Ai Namps

June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 1

Advanced Mobile Advanced Mobile Phone Service Phone Service

(AI-AMPS)(AI-AMPS)


AI-AMPSAI-AMPS

© Copyright 2001 Global Wireless Education Consortium

All rights reserved. This module, comprising presentation slides with notes, exercises, projects and Instructor Guide, may not be duplicated in any way without the express written permission of the Global Wireless Education Consortium. The information contained herein is for the personal use of the reader and may not be incorporated in any commercial training materials or for-profit education programs, books, databases, or any kind of software without the written permission of the Global Wireless Education Consortium. Making copies of this module, or any portion, for any purpose other than your own, is a violation of United States copyright laws.

Trademarked names appear throughout this module. All trademarked names have been used with the permission of their owners.


AI-AMPSAI-AMPS

Partial support for this curriculum material was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement Program under grant DUE-9972380 and Advanced Technological Education Program under grant DUE‑9950039.

GWEC EDUCATION PARTNERS: This material is subject to the legal License Agreement signed by your institution. Please refer to this License Agreement for restrictions of use.


Table of ContentsTable of Contents

Overview 5

Learning Objectives 6

AMPS Implementation 7

AMPS Air Interface Channels 15

AMPS Voice Processing 30

AMPS Cell Structure 32

Narrowband AMPS 37

Summary 40

Contributors 43


OverviewOverview

This module covers the following topics: AMPS history General AMPS characteristics AMPS network structure and interfaces AMPS channel structure and voice processing AMPS cell structure Narrowband AMPS (N-AMPS) Advantages and disadvantages of AMPS


Learning ObjectivesLearning Objectives

Explain how an AMPS network and the AMPS radio interface work

Describe the structure of an AMPS cell and channel Differentiate AMPS from other standards in the

telecommunications industry: N-AMPS, CDMA, TDMA, and GSM

Explain the strengths and weaknesses of AMPS relative to other wireless technologies


AMPS ImplementationAMPS Implementation


AMPS HistoryAMPS History

1958: AT&T proposes AMPS

1971: AMPS technical feasibility demonstrated

1979: Network and marketing trial approved between AT&T and Illinois Bell

1983: Commercial AMPS service launched

1984 and beyond: Definition of dual-mode air interface standards for AMPS and TDMA or CDMA


AMPS OverviewAMPS Overview

• Cellular telephony provides full-duplex communications• Two-way simultaneous conversation requires simultaneous voice paths in both

directions• 25 MHz band of frequencies used for mobile transmission (uplink)• 25 MHz band of frequencies used for cell site transmission (downlink)

• Cellular bands divided equally between two competing operators• A operator• B operator

824 835 845 870 880 894

869

849

846.5825

890

891.5

Uplink Downlink

Paired Bands

Frequency ( MHz)

Uplink

Downlink


AMPS CharacteristicsAMPS Characteristics

Uses 800 MHz – 900 MHz frequency band Has 30 kHz bandwidth for each channel Fully automated service Used in both urban and rural areas Roaming is easy


AMPS CharacteristicsAMPS Characteristics(cont’d)(cont’d)

Uses FM for radio transmission To overlay voice and signaling information on a RF carrier

wave for transmission

Uses FDMA to support multiple simultaneous conversations Uses separate frequency from that used for transmission from

cell site to mobile station


AMPS NetworkAMPS Network

Mobile Station

1

24

57

8*

0

3

6

9

#

Cell Site

Cell Site

Voice Trunks

Data & Control

CellSite

Controller

CellSite

ControllerRadio

Radio

Radio

Radio

Radio

Radio

MobileSwitchingCenter

ToLandLineNetwork

NetworkDatabases (HLR, VLR)

Mobile Station


AMPS Network InterfacesAMPS Network Interfaces

Interfaces connect components of the AMPS network Telecommunications standards established by groups

such as ANSI and TIA Standard for AMPS air interface between mobile stations and

base station radios is ANSI/TIA/EIA 553 Standard for interactions between MSCs and databases is

TIA/EIA IS-41


AMPS Network InterfacesAMPS Network Interfaces

PSTN

RF TestEquipment

12 4

57

8*

0

3

6

9

#

12 4

57

8*

0

3

6

9

#

12

4

57

8*

0

3

6

9

#

CSC

CSC

CSC

MSC

MSC

MSC

Air Interface(Um interface)

Not a Standard Interface

Base Station (Cell Site) to MSC

(A interface)

Radio

Radio

Radio

MSC to PSTN (Ai interface)

MS

MS

MS

Base Station (Cell Site) MSC to HLR

(C interface), MSC to VLR (B interface)


AMPS Air Interface AMPS Air Interface ChannelsChannels


AMPS Air Interface AMPS Air Interface Channel AssignmentChannel Assignment

Forward Control Path

Reverse Control Path

Reverse Voice Path

Forward Voice Path

Control Channel

Voice Channel

Mobile StationCell Site


AMPS Control ChannelAMPS Control Channel

AMPS control channel supports multiple functions, including: Registration Paging Call setup

Data supporting each function is transmitted via: Forward Control Channel (FOCC) data stream Reverse Control Channel (RECC) data stream

Signaling data is digitized for transmission on analog control channels by using frequency shift keying (FSK)


Forward Control Channel Forward Control Channel (FOCC) Messages(FOCC) Messages

Messages include: Mobile station control message Overhead message Control filler message

FOCC data stream has 3 discrete information streams Stream A sends messages with least significant bit of their

mobile ID number equal to “0” Stream B sends messages with least significant bit of their

mobile ID number equal to “1” Busy-idle stream indicates current status of reverse channel

Continuous FOCC data stream contains all information from base station to mobile station necessary for registration, paging, and call setup


Forward Control Channel Forward Control Channel (FOCC) Messages(FOCC) Messages

40-bit field of message 28 left-most bits are content bits

First two bits identify type of message being sent

Each repeat of FOCC message begins with 10-digit dotting sequence 11-bit sync sequence follows Five repeats each of the two data streams follows

Mobile stations use dotting sequence and sync sequence to synchronize with overall data stream


Reverse Control Channel Reverse Control Channel (RECC) Message(RECC) Message

Message consists of five different words each repeated five times

Usage by multiple mobile stations is coordinated using busy-idle bits from FOCC data stream

Digital control code (DCC) is used as identification tag on forward and reverse control channels

Continuous RECC data stream contains all information from mobile station to base station necessary for registration, paging, and call setup


RegistrationRegistration

Mobile station is programed to scan 21 control channels assigned by AMPS service provider

When mobile station is powered on, it scans through FOCCs and selects the one with the strongest signal

Mobile station sends identifying information in the RECC data stream

MSC authenticates mobile station information via AMPS network databases


Other FOCC Message Other FOCC Message ApplicationsApplications

Messages intended for all mobile stations Information about the system Overhead information

Messages intended for specific individual mobile stations If mobile station is in progress to originate a call, mobile station

is notified of which voice channel should be used If mobile station is idle and call comes in, mobile station is

paged over the channel


Other RECC Message Other RECC Message ApplicationsApplications

Origination message Contains directory number of called telephone and other

information about the originating mobile station

Page response message Sent in response to incoming message from cell site


AMPS Voice ChannelsAMPS Voice Channels

Transmit user information (voice conversations or data) between mobile and base station

Use two methods of signaling In-band signaling

Sends control information with voice information or replaces the voice information

Frequency range of 300-3000 Hz Out-of-band signaling

Can be sent without alteration to voice information Frequency range above or below 300-3000 Hz


Voice Channel SignalsVoice Channel Signals

Different signals and tones are sent on the voice channel for call control while a call is in progress: Supervisory audio tone signal Signaling tone signal Dual tone multi-frequency signal Blank and burst signal

FSK is used to encode digital data (1’s and 0’s) as a series of analog waves, for transmission on the analog voice channel


Supervisory Audio Tone Supervisory Audio Tone SignalSignal

Call in Progress:Subscriber 1 connected to Base Station 1 on Channel 432, SAT 0

Everything’s OK here!

Subscriber 2 initiates call: Base Station 2 responds with channel 432, SAT 1Normal call setup for Subscriber 2

Co-channel interference:Subscriber 2 receives transmission on channel 432 from Base Station 1, but receives SAT 0 instead of SAT 1Fade timer starts, after 5 seconds Subscriber 2 call is dropped!

Base Station 2

Base Station 1

Subscriber 1

Subscriber 2

3

2

1


Signaling ToneSignaling Tone

A 10 kHz burst sent via out-of-band signaling Length of burst and current state of mobile station (on-

hook, call in progress, etc.) are used at cell site to interpret meaning of a particular signaling tone burst

Applications include: Indication to cell site of on- or off-hook status of subscriber Indication to cell site that subscriber has performed a hookflash

or equivalent Alert confirmation Handoff order acknowledgment


Dual Tone Multi-Frequency Dual Tone Multi-Frequency (DTMF) Signal(DTMF) Signal

Mobile StationCell Site

Mobile Switching Center

PSTN

End-User Device (Answering Machine, etc.)

DTMF signaling from mobile station to end-user device


Blank and Burst SignalBlank and Burst Signal

Blank and burst signals are used to transmit messages containing more complex call control data while a call is in progress

Blank and burst signals occur in less than a second, and are almost imperceptible to the subscriber

Examples include: Power control Handoff notification Data transmission (e. g., dialed digits) required for use of

custom calling features


AMPS Voice AMPS Voice ProcessingProcessing


AMPS Voice ProcessingAMPS Voice Processing

Baseband processing AMPS baseband processing functions include:

Compression Emphasis Limiting

Modulation AMPS uses FM to overlay modified baseband signal on a RF

carrier wave


AMPS Cell StructureAMPS Cell Structure


AMPS Cell StructureAMPS Cell Structure

AMPS operation requires 60 kHz of spectrum for each active call

Frequency reuse is required to increase the number of simultaneous users that can be accommodated

Typical cellular network design is represented by hexagonal cells for complete geographical coverage


F

B

B

A

A

C

D

E

G

AMPS Frequency Reuse AMPS Frequency Reuse


Cell

OmnidirectionalAntenna

AMPS Omni CellAMPS Omni Cell


Sector

SectoredAntenna

Cell

A1

A2

A3B1

B2B3 C1

C3

C2

AMPS Sectored CellAMPS Sectored Cell


Narrowband AMPS Narrowband AMPS (N-AMPS)(N-AMPS)


N-AMPS CharacteristicsN-AMPS Characteristics

Higher subscriber capacity per unit of spectrum Divides 30 kHz voice channels (transmit or receive) into 3

channels of 10 kHz each Allows for frequency reuse of 4 rather than the 7 channels used

by AMPS

Signaling in voice channel (while call is in progress) uses continuous digital data stream Data is transmitted at sub-voice frequencies (< 300 Hz) Replaces functions performed in AMPS by:

Supervisory audio tone (SAT) Signaling tone (ST) Blank and burst signals

Control channel functions remain the same as AMPS


N-AMPS DeploymentN-AMPS Deployment

N-AMPS deployed in limited market N-AMPS developed by Motorola Required availability of dual mode handsets (N-AMPS and

AMPS) for full network coverage

N-AMPS served as an interim technology between analog (AMPS) and digital Primary application was to provide increased capacity in urban

areas for which AMPS capacity was inadequate Has been replaced largely by digital technologies (e. g., TDMA,

CDMA, and GSM) Scattered deployment still exists outside the U. S.


SummarySummary


AMPS Compared to Other AMPS Compared to Other Wireless TechnologiesWireless Technologies

AMPS N-AMPS IS-136TDMA

IS-95CDMA

GSM

VoiceTransmission

Analog Analog Digital Digital Digital

Modulation FrequencyModulation(FM)

FrequencyModulation(FM)

PhaseModulation(specifically,DQPSK)

DirectSequenceCodeModulation

PhaseModulation(specifically,GMSK)

MultipleAccess

FrequencyDivisionMultipleAccess(FDMA)

FrequencyDivisionMultipleAccess(FDMA)

TimeDivisionMultipleAccess(TDMA)

CodeDivisionMultipleAccess(CDMA)

TimeDivisionMultipleAccess(TDMA)

ChannelBandwidth(eachdirection)

30 kHz 10 kHz 30 kHz 1.25 MHz 200 kHz

SimultaneousUsers perChannel

1 1 3 20 8

FrequencyReuse

7 4 or 7 7 1 4

ComparableCapacity

1 (base) 3 x AMPS(reuse = 7)

5 x AMPS(reuse = 4)

3 x AMPS 8 x AMPS 2 x AMPS

SignalingProtocol

IS-41MAP

IS-41MAP

IS-41MAP

IS-41MAP

GSMMAP


AMPS Strengths and AMPS Strengths and WeaknessesWeaknesses

Strengths Extensive existing coverage (in the United States and

elsewhere) Can interwork with IS-136 TDMA and IS-95 CDMA Equipment is standardized and costs are low

Weaknesses Low capacity per unit of spectrum used Frequency reuse is less efficient than digital technologies Quality of analog transmission is inferior to digital AMPS equipment support may decline as “3rd Generation”

wireless is emphasized


Industry ContributorsIndustry Contributors

Ericsson (http://www.ericsson.com) Lucent (http://www.lucent.com) Motorola (http://www.motorola.com) RF Globalnet (http://www.rfglobalnet.com) Telcordia Technologies, Inc (http://www.telcordia.com)

The following companies provided materials and resource support for this module:


Individual ContributorsIndividual ContributorsThe following individuals and their organization or institution provided materials, resources, and development input for this module: Dr. Cheng Sun

California Polytechnic State University http://www.calpoly.edu/

Dr. David Voltmer Rose-Hulman Institute of Technology http://www.rose-hulman.edu

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