Introduction

Prof. S.-I. Sou EE, NCKU Fall, 2008

Outline

Introduction PCS Architecture Cellular Telephony Cordless Telephony and Low-Tier PCS Third-Generation Wireless Systems Summary

Introduction

PCS

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

PCS Revolution
Third First Generation JTACS High-tier Digit Cellar Systems TACS NMT AMPS Low-tier Telecommunication Systems CT0/1 CT2 GSM NADC PHS PACS DECT
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Second Generation

Generation

Mobile Satellite JDC GSM+,++ IMT-2000 PCS

Examples of Wireless Communications Systems (1/4)

High-tier digital cellular systems For 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

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)

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)

Examples of Wireless Communications Systems (4/4)

PCS umbrella
Paging systems Trunking Radio Mobile-satellite system Unlicensed industrial, scientific, and medical ISMband technologies, as well as wireless local area networksWLANs

PCS Architecture

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PSTN
Public Switched Telephone Network

Switch
subscriber loop Switch Taipei

Taichung

trunk

Switch

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PLMN
Public Land Mobile Network

PLMN

PSTN

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The Basic PCS Architecture

Public Land Mobile Network

Switch for Mobile Applications

Mobility Database

Wireline Transport Network

Base Station Controller

Base Transceiver Station

BTS Radio Network Mobile 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 Network

MSC (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 Also known as User Equipment (UE) in NGN

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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

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GSM Base Station

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Cellular Concept
cluster

cell sector

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Duplex Technologies
Down-link: BS to handset Up-link: handset to BS Two duplex Technologies: FDDFrequency Division Duplex TDDTime Division Duplex

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FDD
Frequency

A1 talks to A2 B1 talks to B2 C1 talks to C2 A2 talks to A1 B2 talks to B1 C2 talks to C1

Time
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Down Link

Up Link

TDD
Frequency

A2 talks to A1

B2 talks to B1

C2 talks to C1 .....

A1 talks to A2

B1 talks to B2

C1 talks to C2 .....

Time
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Multiple Access Technology

FDMAFrequency Division Multiple Access TDMATime Division Multiple Access CDMACode Division Multiple Access

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FDMA
Frequency

30kHz for AMPS

Time
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TDMA
Frequency

200kHz for GSM

4.615 ms/frame 8 time slots for GSM

Time

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CDMA (1/2)
Frequency

1.25MHz for IS-95

20 ms/frame 32 channels
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CDMA (2/2)
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.

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Example of PN (1/3)
Assign PN code A: 00011011, B: 00101110, C: 01011100, D: 01000010 Transfer 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 transmit A=1, B=1, C=1, D=1, then BS will receive
S1=A*1+B*1+C*1+D*1=(-4,0,-2,0,2,0,2,-2)

If 4 MSs want to transmit A=1, B=1, C=0, D=1, then BS will receive
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)
BS will receive from MS C
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

BS will receive from MS A

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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Spread Spectrum Correlation Process

Recovered Data Signal

Data Signal

Received Signal + Wideband Interference

W Hz Direct Sequence Spread Direct Sequence Despread

f : Desired Signal : Interference

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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) 450/900 NTT (Nippon Telephone & Telegraph) , JTACS (1988), NTACS (1993) C450

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

Analog FM radio for voice transmission FSK modulation for signal channels FDMA FDD Total 50 MHz=824-849 MHz(down-link) + 869894 MHz(up-link)
832 full-duplex channels using 1664 discrete frequencies

30kMHz 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 System EIA/TIA IS-95 Digital Cellular System Japanese 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/FDD 935-960 MHz for Downlink 890-915 MHz for Uplink 200 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 management Digital 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-136 The successor to IS-54 The same spectrum used by AMPS
3 times of capacity of AMPS

TDMA/FDD 30 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 1996 Korea in April, 1996.

PLMN
Vocoder

Switch

PSTN

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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 network Advanced Radio Resource Management

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Comparison of Cellular Systems

System AMPS FDD FDMA GSM DCS1800 , FDD FDMA TDMA Downlink (MHz) Uplink (MHz) 870-890 935-960 1805-1880 890-915 1710-1785 200kHz 8 13 kps 270.833 kps IS-136 FDD FDMA TDMA 869-894 IS-95 ,, FDD FDMA CDMA 869-894 JDC FDD FDMA TDMA 810-826

Region Duplex MAC

825-845

824-849

824-849

940-956

Carrier Channels Speech rate Channel bit rate

30kHz 1 10 kps

30kHz 6 7.95kps 48.6 kps

1.25MHz 32 8 kps 1228.8 kps

25kHz 3 11.2 kps 42 kps

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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 rate TDD The maximum transmit power of a CT2 handset is 10 mW CT-2+ CT-3 CT-1 CT-1+

CT-2

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

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

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

Published in 1992 TDMA/TDD 12 voice channels per frequency carrier Sleep 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 wirelessPBX connected to the PSTN. Dynamic channel allocation Time slot transfer Seamless handoff Dual mode: DECT + GSM

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

Developed by Research and Development Center (RCR), Japan 1993 Telecommunication services for homes, offices, and outdoor environment TDMA/TDD 4 multiplexed channels/frequency carrier 1895-1906.1 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 < 10mW 32 Kbps speech coding rate Dynamic channel allocation. Dedicated control channels Sleep Mode J100: 7 hours talk time, 700 hours standby time, 64kbps wireless data Dual 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. TDMA 8 voice channels/frequency carrier Both TDD and FDD are accommodated. The highly effective and reliable mobilecontrolled handoff (MCHO) completes in less than 20 msec.
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Comparison of PCS Systems

System Region Duplex MAC CT-2 , TDD FDMA DECT TDD FDMA TDMA Frequency (MHz) Carrier Channels Speech rate Channel bit rate 864-868 1880-1900 PHS TDD FDMA TDMA 1895-1918 PACS FDD FDMA TDMA 1930-1990(down) 1850-1910(uplink) 300MHz 8 32kps 384kps

100kHz 1 32kps 72kps

1728kHz 24 32kps 1152kps

300kHz 8 32kps 384kps

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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

Systems Cell Size User Speed Coverage Area Handset Complexity Handset power consumption Speech Coding Rate Delay or Latency HIGH-TIER CELLULAR Large(0.5-35 Km) High(<=257Km/hr) Large/Continuous macro cells High High (100-800mW) LOW-TIER PCS Medium(50-500 m) Medium(<=96Km/hr) Medium and picocells Low Low (5-10mW) micro CORDLESS Small(50-100m) Low(<=48Km/hr) Small/Zonal picocells Low Low (5-10mW)

Low (8-13Kbps) High (<= 600ms)

High (32Kbps) Low (<= 10ms)

High (32Kbps) Low (<=20ms)

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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
2G America IS-95A IS-136 2.5G IS-95B cdma2000 1x 3G Cdma2000 3xMC

1xEV-DO EDGE

1xEV-DV

Europe

GSM

GSM GPRS

UMTS

UMTS/ HSDPA

Japan

PDC

P-PDC

W-CDMA
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Summary
PCS Architecture Cellular Telephony Cordless Telephony and Low-Tier PCS Third-Generation Wireless Systems

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