Mobile Station States in IS-95A by

Rahul Chauhan

Mobile Station States

M

MS Initialization

MS Idle State

System Access State

MS Traffic State

Mobile station has acquired timing System

MS receives a message on the paging channel requiring a ack;originates a call or performs registration.

Assigned a traffic channel.

Released traffic channel.

Receives an ack for Access Channel message other than ORM and PRM

Unable to receive Paging Channel

On power Up

Note : Transitions arising from error conditions are not shown in the diagram.

CDMA Message Structure

MSG_TYPE (‘00000001’)

ACK_SEQMSG_SEQACK_REQ

8

33

1VALID ACK

1

ACK_TYPEMSID_TYPE

3

3MSID_LEN 4

MSID 8 x MSID_LEN

AUTH_MODE 20 or 18

0 or 8

AUTHRRANDCCOUNT

REG_TYPE4

4SLOT_CYCLE_INDEX 3

MOB_PREV

SCM

8

8

MOB_TERM 1

RESERVED 6

The figure shows the Registration Message Structure which is sent on the Access Channel.A typical variable length PDU in IS-95A.

Points to Note :

• MSG_TYPE which uniquely identifies a message and helps in parsing.In IS-2000 this 8-bit field is split into a 2 bit field PD(protocol descriptor) and 6 bit message identifier MSG_TYPE.In IS-2000 PD is (01)binary.

•To ensure no messages are not missed, all CDMA messages bear serial numbers and important messages contain a bit requesting acknowledgment.The slide window of 7 is used for transfer of information.

•Addressing fields identify the type of addressing to be used.

•Authentication information to prevent spurious users from accessing the resources of the network.If the values in the PDU match the values generated at the BS,access is allowed.

BitsField

Messages Sent in Initialization and Idle States

Sync Channel

Sync Channel Msg

Pilot Channel

No Messages

Paging Channel

Access Parameters Msg

System Parameters Msg

CDMA Channel List Msg

Extended System Parameters Msg

Extended NeighborList Msg

Global ServiceRedirection Msg

Order Msg•Base Station Acknowledgment

•Lock until Power-Cycled• Maintenance required

many others…..

AuthenticationChallenge Msg

Status Request Msg

Feature Notification Msg

TMSI Assignment Msg

Channel AssignmentMsg

SSD Update Msg

Service Redirection Msg

General Page Msg

Null Msg Data Burst Msg

Access Channel

Registration Msg

Order Msg• Mobile Station Acknowledgment• Long Code Transition Request

• SSD Update Confirmationmany others…..

Origination Msg

Page Response Msg

Authentication Challenge Response Msg

Status Response Msg

TMSI AssignmentCompletion Message

Data Burst Msg

BTS

Messages in Traffic State

Reverse Traffic Channel

Order Message

• Mobile Sta. Acknowledgment

•Long Code Transition Request

• SSD Update Confirmation

• Connect

Authentication Challenge Response Msg

Flash WithInformation Msg

Data Burst Message

Pilot StrengthMeasurement Msg

Power MeasurementReport Msg

Send Burst DTMF Msg

OriginationContinuation Msg

Handoff Completion Msg

Parameters ResponseMessage

Service Request Msg

Service Response Msg

Service ConnectCompletion Message

Service Option ControlMessage

Status Response Msg

TMSI AssignmentCompletion Message

Forward Traffic Channel

Order Msg• Base Station Acknowledgment

• Base Station ChallengeConfirmation

• Message Encryption Mode

AuthenticationChallenge Msg

Alert WithInformation Msg

Data Burst Msg

Analog HandoffDirection Msg

In-Traffic SystemParameters Msg

Neighbor ListUpdate Msg

Send Burst DTMF Msg

Power ControlParameters Msg.

Retrieve Parameters Msg

Set Parameters Msg

SSD Update Msg

Flash WithInformation Msg

Mobile StationRegistered Msg

Status Request Msg

Extended HandoffDirection Msg

Service Request Msg

Service Response Msg

Service Connect Msg

Service OptionControl Msg

TMSI Assignment Msg

•The mobile station synchronizes its long code timing and system timing to those of the CDMA system, using the PILOT_PNs, LC_STATEs, and SYS_TIMEs. •Set PAGECHs to the Primary Paging Channel.

The following values are updated from the Sync Channel Message:Protocol revision level (P_REVs = P_REVr)Minimum protocol revision level (MIN_P_REVs = MIN_P_REVr)System identification (SIDs = SIDr)Network identification (NIDs = NIDr)Pilot PN sequence offset (PILOT_PNs = PILOT_PNr)Long code state (LC_STATEs = LC_STATEr)System Time (SYS_TIMEs = SYS_TIMEr)Paging Channel data rate (PRATs = PRATr)

The following values are updated from the Sync Channel Message:Protocol revision level (P_REVs = P_REVr)Minimum protocol revision level (MIN_P_REVs = MIN_P_REVr)System identification (SIDs = SIDr)Network identification (NIDs = NIDr)Pilot PN sequence offset (PILOT_PNs = PILOT_PNr)Long code state (LC_STATEs = LC_STATEr)System Time (SYS_TIMEs = SYS_TIMEr)Paging Channel data rate (PRATs = PRATr)

MS Initialization State

System Determination Substate

Pilot Channel Acquisition Substate

Sync Channel Acquisition Substate

Timing Change Substate

On power up or

from any other state

CDMA System

selected

Acquires

Pilot Channel

Receives Sync Channel Message

MS Idle State

•Receives the Sync Channel Message in T21ms.

•Compares the value of MOB_P_REV and sets the value of PRAT.

•Receives the Sync Channel Message in T21ms.

•Compares the value of MOB_P_REV and sets the value of PRAT.

•The mobile station shall tune to the CDMA Channel number equal to CDMACHs.•Searches for Pilot in T20ms

•The mobile station shall tune to the CDMA Channel number equal to CDMACHs.•Searches for Pilot in T20ms

Does system selection.Updates the registration parameters ZONE_LIST(SID,NID).Update the value of CDMABAND and CDMACH.Enters the next state if the selected system is a CDMA system.

Does system selection.Updates the registration parameters ZONE_LIST(SID,NID).Update the value of CDMABAND and CDMACH.Enters the next state if the selected system is a CDMA system.

Acquisition failure

Protocol mismatch

Note : Transitions arising from error conditions are not shown in the diagram.

Mobile Station Idle State

"Idle" phone is plenty busy! While a mobile is latched to a particular network, for most of the time is in the idle state. Being in this state the mobile monitors the Paging Channel. If there is a procedure that requires to be carried out for a message received on Paging Channel, the mobile enters the System Access State. Paging Channel messages or user actions can cause the mobile to go from idle state to System Access State.So in this state the mobile station can receive messages, receive an incoming call (mobile station terminated call), initiate a call (mobile station originated call), initiate a registration, or initiate a message transmission.The mobile constantly turning parts of itself on and off; on to perform vital functions and off again to save power so that the battery lasts longer. This periodic on and off of the mobile transceiver is called slotted mode of operation.It the mobile listens to all slots it is in non-slotted mode of operation.The mobile can operate in the slotted mode only in the idle state.While performing idle handoff the mobile has to be in non-slotted mode of operation.

Mobile Station Idle State - 2

While in the Mobile Station Idle State, the mobile station shall perform the following procedures:The mobile station shall perform Paging Channel monitoring procedures .The mobile station shall perform message acknowledgement procedures .The mobile station shall perform registration procedures .The mobile station shall perform idle handoff procedures .The mobile station shall perform the Response to Overhead Information Operation the mobile station receives a system overhead message (System Parameters Message, CDMA Channel List Message, Extended System Parameters Message, Neighbor List Message, Global Service Redirection Message, or Access Parameters Message). The mobile station shall perform the Mobile Station Page Match Operation whenever it receives a General Page Message, Page Message, or Slotted Page Message. The mobile station shall perform the Mobile Station Order and Message ProcessingOperation whenever a message or order directed to the mobile station is received other than a General Page Message, Page Message, or Slotted Page Message.The mobile station shall perform the Mobile Station Origination Operation 5 if directed by the user to initiate a call.If the mobile station supports Data Burst Message transmission, it shall perform theMobile Station Message Transmission Operation if directed by the user to transmit a message.The mobile station shall perform the Mobile Station Power-Down Operation if directed by the user to power down.

System Access State

Update InformationOverhead Substate

MS Origination Attempt Substate

MS Order/MessageResponse Substate

Registration Access Substate Page Response

Substate

MS MessageTransmission Substate

To MS in Idle State To MS on Traffic Channel State

User initiated a Call

Received General Page MessageUser generated Data

Burst Message

Registration access

Received a Message or Order requiring a Ack. Or Response

From MS in Idle State

In this state the MS listens on the Paging channel and responds on the Access Channel associated to the Paging Channel to which listens.The Access Channel is allocated on fair contention by using Slotted ALOHA.

In this state the MS listens on the Paging channel and responds on the Access Channel associated to the Paging Channel to which listens.The Access Channel is allocated on fair contention by using Slotted ALOHA.

In the System Access State the MS uses the Open Loop Power Control.

In the System Access State the MS uses the Open Loop Power Control.

MS remains in Update Information Overhead Substate and monitors the Paging Channel till it has the current set of overhead messages.

MS remains in Update Information Overhead Substate and monitors the Paging Channel till it has the current set of overhead messages.

Note : Transitions arising from error conditions are not shown in the diagram.

MS Control on Traffic Channel State

Traffic ChannelInitialization Substate

Waiting for OrderSubstate

Waiting for Mobile StationAnswer Substate

Conversation Substate

Release Substate

Receives Release Order

Receives Release Order

MS Terminated Call,when MS receives Base Station Ack. Order

MS receives AWI

MS receives AWI

MS user initiates a disconnect or MS receives Release Order.

MS user answers call.

MS Originated Call,when MS receives Base Station Ack. Order

To System Determination Substate of MS Initialization State.

After the of every call the MS goes to System Determination Substate.

•It searches again for the best pilot on the present frequency I.e. CDMACH.

•Read Sync Channel W32.

•Goes to Idle State and listens to Paging Channel.

After the of every call the MS goes to System Determination Substate.

•It searches again for the best pilot on the present frequency I.e. CDMACH.

•Read Sync Channel W32.

•Goes to Idle State and listens to Paging Channel.

From System Access State

Note:Substate transitions due to error conditions are no shown.

Reverse Link Frequencies(Mobile Transmit)

1. How Mobile Selects CDMA Carriers ?

HISTORYLIST

Last-used:Freq/SID xFreq/SID yFreq/SID zFreq/SID tFreq/SID uetc.

FREQUENCY LISTS:

PREFERREDROAMINGLIST

Freq/SID 1Freq/SID 2Freq/SID 3Freq/SID 4Freq/SID 5etc.

Forward Link Frequencies(Base Station Transmit)

A D B E F C unlic.data

unlic.voice A D B E F C

1850MHz. 1910MHz. 1990 MHz.1930MHz.

1900 MHz. PCS Spectrum

824 MHz. 835 845 870 880 894

869

849

846.5825

890

891.5

Paging, ESMR, etc.A B A B

800 MHz. Cellular Spectrum

Power up: self diagnostics, battery checkFind a frequency with CDMA RF

•last frequency used? other recent history?•home market? preferred roaming list?

Scan all PN offsets (Pilot W0), find best Ec/Io meaning of better strengthLock Traffic Correlators on best PN offset, read the sync channel (W32)

•learn true PN offset, SID/NID, time & leap seconds, Long Code state, paging channel

Read the Paging Channel (W1): collect all the current configuration messages.This process is called collection.The configuration messages are repeated on the Paging channel every 1.28 seconds.

•System Parameters Message•Extended System Parameters Message•Access Parameters Message•CDMA Channel List Message•Extended Neighbor List Message•Global Service Redirection Message

Register if requiredNow you’re ready to operate!

Power up: self diagnostics, battery checkFind a frequency with CDMA RF

•last frequency used? other recent history?•home market? preferred roaming list?

Scan all PN offsets (Pilot W0), find best Ec/Io meaning of better strengthLock Traffic Correlators on best PN offset, read the sync channel (W32)

•learn true PN offset, SID/NID, time & leap seconds, Long Code state, paging channel

Read the Paging Channel (W1): collect all the current configuration messages.This process is called collection.The configuration messages are repeated on the Paging channel every 1.28 seconds.

•System Parameters Message•Extended System Parameters Message•Access Parameters Message•CDMA Channel List Message•Extended Neighbor List Message•Global Service Redirection Message

Register if requiredNow you’re ready to operate!

2. How Mobile Selects CDMA Carriers ?

On power on,the mobile uses proprietary algorithms to select a carrier intended for them to use.The MS uses the above procedure whenever it has to select a CDMA system.On power on,the mobile uses proprietary algorithms to select a carrier intended for them to use.The MS uses the above procedure whenever it has to select a CDMA system.

CDMA Forward Traffic ChannelsPilot Walsh 0

Paging Walsh 1

Traffic Walsh 6

Traffic Walsh11

Traffic Walsh19

Traffic Walsh20

Sync Walsh32

Traffic Walsh37

Traffic Walsh41

Traffic Walsh42

Traffic Walsh55

Traffic Walsh56

Traffic Walsh60

Pilot Channel Walsh Code 0The Pilot is a beacon which does not contain a character stream. It is a timing source used in system acquisition and as a measurement device during handoffs.

Pilot Channel Walsh Code 0The Pilot is a beacon which does not contain a character stream. It is a timing source used in system acquisition and as a measurement device during handoffs.

Paging Channel W1-W7There can be from one to seven paging channels as determined by capacity needs.They carry the overhead messages,pages, call setup messages and orders.

Paging Channel W1-W7There can be from one to seven paging channels as determined by capacity needs.They carry the overhead messages,pages, call setup messages and orders.

SYNC: WALSH CODE 32This carries a data stream of system identification and parameter information used by mobiles during system acquisition

SYNC: WALSH CODE 32This carries a data stream of system identification and parameter information used by mobiles during system acquisition

Forward Traffic Channel Renaming Walsh Codes.The traffic channels are assigned to individual users to carry call traffic. All remaining Walsh codes are available, subject to overall capacity limited by noise.

Forward Traffic Channel Renaming Walsh Codes.The traffic channels are assigned to individual users to carry call traffic. All remaining Walsh codes are available, subject to overall capacity limited by noise.

Note: A Forward Channel is identified by:•. its CDMA RF carrier Frequency•. the unique Short Code PN Offset of the sector•. the unique Walsh Code of the user

Note: A Forward Channel is identified by:•. its CDMA RF carrier Frequency•. the unique Short Code PN Offset of the sector•. the unique Walsh Code of the user

CDMA Reverse Traffic ChannelsAccess

Reverse Traffic

ACCESS CHANNELS are used by mobiles not yet in a call; to transmit registration requests, call setup requests, page responses, order responses, and other signaling information• an access channel is really just a public long code offset unique to the BTS sector• Access channels are paired to Paging Channels.Each paging channel can have up to 32 access channels.

ACCESS CHANNELS are used by mobiles not yet in a call; to transmit registration requests, call setup requests, page responses, order responses, and other signaling information• an access channel is really just a public long code offset unique to the BTS sector• Access channels are paired to Paging Channels.Each paging channel can have up to 32 access channels.

TRAFFIC CHANNELS are used by individual users during their actual calls to transmit traffic to the BTS • a reverse traffic channel is really just a user-specific public or private Long Code mask• there are as many reverse Traffic Channels as there are CDMA phones in the world!

TRAFFIC CHANNELS are used by individual users during their actual calls to transmit traffic to the BTS • a reverse traffic channel is really just a user-specific public or private Long Code mask• there are as many reverse Traffic Channels as there are CDMA phones in the world!

A Reverse Channel is identified by:•. its CDMA RF carrier Frequency•. the unique Long Code PN Offset of the individual handset

A Reverse Channel is identified by:•. its CDMA RF carrier Frequency•. the unique Long Code PN Offset of the individual handset

98/05/24 23:14:10.427 [PCH] MSG_LENGTH = 184 bitsMSG_TYPE = Access Parameters MessagePILOT_PN = 168 Offset IndexACC_MSG_SEQ = 27ACC_CHAN = 1 channelNOM_PWR = 0 dB INIT_PWR = 0 dB PWR_STEP = 4 DbNUM_STEP = 5 Access Probes MaximumMAX_CAP_SZ = 4 Access Channel Frames MaximumPAM_SZ = 3 Access Channel FramesPersist Val for Acc Overload Classes 0-9 = 0Persist Val for Acc Overload Class 10 = 0Persist Val for Acc Overload Class 11 = 0Persist Val for Acc Overload Class 12 = 0Persist Val for Acc Overload Class 13 = 0Persist Val for Acc Overload Class 14 = 0Persist Val for Acc Overload Class 15 = 0Persistance Modifier for Msg Tx = 1 Persistance Modifier for Reg = 1 Probe Randomization = 15 PN chipsAcknowledgement Timeout = 320 msProbe Backoff Range = 4 Slots MaximumProbe Sequence Backoff Range = 4 Slots Max.Max # Probe Seq for Requests = 2 SequencesMax # Probe Seq for Responses = 2 SequencesAuthentication Mode = 1Random Challenge Value = Field OmittedReserved Bits = 99

Phone Operation on Access Channel.•The behavior of the mobile while using the Access Channel is determined by the Access Parameter Message.

•MS transmission on the Access Channel using a random access procedure.The parameters to this procedure are supplied by the Access Parameters Message.

•Phones access the BTS by “probing” at power levels determined by a procedure.

•Within an Access attempt, Access probes are grouped into access group sequences.

BTS

Access Channel Msg

MSProbing

A Successful Access Attempt

a Probe Sequence

Success!

an Access Probe

an Access Attempt

ACCESS

PARAMETERS

MESSAGE

Access Channel Attempts

Phone Operation on Access Channel -2

Begin

PROBE=0,SEQ=0

PN Randomization

Access Channel Response

If beginning of slotgenerate RP.

RP < P

Generate random number RA between 0 and ACC_CHAN

Initialize Transmit Power.

Transmit probe on AccessChannel RA at system timing

plus RN chips.Set TA

Ack. Received

Timer TA expired

PROBE = PROBE +1

PROBE < = NUM_STEP

SEQ= SEQ +1

SEQ <=MAX_REQ_SEQMAX_RSP_SEQ

Increase transmitpower by

PWR_STEP dB

Wait RT slots

Generate randomnumber RT betweenPROBE_BKOFF +1

Wait RT slots

Generate randomnumber RT betweenPROBE_BKOFF +1

AccessSuccessful

Access Failure.Enter SDS

YES

YES

YES

YES

YES

NO

NO

NO

NO

Access Procedure

Phone Operation on Access Channel -3