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Mobile Station States in IS-95A by Rahul Chauhan

Mobile Station States in IS-95A by Rahul Chauhan. MS Initialization. Mobile station has acquired timing System. Unable to receive Paging Channel. MS Idle State. MS receives a message on the paging channel requiring a ack;originates a call or performs registration.

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Mobile Station States in IS-95A by Rahul Chauhan

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  1. Mobile Station States in IS-95Aby Rahul Chauhan

  2. MS Initialization Mobile station has acquired timing System Unable to receive Paging Channel MS Idle State MS receives a message on the paging channel requiring a ack;originates a call or performs registration. Receives an ack for Access Channel message other than ORM and PRM System Access State Released traffic channel. Assigned a traffic channel. MS Traffic State Mobile Station States On power Up M Note : Transitions arising from error conditions are not shown in the diagram.

  3. Field Bits CDMA Message Structure • 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. MSG_TYPE (‘00000001’) 8 3 ACK_SEQ 3 MSG_SEQ ACK_REQ 1 VALID ACK 1 3 ACK_TYPE 3 MSID_TYPE MSID_LEN 4 MSID 8 x MSID_LEN AUTH_MODE 2 0 or 18 AUTHR RANDC 0 or 8 COUNT 4 REG_TYPE 4 SLOT_CYCLE_INDEX 3 MOB_PREV 8 SCM 8 MOB_TERM 1 RESERVED 6

  4. BTS Messages Sent in Initialization and Idle States Pilot Channel Sync Channel No Messages Sync Channel Msg Access Channel Paging Channel Registration Msg Access Parameters Msg General Page Msg Order Msg •Mobile Station Acknowledgment •Long Code Transition Request •SSD Update Confirmation many others….. Order Msg •Base Station Acknowledgment •Lock until Power-Cycled • Maintenance required many others….. System Parameters Msg CDMA Channel List Msg Origination Msg Extended System Parameters Msg Channel AssignmentMsg Page Response Msg Feature Notification Msg Extended Neighbor List Msg Authentication Challenge Response Msg Authentication Challenge Msg Global Service Redirection Msg Status Response Msg Service Redirection Msg Status Request Msg TMSI Assignment Completion Message SSD Update Msg TMSI Assignment Msg Data Burst Msg Null Msg Data Burst Msg

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

  6. MS Initialization State On power up or from any other state 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. System Determination Substate CDMA System selected Acquisition failure Pilot Channel Acquisition Substate • The mobile station shall tune to the CDMA Channel number equal to CDMACHs. • Searches for Pilot in T20ms Protocol mismatch Acquires Pilot Channel • Receives the Sync Channel Message in T21ms. • Compares the value of MOB_P_REV and sets the value of PRAT. 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) Sync Channel Acquisition Substate Receives Sync Channel Message • 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. Timing Change Substate MS Idle State Note : Transitions arising from error conditions are not shown in the diagram.

  7. 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.

  8. 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.

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

  10. From System Access State Traffic Channel Initialization Substate MS Control on Traffic Channel State MS Terminated Call,when MS receives Base Station Ack. Order MS Originated Call,when MS receives Base Station Ack. Order Waiting for Order Substate Receives Release Order MS receives AWI • 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. Waiting for Mobile Station Answer Substate Receives Release Order MS user answers call. Conversation Substate MS receives AWI MS user initiates a disconnect or MS receives Release Order. Release Substate To System Determination Substate of MS Initialization State. Note:Substate transitions due to error conditions are no shown.

  11. 800 MHz. Cellular Spectrum 890 894 835 845 849 870 880 824 MHz. A B Paging, ESMR, etc. A B 825 869 891.5 846.5 1900 MHz. PCS Spectrum A D B E F C unlic. data unlic. voice A D B E F C 1850MHz. 1910MHz. 1930MHz. 1990 MHz. FREQUENCY LISTS: HISTORY LIST Last-used: Freq/SID x Freq/SID y Freq/SID z Freq/SID t Freq/SID u etc. PREFERRED ROAMING LIST Freq/SID 1 Freq/SID 2 Freq/SID 3 Freq/SID 4 Freq/SID 5 etc. 1. How Mobile Selects CDMA Carriers ? Reverse Link Frequencies (Mobile Transmit) 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!

  12. 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.

  13. Pilot Walsh 0 Pilot Channel Walsh Code 0 The 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 Walsh 1 Traffic Walsh 6 Traffic Walsh11 SYNC: WALSH CODE 32 This carries a data stream of system identification and parameter information used by mobiles during system acquisition Traffic Walsh19 Traffic Walsh20 Paging Channel W1-W7 There 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 Walsh32 Traffic Walsh37 Traffic Walsh41 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. Traffic Walsh42 Traffic Walsh55 Traffic Walsh56 Traffic Walsh60 • 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 Forward Traffic Channels

  14. CDMA Reverse Traffic Channels Access 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. Reverse Traffic 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

  15. BTS A Successful Access Attempt Access Channel Msg Success! MS Probing an Access Attempt an Access Probe a Probe Sequence • 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. 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 ACCESS PARAMETERS MESSAGE Phone Operation on Access Channel.

  16. Phone Operation on Access Channel -2 Access Channel Attempts

  17. Phone Operation on Access Channel -3 Begin Transmit probe on Access Channel RA at system timing plus RN chips.Set TA PROBE=0,SEQ=0 Increase transmit power by PWR_STEP dB Ack. Received YES Access Successful PN Randomization Wait RT slots Access Channel Response Timer TA expired YES NO NO Generate random number RT between PROBE_BKOFF +1 PROBE = PROBE +1 If beginning of slot generate RP. Wait RT slots PROBE < = NUM_STEP YES RP < P NO YES SEQ= SEQ +1 Generate random number RT between PROBE_BKOFF +1 Generate random number RA between 0 and ACC_CHAN SEQ <= MAX_REQ_SEQ MAX_RSP_SEQ YES NO Initialize Transmit Power. Access Failure. Enter SDS Access Procedure

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