CDMA CALL PROCESSING

To process a call, MS goes through the To process a call, MS goes through the

following stages to get traffic channel.following stages to get traffic channel.

•• SYSTEM INITIALISATION STATESYSTEM INITIALISATION STATE

•• SYSTEM IDLE STATESYSTEM IDLE STATE

•• SYSTEM ACCESS STATESYSTEM ACCESS STATE

•• TRAFFIC CHANNEL STATETRAFFIC CHANNEL STATE

Tune to CDMA Carrier

Mobile acquires pilot channel and sync channel

Mobile acquires paging channel and monitors for messages

Mobile sends messages on access channel, BS sends messages on paging channel.

Speech communication on forward and reverse traffic channel, Power control on forward link

System initialization state

Idle state

Access State

Traffic channel state

CALL PROCESSING

CALL PROCESSING STATE:CALL PROCESSING STATE:

•• In system initialization state the mobile In system initialization state the mobile

acquires a pilot channel by searching the PN off acquires a pilot channel by searching the PN off

sets and selects the strongest pilot signal.sets and selects the strongest pilot signal.

•• Then it acquires synchronization channel using Then it acquires synchronization channel using

WW3232 and detecting timing offset of pilot and detecting timing offset of pilot

channel. Then mobile acquires the system channel. Then mobile acquires the system

configuration and timing information.configuration and timing information.

•• Then the MS enters the system idle state where Then the MS enters the system idle state where

it monitors the paging channel. Now the mobile it monitors the paging channel. Now the mobile

can receive necessary message to initiate or can receive necessary message to initiate or

receive a call.receive a call.

•• If a call is placed or received, MS enters the If a call is placed or received, MS enters the

system access state exchanging necessary system access state exchanging necessary

parameters. MS transmits its response on parameters. MS transmits its response on

access channel and BS transmits on paging access channel and BS transmits on paging

channel.channel.

•• On access, the MS enters traffic channel On access, the MS enters traffic channel

state and communicate. It also transmits state and communicate. It also transmits

control messages replacing speech by control messages replacing speech by

signaling.signaling.

•• Power control messages are sent on forward Power control messages are sent on forward

link channel.link channel.

SYSTEM INITIALIZATION STATESYSTEM INITIALIZATION STATE

Power up and mobile enters

initialization state

System determination sub state

Pilot acquisition sub state

Sync channel acquisition sub state

Timing change sub

state

CDMA system is selected

Pilot channel is acquired

Sync channel is acquired

System timing is acquired

Enter idle stateAnalog

initialization

Begin analog mode

•• System determination sub state :System determination sub state :

Mobile can select analog or CDMA, if the Mobile can select analog or CDMA, if the system selects CDMA, the mobile sets the system selects CDMA, the mobile sets the CDMA channel parameters to channel CDMA channel parameters to channel number.number.

•• Pilot channel acquisition sub state:Pilot channel acquisition sub state:

Mobile acquires pilot channel of CDMA Mobile acquires pilot channel of CDMA system and tunes to CDMA channel and sets system and tunes to CDMA channel and sets its code channel for the pilot channel and its code channel for the pilot channel and searches for pilot channel within 20 msec, the searches for pilot channel within 20 msec, the mobile should acquire pilot channel, else mobile should acquire pilot channel, else mobile enters system determination sub state mobile enters system determination sub state indicating failure.indicating failure.

•• Synchronization acquisition sub state :Synchronization acquisition sub state :

Mobile acquires the sync channel and Mobile acquires the sync channel and obtains system configuration and timing obtains system configuration and timing information for CDMA system and sets its information for CDMA system and sets its code channel for sync channel if mobile does code channel for sync channel if mobile does not receive a sync channel message within not receive a sync channel message within 21 msec, mobile enters the sync 21 msec, mobile enters the sync determination sub state with a protocol determination sub state with a protocol mismatch indication.mismatch indication.

If it receives within 21 msec, mobile If it receives within 21 msec, mobile stores system configuration and timing stores system configuration and timing information.information.

•• Timing change sub state :Timing change sub state :

If a mobile synchronizes its long code If a mobile synchronizes its long code

timing of system timing to those of CDMA timing of system timing to those of CDMA

system after receiving and processing sync system after receiving and processing sync

messages.messages.

After sync channel is acquired and sync After sync channel is acquired and sync

message is received, it stores the message is received, it stores the

following information like system following information like system

identification, network identification, identification, network identification,

system time, long code at system time, system time, long code at system time,

paging channel data rate etc..paging channel data rate etc..

CDMA initialization

Acquires primary paging channel (W1)

• monitors paging channel

•Authentication

•Idle hand off

•Page Response

•Mobile origination

•Receives an incoming call

•Registration

Idle StateIdle State

Idle State :Idle State :

Mobile monitors paging channel. Mobile monitors paging channel. Mobile can receive messages from base Mobile can receive messages from base station to initiate or receive a call. station to initiate or receive a call.

It can also initiate a registration It can also initiate a registration process, message transmission. After process, message transmission. After entering idle state, mobile sets its Walsh entering idle state, mobile sets its Walsh code to the primary paging channel and code to the primary paging channel and sets its rate to the rate obtained from sync sets its rate to the rate obtained from sync message. message.

Paging channel is subdivided into 80 Paging channel is subdivided into 80 msec slots are called paging channel slots.msec slots are called paging channel slots.

•• In In slotted modeslotted mode, the mobile monitors only , the mobile monitors only

certain assigned slots. When paging certain assigned slots. When paging

channel is not monitored, mobile can stop channel is not monitored, mobile can stop

or reduce its processing activities to save or reduce its processing activities to save

battery power.battery power.

•• In the In the non slotted modenon slotted mode, paging and , paging and

control data can be received on any of this control data can be received on any of this

slot. The mobile monitors all the slots on slot. The mobile monitors all the slots on

continuous basis.continuous basis.

•• Idle Hand off :Idle Hand off :

Idle hand off or change of paging channel Idle hand off or change of paging channel occurs when a mobile has moved from occurs when a mobile has moved from coverage of one base station to coverage of coverage of one base station to coverage of another, during idle state. Hand off should another, during idle state. Hand off should occur when it detects new pilot that is stronger occur when it detects new pilot that is stronger than current pilot.than current pilot.

Pilots are identified by short PN offsets. Pilots are identified by short PN offsets. These pilot sets are maintained by active, These pilot sets are maintained by active, candidate, neighbor, remaining. If neighbor candidate, neighbor, remaining. If neighbor set or remaining set is stronger than active set set or remaining set is stronger than active set and candidate set, pilot hand off is performed. and candidate set, pilot hand off is performed. On receiving new message, from new paging On receiving new message, from new paging channel, it resumes operations.channel, it resumes operations.

SYSTEM ACCESS STATE:SYSTEM ACCESS STATE:

It includes following sub states.It includes following sub states.

1.1. Update overhead informationUpdate overhead information

2.2. Mobile State origination AttemptMobile State origination Attempt

3.3. Page ResponsePage Response

4.4. Registration Access sub stateRegistration Access sub state

5.5. Mobile Station TransmissionMobile Station Transmission

Traffic channel sub state:Traffic channel sub state:

Speech communication takes Speech communication takes

associated with control messages.associated with control messages.

There are 5 sub states in this.There are 5 sub states in this.

1.1. Traffic Channel initialization :Traffic Channel initialization :

In this state, mobile verifies it can In this state, mobile verifies it can

receive forward traffic channel and starts receive forward traffic channel and starts

transmit on reverse link.transmit on reverse link.

2.2. Waiting for order sub state:Waiting for order sub state:

In this, MS waits for an alert with In this, MS waits for an alert with

information message.information message.

3.3. Waiting for MS answer sub state:Waiting for MS answer sub state:

In this state, the MS waits for user to In this state, the MS waits for user to

answer the call.answer the call.

4.4. Conversation sub state:Conversation sub state:

Here, the MS exchange primary traffic Here, the MS exchange primary traffic

data packets with base station.data packets with base station.

5.5. Release Sub state:Release Sub state:

In this case, MS disconnects a call.In this case, MS disconnects a call.

CDMA REGISTRATIONCDMA REGISTRATION

Registration is a process in which the Registration is a process in which the

MS tells the base station about the MS tells the base station about the

whereabouts. It notifies base station of whereabouts. It notifies base station of

its location status, identification, slot cycle its location status, identification, slot cycle

and other characteristics.and other characteristics.

Purpose of registration is to enable the Purpose of registration is to enable the

base station to page the mobile in case of base station to page the mobile in case of

an incoming call.an incoming call.

CDMA supports 9 types of registration.CDMA supports 9 types of registration.

1.1. Power up registration :Power up registration : The mobile registers, The mobile registers, when it powers up.when it powers up.

2.2. Power down registration :Power down registration : The mobile The mobile registers, when it powers down informing the registers, when it powers down informing the system that it is no longer active.system that it is no longer active.

3.3. Time based registration :Time based registration : the mobile registers the mobile registers at regular intervals of time. Its use also alerts the at regular intervals of time. Its use also alerts the system to automatically deregister mobile stations system to automatically deregister mobile stations that did not perform a successful power down that did not perform a successful power down registration.registration.

4.4. Distance based registration :Distance based registration : Mobile performs Mobile performs a registration when distance between current a registration when distance between current base station and the base station which it has base station and the base station which it has previous registered exceeds the threshold.previous registered exceeds the threshold.

5. Zone based registration :5. Zone based registration : Mobile registers when it Mobile registers when it enters a new zone.enters a new zone.

6. Parameter changed registration :6. Parameter changed registration : Mobile does a Mobile does a registration when it enters a new system or some of registration when it enters a new system or some of its stored parameters change.its stored parameters change.

7. Ordered registration :7. Ordered registration : mobile registers when a mobile registers when a base station asks for it.base station asks for it.

8. Implicit registration :8. Implicit registration : When a MS sends a When a MS sends a successful origination message or page response successful origination message or page response message, base station can ask a mobile of its location.message, base station can ask a mobile of its location.

9. Traffic channel registration :9. Traffic channel registration : Base station tells Base station tells the mobile, it is registered.the mobile, it is registered.

Only power up, power down, time based, Only power up, power down, time based, location based registrations are presently location based registrations are presently supported.supported.

CALL PROCESSING (Mobile Station to Base Station)

Sends origination message Receives origination messageAccess Channel

Receive Paging Channel Sets up Traffic Channel, starts sending null traffic data

Paging Channel

Sets up reverse traffic chAcquires reverse traffic Ch

Rev traffic ChStarts sending Traffic Ch preamble

Fwd traffic ChReceives Ack from BS

Starts sending null traffic data

Rev traffic Ch

Sends BS Acknowledgement

Receives data from Mobile

Sends origination continuation message

Rev traffic Ch Receives the message

Receives ring back tone Fwd traffic ChSends Alert with info msg

Ring Stops Fwd traffic ChCalled subscriber answers, alert tone off.

Conversation Conversation Fwd/Rev traffic Ch

Mobile originated callMS BTS

CALL PROCESSING (Base Station to Mobile Station)

Sends page message Receives page messagePaging Channel

Receive Paging Response Sends paging Response message

Access Channel

Sets up traffic chReceives traffic data frames

Paging ChStarts sending null Traffic data

Rev traffic ChSends channel assignment

Acquires rev tfc ch sends bs ack order

Fwd traffic Ch

Sets up reverse traffic ch, sends traffic channel preamble

Process primary traffic data

Sends alert with info msg Fwd traffic Ch Starts ringing, user answers, stops ringing

Receives connect order Rev traffic ChSends connect order

Conversation Conversation Fwd/Rev traffic Ch

Mobile Terminated callBS MS

Mobile initiated call disconnect

MS

Detects user initiated , sends Release order

Enters system determination sub state, of mobile station initialization state

Sends release order

Rev Tfc Ch

Fwd Tfc Ch

BS

Base Station initiated call disconnect

BS

Detects user initiated ,

sends Release order

Enters system determination

sub state, of mobile station

initialization state

Fwd Tfc Ch

Rev Tfc Ch

MS

CALL PROCESSING DURING SOFT HAND OFF

Mobile Station Base Station

< User conversation using A > < User conversation using A >

Pilot B level exceeds T_ADD sends “pilot strength Measurement Report”

A receives measurement report, B starts sending data

Receives hand off direction message ( Starts using active

set A&B)

acquires reverse traffic channel, A and B send hand off direction message to use A&B

Sends hand off completion message

A&B receive completion message

Hand off drop timer for pilot A expires

A&B receive measurement report

Continued….

RTCH

RTCH

RTCH

FTCH

CALL PROCESSING DURING SOFT HAND OFF

Mobile Station Base Station

Mobile sends measurement report

A&B send hand off direction message to use pilot B only

Receives hand off direction message

Sends hand off completion message

• A&B receive completion message

• A stops transmitting on fwd ch and receiving on rev traffic channel

< User conversation using B > < User conversation using B >

RTCH

FTCH

RTCH

F/RTCH