WIRELESS AND MOBILE COMMUNICATION

A.M.BALAMURUGAN

Syllabus Overview

Introduction to Wireless Systems and Cellular Concepts

Signal Propagation through the channel

Advanced processing techniques Signal enhancement techniques Wireless Standards

Wireless networks vs wired networks

Media Reliability (Bit Error Probability)

System Capacity

Mobility

Wired Wireless

~ 10-9 10-2 ~ 10-6

Mbit/s, 20 Mbit/sGbit/s, (2 Mbit/s) Tbit /s (expensive)

Almost Variousstationary mobility

• Negative: unreliable, low capacity, expensive.• Positive: wireless, mobility.

Electromagnetic spectrum

-7 -6 -2 -1 0 3 6 10 11-8 -4

Gamma rays

Cosmic rays

X-rays

Ultraviolet Visible lights

Infrared Micro-waves

Radio-waves

LongElectricalOscillations

(wavelength in 10x micrometer)

- Robert J. Hoss et al, “Fiber Optics”, ISBN 0133212416, Prentice-Hall, 1993, pp24.

 

Communication Frequencies

10 km30 kHz

100 m3 MHz

1 m300 MHz

10 mm30 GHz

100 m3 THz

1 m300 THz

visible lightVLF

LF MF

HF VHF UHF SHF EHF infrared UV

optical transmissioncoax cabletwisted pair

Frequency and wave length:

= c/f

wave length , speed of light c 3x108m/s, frequency f

 

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.

Media used for wireless networks

• The range that can be used by WN is only a fraction of the electromagnetic spectrum: Infrared, Microwaves and Radio-waves.

• Wireless network is a sort of shared-media network. The wireless terminals belonging to the same network will share one wireless media (i.e., air interface). • Wireless media/spectra is a scare resource.

Multiple access schemes

How to allow many wireless terminals to share afinite amount of radio spectrum simultaneously?

Fixed Access

Random Access

- T.S. Rappaport, “Wireless communications, principles & practice”, ISBN 0133755363, Prentice-Hall, 1996, pp395-438.

Fixed access schemes

• Time Division Multiple Access (TDMA): Radio spectrum is divided into time slots, and each slot is used by only one user (e.g., GSM, JDC).

• Frequency Division Multiple Access (FDMA): Radio spectrum is divided into sub-frequency band (channel), and each channel is used by only one user (e.g., CT2, DECT).

• Code Division Multiple Access (CDMA): Part/entire spectrum/time alloted to user differentiated by appropriate coding ( e.g. 3rd generation of wireless networks).

- T.S. Rappaport, “Wireless communications, principles & practice”, ISBN 0133755363, Prentice-Hall, 1996, pp395-438.

Multi-Access Radio Techniques

Courtesy of Petri Possi, UMTS World

Courtesy of Suresh Goyal & Rich Howard

CDMA

Courtesy of Suresh Goyal & Rich Howard

Courtesy of Suresh Goyal & Rich Howard

Courtesy of Suresh Goyal & Rich Howard

Random access schemes

1. Contention-based: Aloha, CSMA.2. Controlled-based:

- Central control (Polling);- Distributed control (Token-ring).

• Aspects: application requirements, cost and feasible network topology etc.

• Performance: resource utilization, throughput, fairness and network robustness etc.

Duplexing technologies

Forward channel (downlink)

Reverse channel (uplink)Base-station Mobile

Frequency division duplex (FDD): use two distinct band of frequencies for every user expensive duplexers Time division duplex (TDD): use two different time slots for every user not true full duplex- T.S. Rappaport, “Wireless communications, principles & practice”, ISBN 0133755363, Prentice-Hall, 1996, pp395-396.

Duplexing enables mobile users to send and receive (talk / listen) “simultaneously”:

Wireless Communication System

- Definitions

Base Station, Mobile Station Control / Traffic channels Mobile Switching Center Paging Roamer Handoff

First Mobile Radio Telephone1924

Courtesy of Rich Howard

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[R. Katz, "Does Wireless Data Have a Future?", Plenary Talk, INFOCOM '96]

Seamless Multimedia Networks with Mobility and Freedom from Tethers

WIRELESS DATA VISION

TAXI

Region

Campus

City

In-Building

laptops, PDAs

IMT-2000 Vision IncludesLAN, WAN and Satellite Services

Satellite

MacrocellMicrocell

UrbanIn-Building

Picocell

Global

Suburban

Basic TerminalPDA Terminal

Audio/Visual Terminal

Cellular networks: Development

First generation: Based on analog technology, uses a single base station to communicate with a single portable terminal. (e.g., Advance Mobile Phone Services - AMPS)

Second generation: Based on digital modulation and advanced call processing capabilities . (e.g., Global System for Mobile - GSM and Cordless Telephone - CT2).

Third generation: To provide a single set of standards that can meet a wide range of wireless applications and provide universal access

throughout the world. (e.g., WCDMA, CDMA-2000, etc.)

- T.S. Rappaport, “Wireless communications, principles & practice”, ISBN 0133755363, Prentice-Hall, 1996, pp445-449.

First Generation Advanced Mobile Phone Service (AMPS)

US trials 1978; deployed in Japan (’79) & US (’83) 800 MHz band — two 20 MHz bands TIA-553 Still widely used in US and many parts of the world

Nordic Mobile Telephony (NMT) Sweden, Norway, Demark & Finland Launched 1981; now largely retired 450 MHz; later at 900 MHz (NMT900)

Total Access Communications System (TACS) British design; similar to AMPS; deployed 1985 Some TACS-900 systems still in use in Europe

1G — Separate Frequencies

30 KHz

30 KHz

30 KHz

30 KHz

30 KHz

30 KHz

30 KHz

30 KHzFre

qu

ency

FDMA — Frequency Division Multiple Access

Second Generation — 2G Digital systems Leverage technology to increase capacity

Speech compression; digital signal processing Utilize/extend “Intelligent Network” concepts Improve fraud prevention Add new services There are a wide diversity of 2G systems

IS-54/ IS-136 North American TDMA; PDC (Japan) iDEN DECT and PHS IS-95 CDMA (cdmaOne) GSM

D-AMPS/ TDMA & PDC Speech coded as digital bit stream

Compression plus error protection bits Aggressive compression limits voice quality

Time division multiple access (TDMA) 3 calls per radio channel using repeating time slices

Deployed 1993 (PDC 1994) Development through 1980s; bakeoff 1987

IS-54 / IS-136 standards in US TIA ATT Wireless & Cingular use IS-136 today

Plan to migrate to GSM and then to W-CDMA PDC dominant cellular system in Japan today

NTT DoCoMo has largest PDC network

iDEN Used by Nextel Motorola proprietary system

Time division multiple access technology Based on GSM architecture

800 MHz private mobile radio (PMR) spectrum Just below 800 MHz cellular band

Special protocol supports fast “Push-to-Talk” Digital replacement for old PMR services

2G — TDMATime Division Multiple Access

Fre

qu

ency

Time

200 KHz

200 KHz

200 KHz

200 KHz

One timeslot = 0.577 ms One TDMA frame = 8 timeslots

DECT and PHS Also based on time division multiple access Digital European Cordless Telephony

Focus on business use, i.e. wireless PBX Very small cells; In building propagation issues Wide bandwidth (32 kbps channels) High-quality voice and/or ISDN data

Personal Handyphone Service Similar performance (32 kbps channels) Deployed across Japanese cities (high pop.

density) 4 channel base station uses one ISDN BRI line Base stations on top of phone booths

GSM « Groupe Special Mobile », later changed to

« Global System for Mobile » Joint European effort beginning in 1982 Focus on seamless roaming across Europe

Services launched 1991 Time division multiple access (8 users per 200KHz) 900 MHz band; later extended to 1800MHz Added 1900 MHz (US PCS bands)

GSM is dominant world standard today Well defined interfaces; many competitors Tri-band GSM phone can roam the world today

Distribution of GSM Subscribers

GSM is used by 70% of subscribers worldwide 564 M subs / 800 M subs in July 2001

Most GSM deployments in Europe (59%) and Asia (33%)

Number of subscribersin the world (Jul 2001)

GSM71%

US TDMA10%

CDMA12%

PDC7%

Source: EMC World Cellular / GSM Association

North American CDMA (cdmaOne) Code Division Multiple Access

All users share same frequency band CDMA is the basis for 3G networks

Qualcomm demo in 1989 Claimed improved capacity & simplified

planning First deployment in Hong Kong late 1994 Major success in Korea (1M subs by 1996) Used by Verizon and Sprint in US Simplest 3G migration story today

cdmaOne — IS-95 TIA standard IS-95 (ANSI-95) in 1993 IS-95 deployed in the 800 MHz cellular band

J-STD-08 variant deployed in 1900 MHz US “PCS” band

Evolution fixes bugs and adds data IS-95A provides data rates up to 14.4 kbps IS-95B provides rates up to 64 kbps (2.5G) Both A and B are compatible with J-STD-08

All variants designed for TIA IS-41 core networks (ANSI 41)

2G & 3G — CDMACode Division Multiple Access Spread spectrum modulation

Originally developed for the military Resists jamming and many kinds of interference Coded modulation hidden from those w/o the code

All users share same (large) block of spectrum One for one frequency reuse Soft handoffs possible

Almost all accepted 3G radio standards are based on CDMA

CDMA2000, W-CDMA and TD-SCDMA

Other Wireless Systems Paging Systems

Simplex Limited to worldwide coverage possible Broadcast / simulcast Reliable large Txd. Power, Low data

rate

PSTNPagingControlcenter

Pagingtowers

Pagingtowers

Other Wireless Systems Cordless telephone systems

Dedicated Base Station Limited coverage No handoff support

PSTNFixed Base

Station

A general WLL setup

Satellite networks: GEO

Publicnetworks

Gateway

Control station

Publicnetworks

Gateway

Controlstation

Japan SingaporeGEO

Satellite networks: LEO

Publicnetworks

Gateway

Control station

Publicnetworks

Gateway

Controlstation

Japan Singapore

LEO LEOInter-satellite link

Satellite networks: Comparison

MEOLEO GEOSatellite cost (unit)

Satellite life (year)

Hand-held terminal

Propagation delay

Propagation loss

Network complexity

Hand-off

Development period

Visibility of satellite

Minimum

3-7

Possible

Short

Low

Complex

Very

Long

Short

Medium

10-15

Possible

Medium

Medium

Medium

Medium

Short

Medium

Maximum

10-15

Very Difficult

Large

High

Simple

No

Long

Always

-A. Jamalipour, “Low Earth Orbital Satellites for Personal Communication Networks”, ISBN 0890069557, Artech-House, 1998, pp17.

Satellite networks: Orbit altitude

GEOMEO

LEO

GEO=Geostationary EOMEO=Medium EOLEO=Low EOEO=Earth Orbit

35,786 (km)

10,000~20,000

>1,500

-A. Jamalipour, “Low Earth Orbital Satellites for Personal Communication Networks”, ISBN 0890069557, Artech-House, 1998, pp15.

Ad-hoc networks

-Nodes can communicate each other directly without needing a central co-ordination, and move arbitrarily during communication.

-http://www.ericsson.se/Review/er3_98/art1/art1.html

STANDARDS AND FUTURE SYSTEMS

• Bluetooth

• Wireless LANs

• High-Speed Digital Cellular (3G)

• 4G Cellular

• Wireless "Cable"– Multichannel Multipoint Distribution Service (2.2 GHz)– Local Multipoint Distribution Service (28 GHz)

• Satellite Networks- Iridium, Globalstar, Others

• HomeRF

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Bluetooth

A new global standard for data and voice Cable replacement RF technology

• Short range (10 meters)• 2.4 GHz band• 1 Data (700 Kbps) and 3 Voice channels • Supported by over 200 telecommunications and computer companies

Goodbye Cables !

Ultimate Headset

Cordless Computer

Automatic Synchronization

In the Office

At Home

Bluetooth Specifications

Connection Type Spread Spectrum (Frequency Hopping)

MAC Scheme FH-CDMA

Spectrum 2.4 GHz ISM

Modulation Gaussian Frequency Shift Keying

Transmission Power 1 mw – 100 mw

Aggregate Data Rate 1 Mbps

Range 30 ft

Supported Stations 8 devices

Voice Channels 3

Data Security- Authentication Key 128 bit key

Data Security-Encryption Key 8-128 bits (configurable)

• 802.11b: standard for 2.4 GHz ISM band

• Frequency hopped spread spectrum

• 1.6 Mbps data rates, 500 foot range

• Star or peer-to-peer architecture

• 802.11a extends rates to 10-70 Mbps

• Extensions trying to add QoS

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802.11 Wireless LANs

 

Wireless LANIEEE 802.11a/b/g/h/j/n

• b : 1999 ~2.4 GHz ISM• a : 2002 – 2003 ~5.0 GHz ISM• g : 2002 – 2003 ~2.4 GHz ISM• h : 2003 – 2004 ~5.0 GHz ISM• j : 2004 ~5.0 GHz ISM• n : 2006

 

Modulation & Filter type• b DBPSK / DQPSK ( 11Mbps )

Gaussian filter or vendor specific

• a/g/h/j upto 64 QAM on 52 OFDM subcarriers, rectangular filter or vendor specific (54 Mbps )

• n upto 64 QAM on 108 OFDM subcarriers, rectangular filter or vendor specific ( yet to be defined )

HIPERLAN

• Types 1-4 for different user types- Frequency bands: 5.15-5.3 GHz, 17.1- 17.3 GHz

• Type 1- 5.15-5.3 GHz band- 23 Mbps, 20 MHz Channels- 150 foot range (local access only)- Protocol support similar to 802.11- Peer to peer architecture- ALOHA channel access

• Types 2-3- Wireless ATM- Local access and wide area services- Standard under development- Two components: access and mobility support

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HIGH-SPEED DIGITAL CELLULAR

• North American Digital Cellular– CDMA (IS-95) enhancements– TDMA (IS-136) enhancements– IS-136+ 32-64 kbps– IS-136HS 384 kbps

• GSM– General Packet Radio System (GPRS)– Enhanced Data Rates for GSM Evolution (EDGE)

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• Evolution of GSM / GPRS

• ETSI standardization as GSM evolution chosen for data services for IS136HS

• Higher-level modulation (adaptive)

• 200 kHz carrier spacing

• Up to 384 kbps in 200 kHz

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EDGE

WIDEBAND CDMA (3G)

• The W-CDMA concept:

– 4.096 Mcps Direct Sequence CDMA

– Variable spreading and multicode operation

– Coherent in both up-and downlink

= Codes with different spreading, giving 8-500 kbps

f

t

10 ms frame

4.4-5 MHz

High ratemulticode user

Variable rate users

....P

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W-CDMAKEY TECHNICAL FEATURES

• High bit-rate services require wideband

• Flexibility for different services

• Optimized for packet data transfer

• Capacity and coverage gain from frequency diversity

• Built in support for– adaptive antenna arrays– multi-user detection– hierarchical cell structures– transmitter diversity

• Low infrastructure cost (many users/ transceiver)

• BS synchronization not required

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Spectral Allocation 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

3G Vision Universal global roaming Multimedia (voice, data & video) Increased data rates

384 kbps while moving 2 Mbps when stationary at specific locations

Increased capacity (more spectrally efficient) IP architecture Problems

No killer application for wireless data as yet Vendor-driven

CDMA

GSM

TDMA

PHS (IP-Based)

64 Kbps

GPRS

115 Kbps

CDMA 1xRTT

144 Kbps

EDGE

384 Kbps

cdma20001X-EV-DV

Over 2.4 Mbps

W-CDMA (UMTS)

Up to 2 Mbps

2G2.5G

2.75G 3G

1992 - 2000+2001+

2003+

1G

1984 - 1996+

2003 - 2004+

TACS

NMT

AMPS

GSM/GPRS

(Overlay) 115 Kbps

9.6 Kbps

9.6 Kbps

14.4 Kbps/ 64 Kbps

9.6 Kbps

PDC

Analog Voice

Digital Voice

Packet Data

IntermediateMultimedia

Multimedia

PHS

TD-SCDMA

2 Mbps?

9.6 Kbps

iDEN

(Overlay)

iDEN

Source: U.S. Bancorp Piper Jaffray

Migration To 3G