

An

n!

1 + + ... +A1!

An

n!

Pn(A) = Blocking Rate (%)with n trunksas function of traffic A

A = Traffic (Erlangs)

Offered Trafficlost due toblocking

Number

of Trunks

max # of

trunks

average# of busychannelsOffered

Traffic,A



1 - 338

n = Number of Trunks time

Wireless Traffic Variation with Time:

A Cellular Example• Peak traffic on cellular systems

is usually daytime business-related traffic; on PCS systems,

evening traffic becomes muchmore important and may actuallycontain the system busy hour

• Evening taper is more gradualthan morning rise

• Wireless systems for PCS andLEC-displacement have peaks of residential traffic during earlyevening hours, like wireline

systems• Friday is the busiest day,

followed by other weekdays inbackwards order, then Saturday,then Sunday

Typical Traffic Distribution

on a Cellular System

0%

10%

20%

30%

40%50%

60%

70%

80%

90%

100%

Hour

SUN

MON

TUE

WED

THU

FRI

SAT

Actual traffic from a cellular system in the



1 - 339

• There are seasonal and annualvariations, as well as longterm growth trends

mid-south USA in summer 1992. Thissystem had 45 cells and served an areaof approximately 1,000,000 population.

Busy-Hour

• In telephony, it is customary to collect and analyze traffic in hourlyblocks, and to track trends over months, quarters, and years

• When making decisions about number of trunks required, we plan

the trunks needed to support the busiest hour of a normal day• Special events (disasters, one-of-a-kind traffic tie-ups, etc.) are not

considered in the analysis (unless a marketing-sponsored event)

• Which Hour should be used as the Busy-Hour?

• Some planners choose one specific hour and use it every day

• Some planners choose the busiest hour of each individual day(“floating busy hour”)

• Most common preference is to use “floating (bouncing)” busy hour

determined individually for the total system and for each cell, but toexclude special events and disasters

• In the example just presented, 4 PM was the busy hour every day



1 - 340

Where is the Traffic?

• Wireline telephone systems have abig advantage in traffic planning.

• They know the addresses wheretheir customers generate thetraffic!

• Wireless systems have to guesswhere the customers will be next

• on existing systems, usemeasured traffic data by sector

and cell• analyze past trends

• compare subscriber forecast

t d i t f t fi d l d

117

11

10

19

85

7

65

2

7

3

8

167

166

9

9

7

Existing SystemTraffic In Erlangs



1 - 341

• trend into future, find overloads

• for new systems or new cells,we must use all available clues

Traffic Clues• Subscriber Profiles:

• Busy Hour Usage, Call Attempts, etc.

• Market Penetration:

• # Subscribers/Market Population

• use Sales forecasts, usage forecasts

• Population Density

• Geographic Distribution• Construction Activity

• Vehicular Traffic Data

• Vehicle counts on roads

• Calculations of density on major roadways from knowledge of vehiclemovement, spacing, marketpenetration

L d U D t b A P fil

22,100

3620 66201230

5110

4215

920

Vehicular Traffic

Land UseDatabases

Population Density

27 mE/Sub in BH

103,550 Subscribers

1,239,171 Market Population

adding 4,350 subs/month

newShopping Center



• Land Use Database: Area Profiles

• Aerial Photographs: Count Vehicles!

1 - 342

Traffic Density Along Roadways

• Number of lanes and speed are the mainvariable determining number of vehicleson major highways• Typical headway ~1.5 seconds

• Table and figure show capacity of 1lane

• When traffic stops, users generallyincrease calling activity

• Multiply number of vehicles bypercentage penetration of population toestimate number of subscriber vehicles

VehicleSpeed,MPH

VehicleSpacing,

feet

Vehiclesper mile,per lane

0 20 264

10 42 126

20 64 83

30 86 61

45 119 44

60 152 35

Vehicle spacing 20 ft. @stopRunning Headway 1.5 seconds

Vehicles per mile

Vehicle Spacing At Common Roadway Speeds

0

40 MPH30 MPH20 MPH10 MPH0 MPH

100 200 300 400 500 600 700 800 feet



1 - 343

50 MPH40 MPH

Methodical Estimation of Required

TrunksModern propagation prediction

tools allow experimentation andestimation of traffic levels

• Estimate total overall trafficfrom subscriber forecasts• Form traffic density outlines

from market knowledge,forecasts

• Overlay traffic density on landuse data; weight by land use

• Accumulate intercepted trafficinto serving cells,

• obtain Erlangs per cell & sector

• From tables, determine number of trunks required per cell/sector

• Modern software tools

Cell Grid

Land Use

TrafficDensity

3.5%

27mE



1 - 344

• Modern software toolsautomate major parts of thisprocess

Profile of Typical Cellular Usage

Number of call attempts per subscriber in busy hour

Mobile originated calls

Mobile terminated calls

Number of handoffs per call

Registration attempts per subscriber during busy hour

proportion of total calls on systemsuccessful callsCalls not answeredcalls to a busy line

proportion of total calls on systemsuccessful calls

Calls not answeredpaging requests not answered

25 mE

0.87

2

87 %70 %15 %15 %

13 %15 %10 %75 %

Offered Traffic, mE per subscriber in busy hour

Average Call Duration

1.667

150 sec. (41.7 mE)



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Registration attempts per subscriber during busy hour 2



Dimensioning

System Administrative Functions

System administrative functions also require traffic engineering input.While these functions are not necessarily performed by the RFengineer, they require RF awareness and understanding.

• Paging• The paging channel has a definite capacity which must not be

exceeded. When occupancy approaches this limit, the system mustbe divided into zones, and zone paging implemented.

• Impact of Short Message Service (and others) must be considered• Autonomous Registration

• Autonomous registration involves numerous parameters and theregistration attempts must be monitored and controlled to avoid

overloading



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overloading.

Question and Answer



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Question and Answer:Basic Traffic Engineering

• Name three units for measuring traffic, and explain howto convert between them.

• What is offered traffic, what is carried traffic, and how arethey related?

• What percentage blocking is a P.02 GOS?

• How many erlangs can one trunk carry if you keep itcontinuously busy? What would the blocking probabilitybe for a trunk like that?

• Imagine a GSM cell with 2 TRXs. Suppose one timeslot

is used for BCCH and two for SDCCHs. How manyerlangs of traffic can it carry at 2% blocking probability?• What is a “bouncing busy hour”?• What is the busy hour traffic on your system’s busiest

cell? What is the blocking percentage?



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cell? What is the blocking percentage?

GLOBAL SYSTEM FOR


R

Lesson 7.GSM Call Processing



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Idle Mode Procedures – Mobile Side



1 - 351

Call Control Procedures – System Side



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Call Control Procedures – Mobile Side



1 - 353

Call Control ProceduresExtension to Mobile Side



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Message TypesRadio Resource Mgt. 1

Table 10.1/GSM 04.08 (page 1 of 2): Message types for Radio Resourcemanagement

+---------------------------------------------------+¦ 8 7 6 5 4 3 2 1 ¦¦ ¦

¦ 0 0 1 1 1 - - - Channel establishment messages: ¦¦ 1 0 0 - RR INITIALISATION REQUEST ¦¦ 0 1 1 - ADDITIONAL ASSIGNMENT ¦¦ 1 1 1 - IMMEDIATE ASSIGNMENT ¦¦ 0 0 1 - IMMEDIATE ASSIGNMENT EXTENDED ¦¦ 0 1 0 - IMMEDIATE ASSIGNMENT REJECT ¦¦ ¦¦ 0 0 1 1 0 - - - Ciphering messages: ¦¦ 1 0 1 - CIPHERING MODE COMMAND ¦¦ 0 1 0 - CIPHERING MODE COMPLETE ¦¦ ¦¦ 0 0 1 1 0 - - - Configuration change messages: ¦¦ 0 0 0 - CONFIGURATION CHANGE COMMAND ¦¦ 0 0 1 - CONFIGURATION CHANGE ACK. ¦¦ 0 1 1 - CONFIGURATION CHANGE REJECT ¦¦ ¦¦ 0 0 1 0 1 - - - Handover messages: ¦¦ 1 1 0 - ASSIGNMENT COMMAND ¦¦ 0 0 1 - ASSIGNMENT COMPLETE ¦

¦ 1 1 1 - ASSIGNMENT FAILURE ¦¦ 0 1 1 - HANDOVER COMMAND ¦¦ 1 0 0 - HANDOVER COMPLETE ¦¦ 0 0 0 - HANDOVER FAILURE ¦¦ 1 0 1 - PHYSICAL INFORMATION ¦¦ ¦¦ 0 0 0 0 1 0 0 0 - RR-CELL CHANGE ORDER ¦¦ 0 0 1 0 0 0 1 1 - PDCH ASSIGNMENT COMMAND ¦¦ ¦¦ 0 0 0 0 1 - - - Channel release messages: ¦

¦ 1 0 1 - CHANNEL RELEASE ¦¦ 0 1 0 - PARTIAL RELEASE ¦¦ 1 1 1 - PARTIAL RELEASE COMPLETE ¦¦ ¦¦ 0 0 1 0 0 - - - Paging and Notification messages:¦¦ 0 0 1 - PAGING REQUEST TYPE 1 ¦¦ 0 1 0 - PAGING REQUEST TYPE 2 ¦¦ 1 0 0 - PAGING REQUEST TYPE 3 ¦¦ 1 1 1 - PAGING RESPONSE ¦¦ 0 0 0 - NOTIFICATION/NCH ¦

¦ 1 0 1 - NOTIFICATION/FACCH ¦¦ 1 1 0 - NOTIFICATION RESPONSE ¦¦ 0 0 0 0 1 0 1 1 Reserved (see NOTE) ¦



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¦ 0 0 0 0 1 0 1 1 - Reserved (see NOTE) ¦+---------------------------------------------------+

Message TypesRadio Resource Mgt. 2

Table 10.1/GSM 04.08 (page 2 of 2): Message types for Radio Resourcemanagement

+---------------------------------------------------+¦ 8 7 6 5 4 3 2 1 ¦¦ ¦¦ 0 0 0 1 1 - - - System information messages: ¦

¦ 0 0 0 - SYSTEM INFORMATION TYPE 8 ¦¦ 0 0 1 - SYSTEM INFORMATION TYPE 1 ¦¦ 0 1 0 - SYSTEM INFORMATION TYPE 2 ¦¦ 0 1 1 - SYSTEM INFORMATION TYPE 3 ¦¦ 1 0 0 - SYSTEM INFORMATION TYPE 4 ¦¦ 1 0 1 - SYSTEM INFORMATION TYPE 5 ¦¦ 1 1 0 - SYSTEM INFORMATION TYPE 6 ¦¦ 1 1 1 - SYSTEM INFORMATION TYPE 7 ¦¦ ¦¦ 0 0 0 0 0 - - - System information messages: ¦

¦ 0 1 0 - SYSTEM INFORMATION TYPE 2bis ¦¦ 0 1 1 - SYSTEM INFORMATION TYPE 2ter ¦¦ 1 0 1 - SYSTEM INFORMATION TYPE 5bis ¦¦ 1 1 0 - SYSTEM INFORMATION TYPE 5ter ¦¦ 1 0 0 - SYSTEM INFORMATION TYPE 9 ¦¦ 0 0 0 - SYSTEM INFORMATION TYPE 13 ¦¦ ¦¦ 0 0 1 1 1 - - - System information messages: ¦¦ 1 0 1 - SYSTEM INFORMATION TYPE 16 ¦¦ 1 1 0 - SYSTEM INFORMATION TYPE 17 ¦

¦ ¦¦ 0 0 0 1 0 - - - Miscellaneous messages: ¦¦ 0 0 0 - CHANNEL MODE MODIFY ¦¦ 0 1 0 - RR STATUS ¦¦ 1 1 1 - CHANNEL MODE MODIFY ACKNOWLEDGE¦¦ 1 0 0 - FREQUENCY REDEFINITION ¦¦ 1 0 1 - MEASUREMENT REPORT ¦¦ 1 1 0 - CLASSMARK CHANGE ¦¦ 0 1 1 - CLASSMARK ENQUIRY ¦¦ 0 0 1 1 0 1 1 0 - EXTENDED MEASUREMENT REPORT ¦

¦ 0 0 1 1 0 1 1 1 - EXTENDED MEASUREMENT ORDER ¦¦ 0 0 1 1 0 1 0 0 - GPRS SUSPENSION REQUEST ¦¦ ¦¦ VGCS uplink control messages: ¦¦ ¦¦ 0 0 0 0 1 0 0 1 - VGCS UPLINK GRANT ¦¦ 0 0 0 0 1 1 1 0 - UPLINK RELEASE ¦¦ 0 0 0 0 1 1 0 0 - UPLINK FREE ¦¦ 0 0 1 0 1 0 1 0 - UPLINK BUSY ¦¦ 0 0 0 1 0 0 0 1 - TALKER INDICATION ¦¦ ¦¦ Application messages: |



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¦ ¦| 0 0 1 1 1 0 0 0 - Application Information |+---------------------------------------------------+

Message TypesRadio Resource Mgt. Short Protocol

Mobility Mgt.

Table 10.1a/GSM 04.08: Message types for Radio Resourcemanagement messages using the RR

short protocol discriminator +---------------------------------------------------+

¦ 5 4 3 2 1 ¦¦ ¦¦ 0 0 0 0 0 SYSTEM INFORMATION TYPE 10 ¦¦ 0 0 0 0 1 NOTIFICATION/FACCH ¦¦ 0 0 0 1 0 UPLINK FREE ¦¦ ¦+---------------------------------------------------+Table 10.2/GSM 04.08: Message types for Mobility Management+---------------------------------------------------+¦ ¦

¦ 8 7 6 5 4 3 2 1 ¦¦ ¦¦ 0 x 0 0 - - - - Registration messages: ¦¦ 0 0 0 1 - IMSI DETACH INDICATION ¦¦ 0 0 1 0 - LOCATION UPDATING ACCEPT ¦¦ 0 1 0 0 - LOCATION UPDATING REJECT ¦¦ 1 0 0 0 - LOCATION UPDATING REQUEST ¦¦ ¦¦ 0 x 0 1 - - - - Security messages: ¦¦ 0 0 0 1 - AUTHENTICATION REJECT ¦

¦ 0 0 1 0 - AUTHENTICATION REQUEST ¦¦ 0 1 0 0 - AUTHENTICATION RESPONSE ¦¦ 1 0 0 0 - IDENTITY REQUEST ¦¦ 1 0 0 1 - IDENTITY RESPONSE ¦¦ 1 0 1 0 - TMSI REALLOCATION COMMAND ¦¦ 1 0 1 1 - TMSI REALLOCATION COMPLETE ¦¦ ¦¦ 0 x 1 0 - - - - Connection management messages: ¦¦ 0 0 0 1 - CM SERVICE ACCEPT ¦¦ 0 0 1 0 - CM SERVICE REJECT ¦¦ 0 0 1 1 - CM SERVICE ABORT ¦¦ 0 1 0 0 - CM SERVICE REQUEST ¦¦ 0 1 0 1 - CM SERVICE PROMPT ¦¦ 0 1 1 0 - Reserved (see NOTE) ¦¦ 1 0 0 0 - CM RE-ESTABLISHMENT REQUEST ¦¦ 1 0 0 1 - ABORT ¦¦ ¦¦ 0 x 1 1 - - - - Miscellaneous messages: ¦¦ 0 0 0 0 - MM NULL ¦

¦ 0 0 0 1 - MM STATUS ¦¦ 0 0 1 0 - MM INFORMATION ¦+---------------------------------------------------+



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Message TypesCall Control

Table 10.3/GSM 04.08: Message types for Call Control and call related SS messages+---------------------------------------------------+¦ 8 7 6 5 4 3 2 1 ¦¦ 0 x 0 0 0 0 0 0 escape to nationally specific ¦

¦ message types ; see 1) below ¦¦ ¦¦ 0 x 0 0 - - - - Call establishment messages: ¦¦ 0 0 0 1 - ALERTING ¦¦ 1 0 0 0 - CALL CONFIRMED ¦¦ 0 0 1 0 - CALL PROCEEDING ¦¦ 0 1 1 1 - CONNECT ¦¦ 1 1 1 1 - CONNECT ACKNOWLEDGE ¦¦ 1 1 1 0 - EMERGENCY SETUP ¦¦ 0 0 1 1 - PROGRESS ¦

¦ 0 1 0 0 - CC-ESTABLISHMENT ¦¦ 0 1 1 0 - CC-ESTABLISHMENT CONFIRMED ¦¦ 1 0 1 1 - RECALL ¦¦ 1 0 0 1 - START CC ¦¦ 0 1 0 1 - SETUP ¦¦ ¦¦ 0 x 0 1 - - - - Call information phase messages: ¦¦ 0 1 1 1 - MODIFY ¦¦ 1 1 1 1 - MODIFY COMPLETE ¦¦ 0 0 1 1 - MODIFY REJECT ¦¦ 0 0 0 0 - USER INFORMATION ¦¦ 1 0 0 0 - HOLD ¦¦ 1 0 0 1 - HOLD ACKNOWLEDGE ¦¦ 1 0 1 0 - HOLD REJECT ¦¦ 1 1 0 0 - RETRIEVE ¦¦ 1 1 0 1 - RETRIEVE ACKNOWLEDGE ¦¦ 1 1 1 0 - RETRIEVE REJECT ¦¦ ¦¦ 0 x 1 0 - - - - Call clearing messages: ¦¦ 0 1 0 1 - DISCONNECT ¦¦ 1 1 0 1 - RELEASE ¦¦ 1 0 1 0 - RELEASE COMPLETE ¦¦ ¦¦ 0 x 1 1 - - - - Miscellaneous messages: ¦¦ 1 0 0 1 - CONGESTION CONTROL ¦¦ 1 1 1 0 - NOTIFY ¦¦ 1 1 0 1 - STATUS ¦¦ 0 1 0 0 - STATUS ENQUIRY ¦¦ 0 1 0 1 - START DTMF ¦

¦ 0 0 0 1 - STOP DTMF ¦¦ 0 0 1 0 - STOP DTMF ACKNOWLEDGE ¦¦ 0 1 1 0 - START DTMF ACKNOWLEDGE ¦



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¦ 0 1 1 1 - START DTMF REJECT ¦¦ 1 0 1 0 - FACILITY ¦+---------------------------------------------------+

Message TypesGPRS Mobility Mgt. Table 10.4/GSM 04.08: Message types for GPRS mobility management

Bits8 7 6 5 4 3 2 10 0 - - - - - - Mobility management messages0 0 0 0 0 0 0 1 Attach request0 0 0 0 0 0 1 0 Attach accept0 0 0 0 0 0 1 1 Attach complete0 0 0 0 0 1 0 0 Attach reject0 0 0 0 0 1 0 1 Detach request0 0 0 0 0 1 1 0 Detach accept0 0 0 0 1 0 0 0 Routing area update request

0 0 0 0 1 0 0 1 Routing area update accept0 0 0 0 1 0 1 0 Routing area update complete0 0 0 0 1 0 1 1 Routing area update reject0 0 0 1 0 0 0 0 P-TMSI reallocation command0 0 0 1 0 0 0 1 P-TMSI reallocation complete0 0 0 1 0 0 1 0 Authentication and ciphering req0 0 0 1 0 0 1 1 Authentication and ciphering resp0 0 0 1 0 1 0 0 Authentication and ciphering rej0 0 0 1 0 1 0 1 Identity request0 0 0 1 0 1 1 0 Identity response

0 0 1 0 0 0 0 0 GMM status0 0 1 0 0 0 0 1 GMM informationTable 10.4a/GSM 04.08: Message types for GPRS session managementBits8 7 6 5 4 3 2 10 1 - - - - - - Session management messages0 1 0 0 0 0 0 1 Activate PDP context request0 1 0 0 0 0 1 0 Activate PDP context accept0 1 0 0 0 0 1 1 Activate PDP context reject0 1 0 0 0 1 0 0 Request PDP context activation

0 1 0 0 0 1 0 1 Request PDP context activation rej.0 1 0 0 0 1 1 0 Deactivate PDP context request0 1 0 0 0 1 1 1 Deactivate PDP context accept0 1 0 0 1 0 0 0 Modify PDP context request0 1 0 0 1 0 0 1 Modify PDP context accept0 1 0 1 0 0 0 0 Activate AA PDP context request0 1 0 1 0 0 0 1 Activate AA PDP context accept0 1 0 1 0 0 1 0 Activate AA PDP context reject0 1 0 1 0 0 1 1 Deactivate AA PDP context request0 1 0 1 0 1 0 0 Deactivate AA PDP context accept

0 1 0 1 0 1 0 1 SM Status



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GLOBAL SYSTEM FOR


R

Lesson 8.

Performance Analysis from

System Statistics



1 - 360

Voice Key Performance Indicators (KPIs)

• Dropped Call Rate

• Call Success Rate

• Handover Success Rate• Handover Failure Rate

• Blocking Statistics

• at Cell level

• at BSC resource level

• at Switch resource level

• at PSTN trunking level

• Uplink FER• AMR link and channel mode

adaptation

• GPRS/EDGE link adaptation

• Other events, anomalies

Performance Data from the system isthe most important single source of information on the overallperformance and quality of your wireless product.

System data has the advantage that itincludes the total picture – all callprocessing for all users, in all

locations throughout the system.System data is excellent for detecting

and tracking small changes inperformance and subtle problemsthat wouldn’t be noticed fromindividual user experiences.

System data is NOT very good atidentifying causes for some typesof field events; actual physical

diagnosis and drive-test data maybe required in these cases.



1 - 361

q

Data Key Performance Indicators (KPIs)

• Reliability

• from RLC ACKs,retransmission

• Throughput

• Throughput per Cell/Sector

• Throughput Reduction Factor

• timeslots/users• Delay (Latency)

• (E)GPRS Load

• TSL Utilization or DataErlangs

• TSL Capacity

• throughput per cell/dataerlangs

• TBF blocking

The GPRS and E-GPRS services usethe same network as GSM voiceservices, and suffer from all thesame RF and hardwarevulnerabilities of GSM voiceoperation.

However, the data services have their own unique processes and

performance indicators.In addition, the core network path is

different for data than for voice,introducing a whole new IPenvironment in which data-uniqueblocking and failure mechanismsmay exist.



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BER reported as RXQUAL



1 - 363

Total Blocked Call PercentageExample

Total Block Call Percentage

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%4.5%

5.0%

5.5%

6.0%

6.5%

7.0%

7.5%

8.0%

Date

P e r c e n

Blkd



1 - 364

Dropped Call Rate TrackingExample

Total Drop Call Percentage

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

4.5%

5.0%

Date

P e r c e n

%Drops



1 - 365

Total System Daily MOUExample

Daily Total System MOU

0

50000

100000

150000

200000

250000

300000

Date

M O

Daily Total SystemMOU



1 - 366



Exercise



1 - 3685/19/2004 368

In-Class Exercise

• Access your system’s available Performance Data

• Daily Totals by cell

• what are the busiest BTS, cells? how much traffic do they carry?

• do any cells have abnormally low traffic?

• what are the worst cells for Dropped Call Rate? why?

• what are the worst cells for Handoff failure rate? why? – is field measurement needed using drive-test equipment?

• Busy Hour Totals by cell

• what cells have the highest blocking?

• is this because of known steady overload, or a transient problem?• what solutions are possible for these blockings?

• what cells have the highest origination failure rate?

• what is the cause? what solutions are possible?

– is field measurement needed using drive-test equipment?



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GLOBAL SYSTEM FOR


R

Lesson 9.

Performance Analysis from

Mobile Field Data



1 - 370

Drive-Test Performance Indicators

• Downlink Bit Error Rate

• RXQual

• Downlink Frame ErasureRate

• Bit Error Probability

• Dropped Call Rate

• Receive Power • Transmit Power

• Timing Advance

• Signal strength of neighbors

Drive-test data is an essential part of the complete picture of systemperformance. Like system data, ithas its own unique advantages and

disadvantages:

Drive-test data provides a good viewof the forward link performance, butdoes not see the performance of

the reverse link as well as thesystem sees it.

Drive-test data is excellent for researching causes of specificproblems in the field. It is NOT

very good for noticing smallchanges in overall systemperformance.



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Andrew’s Invex3G Tool (formerly Grayson)

• In 1Q2001 Graysonintroduced its newInvex3G tool, with newfeatures• 100 MB ethernet connection

to PC• the eight card slots can hold

receivers or dual-phone

cards• there’s also room for two

internal PN scanners• Multiple Invex units can be

cascaded for multi-phoneload-test applications• Cards are field-swappable -

Users can reconfigure theunit in the field for different

tasks without factoryassistance



1 - 372

Agilent Drive-Test Tools

• Agilent offers Drive-Testtools• Serial interfaces for up to

four CDMA phones

• A very flexible digitalreceiver with severalmodes

• Spectrum Analyzer • Can scan entire 800 or

1900 mHz. Bands



1 - 373

Post-Processing Tools

Post-Processing toolsdisplay drive-test filesfor detailed analysis -Faster, more effectivethan studying dataplayback withcollection tools alone

• Actix Analyzer • Imports/analyzes data

from almost everybrand of drive-test

collection tool• Andrew (Grayson)

Interpreter • Imports/analyzes data

from Invex3G



1 - 374

Exercise



1 - 3755/19/2004 375

In-Class Exercise

• Using your post-processing tool, examine somedrive-tests in problem areas on your network

• Isolate a dropped call

• where and when did it occur?

• what was the serving cell at the time of the drop?

• was a better signal available at the time of the drop?• YES: why no handoff? trace triggers and algorithm steps

• NO: what solutions are possible to improve coverage?

• Isolate a failed call origination or termination• analyze to identify involved cells and root cause

• Isolate a failed handoff

• analyze to identify involved cells and root cause



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GLOBAL SYSTEM FOR


R

Lesson 10.

Common Problems and Solutions,

Front-Line Issues



1 - 377



More General Problemsfrom Class Discussions

• Notable RF trouble cases

• failure of one sector caused severe call performance problems

on another sector due to changed neighbor relationships andpresence of new signals

• long-distance sporadic coverage introduces call processingproblems due to time advance issues

• Administrative accidents• configuration problems solved by parameter changes, but pre-

solution parameters were accidentally restored from old backup

files during other activities• cells taken down for changes or repair and inadvertently left out

of service until noticed by others

• Cells unintentionally taken out of service due to on-siteactivity by contractors and other inattentive personnel



1 - 379

Area for Improvement:GSM Base Station Test

• BTS test procedures currently performed

• antenna sweeps

• power output measurements/adjustment• T-1/E-1 testing

• Additional BTS test procedures useful for finding causes

of poor RF performance• receiver sensitivity measurement

• transmitter phase error measurement (GSM/GPRS), error vector magnitude (E-GPRS, EDGE, WCDMA)

• portable BTS testers are available to perform thesemeasurements

• Alternative to additional BTS test procedures:

• trial transceiver and PA swapout as troubleshooting technique



1 - 380

Background on EVM and Phase Error

• Recommended reading:

• Agilent application note 1312, “Understanding

GSM/EDGE Transmitter and Receiver Measurementsfor Base Transceiver Stations and their Components



1 - 381

GSM/GPRS/E-GPRS Field BTS Test Equipment

for EVM and Phase Error Measurements

Agilent E7495B

Tektronix YBT250



1 - 382

GLOBAL SYSTEM FOR


R

Lesson 11.

Available Technology Improvements

SAIC, Synchronized Networks



1 - 383

Capacity-Enhancing TechniquesAlready in General Use or Available for Use

• Discontinuous Transmission (DTX)• Frequency Hopping

• Half-rate Codecs

• AMR dynamic rate adaptation

• Reuse Partitioning

• Dynamic Power Control

• GPRS/E-GPRS dynamic CS adaptation

• Together these techniques maximize available capacity,but they still fall short of allowing 1x frequency reuse



1 - 384

SAIC:Single Antenna Interference Cancellation

• SAIC – New DSP algorithms implemented in a handset’s

baseband digital processor • Phillips’ implementation: MIC Mono Interference Cancellation

• 20% capacity increase achieved in operator trials

• SAIC uses precise analysis of GSM training sequencesto characterize the channel

• interfering signals are cancelled out in the same way multipath iscancelled out in original GSM phones

• advanced version of the technique is expected to read thetraining sequence of co-channel interferors and removeindividual interferors very effectively

• SAIC works most effectively in synchronized networks



1 - 385

Variations in SAIC Implementation

• In synchronized networks: JD - Joint Detection• BTS frame and bursts are time-aligned closely

• this allows actual measurement and calculation of the specificinterferors’ actual waveforms, which can then be subtracted fromthe received total waveform

• 40-70% capacity gains are believed possible with JD in

synchronous networks

• In non-synchronized networks: BIC - Blind InterferenceCancellation

• BIC algorithms only estimate the difference between the desiredsignal and the total received envelope

• BIC does not provide as effective cancellation as JD

• BIC works best in a synchronized network, but works acceptably

well even in unsynchronized networks



1 - 386

Implications of SAIC Implementation

• SAIC algorithms are equally applicable to voiceand data applications, and should benefit GPRS

and E-GPRS as much as GSM voice service• The benefits of SAIC are entirely handset-

dependent – no change in the system is needed

• SAIC handsets demand less power from the BTS,reducing interference and working well in worseconditions

• If SAIC improves the downlink enough to causethe system to be uplink limited, an additionaltechnique Interference Rejection Combining

(IRC) can be applied to re-balance the links



1 - 387

1 388

Benefits of Synchronized Networks

• Entirely unrelated to SAIC, 10-20% gains in capacity alsoappear possible for networks using synchronized

frequency hopping• with synchronization, interference areas can be physically guided

away from heavily traveled routes

• One form of Synchronized Hopping is called DynamicFrequency and Channel Allocation, DFCA• Synchronization also speeds up the MAHO process, roughly

halving the time necessary to make handoff decisions

• Both DFCA and SAIC are being studied by the 3GPPstandards committees and additional messaging andfeatures are expected to be implemented in near-future

upcoming standards revisions



1 - 388

1 389

GLOBAL SYSTEM FOR


R

Bibliography



1 - 389

1 - 390

Bibliography – Performance Optimization

“GSM, GPRS and EDGE Performance”, 2nd. edition, edited

by Timo Halonen, Javier Romero and Juan Melero, 615pp. 2002 John Wiley, ISBN 0 470 84457 4, $110. Anexcellent reference on GSM/GPRS/EDGE optimization,operation and the basic internal technical processes and

algorithms of GSM/GPRS/EDGE call processing. One of the few books to present practical optimization details for GSM/GPRS/EDGE systems. Also includes details of migration to WCDMA and performance simulation results

for new 3G processes. Highly recommended!

Also available at same price in an ebook version for same-day download from www.amazon.com.



1 - 390

1 - 391

Bibliography, 3G Technologies

“3G Wireless Demystified” by Harte, Levine, and Kitka488pp. Paperback, 2001 McGraw Hill, ISSBN 0-07-136301-7 $50. For both

non-technical and technical readers. An excellent starting point for

understanding all the major technologies and the whole 3G movement.Comfortable plain-language explanations of all the 2G and 3G air interfaces, yet including very succinct, complete, and rigorously correcttechnical details. You will still want to read books at a deeper technicallevel in your chosen technology, and may sometimes turn to the

applicable standards for finer details, but this book will give you what youwon’t find elsewhere -- how everything relates in the big picture, andprobably everything you care to know about technologies other than your own.

“WCDMA: Towards IP Mobility and Mobile Internet” by Tero Ojanpera andRamjee Prasad. 476pp. 2001 Artech House, ISSBN 1-58053-180-6.$100. The most complete and definitive work on UMTS (excellentCDMA2000, too!). CDMA principles, Mobile Internet, RF Environment &Design, Air Interface, WCDMA FDD standard, WCDMA TDD,CDMA2000, Performance, Heirarchical Cell Structures, Implementation,Network Planning, Basic IP Principles, Network Architectures,Standardization, Future Directions. This is a MUST HAVE for a one-booklibrary!



1 391

1 - 392

More Bibliography, 3G Technologies

“The UMTS Network and Radio Access Technology” by Dr. JonathanP. Castro, 354 pp. 2001 John Wiley, ISBN 0 471 81375 3, $120.

An excellent, well-organized, and understandable exploration of

UMTS. Includes radio interface, channel explanations, linkbudgets, network architecture, service types, ip networkconsiderations, a masterful tour de force through the entire subjectarea. Very readable, too!

“WCDMA for UMTS” by Harri Holma and Antti Toskala, 322 pp. 2000Wiley, ISBN 0 471 72051 8, $60. Very good overall treatment of UMTS. Excellent introduction to 3G and summary of standardization activities, every level of UMTS/UTRA. Good

overview of CDMA-2000, too!

“The GSM Network - GPRS Evolution: One Step Towards UMTS”2nd Edition by Joachim Tisal, 227pp. paperback, 2001 Wiley,ISBN 0 471 49816 5, $60. Readable but not overwhelming

introduction to GSM in all its aspects (140pp), DECT (11pp),GPRS (6pp), UMTS (7pp), WAP (25pp), EDGE (10pp).



1 - 393

Bibliography, The IP Aspect of 3G

“Mobile IP: Design, Principles and Practices” by Charles E. Perkins, 275 pp.,200, 1998 Addison-Wesley, ISBN 0-201-63469-4. $60. Comprehensiveview of Mobile IP including home and foreign agents, advertisement,discovery, registration, datagrams, tunneling, encapsulation, routeoptimization, handoffs, firewalls, IPv6, DHCP. Tour-de-force of mobile IPtechniques.

“Mobile IP Technology for M-Business” by Mark Norris, 291 pp., 2001 ArtechHouse, ISSBN 1-58053-301-9. $67. GPRS overview and background,Mobile IP, Addressing, Routing, M-business, future prospects, IPv4, IPv6,Bluetooth & IrDA summaries.

“TCP/IP Illustrated, Volume 1, The Protocols” by W. Richard Stevens, 1994 Addison-Wesley, ISBN-0-201-63346-9, 576pp., $66. Comprehensive,definitive, and authoritative exposition of each protocol in modern

networking – IP, ARP, RARP, ICMP, IP, dynamic routing, UDP,Broadcasting & multicasting, IGMP, DNS, TFTP, BOOTP, TCP includingsections on connection establishment and termination, interactive dataflow, bulk data flow, timeout and retransmission, all its parameters; SNMP,Telnet, FTP, SMTP, NFS, and much, much more. Very highly

recommended.



1 - 394

Bibliography - General Wireless

“Mobile and Personal Communication Services and Systems” by RajPandya, 334 pp. 2000 IEEE Press, $60. IEEE order #PC5395, ISBN0-7803-4708-0. Good technical overview of AMPS, TACS< NMT,NTT, GSM, IS-136, PDC, IS-95, CT2, DECT, PACS, PHS, mobile

data, wireless LANs, mobile IP, WATM, IMT2000 initiatives byregion, global mobile satellite systems, UPT, numbers and identities,performance benchmarks.

“Wireless Telecom FAQs” by Clint Smith, 2001 McGraw Hill, ISBN 0-07-134102-1. Succint, lucid explanations of telecom terms in bothwireless and landline technologies. Includes cellular architecture,

AMPS, GSM, TDMA, iDEN, CDMA. Very thorough coverage; anexcellent reference for new technical people or anyone wishing for

clear explanations of wireless terms.

"Mobile Communications Engineering" 2nd. Edition by William C. Y. Lee.689 pp. McGraw Hill 1998 $65. ISBN 0-07-037103-2 Lee’slatest/greatest reference work on all of wireless; well done.



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Some Web Resources

www.gsmworld.comwww.3gpp.orgwww.3gamericas.com

www.trellisware.orgwww.wireless.iop.orgwww.semiconductors.phillips.com, search “SAIC”

www.tonex.com for technical training

http://www.gsmworld.com/

http://www.3gamericas.com/


http://www.wireless.iop.org/

http://www.semiconductors.phillips.com./news


http://www.tonex.com/

http://www.tonex.com/


http://www.wireless.iop.org/

http://www.trellisware.org/


http://www.gsmworld.com/



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Documents

Gsm Opt Pres