CDMA - Mobile_States

Mobile Station States in IS-95A by Rahul Chauhan : 

Mobile Station States in IS-95A by Rahul Chauhan

Mobile Station States : 

Mobile Station States M On power Up Note : Transitions arising from error conditions are not shown in the diagram.

CDMA Message Structure : 

CDMA Message Structure MSG_TYPE (‘00000001’) ACK_SEQ MSG_SEQ ACK_REQ 8 3 3 1 VALID ACK 1 ACK_TYPE MSID_TYPE 3 3 MSID_LEN 4 MSID 8 x MSID_LEN AUTH_MODE 2 0 or 18 0 or 8 AUTHR RANDC COUNT REG_TYPE 4 4 SLOT_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. Bits Field

Messages Sent in Initialization and Idle States : 

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 Neighbor List Msg Global Service Redirection Msg Order Msg •Base Station Acknowledgment •Lock until Power-Cycled • Maintenance required many others….. Authentication Challenge 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 Confirmation many others….. Origination Msg Page Response Msg Authentication Challenge Response Msg Status Response Msg TMSI Assignment Completion Message Data Burst Msg

Messages in Traffic State : 

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 With Information Msg Data Burst Message Pilot Strength Measurement Msg Power Measurement Report Msg Send Burst DTMF Msg Origination Continuation Msg Handoff Completion Msg Parameters Response Message Service Request Msg Service Response Msg Service Connect Completion Message Service Option Control Message Status Response Msg TMSI Assignment Completion Message Forward Traffic Channel Order Msg • Base Station Acknowledgment • Base Station Challenge Confirmation • Message Encryption Mode Authentication Challenge Msg Alert With Information Msg Data Burst Msg Analog Handoff Direction Msg In-Traffic System Parameters Msg Neighbor ListUpdate Msg Send Burst DTMF Msg Power Control Parameters Msg. Retrieve Parameters Msg Set Parameters Msg SSD Update Msg Flash With Information Msg Mobile Station Registered Msg Status Request Msg Extended Handoff Direction Msg Service Request Msg Service Response Msg Service Connect Msg Service Option Control Msg TMSI Assignment Msg

MS Initialization State : 

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) 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. 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. Acquisition failure Protocol mismatch Note : Transitions arising from error conditions are not shown in the diagram.

Mobile Station Idle State : 

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 : 

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 Processing Operation 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 the Mobile 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 : 

System Access State Update Information Overhead Substate MS Origination Attempt Substate MS Order/Message Response Substate Registration Access Substate Page Response Substate MS Message Transmission Substate To MS in Idle State To MS on Traffic Channel State User initiated a Call Received General Page Message User 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 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. Note : Transitions arising from error conditions are not shown in the diagram.

MS Control on Traffic Channel State : 

MS Control on Traffic Channel State Traffic Channel Initialization Substate Waiting for Order Substate Waiting for Mobile Station Answer 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. From System Access State Note:Substate transitions due to error conditions are no shown.

1. How Mobile Selects CDMA Carriers ? : 

Reverse Link Frequencies (Mobile Transmit) 1. How Mobile Selects CDMA Carriers ? Forward Link Frequencies (Base Station Transmit) Power up: self diagnostics, battery check Find 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 strength Lock 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 required Now you’re ready to operate!

2. How Mobile Selects CDMA Carriers ? : 

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.

CDMA Forward Traffic Channels : 

CDMA Forward Traffic Channels

CDMA Reverse Traffic Channels : 

CDMA Reverse Traffic Channels Access 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. 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

Phone Operation on Access Channel. : 

98/05/24 23:14:10.427 [PCH] MSG_LENGTH = 184 bits MSG_TYPE = Access Parameters Message PILOT_PN = 168 Offset Index ACC_MSG_SEQ = 27 ACC_CHAN = 1 channel NOM_PWR = 0 dB INIT_PWR = 0 dB PWR_STEP = 4 Db NUM_STEP = 5 Access Probes Maximum MAX_CAP_SZ = 4 Access Channel Frames Maximum PAM_SZ = 3 Access Channel Frames Persist Val for Acc Overload Classes 0-9 = 0 Persist Val for Acc Overload Class 10 = 0 Persist Val for Acc Overload Class 11 = 0 Persist Val for Acc Overload Class 12 = 0 Persist Val for Acc Overload Class 13 = 0 Persist Val for Acc Overload Class 14 = 0 Persist Val for Acc Overload Class 15 = 0 Persistance Modifier for Msg Tx = 1 Persistance Modifier for Reg = 1 Probe Randomization = 15 PN chips Acknowledgement Timeout = 320 ms Probe Backoff Range = 4 Slots Maximum Probe Sequence Backoff Range = 4 Slots Max. Max # Probe Seq for Requests = 2 Sequences Max # Probe Seq for Responses = 2 Sequences Authentication Mode = 1 Random Challenge Value = Field Omitted Reserved 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. ACCESS PARAMETERS MESSAGE

Phone Operation on Access Channel -2 : 

Access Channel Attempts Phone Operation on Access Channel -2

Phone Operation on Access Channel -3 : 

Begin PROBE=0,SEQ=0 PN Randomization Access Channel Response If beginning of slot generate RP. RP < P Generate random number RA between 0 and ACC_CHAN Initialize Transmit Power. Transmit probe on Access Channel 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_SEQ MAX_RSP_SEQ Increase transmit power by PWR_STEP dB Wait RT slots Generate random number RT between PROBE_BKOFF +1 Wait RT slots Generate random number RT between PROBE_BKOFF +1 Access Successful Access Failure. Enter SDS YES YES YES YES YES NO NO NO NO Access Procedure Phone Operation on Access Channel -3