1. Mobile Station States in IS-95A by Rahul Chauhan

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

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

4. Messages Sent in Initialization and Idle States
Pilot Channel
Sync Channel
BTS
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…..
System Parameters Msg
Order Msg
•Base Station Acknowledgment
•Lock until Power-Cycled
• Maintenance required
many others…..
CDMA Channel List Msg
Origination Msg
Extended System Parameters Msg
Channel Assignment Msg
Page Response Msg
Extended Neighbor
List Msg
Feature Notification Msg
Authentication Challenge
Response Msg
Global Service
Redirection Msg
Authentication
Challenge 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
Service Request Msg
Service Request Msg
Origination
Continuation Msg
Authentication
Challenge Msg
Service Response Msg
Service Response Msg
Authentication Challenge
Response Msg
TMSI Assignment Msg
Service Connect Msg
Service Connect
Completion Message
TMSI Assignment
Completion Message
Send Burst DTMF Msg
Service Option
Control Msg
Service Option Control
Message
Send Burst DTMF Msg
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 List Update 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
The Mobile Station Initialization State consists of the following substates:
• System Determination Substate -The mobile station selects which system to use.Enters the next state if the selected system is a CDMA system.
• Pilot Channel Acquisition Substate -The mobile station acquires the Pilot Channel of a CDMA system.The MS shall tune to the CDMA Channel number in CDMACH and search for Pilots.Goes to the next state if it acquires the Pilot in T20ms.
• Sync Channel Acquisition Substate -The mobile station obtains system configuration and timing information for a CDMA system.On entering this state the mobile shall set the code channel to W32.The moble shall wait for a valid Sync Channel fo T21ms.It goes to the next state of MOB_P_REV is greater than the MIN_P_REV in mobile.
• Timing Change Substate -Tthe mobile station synchronizes its timing to that of a CDMA system.
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. Transmission Substate
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. MS Control on Traffic Channel State
From System Access State
Traffic Channel
Initialization Substate
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. 1. How Mobile Selects CDMA Carriers ?
Reverse Link Frequencies
(Mobile Transmit)
Forward Link Frequencies
(Base Station Transmit)
824 MHz.
835
845
870
880
894
869
849
846.5
825
890
891.5
Paging, ESMR, etc. A B
800 MHz. Cellular Spectrum A D B E F C
unlic.
data
voice
1850MHz.
1910MHz.
1990 MHz.
1930MHz.
1900 MHz. PCS Spectrum
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!
HISTORY
LIST
Last-used:
Freq/SID x
Freq/SID y
Freq/SID z
Freq/SID t
Freq/SID u
etc.
FREQUENCY LISTS:
PREFERRED
ROAMING
Freq/SID 1
Freq/SID 2
Freq/SID 3
Freq/SID 4
Freq/SID 5

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. CDMA Forward Traffic Channels
Pilot 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 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 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: WALSH CODE 32
This 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.
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

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. 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.
98/05/24 23:14: [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
BTS
Access Channel Msg MS
Probing
A Successful Access Attempt
a Probe Sequence
Success!
an Access Probe
an Access Attempt

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
YES
Ack. Received
Increase transmit
power by
PWR_STEP dB
Access
Successful
PN Randomization
Wait RT slots
Access Channel
Response
Timer TA expired
YES NO NO
Generate random
number RT between
PROBE_BKOFF +1
If beginning of slot
generate RP.
PROBE = PROBE +1
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
YES
SEQ <=
MAX_REQ_SEQ
MAX_RSP_SEQ NO
Initialize Transmit Power.
Access Failure.
Enter SDS
Access Procedure