New Standards for Wireless LANs - Module 1 Standards for Wireless LANs Summer Term 2014 Dr.-Ing. ... Mobile and Wireless Communications Basics ... LF = Low Frequency SHF = Super High

New Standards forWireless LANs

Summer Term 2014

Dr.-Ing. Andreas KönsgenDr.-Ing. Koojana Kuladinithi

Communication Networks TZI – University of Bremen

TZI – FB 1 – Kommunikationsnetze Andreas Könsgen – Summer Term 2014

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Organisational IssuesHow to reach us? • Andreas Könsgen

– Room S2310

– [email protected]

– Tel: 0421 218 62380

• Koojana Kuladinithi

– Room N2240

– [email protected]

– Tel: 0421 218 62382

mailto:[email protected]

mailto:[email protected]


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Organisational IssuesExam: • Oral Exam (30min) after the end of the termQuestions, Critics etc.: • always welcomeExercises: • After the lecture, N 1250, 12:00 to 12:45• deepen understanding, open discussion, some

labs/demos/simulation• Slides available on www.comnets.uni-bremen.de

under “Education” “Lectures & Tutorials”→ “New Standards for Wireless LANs”→

http://www.comnets.uni-bremen.de/


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Acknowledgement This lecture is based on material byProf. Dr.-Ing. Andreas Timm-GielInstitute of Communication NetworksTechnical University of Hamburg-HarburgGermany


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Objective of the Lecture

● Understand wireless technologies: how do they work?

● Give an overview on existing and emerging wireless standards

● Give an idea what is coming up in the future in Wireless Communications


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Course Overview (1)

Overview:● History of Wireless Communication● Mobile and Wireless Communications Basics

― radio propagation― modulation and coding― multiple access, duplex schemes, access protocols

● IEEE 802.11(Wireless LAN) — Overview 802.11 a, b, g, h... — Physical Layer — MAC Layer — Security


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Course Overview (2)● IEEE 802.22 – Wireless Regional Area Network (WRAN)● IEEE 802.15 – Wireless Personal Area Network (WPAN):

Bluetooth and Zigbee ● Sensor Networks (Dr. Koojana Kuladinithi)


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Literature

• Jochen Schiller: Mobile Communications, Pearson/Addison-Wesley, 2003

• James F. Kurose, Keith W. Ross, Computer Networking – A top-Down Approach, 4th Edition, 2008, Pearson International Edition

• Matthew Gast: 802.11 Wireless Networks, O'Reilly, 2005• Bernhard H. Walke – Mobile Radio Networks, J. Wiley & Sons, 1999• Brent Miller, Chatschik Bisdikian: Bluetooth Revealed, Prentice Hall

2001• Holger Karl, Andreas Willig, Protocols and Architectures for Wireless

Sensor Networks, John Wiley and Sons, 2007• Zach Shelby, Carsten Bormann, 6LoWPAN: The Wireless Embedded

Internet, John Wiley and Sons, 2009• IEEE Standardisation documents (link on website)

Chapter 1: First Mobile and Wireless Communication Systems


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Definition of Wireless and Mobile

• Wireless– Communication without wires, can be mobile

and fixed• Mobile

– Portable devices (laptops, notebooks etc.) connected at different location to wired networks (e.g. LAN or PSTN)

– Portable devices (phones, notebooks, PDAs etc.) connected to wireless networks (UMTS, GSM, WLAN….)


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Early History of Wireless Communications• In history first light and sound have been used to transmit

messages over wide distances

Pics from http://www.connected-earth.com


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Transmission of Electromagnetic Waves

• 1831: Faraday demonstrates magnetic induction

• 1865: Maxwell theory of electromagnetic fields, wave equation

• 1876 Patent on phone, Alexander Graham Bell (Antonio Meucci 1849)

• 1888: H. Hertz: demonstratesthe wave character of electrical transmission through space

• Nikola Tesla extends the transmission range

Pics from www.wikipedia.org


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History of Wireless Communication• 1895 Guglielmo Marconi

– first demonstration of wireless telegraphy (digital!)

– 1901 transatlantic transmission– long wave transmission, high

transmission power necessary (> 200kW)

• 1907 Commercial transatlantic connections– huge base stations

(30 100m high antennas)• 1915 Wireless voice transmission New York – San Francisco• 1920 Discovery of short waves by Marconi

– reflection at the ionosphere– smaller sender and receiver, possible due to the invention of the vacuum

tube (1906, Lee DeForest and Robert von Lieben)

Photo from www.wikipedia.org


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Beginning of Mobile Communications• 1911 mobile transmitter on Zeppelin• 1926 train (Hamburg – Berlin)• 1927 first commercial car radio (receive only)• First Mobile Communication Systems started

in the 40s in the US and in the 50s in Europe.

CONCEPTS:• Large Areas per Transmitter• „Mobiles“ large, high power

consumption• Systems low capacity,

interference-prone• Expensive !!!

1924


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Today's Wireless Communication (1)1984 CT-1 standard (Europe) for cordless telephones

– In Germany selling no longer permitted since 2009

1992 DECT– Digital European Cordless Telephone (today: Digital Enhanced

Cordless Telecommunications)– 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s

data transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries

1996 HiperLAN (High Performance Radio Local Area Network)– ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s– recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as

wireless ATM-networks (up to 155Mbit/s)– Did not enter market


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Today's Wireless Communications (2)

In the 1990s: many proprietary products for wireless networks1997 Wireless LAN – IEEE standard 802.11

2.4-2.5 GHz and infrared, 2Mbit/s1999 IEEE 802.11b, 2.4 GHz, 11Mbit/s1999 IEEE 802.11a, 5 GHz, 54 Mbit/s1999/2001 Bluetooth/IEEE 802.15.1 for piconets, 2.4 GHz, < 1Mbit/s2003 IEEE 802.11g, 2.4 GHz, 54 Mbit/s2003/2004 Zigbee/IEEE 802.15.4 for sensor networks2009 IEEE 802.11n, 2.4 and 5 GHz, 600 Mbit/s2012 IEEE 802.11ad, 60 GHz, 7 Gbit/s

Chapter 2 – Mobile Communications

Definitions & Basics


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Chapter 2 - Overview• Part 1 (today)

– Digital Transmission System– Frequencies, Spectrum Allocation– Radio Propagation and Radio Channels

• Part 2 (next week)– Modulation, Coding, Error Correction

• Part 3 (in 2 weeks)– Capacity limits– Duplexing schemes– Media Access Protocols


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Acknowledgement• Pictures and some slides of this chapter are taken

from:– B. Walke, P. Seidenberg, M. P. Althof, UMTS:

the fundamentals, Wiley – Schiller: Mobilkommunikation (Mobile

Communications), Pearson Studium/Addison Wesley, 2003/2002

– David/Benkner: Digitale Mobilfunksysteme, Teubner 1996

– Proakis/Saleh, Grundlagen der Kommunikationstechnik, Pearson Studium 2004


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Simple Reference Model

Application

Transport

Network

Data Link

Physical

Wired Medium

Data Link

Physical

Application

Transport

Network

Data Link

Physical

Data Link

Physical

Network Network

Radio


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– Web, mail– service location– multimedia– adaptive applications

congestion and flow control– quality of service

– addressing, routing, device location

– hand-over

– media access– multiplexing– media access control

– modulation– interference cancellation– compensation of fading– frequency channel selection

• Application layer

• Transport layer• Network layer

• Data link layer

• Physical layer

More Detailed Reference Model


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– Web, mail– service location– multimedia– adaptive applications

congestion and flow control– quality of service

– addressing, routing, device location

– hand-over

– media access– multiplexing– media access control

– modulation– interference cancellation– compensation of fading– frequency channel selection

• Application layer

• Transport layer• Network layer

• Data link layer

• Physical layer

More Detailed Reference Model

Authentication and encryption

in the framework of this lecture here

here

here


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Structure of Digital Transmission System

Digital Source

Sink


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Structure of Digital Transmission System

Digital Source

Sink


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Frequencies for Communication

VLF = Very Low Frequency UHF = Ultra High FrequencyLF = Low Frequency SHF = Super High FrequencyMF = Medium Frequency EHF = Extra High FrequencyHF = High Frequency UV = Ultraviolet LightVHF = Very High Frequency

Frequency and wave length:

λ = c /f

With wave length λ, speed of light c ≈ 3108 m/s, frequency f

1000 km300 Hz

10 km30 kHz

100 m3 MHz

1 m300 MHz

10 mm30 GHz

100 μm3 THz

1 μm300 THz

visible lightVLF LF MF HF VHF UHF SHF EHF infrared UV

optical transmissioncoax cabletwisted pair


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Frequencies for Mobile Communication

• VHF-/UHF-ranges for mobile radio– simple, small antenna for cars– deterministic propagation characteristics, reliable connections

• SHF and higher for directed radio links, satellite communication– small antenna, focusing– large bandwidth available

• Wireless LANs use frequencies in UHF to SHF spectrum– some systems planned up to EHF– limitations due to absorption by water and oxygen molecules

(resonance frequencies)• weather dependent fading, signal loss caused by heavy rainfall

etc.


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Frequency Regulations• Frequency assignments are managed by the International

Telecommunication Union –Radiocommuncation Sector (ITU-R)– holds auctions for new frequencies, manages frequency bands

worldwide (WRC, World Radio Conferences)• National regulation authorities

– Germany: Bundesnetzagentur (Federal Network Agency)– USA: Federal Communications Commission (FCC)


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Important Frequency Assignments Europe USA Japan

Cellular Phones

GSM 450-457, 479-486/460-467,489-496, 890-915/935-960, 1710-1785/1805-1880 UMTS (FDD) 1920-1980, 2110-2190 UMTS (TDD) 1900-1920, 2020-2025

AMPS, TDMA, CDMA 824-849, 869-894 TDMA, CDMA, GSM 1850-1910, 1930-1990

PDC 810-826, 940-956, 1429-1465, 1477-1513

Cordless Phones

CT1+ 885-887, 930-932 CT2 864-868 DECT 1880-1900

PACS 1850-1910, 1930-1990 PACS-UB 1910-1930

PHS 1895-1918 JCT 254-380

Wireless LANs

IEEE 802.11 2400-2483 HIPERLAN 2 5150-5350, 5470-5725

902-928 IEEE 802.11 2400-2483 5150-5350, 5725-5825

IEEE 802.11 2471-2497 5150-5250

Others RF-Control 27, 128, 418, 433, 868

RF-Control 315, 915

RF-Control 426, 868


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ISM Bands: General factsIndustrial, scientific, and medical (ISM) radio bands• originally reserved internationally by ITU-R for non-commercial

use of RF electromagnetic fields for industrial, scientific and medical purposes

• Individual countries' use may differ due to variations in national radio regulations

• In recent years permission for license-free short-range communication applications such as walkie-talkies, remote controls, Wireless LANs, Bluetooth

Source: ITU, FCC


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Some typical ISM bands

ISM Bands: Assignments

Frequency Comment

13.553-13.567 MHz

26.957-27.28 MHz

40.66-40.70 MHz

433-434 MHz Europe

900-928 MHz America

2.4-2.5 GHz WLAN/WPAN

5.725-5.875 GHz WLAN

24-24.25 GHz


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Signal Propagation

reflection scattering diffractionrefraction

● Propagation in free space always like light (straight line)● Receiving power in free space proportional to 1/d²

(d = distance between sender and receiver)● Sources of distortion

● Reflection/refraction – bounce of a surface; enter material● Scattering – multiple reflections at rough surfaces● Diffraction – start “new wave” from a sharp edge● Doppler fading – shift in frequencies (loss of center)● Attenuation – energy is distributed to larger areas with increasing

distance


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Signal Propagation

reflection scattering diffractionrefraction

● Propagation in free space always like light (straight line)● Receiving power in free space proportional to 1/d²

(d = distance between sender and receiver)● Sources of distortion

● Reflection/refraction – bounce of a surface; enter material● Scattering – multiple reflections at rough surfaces● Diffraction – start “new wave” from a sharp edge● Doppler fading – shift in frequencies (loss of center)● Attenuation – energy is distributed to larger areas with increasing

distance


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Attenuation results in path loss• Effect of attenuation: received signal strength is a function

of the distance d between sender and transmitter• Captured by Frii's free-space equation

– Describes signal strength at distance d relative to some reference distance d0 < d for which strength is known

– d0 is far-field distance, depends on antenna technology


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Pathloss in Free Space• Received power depends on frequency, transmitted

power, antenna gains, distance and constants only

• EIRP: effective isotropic radiated power:– EIRP = PTGT

RTTR GGd

PP2

4

=

πλ

56.147log20log20log10log10)(

log10)(

+−−+=

=

dfGGdBL

P

PdBL

RTF

T

RF [Hz]Frequency :

[m] Distance:

[m] Wavelength:

r/ReceiverTransmitteGain Antenna:

Powerreceived/dtransmitte:

/

/

f

d

G

P

RT

RT

λ


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Attenuation of different frequencies

● Attenuation depends on the used frequency

● Can result in a frequency-selective channel

― If bandwidth spans frequency ranges with different attenuation properties

Attenuation

moderate rain

molecular dispersion

fog / clouds

strong rain

frequency


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Attenuation in Atmosphere

David Benkner:Digitale Mobilfunksysteme

Atm

osph

eric

att

e nua

tion

(dB/

km)

10

10 20 40 60 80 100 300 f (GHz)

1

0.01

0.1

oxygen

vapor


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• Signal can take many different paths between sender and receiver due to reflection, scattering, diffraction

• Time dispersion: signal is dispersed over time interference with “neighbor” symbols, Inter Symbol Interference (ISI)• The signal reaches a receiver directly and phase shifted distorted signal depending on the phases of the different parts

Multipath Propagation

signal at sendersignal at receiver

LOS pulsesmultipathpulses


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Channel characteristics change over time and location – signal paths change– different delay variations of different signal parts– different phases of signal parts quick changes in the power received (short term/fast fading)

Additional changes in– distance to sender– obstacles further away

slow changes in the average power received (long term/slow fading)

All fading effects are frequency-dependent short term fading

long termfading

t

power

Multipath Propagation


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Radio Channel Characteristics• Superposition of

numerous direct and reflected multipath components with different attenuation and phasing

• time variant• Differentiation of fast

and slow fading

A

B

• Fast fading due to superposition of different phases• Slow fading is due to the change of propagation environment• Both fading types depend on the frequency


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Real World Example: Propagation


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Real World Example: Time variation

time (s)

Sig

nal

amplit

ude

Frequency (GHz)0

0.5

15.18

5.22

Carrier frequency: 5.2 GHzChannel bandwidth: 40 MHz


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Real World Example: Path Loss

• Received power of a sender is decreasing with the distance between sender and receiver

• Depends on Frequency

• Many models, e.g. Okumura-Hata Walfish-Ikegami UMTS 30.03

• Mostly shown in dB (attenuation)

Distance [m]

Path

los s

[dB]

0 200 400 600 800 1000

40

60 8

0 1

00 1

20 1

40 1

60

UMTS 30.03 VehicularFrom Walke: UMTS - the fundamentals


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Noise and Interference• So far: only a single transmitter assumed

– Only disturbance: self-interference of a signal with multi-path “copies” of itself

• In reality, two further disturbances– Noise – due to effects in receiver electronics, depends on

temperature• Typical model: an additive Gaussian variable, mean 0, no

correlation in time

– Interference from third parties• Co-channel interference: another sender uses the same spectrum• Adjacent-channel interference: another sender uses some other

part of the radio spectrum, but receiver filters are not good enough to fully suppress it

• Effect: Received signal is distorted by channel, corrupted by noise and interference


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Channel models• Simplest model: assume transmission power and

attenuation are constant, noise an uncorrelated Gaussian variable – Additive White Gaussian Noise model

• Situation with no line-of-sight path, but many indirect paths: Amplitude of resulting signal has a Rayleigh distribution (Rayleigh fading)

• One dominant line-of-sight plus many indirect paths: Signal has a Rice distribution (Rice fading)

• Raytracing model– Given location of transmitters, receivers, obstacles– Calculate current SINR for each transmission path

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New Standards for Wireless LANs - Module 1 Standards for Wireless LANs Summer Term 2014 Dr.-Ing. ... Mobile and Wireless Communications Basics ... LF = Low Frequency SHF = Super High