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June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 1
Advanced Mobile Advanced Mobile Phone Service Phone Service
(AI-AMPS)(AI-AMPS)
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 2
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.
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 3
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.
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 4
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
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 5
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
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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
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AMPS ImplementationAMPS Implementation
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 8
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
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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
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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
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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
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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
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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
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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)
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AMPS Air Interface AMPS Air Interface ChannelsChannels
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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AMPS Voice AMPS Voice ProcessingProcessing
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 31
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
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AMPS Cell StructureAMPS Cell Structure
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 33
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
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F
B
B
A
A
C
D
E
G
AMPS Frequency Reuse AMPS Frequency Reuse
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Cell
OmnidirectionalAntenna
AMPS Omni CellAMPS Omni Cell
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Sector
SectoredAntenna
Cell
A1
A2
A3B1
B2B3 C1
C3
C2
AMPS Sectored CellAMPS Sectored Cell
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Narrowband AMPS Narrowband AMPS (N-AMPS)(N-AMPS)
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 38
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
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 39
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.
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SummarySummary
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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
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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
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 43
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:
June 2001 Copyright 2001 Global Wireless Education Consortium AI-AMPS 44
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