1

Introduction

2

Reference

[1] Wireless and Mobile Network Architectures，Yi-Bing Lin and ImrichChlamtac，Wiley Computer Publishing。

[2] Introduction to GSM，陳俊宏，遠傳教育訓練中心。

[3] GPRS and 3G Wireless Applications，Christoffer Andersson，Wiley Computer Publishing。

3

Outline

IntroductionPCS ArchitectureCellular TelephonyCordless Telephony and Low-Tier PCSThird-Generation Wireless SystemsSummary

4

Introduction

5

PCS

Personal Communications Services (PCS)refers to a wide variety of wireless access and personal mobility services.PCS systems can connected to Public Switched Telephone Network (PSTN).Goal of PCS：enabling communications with a person at anytime, at any place and in any terminal form.

6

PCS Revolution

JTACS

First Generation Second Generation Third Generation

High-tier Digit Cellar Systems

Low-tier Telecommunication Systems

TACS

AMPS

GSM

CT0/1

PHS

CT2

PACS

DECT

JDC

NADC PCS

NMT IMT-2000GSM+,++

Mobile Satellite

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Examples of Wireless Communications Systems (1/4)

High-tier digital cellular systemsFor vehicular and pedestrian services• Global System for Mobile Communication (GSM),

Digital Communication System-1800 (DCS1800)• IS-136 TDMA based Digital Advanced Mobile

Phone Service (DAMPS)• Personal Digital Cellular (PDC)• IS-95 CDMA-based cdmaOne System

8

Examples of Wireless Communications Systems (2/4)

Low-tier telecommunication systems For residential, business, and public cordless access applications• Cordless Telephone 2 (CT2)• Digital European Cordless Telephone (DECT)• Personal Access Communications Systems

(PACS)• Personal Handy Phone System (PHS)

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Examples of Wireless Communications Systems (3/4)

Wideband wireless systems To accommodate Internet and multimedia services.• cdma2000 (evolved from cdmaOne)• W-CDMA (proposed by Europe)• TD-SCDMA (proposed by China/Europe)

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Examples of Wireless Communications Systems (4/4)

PCS umbrella• Paging systems• Trunking Radio • Mobile-satellite system• Unlicensed industrial, scientific, and medical（ISM）band technologies, as well as wireless local area networks（WLANs）

11

PCS Architecture

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PSTN

Public Switched Telephone Network

Switch

Switch

SwitchTaipei

Taichung

trunksubscriber loop

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PLMN

Public Land Mobile Network

PSTN

PLMN

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The Basic PCS Architecture

Public LandMobile Network

Switch forMobile

Applications

MobilityDatabase

Base StationController

Mobile Station

BTS

Radio Network

Wireline Transport Network

Base Transceiver Station

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PCS Architecture

Each PCS technology has similar architectures which consists two parts：• Radio Network

MS (Mobile Station)BS (Base Station) System

• Wireline Transport NetworkMSC (Mobile Switching Center)The Mobility Database connected to MSC is used to track the locations of mobile station.

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Mobile Station (MS)

Handset, mobile phone, subscriber unit, portable Multi-mode handset

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Base Station (BS)

The radio coverage of a BS is called a Cell.The BS system is partitioned into • a controller• radio

transmitters/receivers The BSs usually reach the wireline core network via land links or dedicated microwave links.

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GSM Antenna

19

GSM Base Station

20

Cellular Concept

cluster

sector

cell√

√

√√

√

√

21

Duplex Technologies

Down-link: BS to handsetUp-link: handset to BSTwo duplex Technologies:• FDD（Frequency Division Duplex）• TDD（Time Division Duplex）

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FDDFrequency

Time

A1 talks to A2

B1 talks to B2

B2 talks to B1

A2 talks to A1

C2 talks to C1

C1 talks to C2

Down Link

Up Link

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TDDFrequency

Time

A2 talks to A1

C2 talks to C1

B2 talks to B1

A1 talks to A2

C1 talks to C2

B1 talks to B2

..... .....

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Multiple Access Technology

FDMA（Frequency Division Multiple Access）TDMA（Time Division Multiple Access）CDMA（Code Division Multiple Access）

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FDMAFrequency

Time

30kHz for AMPS

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TDMAFrequency

Time

200kHz for GSM

4.615 ms/frame

8 time slots for GSM

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CDMA (1/2)Frequency

20 ms/frame 32 channels

1.25MHz for IS-95

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Code Division Multiple Access (CDMA)• Direct Sequence Spread Spectrum (DSSS)• Frequency Hopping Spread Spectrum (FHSS)

In DS-CDMA, every signal is processed with PN sequence (pseudo-noise sequence).• Faster-rate, wide-bandwidth digital signal• Each PN sequence is a unique orthogonal code.• User signals are distinguished by different PN

sequences.

CDMA (2/2)

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Example of PN (1/3)

Assign PN code A: 00011011, B: 00101110, C: 01011100, D: 01000010Transfer the PN to Bipolar chip sequences:• A=(-1,-1,-1,1,1,-1,1,1) B=(-1,-1,1,-1,1,1,1,-1)• C=(-1,1,-1,1,1,1,-1,-1) D=(-1,1,-1,-1,-1,-1,1,-1)

Check:• A*A=1+1+1+1+1+1+1+1=8• A*B=1+1-1-1+1-1+1-1=0• A*C=1-1+1+1+1-1-1-1=0• A*D=1-1+1-1-1+1+1-1=0

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Example of PN (2/3)

If 4 MSs want to receive A=1, B=1, C=1, D=1, then BS will send • S1=A*1+B*1+C*1+D*1=(-4,0,-2,0,2,0,2,-2)

If 4 MSs want to receive A=1, B=1, C=0, D=1, then BS will send • S2 =A*1+B*1+C*(-1)+D*1 =(-2,-2,0,-2,0,-2,4,0)

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Example of PN (3/3)

MS C will receive• 1/8* C*S1

= 1/8 * (-4,0,-2,0,2,0,2,-2) * (-1,1,-1,1, 1,1,-1,-1) = 1/8 * (4+0+2+0+2+0-2+2)= 1

• 1/8 * C*S2 = 1/8 * (-2,-2,0,-2,0,-2,4,0) * (-1,1,-1,1, 1,1,-1,-1) = 1/8 * (2-2+0-2+0-2-4+0)= -1

-1 means “0”

MS A will receive• A*S1=A*(A*1+B*1+C*1+D*1)=A*A*1+A*B*1+A*C*1

+A*D*1=8*1+0+0+0=8

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Data Signal

0 f

: Desired Signal

: Interference

0

W Hz

f

Received Signal +Wideband Interference

RecoveredData Signal

0 f

Direct SequenceSpread

Direct SequenceDespread

Spread Spectrum Correlation Process

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Cellular Telephony

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1G Cellular Telephony

Advanced Mobile Phone Service (AMPS)Total Access Communication System (TACS)NMT (Nordic Mobile Telephone) 450/900NTT (Nippon Telephone & Telegraph) , JTACS (1988), NTACS (1993)C450

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Advanced Mobile Phone Service (AMPS) (1/2)

Analog FM radio for voice transmissionFSK modulation for signal channelsFDMAFDDTotal 50 MHz=824-849 MHz(down-link) + 869-894 MHz(up-link) • 832 full-duplex channels using 1664 discrete

frequencies30kMHz spacing

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Advanced Mobile Phone Service (AMPS) (2/2)

Frequency reuse scheme for radio communication• 12-cell cluster using omni-directional antennas • 7-cell cluster using three sectors per BS• 4-cell cluster, 6-sector design in Motorola AMPS

system. There are about 50 channels per cell. EIA/TIA IS-41 standard for roaming management.

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2G Cellular Telephony

Global System for Mobile Communications (GSM)EIA/TIA IS-136 Digital Cellular SystemEIA/TIA IS-95 Digital Cellular SystemJapanese Digital Cellular (JDC) in Japan

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Global System for Mobile Communications (GSM) (1/2)

“Digital” cellular system • Groupe Special Mobile of Conference Europeenne

des Posts et Telecommunications (CEPT) and European des Postes et Telecommunications (ETSI)

TDMA/FDD935-960 MHz for Downlink890-915 MHz for Uplink200 kHz for RF channel spacing Speech coding rate 13 Kbps

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Global System for Mobile Communication (GSM) (2/2)

Frequency carrier is divided into 8 time slots• Every pair of radio transceiver-receiver supports 8

voice channels.GSM Mobile Application Part (MAP) for roaming managementDigital switch can provide many applications:• Example: point-to-point short messaging, group

addressing, call waiting, multiparty services

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EIA/TIA IS-136 Digital Cellular System (1/2)

Digital AMPS (DAMPS), American Digital Cellular (ADC), or North American TDMA (NA-TDMA), IS-136The successor to IS-54The same spectrum used by AMPS• 3 times of capacity of AMPS

TDMA/FDD30 KHz frequency spacing

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EIA/TIA IS-136 Digital Cellular System (2/2)

2 types of channel usage: • Full-rate: use 2 timeslot for a voice channel• Half-rate: use 1 timeslot for a voice channel

Digital switch can provide many applications:• Example: point-to-point short messaging,

broadcast messaging, group addressing, private user groups

IS-41 standard for mobility management

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EIA/TIA IS-95 Digital Cellular System (1/2)

Qualcomm cdmaOne in USA since 1996Korea in April, 1996.

PSTN

PLMN

Vocoder

Switch

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EIA/TIA IS-95 Digital Cellular System (2/2)

CDMA/DSSS for the air interface.• A shared 1.25 MHz channel bandwidth • User signals distinguished with different codes• MSs links to many BSs during phone calls.• No cell plan question• GPS for synchronization of BSs

Interference-based capacity (soft capacity)• The capacity of IS-95 is 3-6 times of IS-136

system, and 10 times of AMPS.IS-41 for core networkAdvanced Radio Resource Management

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Comparison of Cellular Systems

42 kps1228.8 kps48.6 kps270.833 kpsChannel bit rate

11.2 kps8 kps7.95kps13 kps10 kpsSpeech rate

日美,韓,中國美歐,台灣美Region

FDMATDMA

FDMACDMA

FDMATDMA

FDMATDMA

FDMAMAC

940-956824-849824-849890-915 1710-1785

825-845Uplink (MHz)

332681Channels

25kHz1.25MHz30kHz200kHz30kHzCarrier

FDDFDDFDDFDDFDDDuplex

810-826869-894869-894935-960 1805-1880

870-890Downlink (MHz)

JDCIS-95IS-136GSM DCS1800

AMPSSystem

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Cellular Characteristics

The characteristics of the cellular system:• Support high mobility• Large coverage area• High transmission power of BS and handset• High signal process power (for handset)• Low voice quality• High network complexity

Microcell is developed for:• Low transmission power• Low base station cost• Increase capacity

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Low-Tier PCS

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Examples of Low-Tier PCS

Cordless Telephone, Second Generation (CT2)Digital European Cordless Telephone (DECT)Personal Handy Phone System (PHS)Personal Access Communications System (PACS)

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Cordless Telephone, Second Generation (CT2) (1/2)

Developed in Europe since 1989.40 FDMA channels 32-Kbps speech coding rateTDDThe maximum transmit power of a CT2 handset is 10 mW

CT-1

CT-2

CT-2+

CT-1+

CT-3

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Cordless Telephone, Second Generation (CT2) (2/2)

No handoff in CT2No call delivery in CT2In CT2+, both handoff and call delivery are OK.

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Digital European Cordless Telephone (DECT) (1/2)

Published in 1992TDMA/TDD12 voice channels per frequency carrierSleep mode is employed in DECT to conserve the power of handsets.32 Kbps speech coding rate

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Digital European Cordless Telephone (DECT) (2/2)

DECT is typically implemented as a wireless-PBX connected to the PSTN.Dynamic channel allocationTime slot transferSeamless handoff Dual mode: DECT + GSM

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Personal Handy Phone System (PHS) (1/2)

Developed by Research and Development Center (RCR), Japan 1993Telecommunication services for homes, offices, and outdoor environmentTDMA/TDD 4 multiplexed channels/frequency carrier1895-1906.1 MHz = 300 KHz × 37 channels (home/office)1906.1-1918.1 MHz = 300 KHz × 40 channels (public system)

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Personal Handy Phone System (PHS) (2/2)

BS: 500 mW; handset < 10mW32 Kbps speech coding rateDynamic channel allocation.Dedicated control channels Sleep ModeJ100: 7 hours talk time, 700 hours standby time, 64kbps wireless dataDual mode: PHS + GSM

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Personal Access Communications System (PACS)

Developed at Telcordia, U.S.A.PACS is designed for wireless local loop and PCS.TDMA8 voice channels/frequency carrierBoth TDD and FDD are accommodated.The highly effective and reliable mobile-controlled handoff (MCHO) completes in less than 20 msec.

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Comparison of PCS Systems

384kps384kps1152kps72kpsChannel bit rate

32kps32kps32kps32kpsSpeech rate

美日本歐歐,台灣Region

FDMATDMA

FDMATDMA

FDMATDMA

FDMAMAC

88241Channels

300MHz300kHz1728kHz100kHzCarrier

FDDTDDTDDTDDDuplex

1930-1990(down) 1850-1910(uplink)

1895-19181880-1900864-868Frequency (MHz)

PACSPHSDECTCT-2System

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Low-tier PCS Characteristics

The characteristics of the low-tier system:• Low transmission power• Long talk time• Small coverage area• Large no. of base station• Low transmission delay• High voice quality• Low mobility• Low network complexity• Low cost

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Characteristics of Cellular and Cordless Low-Tier PCS Technologies

Low(<=48Km/hr)Medium(<=96Km/hr)High(<=257Km/hr)User Speed

Small/Zonal picocells

Medium micro and picocells

Large/Continuous macro cells

Coverage Area

Low (5-10mW)Low (5-10mW)High (100-800mW)Handset power consumption

High (32Kbps)High (32Kbps)Low (8-13Kbps)Speech Coding Rate

Low (<=20ms)Low (<= 10ms)High (<= 600ms)Delay or Latency

LowLowHighHandset Complexity

Small(50-100m)Medium(50-500 m)Large(0.5-35 Km)Cell Size

CORDLESSLOW-TIER PCSHIGH-TIER CELLULAR

Systems

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Third-Generation Wireless System

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Generations of Wireless Systems

First Generation System: AMPS• Analog voice calls

Second Generation Systems: GSM, IS-136, IS-95, and low-tier systems• Digital speech with low-bit-rate data services

Third-Generation:• Better system capacity• High-speed and wireless Internet access (to

2Mbps)• Wireless multimedia services (audio and video)

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Third-Generation Wireless Systems

2.5G: GPRS and EDGE• Bridge 2G into 3G

The new features for 3G includes• High bit rates, QoS, Bit rates dependent on

distance• Asynchronous Transfer Mode (ATM) backbone• Wideband CDMA (DS-CDMA FDD), SCDMA and

cdma2000 (multi-carrier FDD) for air interface

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3G Revolution

IS-95A

2 G 2.5G 3G

Japan

cdma20001x

GSM

EDGE

PDC P-PDC W-CDMA

IS-95B

GSM GPRS UMTS

IS-136 1xEV-DO

UMTS/HSDPA

Cdma2000 3xMCAmerica

Europe

1xEV-DV?

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Summary

PCS ArchitectureCellular TelephonyCordless Telephony and Low-Tier PCSThird-Generation Wireless Systems