1

What is PCS

Personal Communication

Services

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What is PCS

Personal Communication Services

A wide variety of network services that includes

wireless access and personal mobility services

Provided through a small terminal

Enables communication at any time, at any place,

and in any form.

The market for such services is tremendously

big

Think of cell-phone market

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Several PCS systems

High-tier Systems

GSM: Global System for Mobile Communications

The mobile telephony system that we are using

IS-136

USA digital cellular mobile telephony system

TDMA based multiple access

Personal Digital Cellular

IS-95 cdmaOne System

CDMA based multiple access

4

Several PCS systems

Low-tier systems

Residential, business and public cordless access

applications and systems

Cordless Telephone 2 (CT2)

Digital Enhanced Cordless Telephone (DECT)

Personal Access Communication Systems (PACS)

Personal Handy Telephone System (PHS)

5

Several PCS systems

Wideband wireless systems

For Internet access and multimedia transfer

Cdma2000

W-CDMA, proposed by Europe

SCDMA, proposed by Chine/Europe

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Several PCS systems

Other PCS Systems

Special data systems

CDPD: Cellular Digital Packet Data

RAM Mobile Data

Advanced Radio Data Information System (ARDIS)

Paging Systems

Mobile Satellite Systems

LEO, MEO, HEO satellites for data/voice

ISM band systems: Bluetooth, 802.11, etc.

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PCS Problems

How to integrate mobile and wireless users to

the Public Switched Telephone Network

(PSTN) (Voice Network) Cellular mobile telephony system

How to integrate mobile and wireless users to

the Internet (Data Network) Mobile IP, DHCP, Cellular IP

How to integrate all of them together and also

add multimedia services (3G Systems)

8

Internet PSTN

(Telephone Network)

Looking to PCS from different

Angles

Mobile Users

-Cell phone users

-Cordless phone users

Mobile Users

-Laptop users

-Pocket PC users

-Mobile IP, DHCP enabled

computers

Wireless Access

Telecom People View Data Networking People View

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Telecom and Data Networking

-Radio Propagation

-Link Characteristics

-Error Models

-Wireless Medium

Access (MAC)

- Error Control

-Data Transmission

-Mobile IP (integrating

mobile hosts to

internet)

-Ad-hoc Networks

-TCP over Wireless

-Service Discovery

- Voice Transmission

- Frequency Reuse

- Handoff

Management

-Location Tracking

-Roaming

-QoS

-GSM, CDMA,

Cordless Phones,

-GPRS, EDGE

Telecom Interest Data Networking Interest

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Very Basic Cellular/PCS Architecture

Base Station

(BS) Mobile Station

Base Station

Controller

Mobility

Database

Mobile

Switching

Center

(MSC)

Radio Network

Public Switched

Telephone Network

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Wireless System Definitions

Mobile Station A station in the cellular radio service intended for use while

in motion at unspecified locations. They can be either hand-

held personal units (portables) or installed on vehicles

(mobiles)

Base station A fixed station in a mobile radio system used for radio

communication with the mobile stations. Base stations are

located at the center or edge of a coverage region. They

consists of radio channels and transmitter and receiver

antennas mounted on top of a tower.

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Wireless System Definitions

Mobile Switching Center Switching center which coordinates the routing of calls in a

large service area. In a cellular radio system, the MSC

connections the cellular base stations and the mobiles to

the PSTN (telephone network). It is also called Mobile

Telephone Switching Office (MTSO)

Subscriber A user who pays subscription charges for using a mobile

communication system

Transceiver A device capable of simultaneously transmitting and

receiving radio signals

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Wireless System Definitions

Control Channel Radio channel used for transmission of call setup, call

request, call initiation and other beacon and control

purposes.

Forward Channel Radio channel used for transmission of information from

the base station to the mobile

Reverse Channel Radio channel used for transmission of information from

mobile to base station

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Wireless System Definitions

Simplex Systems Communication systems which provide only one-way

communication

Half Duplex Systems Communication Systems which allow two-way

communication by using the same radio channel for both

transmission and reception. At any given time, the user can

either transmit or receive information.

Full Duplex Systems Communication systems which allow simultaneous two-way

communication. Transmission and reception is typically on

two different channels (FDD).

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Wireless System Definitions

Handoff The process of transferring a mobile station from one

channel or base station to an other.

Roamer A mobile station which operates in a service area (market)

other than that from which service has been subscribed.

Page A brief message which is broadcast over the entire service

area, usually in simulcast fashion by many base stations at

the same time.

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PCS Systems Classification

Cordless Telephones

Cellular Telephony (High-tier)

Wide Area Wireless Data Systems (High-tier)

High Speed Local and Personal Area Networks

Paging Messaging Systems

Satellite Based Mobile Systems

3G Systems

…

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Major Mobile Radio Standards - USA

Standard Type Year

Intro

Multiple

Access

Frequency

Band

(MHz)

Modulation Channel

BW

(KHz)

AMPS Cellular 1983 FDMA 824-894 FM 30

USDC Cellular 1991 TDMA 824-894 DQPSK 30

CDPD Cellular 1993 FH/Packet 824-894 GMSK 30

IS-95 Cellular/PCS 1993 CDMA 824-894

1800-2000

QPSK/BPSK 1250

FLEX Paging 1993 Simplex Several 4-FSK 15

DCS-1900

(GSM)

PCS 1994 TDMA 1850-1990 GMSK 200

PACS Cordless/PCS 1994 TDMA/FDMA 1850-1990 DQPSK 300

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Major Mobile Radio Standards - Europe

Standard Type Year

Intro

Multiple

Access

Frequency

Band

(MHz)

Modulation Channel

BW

(KHz)

ETACS Cellular 1985 FDMA 900 FM 25

NMT-900 Cellular 1986 FDMA 890-960 FM 12.5

GSM Cellular/PCS 1990 TDMA 890-960 GMSK 200KHz

C-450 Cellular 1985 FDMA 450-465 FM 20-10

ERMES Paging 1993 FDMA4 Several 4-FSK 25

CT2 Cordless 1989 FDMA 864-868 GFSK 100

DECT Cordless 1993 TDMA 1880-1900 GFSK 1728

DCS-1800 Cordless/PCS 1993 TDMA 1710-1880 GMSK 200

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Cordless Telephones

Cordless

Phone

Base unit

PSTN

Telephone

Network

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Cordless Telephones

Characterized by Low mobility (in terms of range and speed)

Low power consumption

Two-way tetherless (wireless) voice communication

High circuit quality

Low cost equipment, small form factor and long talk-time

No handoffs between base units

Appeared as analog devices

Digital devices appeared later with CT2, DECT standards in Europe and ISM band technologies in USA

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Cordless Telephones

Usage

At homes

At public places where cordless phone base units are available

Design Choices

Few users per MHz

Few users per base unit Many base units are connected to only one handset

Large number of base units per usage area

Short transmission range

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Cordless Phone

Some more features

32 Kb/s adaptive differential pulse code

modulation (ADPCM) digital speech encoding

Tx power <= 10 mW

Low-complexity radio signal processing No forward error correction (FEC) or whatsoever.

Low transmission delay < 50ms

Simple Frequency Shift Modulation (FSK)

Time Division Duplex (TDD)

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Cellular Telephony

Characterized by

High mobility provision

Wide-range

Two-way tetherless voice communication

Handoff and roaming support

Integrated with sophisticated public switched

telephone network (PSTN)

High transmit power requires at the handsets

(~2W)

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Cellular Telephony - Architecture

Radio tower

PSTN

Telephone

Network

Mobile Switching

Center

Wired connection

A Cellular Network

Public

Switched

Telephone

Network

(PSTN)

Mobile

Telephone

Switching

Center

(MTSC)

Base Transceiver Station (BTS) Mobile User

Cell 1

Cell 2

Cordless connection

HLR VLR

HLR = Home Location Register

VLR = Visitor Location Register

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Cellular System

Handoffs (typically 30 mseconds):

1. At any time, mobile station (MS) is in one cell and under the control of

a BS

2. When a MS leaves a cell, BS notices weak signal

3. BS asks surrounding BSs if they are getting a stronger signal

4. BS transfers ownership to one with strongest signal

5. MTSO assigns new channel to the MS and notifies MS of new boss

Public

Switched

Telephone

Network

(PSTN)

Mobile

Telephone

Switching

Center

(MTSC)

Cell 1

Cell 2

HLR VLR

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Cellular Telephony Systems

Mobile users and handsets

Very complex circuitry and design

Base stations

Provides gateway functionality between wireless

and wireline links

~1 million dollar

Mobile switching centers

Connect cellular system to the terrestrial

telephone network

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Frequency Reuse

The concept of frequency reuse is based on

assigning to each cell a group of radio

channels used within a small geographic area Cells are assigned a group of channels that is completely different

from neighbouring cells

The coverage area of cells is called the footprint and is limited by a

boundary so that the same group of channels can be used in cells

that are far enough apart

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Frequency Reuse

Cells with the

same number

have the same

set of frequencies

Frequency

Reuse

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Frequency Reuse using 7

frequencies allocations

f4

f3 f2

f1 f6

f7

f5 f4

f3 f2

f1 f6

f7

f5

f4

f3 f2

f1 f6

f7

f5

f4

f3 f2

f1 f6

f7

f5

f4

f3 f2

f1 f6

f7

f5

Each cell is generally 4 to 8 miles (6 to 16 KM) in diameter with

a lower limit around 2 miles.

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Problem with Smaller Clustersize

Interfering cells are closer by when cluster size is smaller.

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World Cellular Subscriber Growth

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Cellular Networks

First Generation Analog Systems

Analog Modulation, mostly FM

AMPS

Voice Traffic

FDMA/FDD multiple access

Second Generation (2G) Digital Systems

Digital Modulation

Voice Traffic

TDMA/FDD and CDMA/FDD multiple access

2.5G Digital Systems

Voice + Low-datarate Data

Third Generation Digital

Voice + High-datarate Data

Multimedia Transmission also

Cellular networks: From 1G to 3G

1G: First generation wireless cellular: Early 1980s Analog transmission, primarily speech: AMPS (Advanced

Mobile Phone Systems) and others

2G: Second generation wireless cellular: Late 1980s Digital transmission

Primarily speech and low bit-rate data (9.6 Kbps)

High-tier: GSM, IS-95 (CDMA), etc

Low-tier (PCS): Low-cost, low-power, low-mobility e.g. PACS

2.5G: 2G evolved to medium rate (< 100kbps) data

3G: future Broadband multimedia 144 kbps - 384 kbps for high-mobility, high coverage

2 Mbps for low-mobility and low coverage

Beyond 3G: research in 4G

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1G

(<1Kbps)

1 Kbps

10 Kbps

100 Kbps

2 Mbps

1 Mbps

Data Rates

1980 1990 2000 2010

2G

(9.6Kbps)

2.5G

(10-150Kbps)

3G

(144Kbps to 2Mbps)

Years

40

Wireless Network Evolution to 3rd Generation

Enabling Technologies

AMPS

GSM

IS-95

GPRS

CDMA-2000

1XRTT

EDGE

CDMA2000

3XRTT

(UMTS)

2.5G

3G

2G

2 Mbps

500 kbps

150 Kbps

100 Kbps

50 Kbps

10 Kbps

1999 2000 2001 2002 2003

TDMA Migration

1G-2G Migration

CDMA Migration

1980

1G

1 Kbps

W-CDMA

(UMTS)

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2G Technologies cdmaOne (IS-95) GSM, DCS-1900 IS-54/IS-136

PDC

Uplink Frequencies

(MHz)

824-849 (Cellular)

1850-1910 (US PCS)

890-915 MHz (Eurpe)

1850-1910 (US PCS)

800 MHz, 1500 Mhz

(Japan)

1850-1910 (US PCS)

Downlink Frequencies 869-894 MHz (US

Cellular)

1930-1990 MHz (US

PCS)

935-960 (Europa)

1930-1990 (US PCS)

869-894 MHz (Cellular)

1930-1990 (US PCS)

800 MHz, 1500 MHz

(Japan)

Deplexing FDD FDD FDD

Multiple Access CDMA TDMA TDMA

Modulation BPSK with Quadrature

Spreading

GMSK with BT=0.3 p/4 DQPSK

Carrier Seperation 1.25 MHz 200 KHz 30 KHz (IS-136)

(25 KHz PDC)

Channel Data Rate 1.2288 Mchips/sec 270.833 Kbps 48.6 Kbps (IS-136)

42 Kbps (PDC)

Voice Channels per

carrier

64 8 3

Speech Coding CELP at 13Kbps

EVRC at 8Kbps

RPE-LTP at 13 Kbps VSELP at 7.95 Kbps

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2G and Data

2G is developed for voice communications

You can send data over 2G channels by

using modem

Provides adat rates in the order of ~9.6 Kbps

Increased data rates are requires for internet

application

This requires evolution towards new systems:

2.5 G

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2.5 Technologies

Evolution of TDMA Systems

HSCSD for 2.5G GSM Up to 57.6 Kbps data-rate

GPRS for GSM and IS-136 Up to 171.2 Kbps data-rate

EDGE for 2.5G GSM and IS-136 Up to 384 Kbps data-rate

Evolution of CDMA Systems

IS-95B Up to 64 Kbps

45

3G Systems

Goals

Voice and Data Transmission

Simultanous voice and data access

Multi-megabit Internet access

Interactive web sessions

Voice-activated calls

Multimedia Content

Live music

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3G Systems (Con’t)

Evolution of Systems CDMA sysystem evaolved to CDMA2000

CDMA2000-1xRTT: Upto 307 Kbps

CDMA2000-1xEV:

CDMA2000-1xEVDO: upto 2.4 Mbps

CDMA2000-1xEVDV: 144 Kbps datarate

GSM, IS-136 and PDC evolved to W-CDMA (Wideband CDMA) (also called UMTS)

Up to 2.048 Mbps data-rates

Future systems 8Mbps

Expected to be fully deployed by 2010-2015

New spectrum is allocated for these technologies

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Interest to 3G Applications

Western Eastern USA

Europe Europe

Emails 4.5 4.7 4.3

City maps/directions 4.3 4.2 4.2

Latest news 4.0 4.4 4.0

Authorize/enable payment 3.4 3.8 3.0

Banking/trading online 3.5 3.4 3.2

Downloading music 3.1 3.4 3.2

Shopping/reservation 3.0 3.1 2.9

Animated images 2.4 2.7 2.6

Chat rooms, forums 2.3 2.9 2.2

Interactive games 2.0 2.2 2.4

Games for money 1.8 1.8 1.8

(Means based upon a six-point interest scale, where 6 indicates high interest and 1 indicates low interest.)

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Upgrade Paths for 2G Technologies

IS-136

PDC GSM IS-95

IS-95B HSCSD

GPRS

EDGE

W-CDMA EDGE

TD-SCDMA

cdma200-1xRTT

cdma2000-1xEV,DV,DO

cdma200-3xRTT

2G

2.5G

3G

GSM Protocol Architecture

BSSMAP = BSS Mobile Application part

BTSM = BTS management

CM = Connection Management

LAPD = Link Access Protocol, D Channel

Base Transceiver

Station

Mobile

Station

Radio

LAPDm

RRM

Radio

LAPDm

RRM

MM

CM

64 Kbps

LAPD

BTSM

64 Kbps

MTP

SCCP

Base Station

Controller

64 Kbps

LAPD

BTSM

BSSMA

P

64Kbp

s

MTP

SCCP

MM

CM

BSSMA

P

Mobile Service

Switching Center

MM = Mobility Management

MTP = Message Transfer Part

RRM = Radio Resources Management

SCCP = Signal Connection Control Point

49

50

Subscriber / Technologies

51

GSM and CDMA Coverage Map

Worldwide

52

Mobile Phone Market Share

Alternatives to 3G Cellular

Major technical undertaking with many organizational and marketing overtones.

Questions about the need for the additional investment for 3G (happy with 2.5G)

Wireless LAN in public places such as shopping malls and airports offer options

Other high-speed wireless-data solutions compete with 3G

Mobitex low data rates (nominally 8 Kbps), it uses a narrowband (2.5KHz) as compared to 30 KHz (GSM) and 5 MHz (3G).

Ricochet: 40 -128 kbps data rates. Bankruptcy

Flash-OFDM: 1.5 Mbps (upto 3 Mbps)

53

4G Systems

Wireless networks with cellular data rates of 20

Mbits/second and beyond.

AT&T has began a two-phase upgrade of its wireless

network on the way to 4G Access.

Nortel developing developing features for Internet

protocol-based 4G networks

Alcatel, Ericsson, Nokia and Siemens found a new

Wireless World Research Forum (WWRF) for

research on wireless communications beyond 3G.

Many new technologies and techniques (multiplexing,

intelligent antennas, digital signal processing)

Industry response is mixed (some very critical)

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Engineering Issues

Steps in MTSO controlled call

TDMA design

CDMA design

Handoff

Power control

Traffic engineering

55

Steps in an MTSO Controlled

Call between Mobile Users Mobile unit initialization

Mobile-originated call

Paging

Call accepted

Ongoing call

Handoff

Call blocking

Call termination

Call drop

Calls to/from fixed and remote mobile subscriber

56

Mobile Wireless TDMA Design

Considerations

Number of logical channels (number of time slots in TDMA frame): 8

Maximum cell radius (R): 35 km

Frequency: region around 900 MHz

Maximum vehicle speed (Vm):250 km/hr

Maximum coding delay: approx. 20 ms

Maximum delay spread (m): 10 s

Bandwidth: Not to exceed 200 kHz (25 kHz per channel)

57

Mobile Wireless CDMA Design

Considerations

Soft Handoff – mobile station temporarily connected to more than one base station simultaneously

RAKE receiver – when multiple versions of a signal arrive more than one chip interval apart, RAKE receiver attempts to recover signals from multiple paths and combine them This method achieves better performance than simply

recovering dominant signal and treating remaining signals as noise

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What is WiMax?

Worldwide Interoperability for Microwave

Access

Last mile wireless broadband access

Alternative to cable and DSL

Deliver data, voice, video

Support hundreds to thousands of

homes/business

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Defined by IEEE as 802.16

Typical target environment:

Targets fixed, portable, and mobile

stations

Environments with and without line of

sight

Cell radius of 3-10 kilometers

Capacities of up to 40 Mbps per channel

Mobile network deployments of up to 15

Mbps, 3 km radius

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Builds on and

Extends WiFi Technology

Advantages of WiFi are:

Easy to deploy, unlicensed spectrum, low

cost

Supports (limited) mobility

But WiMax needs to address the

following:

61

WiFi limitations Susceptible to interference

802.11 targets short-range indoor

operation (mostly)

Security is a concern

Limited level of mobility

WiMax is intended to complement WiFi

WiMax Forum: promotes WiMax and looks

after interoperability

62

WiMax Deployment

63

LTE Key Features

64

Uses Multi-input Multi-output (MIMO) for enhanced throughput

Reduced power consumption

Higher RF power amplifier efficiency (less battery power used by handsets)

Lower latency to get access to the medium

Performance sometimes better than WiFi!

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