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1G PERSONAL COMMUNICATION 1G PERSONAL COMMUNICATION SYSTEMS: AMPSSYSTEMS: AMPS

(PART III) (PART III)

Ian F. AkyildizIan F. Akyildiz

Broadband & Wireless Networking LaboratoryBroadband & Wireless Networking Laboratory

School of Electrical and Computer EngineeringSchool of Electrical and Computer Engineering

Georgia Institute of TechnologyGeorgia Institute of Technology

Tel: 404-894-5141; Fax: 404-894-7883 Tel: 404-894-5141; Fax: 404-894-7883

Email: [email protected]: [email protected]

Web: http://www.ece.gatech.edu/research/labs/bwnWeb: http://www.ece.gatech.edu/research/labs/bwn

2IFA’2004

AMPS (Advanced Mobile Phone AMPS (Advanced Mobile Phone Service)Service)

AT&T Bell Labs developed the first cellular AT&T Bell Labs developed the first cellular tel system in the late 70s.tel system in the late 70s.

First system was deployed in Chicago in First system was deployed in Chicago in 1983.1983.

A total of 40 MHz spectrum in the 800 MHz A total of 40 MHz spectrum in the 800 MHz band was allocated by FCC.band was allocated by FCC.

In 1989, additional 10 MHz (called “Extended In 1989, additional 10 MHz (called “Extended Spectrum”) was allocated.Spectrum”) was allocated.

Large cells and omni-directional BS antennas Large cells and omni-directional BS antennas were used.were used.

3IFA’2004


AMPS uses a 7-cell reuse pattern with cell AMPS uses a 7-cell reuse pattern with cell splitting and sectoring (120 degrees).splitting and sectoring (120 degrees).

It requires S/I of 18 dB for satisfactory system It requires S/I of 18 dB for satisfactory system performance.performance.

It uses frequency modulation (FM) for radio It uses frequency modulation (FM) for radio transmission.transmission.

Mobile-> BS (reverse link) uses frequencies Mobile-> BS (reverse link) uses frequencies between 824-849 MHz. between 824-849 MHz.

BS -> Mobile (forward link) uses frequencies BS -> Mobile (forward link) uses frequencies between 869-894 MHz.between 869-894 MHz.

Separation for forward and reverse channels is Separation for forward and reverse channels is 45 MHz.45 MHz.

4IFA’2004

1G ARCHITECTURE 1G ARCHITECTURE (AMPS)(AMPS)

BACKBONE TELEPHONE NETWORK

(HLR)

Mobile Switching Center

Visitor Location Register

Mobile Terminal(MT)

MSC

VLR(MSC)

(VLR)

Home Location Register

5IFA’2004


Each BS has one control channel Each BS has one control channel transmitter (broadcasts on the forward transmitter (broadcasts on the forward control channel)control channel)

One control receiver (that listens on the One control receiver (that listens on the reverse control channel for any cellular reverse control channel for any cellular phone trying to set up a control) and 8 phone trying to set up a control) and 8 or more FM duplex voice channels.or more FM duplex voice channels.

BS supports as many as 57 voice BS supports as many as 57 voice channels.channels.

6IFA’2004


Forward Voice Channel (FVC) carries the portion Forward Voice Channel (FVC) carries the portion of the tel conversation originating from the of the tel conversation originating from the landline tel network caller and going to mobile landline tel network caller and going to mobile user.user.

Reverse voice channels (RVC) carry the portion of Reverse voice channels (RVC) carry the portion of the tel conversation originating from the mobile the tel conversation originating from the mobile user and going to landline tel network caller.user and going to landline tel network caller.

The number of control and voice channels used The number of control and voice channels used at a BS varies based on load of the system.at a BS varies based on load of the system.

7IFA’2004


Each BS continuously transmits digital FSK Each BS continuously transmits digital FSK data on the Forward Control Channel at all data on the Forward Control Channel at all times so that idle mobile users can lock onto times so that idle mobile users can lock onto the strongest FCC wherever they are.the strongest FCC wherever they are.

All users must be locked or “camped” onto an All users must be locked or “camped” onto an FCC in order to originate or receive calls.FCC in order to originate or receive calls.

The BS reverse control channel (RCC) receiver The BS reverse control channel (RCC) receiver constantly monitors transmissions from constantly monitors transmissions from

mobile users that are locked onto the mobile users that are locked onto the matching FCC. matching FCC.

There are 21 control channels and they are There are 21 control channels and they are scanned to find the best serving base station.scanned to find the best serving base station.

8IFA’2004

AMPS (Advanced Mobile Phone AMPS (Advanced Mobile Phone Service)Service)CALL HANDLINGCALL HANDLING

A Wired User calls a Mobile UserA Wired User calls a Mobile User

The call arrives at MSC and a paging message is The call arrives at MSC and a paging message is sent out with the mobile’s MIN (Mobile sent out with the mobile’s MIN (Mobile Identification Number) simultaneously on every Identification Number) simultaneously on every BS forward control channel in the system.BS forward control channel in the system.

When the target callee receives the page, it will When the target callee receives the page, it will respond with ACK transmission on reverse respond with ACK transmission on reverse control channel.control channel.

The MSC then directs the BS to assign a FVC The MSC then directs the BS to assign a FVC and RVC pair to the mobile so that this call can and RVC pair to the mobile so that this call can take place on a dedicated voice channel.take place on a dedicated voice channel.

9IFA’2004


The BS also assigns the mobile a The BS also assigns the mobile a Supervisory Audio Tone (SAT tone) and Supervisory Audio Tone (SAT tone) and a Voice Mobile Attenuation Code a Voice Mobile Attenuation Code (VMAC) as it moves the call to the (VMAC) as it moves the call to the voice channel.voice channel.

The mobile automatically changes its The mobile automatically changes its frequency to the assigned voice frequency to the assigned voice channel pair.channel pair.

10IFA’2004


Mobile User places a Call:Mobile User places a Call: It transmits a message on the RCC containing its It transmits a message on the RCC containing its

MIN, Electronic Serial Number (ESN), Station MIN, Electronic Serial Number (ESN), Station Class Mark (SCM) and the destination tel Class Mark (SCM) and the destination tel number.number.

If received correctly by the BS, this information If received correctly by the BS, this information is sent to the MSC which checks to see if the is sent to the MSC which checks to see if the mobile is properly registered, connects the mobile is properly registered, connects the mobile to the PSTN, assigns the call to a forward mobile to the PSTN, assigns the call to a forward and reverse voice channel pair with a specific and reverse voice channel pair with a specific SAT and VMAC and commences the conversation.SAT and VMAC and commences the conversation.

11IFA’2004


Handoff decisions are made by the MSC when Handoff decisions are made by the MSC when the signal strength on the reverse voice channel the signal strength on the reverse voice channel (RVC)(RVC)

of the serving BS drops below a preset of the serving BS drops below a preset threshold or when the SAT tone experiences a threshold or when the SAT tone experiences a certain level of interference.certain level of interference.

MSC uses scanning receivers called “locate MSC uses scanning receivers called “locate receivers” in nearby BSs to determine the signal receivers” in nearby BSs to determine the signal level of a particular user which needs a handoff.level of a particular user which needs a handoff.

In doing so, the MSC is able to find the best In doing so, the MSC is able to find the best neighboring BS which can accept the handoff.neighboring BS which can accept the handoff.

12IFA’2004

AMPS (Advanced Mobile Phone AMPS (Advanced Mobile Phone Service) Service) Autonomous Autonomous RegistrationRegistration

Mobile notifies a serving MSC of its presence and Mobile notifies a serving MSC of its presence and location by periodically keying up and transmitting location by periodically keying up and transmitting its identity information, which allows the MSC to its identity information, which allows the MSC to constantly update its customer list.constantly update its customer list.

Registration command is sent in the overhead Registration command is sent in the overhead message of each control channel at 5-10 minute message of each control channel at 5-10 minute intervals and includes a timer value which each intervals and includes a timer value which each mobile uses to determine the precise time at which it mobile uses to determine the precise time at which it should respond to the serving BS with a registration should respond to the serving BS with a registration transmission.transmission.

Each mobile reports its MIN and ESN during the brief Each mobile reports its MIN and ESN during the brief registration transmission so that the MSC can registration transmission so that the MSC can validate and update the customer list.validate and update the customer list.

13IFA’2004

OVERVIEWOVERVIEW

Multiple AccessMultiple AccessDuplexingDuplexingChannel BWChannel BWReverse Channel FreqReverse Channel FreqForward Channel FreqForward Channel FreqVoice ModulationVoice ModulationData Rate on Data Rate on

Control/Voice ChannelsControl/Voice Channels

Number of ChannelsNumber of Channels

Coverage radius by 1 BSCoverage radius by 1 BS

FDMAFDMAFDDFDD30 KHz30 KHz824-849 MHz824-849 MHz869-894 MHz869-894 MHzFMFM

10 kbps10 kbps

666-832666-832

2-25 km2-25 km