Advance Computer Networks

Wireless Communication

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Question: Why do we need a new technology when we have such a developed public telephone network.

Answer: Mobility.

Confinement Versus Freedom

Why Wireless Communication?

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Challenges of Mobility

Challenges of using a radio channel: The use of radio channels necessitates methods of sharing them – channel access. (FDMA, TDMA, CDMA)

The wireless channel – poses a more challenging problem than with wires.

Bandwidth: it is possible to add wires but not bandwidth. So it is important to develop technologies that provide for spectrum reuse.

Privacy and security - a more difficult issue than with wired phone.

Others: low energy (battery), hand off, roaming, etc.

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Cellular concept emerges in early 1970s.

Cellular technology allows frequency-reuse. With this we need to have Handoff (handover)

In 1G we had analog voice but Control Link was digital

First Generation Systems

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Examples of First Generation Cellular Systems (FDMA

based)1) Advanced Mobile Phone System (AMPS)

2) Narrowband AMPS (NAMPS)

3) Nordic Mobile Telephone (NAMPS)

4) European Total Access System (ETACS)

5) Japanese TACS (JTACS)

6) Nippon Telephone and Telegram (NTT)

7) Cordless Telephone 2 (CT2)

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First Generation – AMPS and European Total Access Cellular

System (ETACS) Parameter AMPS ETACS

Multiple Access FDMA FDMA

Duplexing FDD FDD

Channel Bandwidth 30kHz 25kHz

Traffic Channel per RF Channel 1 1

Reverse Channel Frequency 824 – 849 MHz 890 – 915 MHz

Forward Channel Frequency 869 – 894 MHz 935 – 960 MHz

Voice Modulation FM FM

Peak Deviation: Voice Channels

Control/Wideband Data

± 12 kHz

± 8 kHz

± 10 kHz

± 6.4 kHz

Channel Coding for Data Transmission

BCH(40,28) on FC/BCH(48,36) on RC

BCH(40,28) on FC/BCH(48,36) on RC

Data Rate on Control channel 10kbps 8kbps

Spectral Efficiency 0.33 bps/Hz 0.33 bps/Hz

Number of Channels 832 1000

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Digital Communication: Transmitter

Analog input

1 0 1 0 0 1 0Analog to

Digital Converter Bits Encoded

Bits

Source Encode

1 0 1 1 0

EncryptEncrypted

Data

0 1 1 0 1

Bit to Sym. & Pulse

Modulate

Pulse modulated waveform

Digital Bandpass waveform

Bandpass modulate

Multiplex

0 1 1 0 1

0 1 0 1 0

1 0 1 0 1

From Other Channels

Multiplexed Data

Channel Encode

Channel Encoded

Data

1 0 0 1 1 0 1

Scrambler

Scrambled data

1 0 0 0 1

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Equalizer, Timing

and Sym. to Bits

Bits

Digital Communication: Receiver

Decrypted Bits

1 0 1 1 0 DecryptAnalog

output

D/A

De-modulate

Digital Baseband waveform

Digital Bandpass waveform

Channel Decode

Channel Decoded

Data

0 1 1 0 1

Source Decoded

Bits

1 0 1 0 0 1 0

Source Decode

De- Multiplex

To other Channels

De- multiplexe

d Bits

Descrambled Bits 1 0 0 0 1

De-scramble

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Performance Metrics

• Analog Communication Systems– Metric is fidelity: want m(t)m(t)– SNR typically used as performance metric

• Digital Communication Systems– Metrics are data rate (R bps) and probability of bit

error (Pb=p(bb))

– Symbols already known at the receiver– Without noise/distortion/sync. problem, we will

never make bit errors

^

^

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Second Generation Cellular Systems (TDMA and CDMA

based)1) GSM (Global System for Mobile)

2) PDC (Personal Digital Cellular)

3) PHS (Personal Handy System)

4) DAMPS (Digital AMPS)

5) CDMAone (IS-95)

6) Personal Communication System (PCS)-1900 (IS-136)

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Second Generation – IS136/CDMA/GSM

Parameter IS-136 IS-95 GSM

Multiple Access TDMA/FDD CDMA/FDD TDMA/FDD

Modulation π/4 DQPSK BPSK GMSK

Channel Bandwidth 30 kHz 1.25 MHz 200 kHz

Reverse Channel Frequency Band

824 – 849 MHz

1.85 – 1.99 GHz

824 – 849 MHz

1.85 – 1.99 GHz

890 – 915 MHz

1.85 – 1.99 GHz

Forward Channel Frequency Band

869 – 894 MHz

1.85 – 1.99 GHz

869 – 894 MHz

1.85 – 1.99 GHz

935 – 960 MHz

1.85 – 1.99 GHz

Channel Data Rate 48.6 kbps 1.2288 Mcps 270.83 kbps

Carrier Spacing 30 kHz 1.25 MHz 200 KHz

Speech Coding VSELP(Vector Sum excited linear prediction)

CELP RPE-LTP

Users per carrier 3 variable 8

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Second Generation –Benefits

Higher Capacity, Mobility

Easy frequency planning

-Dynamic Channel Allocation (GSM)

-Single Frequency Band (CDMA)

Better performance

-Low dropped call rate

-Faster switching

MAHO (Soft Handoff in CDMA)

Error correction

-FEC

-Interleaving

Value-added Services

-SMS

-Limited data transmission capabilities

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Second Generation - Success

Four operational digital cellular technology: Dec’ 2000Source: EMC Database

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Evolution to 2.5G Mobile Radio Networks (data-centric)

1. High speed circuit switched data (HSCSD): GSM

2. GPRS for 2.5G GSM and IS-136

3. EDGE for 2.5G GSM and IS-136

4. IS95B and CDMA2000 1x

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General Packet Radio Service (GPRS)

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Enhanced Data for Global Evolution (EDGE) • EDGE uses 8PSK as opposed to GMSK as a modulation scheme. Essentially squeezing in more data in the available bandwidth.• Data rates closer to 3G. Intended to be used by operators who don’t have a 3G license but wish to deliver higher data rates.• Requires all the radio cards in the existing GSM/GPRS network to be replaced.• Expensive solution to obtain similar data rates to the lowest expected 3G performance.• Raw data rate using one GSM carrier can go up to 547.2 kbps (practical 384 kbps)

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IS 95 B and CDMA2000 1x• The 2.5 G Evolution of IS95 A.• Uses extra codes for increased data rates• Data Rates upto 115.2 kbps• Easy upgrade to CDMA2000• Intermediate steps to 3G:

– CDMA2000 1x, Release 0: Data rates of up to 153.6kbps

– CDMA2000 1x, Release A: Data rates of up to 307.2 kbps

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• The International Telecommunications Union (ITU) defined the key requirements for International Mobile Telecommunications 2000 (IMT-2000) services.• These requirements were that the system should support data rates of:

• 2 Mbps in fixed or in-building environments• 384 kbps in pedestrian or urban environments•144 kbps in wide area mobile environments

• IMT-2000 is more commonly known as… 3G.

IMT-2000 (3G)

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Europe

2000 2001 2002 2003

Japan

America

PDC

GSM

AMPS/D-AMPS

IS-95A IS-95B

D-AMPS

GPRS EDGE

W-CDMA

HSCSD

CDMA2000

2G System

3G System

Easy upgradeUpgrade requiring new modulationUpgrade requiring entire new radio system

Migration Path

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C

B D

F

G E

A

C

B D

F

G E

A

C

B D

F

G E

A

Universal Frequency ReuseUniversal Frequency Reuse

A

A A

A

A A

A

A

A A

A

A A

A

A

A A

A

A A

A

FrequencyReuse Factor = 7 for AMPS

FrequencyReuse Factor = 7 for AMPS

CC

BB DD

EEAA

FFGG

AA

CDMA UniversalFrequency ReuseCDMA Universal

Frequency Reuse

Frequency Reuse Factor = 4 for TDMA systems

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CDMA2000 • Evolution of 1x RTT concept

• High data rate service which is compatible to IS 95

• 1x EVDO: Evolution of the 1x system data optimized• As in 1x-RTT technology utilizes 1.25 MHz

of band• System requires a separate carrier for the

data• 2.4 Mbps forward link, 153.3 kbps reverse

link• Rev. A: Support for VoIP: 3.1 Mbps FL, 1.8

Mbps RL• New revisions: B and other enhancement

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3G W-CDMA (UMTS)

• High-Speed Downlink Packet Access (HSDPA)• HSUPA and HSPA, HSPA+ Phase 1 and 2

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TD-SCDMA

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Timeline: For UMTS and CDMA2000

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5) Wireless Local Loop

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WIRELESS LOCAL LOOP• Definition: A telephone system where subscribers are

connected to the public switched telephone network using radio signals rather than copper wire for part or all of the communication between the subscriber and the switch.

• Countries with available elaborate telecommunication infrastructure used it to increase competition

• Countries without available elaborate telecommunication infrastructure use it for efficient and feasible method of broadband delivery

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Algeria, Azerbaijan, Bermuda, Brazil, Cambodia, China, Columbia, Dem. Rep. of Congo,Dominican Republic, Egypt, Ethiopia, Fiji, Guatemala, Haiti, India, IndonesiaKenya, Kuwait, Laos, Malaysia, Mauritius, Mexico, Moldova, Nepal, Nigeria, Pakistan, Poland, Puerto Rico, Romania, Russia, Uganda, Ukraine,Vietnam,Yemen

Some Countries using CDMA for WLL

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6) Other Systems

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WIRELESS LOCAL AREA NETWORKS (WLANs)

• Network- group of two or more computer systems linked together. Local area networks are usually confined to one building.

• Wireless Fidelity (Wi-Fi)– 802.11a (DS-SS) became standard (2Mpbs).– 802.11b is common (11Mbps) 2.4 GHz. Also has the

FH-SS extension.– 802.11g also uses the 2.4 GHz band. Data Rate: 54

Mbps. Uses OFDM– 802.11n: Uses OFDM and MIMO

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Other Standards • Long Term Evolution

– Initial Deployment in the 700 MHz Frequency Band– Data Rate of tens of Mbps– Uses OFDM and MIMO

• Worldwide Interoperability for Microwave Access (WiMax)– Operate in the 2.5, 3.5, or 5.8 GHz bands.– Data Rates of tens of Mbps. – Versions: IEEE 802.16d and e with amendments like: 802.16f, g,

h, i, j and k– Uses OFDM and MIMO

• Variants of both are candidates for IMT-Advanced (4G)

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7) IMT-Advanced(4G)

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IMT-Advanced (4G)• The min requirements for peak spectral efficiencies

– Downlink peak spectral efficiency is 15 bit/s/Hz– Uplink peak spectral efficiency is 6.75 bit/s/Hz.

• Six Proposals are under review

• Some are based on WiMax 802.16m and some on LTE

• Both uses OFDM and MIMO

• Final Decision by October 2010

Steps in radio interface development process:

Step1 and 2

No.1 No.2 No.3 No.4 No.5 No.6 No.7 No.8 No.9

Step 3(0)

(1)

(20 months)

Step 4

(8 months)

(16 months) (2)Steps 5,6 and 7

(3)Steps 8

(4)(12 months)

(20 months)

WP 5D meetings

Step 1: Issuance of the circular letterStep 2: Development of candidate RITs and SRITsStep 3: Submission/Reception of the RIT and SRIT proposals

and acknowledgement of receiptStep 4: Evaluation of candidate RITs and SRITs

by evaluation groups

Step 5: Review and coordination of outside evaluation activitiesStep 6: Review to assess compliance with minimum requirementsStep 7: Consideration of evaluation results, consensus building

and decision Step 8: Development of radio interface Recommendation(s)

Critical milestones in radio interface development process:(0): Issue an invitation to propose RITs March 2008(1): ITU proposed cut off for submission October 2009

of candidate RIT and SRIT proposals

(2): Cut off for evaluation report to ITU June 2010(3): WP 5D decides framework and key October 2010

characteristics of IMT-Advanced RITs and SRITs(4): WP 5D completes development of radio February 2011

interface specification Recommendations

2008 2009 2010No.10

2011

IMT-Advanced A2-01

IMT-Advanced (4G): Time-Line

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Cellular Technology Roadmap

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8) Wireless Operators in Pakistan

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Cellular Operators in Pakistan1) Mobilink

Technology: GSM, GPRS, EDGE (WiMAx deployment: Infinity)2) Ufone

Technology: GSM, GPRS, EDGE3) China Mobile Pakistan (CMPak, Paktel): Zong

Technology: EGSM, GPRS, EDGE4) Warid

Technology: GSM, GPRS, EDGE (Associated company Wateen: WiMax)

5) TelenorTechnology: GSM, GPRS, EDGE

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WLL Operators1) V-PTCLWirless

Technology: CDMA2000, EVDO Rev. A2) TeleCard

Technology: CDMA20003) WorldCall

Technology: CDMA2000, EVDO Rev. A4) Diallog (negotiation going on with World Call)

Technology: CDMA2000 1x, EVDO 5) SCO

Technology: CDMA2000 1x, EVDO (?)

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Latest News (Pakistan)• Auction of 3G spectrum????????• Only Mobile operators are eligible to bid ??• Three licenses to be issued??• Possible (UMTS FDD Band I):

– 1920 to 1980 MHz (Up link)– 2110 to 2170 MHz (Down link)

• WiMax has been deployed

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Why are new services/mobile content required? Tough competition Low ARPU No differentiation in Service Offerings

Problem: What services will differentiate one operator from the other? How would these services be delivered?

Issues with widespread usage of wireless data

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Technologies

2G: Mainly Voice & SMS

2.5G: Limited Data Capability

3G and Beyond: High Speed Data coupled with data centric applications and services

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Services Evolution With Enriched User Experiences

Wallpaper

Location BasedServices2D Gaming

Ringtones

Mobile TV

3D Gaming

Music & Video on Demand

Services Evolution

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meeting go?

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