chapter 3

Company Confidential 10/4/99 1

Air

MTP Level 2 & 3

SCCP

TCAP

ISUPTUP

MAP

BSSAP

MTP Level 1

DTAPBSSMAP

Databases PSTN

MSC

G.703

LAPD

RSM08.58

MTP Level 2 ,3

SCCP

BSSAP

MTP Level 1

BSSMAP

LAPDm

RIL3

Rad Int

DTAP RR

MS

G.703

LAPD

RSM08.58

LAPDm

RIL3

Rad Int

BTS BSC

Abis A

GSM Signaling MatrixGSM Signaling Matrix


VLR

HLR/AUC

EIR

PSTN GMSC GSMSC

VLR

HLR/AUC

Abis A

B

C

F

E

G

D

SS7/R2

MSCBSC

BTS

OMLOMC

A,B,C,D,E,F,G,H,I = SS7Abis = LAPDOML = X.25

SUPP

I

H

IWMSC

Map InterfacesMap Interfaces


MAP messages are between Switching and Database interfaces

MAP messages are not present on the Air Interface

Not much significance related to Drive Testing

Can be useful in analyzing some Protocol failures experienced on the air interface during drive testing.

MAP Messages - Points to be notedMAP Messages - Points to be noted


SCCP

BSSAP

MTP

DTAP

BSSMAP

Distribution Layer

SCCP

BSSAP

MTP

DTAP

BSSMAP

Distribution Layer

MSCBSCBTS

DTAP

BSSMAP

Base Station Application Part ( BSSAP ) Base Station Application Part ( BSSAP )


BSSMAP ( Base Station Subsystem Mobile Application Part)

Between BSC and MSC Linked to certain messages on the Air Interface Useful in troubleshooting certain Blocked Calls and Dropped Calls

problems in conjunction with Drive Testing

DTAP (Direct Transfer Application Part)

Transparent Messages between MSC and MS Further divided into sub-categories ( MM ,CC,SMS,SS)

BSSMAP & DTAP message BSSMAP & DTAP message


Connection Oriented MessagesAssignment CompleteAssignment FailureAssignment RequestCandidate ResponseCipher Mode CommandCipher Mode CompleteClassmark UpdateComplete Layer 3 InformationHandover Candidate EnquiryHandover CommandHandover CompleteHandover DetectHandover FailureHandover PerformedHandover RequestHandover Request AcknowledgeHandover Required RejectTrace InvocationQueuing Indication

Connectionless MessagesBlockBlock AcknowledgePagingResetReset AcknowledgeReset CircuitReset Circuit AcknowledgeResource IndicationResource RequestUnblockUnblocking Acknowledge

BSSMAP MessagesBSSMAP Messages


Types of DTAP Messages*

CC : Call control and call related SS Messages -- related to call setup and activation/deactivation

of SS between .

MM : Mobility Management Messages --- location updates, security procedures and

connection management .

SS : Non-Call related Supplementary Messages --- like call barring, call forwarding etc.

SMS : Short Message Service Messages --- related of transmission and reception of SMS.

DTAP MessagesDTAP Messages


CC MessagesAlertingCall ConfirmedCall ProceedingConnectConnect AcknowledgeDisconnectEmergency SetupFacilityHoldHold AcknowledgeModifyModify CompleteNotifyProgressReleaseRelease CompleteRetrieveRetrieve AcknowledgeSetup

MM MessageAuthentication RequestAuthentication ResponseCM Re-Establishment RequestCM Service AcceptCM Service RejectCM Service RequestIdentity RequestIdentity ResponseIMSI DetachLocation Updating AcceptLocation Updating RejectLocation Updating RequestTMSI Reallocation CommandTMSI Reallocation Complete

SS MessagesHold Hold AcknowledgeHold RejectRetrieveRetrieve AcknowledgeRetrieve RejectFacilityRegister

SMS MessagesCP-AckCP-DataCP-ErrorRP-AckRP-DataRP-Error

DTAP MessagesDTAP Messages


LAPDm

RIL3

Rad Int

BTS

LAPDm

RIL3

Rad Int

DTAP

RR

MS

04.0404.04

04.08/ 04.10 04.08/ 04.10

Air InterfaceAir Interface


--- The Physical Layer on the Air interface is Radio--- Messages are sent on Radio Interface through appropriate logical channels

Functions of Layer 1

--- Mapping of Logical Channels to Physical Channel--- Channel Coding--- Ciphering--- Cell Selection and Reselection--- Connection Establishment on Logical Channels--- Measurement of serving and neighbouring cells signal level--- Setting of Timing Advance--- Transmit Power Control as commanded by BTS.

Radio Interface ( Layer 1 ) Radio Interface ( Layer 1 )


Air Interface L3 Message categories

DTAP Messages : transparent to BTS -- CC -- MM -- SS -- SMS

RR : Radio Resource messages specific to MS and BTS

Test Messages : Related to testing procedures ( like loopback etc.)

Radio Interface (Layer 3) Radio Interface (Layer 3)


DTAP

MM MessageAuthentication RequestAuthentication ResponseCM Re-Establishment RequestCM Service AcceptCM Service RejectCM Service RequestIdentity RequestIdentity ResponseIMSI DetachLocation Updating AcceptLocation Updating RejectLocation Updating RequestTMSI Reallocation CommandTMSI Reallocation Complete

SS MessagesHold Hold AcknowledgeHold RejectRetrieveRetrieve AcknowledgeRetrieve RejectFacilityRegister

SMS MessagesCP-AckCP-DataCP-ErrorRP-AckRP-DataRP-Error

CC MessagesAlertingCall ConfirmedCall ProceedingConnectConnect AcknowledgeDisconnectEmergency SetupFacilityHoldHold AcknowledgeModifyModify CompleteNotifyProgressReleaseRelease CompleteRetrieveRetrieve AcknowledgeSetup

Message Type

RIL3 MessagesRIL3 Messages


Assignment CommandAssignment CompleteAssignment FailureChannel Mode ModifyChannel Mode Modify AcknowledgeChannel ReleaseChannel RequestCiphering Mode CommandCiphering Mode CompleteClassmark ChangeFrequency RedefinitionHandover AccessHandover CommandHandover CompleteHandover Failure

Immediate AssignmentImmediate Assignment ExtendedImmediate Assignment RejectMeasurement ReportPaging Request Type 1Paging Request Type 2Paging Request Type 3System Information Type 1System Information Type 2System Information Type 3System Information Type 4System Information Type 5System Information Type 6System Information Type 2bis

RR

Message Type

RIL3 Messages RIL3 Messages


RR Idle Mode

RR Connection Establishment Mode

RR Connected Mode

MM Connection Establishment Mode

MM Connected Mode

Call Control Process

BCCH &PCH

RACH &AGCH

SDCCH

Initial Message

Initial Message Ack

CC Release

MM Release

RR Release

Mobile Phone ModeMobile Phone Mode


Access Procedure( RACH/AGCH)

MM CM Procedure ( SDDCH)

MM Common Procedures ( SDDCH)

MM Specific Procedures ( SDDCH)

Release Procedures ( SDDCH)

Access Procedure( RACH/AGCH)

MM CM Procedure ( SDDCH)

MM Common Procedures ( SDDCH)

CC Procedures ( SDDCH)

RR Procedures ( TCH )

CC Procedures (TCH)

Release Procedures ( SDDCH)

Non-call Related Call Related

Air Interface Communication ProceduresAir Interface Communication Procedures


Criteria for Camp on to a cell

Reliably decode downlink data

High probability of communications on the uplink

Cell Selection & ReselectionCell Selection & Reselection


Available PLMN

Definitions

-- one for which at least 1 cell is unbarred and C1>0

Suitable Cell

-- part of selected PLMN-- unbarred-- C1 > 0

The MS uses BA list for camp on

Cell Selection and ReselectionCell Selection and Reselection


BTS

Every Mobile has an access class on the SIM

Every cell defines the Mobile classes which are barred access.

WHAT IS CELL BARRING ?WHAT IS CELL BARRING ?


Reserving Cells for Handovers.

Reserving Cells for a certain Mobile Class.

USE OF CELL BARRINGUSE OF CELL BARRING


In the camp on process, mobile checks for ' C 1 ’

' C1 ' is the path loss criteria.

' C1' calculations are done by mobile while camping On and for cell reselection.

Cell reselection means leaving the existing cell and selecting a new cell in the idle mode.

Cell Selection & ReselectionCell Selection & Reselection


C1 = A - max ( B,0 )

A = Average Received signal Level - Min Receive Level

B = Access Power - Max power of Mobile ( Classmark )

A = + = Good Downlink PathB = -- = Good Uplink Path

For Cell selection C1 > 0 For Cell Reselection C1 of new cell > C1 of current cell or C1

falls below 0, both for a period of 5 seconds.

Path Loss Criterion ' C1 'Path Loss Criterion ' C1 '


A Mobile Subscriber is issued with a SIM to access the network.

The SIM card has the preferred list which contains8 PLMN codes. This list can be updated by the user

The Mobile also has forbidden list , which is dynamically updated by the mobile. It has 4 PLMN codes.

Mobile Camp OnMobile Camp On


Scans 124 ARFCN's

Locks on to best

Searches for FCH

IFFound

Read BCCH Info

NCmatches

Lock on to next best

Yes

No

Yes

A

A

Cellbarred

C1 > 0

CAMP ON

No

Yes

Yes

No

5 samples/ARFCN spread over 3 to 5 secs

No

Locks on to nextbest in BA list

Camp on with preferred listCamp on with preferred list


Scans 124 ARFCN's

Locks on to best

Searches for FCH

IFFound

Read BCCH Info

Lock on to next best

Yes

Yes

Successful

No

Stores the BA list

A

Location Update

No

Cellbarred

C1 > 0

Yes

No

A

Next in BA list

Puts PLMN in forbidden list

No preferred list No preferred list


Invalid Network Response

PLMN not allowed. IMSI unknown or illegal MS

Does Cell Reselection, if still PLMN not allowed

Search 30 strongest RF channels

Camps on to determine next PLMN availability

If 30 RF channels are scanned and no suitable PLMN is found (provided 1 of 30 is BCCH ), Mobile goes to No SIM state .

Abnormal CasesAbnormal Cases


No suitable cell found

Cell reselection as per BA

If no suitable cell found, then

No SIM sate

Abnormal CaseAbnormal Case


No SIM State

Only Emergency Calls allowed

Will do Cell Reselection

Abnormal CaseAbnormal Case


The purpose of Synchronizing is to read the BCCH message

Mobile gets Synchronized with the cell by SCH

Mobile locates SCH with the help of FCCH

FCCH has a easily recognizable structure with all zeros

Mobile knows that SCH follows FCCH

The maximum time allowed for synchronization is 0.5s, and the maximum time allowed to read the BCCH data, when being synchronized with the BCCH carrier, is 1.9 secs.

Fixed Bits ( all zeros )142

FCCH Burst

TB3 TB3 GP

Mobile Frame SynchronizationMobile Frame Synchronization


Information 39

Midamble 64

Information 39

TB3 TB3

SCH Burst Contains the TDMA Frame No and BSIC

Frame No = 11bits ( To point Superframe No out of 2048 Superframes ) 5bits ( To point Multiframe No out of 26 Mulitframes )

3bits ( To Point out the SCH Frame No out of 5 in 1 Multiframe )

MS calculates the TDMA Frame no from this information

SCH Burst

Actual Information in SCH

1 Multiframe

Frame Number(19 Bits)

BSIC(6 Bits)

Superframe No11 Bits

Multiframe No5 Bits

SCH Frame No3 Bits

0 1 11 21 31 41 50

S1

S2

S3

S4

S5

Mobile Frame SynchronizationMobile Frame Synchronization


Primarily based on comparison of C1 of serving and neighbor cells.

In order to optimize cell reselection, C2 calculations can be optionally implemented , for which additional parameters are broadcasted on the BCCH of each cell.

Cell ReselectionCell Reselection


CELL_RESELECT_OFFSET : ( 0 - 126 dB // 2 dB steps )Used to achieve cell prioritization, i.e to encourage MS's to select some suitable cells in the presence of others.More useful for Multiband and Umbrella cells architecture.Applies a positive or a negative offset to each cell

TEMPORARY_OFFSET : ( 0 - 60 dB // 10 dB steps)For a neighbor cell , when placed on the list of the strongest carriers by the MS, it starts a timer and applies a negative offset to the C1 of that neighbor for the duration of this timer. The offset can also be infinite, which means the cell never be selected in the reselection process.

PENALTY_TIME : ( 20s to 620s // 20secs steps)The duration for which the Temporary_Offset is applied.

C2 Calculations - ParametersC2 Calculations - Parameters


For Serving Cell,

C2 = C1 + CELL_RESELECT_OFFSET

If Penalty Time = 620 secs, then

C2 = C1 - CELL_RESELECT_OFFSET

"C2" Calculations"C2" Calculations


For Neighbor Cells,

C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET(t)

t = 1 , till the Penalty timer equals the set valuet = 0 , after the Penalty timer has expired

C2 = C1 - CELL_RESELECT_OFFSET

If Penalty Time = 620 secs, then

"C2" Calculations"C2" Calculations


F S B B B B

P0

P

0

P0

P

0

"ON"

"ON"Measurements

Measurements(optional to MS)

Measurements for Cell ReselectionMeasurements for Cell Reselection


Serving Cell

A running average of 5 measurement samples are required per receive level average value.

Measurement samples should be collected over a period of :5 secs to Max ( 5s, five consecutive paging blocks of that MS)

A running average of 5 measurement samples are required per receive level average value of each neighbor cell.

Measurement samples should be collected over a period of :5 secs to Max [ 5s, (5*N + 6) DIV 7) * BS_PA_MFRMS / 4 ]N is the number of non-serving cell BCCH carriers in the BA list

Neighbor Cells

Measurements for Cell ReselectionMeasurements for Cell Reselection


MS shall calculate the C1 and C2 for serving and non-serving cells every 5 secs.

MS shall attempt to decode the full BCH data of the serving cell at least every 30 seconds.

MS shall attempt to decode the BCCH data block that contains the parameters affecting cell reselection for each of the 6 strongest neighbor cell BCCH carriers at least every 5 minutes.

When MS recognizes a new BCCH carrier has become one of the 6 strongest, the BCCH data for the new carrier within 30 seconds.

MS shall attempt to decode the BSIC for each of the 6 strongest carriers at least 20 seconds, to confirm that it is monitoring the same cell.

If the change in BSIC is detected,then the carrier would be treated as a new carrier.

Cell Reselection - Measurements and BCCH decodeCell Reselection - Measurements and BCCH decode


Cell in the same LA C2 for new cell should exceed C2 of current cell and should

remain high for a period of 5 secs.

C1 of current cell falls below zero.

Cell reselection occurring within 15 secs, C2 of the new cell shall exceed the C2 of the serving cell by at least 5 dB for a period of 5 secs.

The left cell on reselection shall not be returned within 5 secs if another suitable cell can be found.

Cell in the different LA Depends on Reselect hysteresis.

Cell ReselectionCell Reselection


Reselect Hysterisis Value is broadcasted on BCCH

For the new cell in different Location Area, the value for C1 for new cell > the C1 for serving cell by the hysterisis value broadcasts on the serving cell BCCH for a period of 5 secs.

This hysterisis is to avoid exorbitant Location Updates when the mobile is on border of two location areas.

Reselect HysterisisReselect Hysterisis


Location Area 1

Location Area 2

C1 = 10 dBHysterisis = 5 db

C1 = 13 dB

Reselect HysterisisReselect Hysterisis


Location Update Signaling Diagram

MSCBSCBTS

Complete Layer 3 InfoLoc Upd Req ( SABM )

Authentication Request

Clear Command

Clear Complete

Channel ReqChannel Reqd

Channel Activation

Chan Actvn Ack

Imm Assgn CmdImmediate Assgn

Establish Ind

Auth ReqData Request

Auth RespData Ind

Authentication Response

Loc Upd AcceptData Request

Loc Upd Accept

Mobile - Cell AccessMobile - Cell Access


Reserves SDCCH

RACHT3120

Re-transmission

AGCH

T3101Response

T3120

Channel Request

Immediate Assignment

Mobile Cell AccessMobile Cell Access


Channel Required

Channel Activation

Channel Activation Ack

Channel Request


BTS BSC

Immediate Assign Command

T3120

T3101

Immediate Assignment ProcedureImmediate Assignment Procedure


5 bits 3 bits 6 bits

Random Access

Channel Request

Establishment Cause100 -- Answer to paging101 -- Emergency Call110 -- Call re-establishment111 -- Originating Call0000 -- Location Update0001 -- IMSI Detach, SMS, SS Management011 - Reserved for future use

TB8

SYNCH 41

Information 36

TB3

GP

Random Reference No.

Establishment Cause

BSIC (coded in parity bits)

Message ContentsMessage Contents


Channel Required

Channel Number --- Indicates on which channel the message was received ( RACH )Request Reference --- Contains RACH info ( Random No, Cause ), Frame NoAccess Delay ---- Delay in terms of bit period ( 0- 63 )Physical Context --- Optional for manufacturer to add more information ( RxLev etc, )

Immediate Assignment Command

Channel Number --- channel on which the message is to be sent ( AGCH )Message type --- Immediate AssignmentChannel Description --- SDCCH/4 or SDCCH/8. Sub-channel Number TSC, ARFCN, Single or Hopping, HSN Mobile Allocation TableRequest Reference --- Contains RACH info ( Random No, Cause ), Frame NoTiming Advance ---- Timing Advance value ( 0 -63 )Mobile Allocation --- MAI table if hopping is usedStarting time --- TDMA Frame No if frequency for new channel changes ( NC - case )



Immediate Assignment Extended

Channel Description 1Request Reference 1Timing Advance 1Channel Description 2Request Reference 2Timing Advance 2Mobile AllocationStarting time

Channel Request

Channel Request

Immediate Assign CommandImmediate Assign Extended

BTS BSC


Channel Number -- AGCHMessage type -- Immediate Assign ExtendedChannel Description 1Request Reference 1Timing Advance 1Channel Description 2Request Reference 2Timing Advance 2Mobile AllocationStarting time



BTS

Channel Request


RACH

AGCH

SDCCH(Location Update RequestCM Service RequestPaging ResponseCM Reestablishment RequestIMSI Detach)

Stops T3120

Initial MS message

Immediate Assignment Procedure CompletionImmediate Assignment Procedure Completion


No Channel ( SDCCH ) available

Channel Request


BTS BSC

Channel Required

Immediate Assignment Reject


Channel Number -- AGCHMessage type -- Immd Assgn RejectRequest Reference 1 -- EC, Ref no, Fr.NoWait Indication -- T3122 .........Request Reference 5 -- EC, Ref no, Fr.NoWait Indication -- T3122

Immediate Assignment Reject

Request Reference 1 -- EC, Ref no, Fr.NoWait Indication -- T3122 .........Request Reference 5 -- EC, Ref no, Fr.NoWait Indication -- T3122

Stops T3120Starts T3122



Lower Layer Failure on MS before establishment on SDCCH

-- Allocated Channels are released-- MS returns to Idle Mode-- Transaction is process are aborted-- Cell reselection may take place

Timer T3101 on Network expires before MS responses

-- Allocated Channels are released-- Request Forgotten



TWO Mobiles Send RACH at same Frame Nowith same Reference No and EC

both strongIf A

One may reach and one may not reach

Network assigns AGCH with the same RRN

Both will tune to SDCCH

One will release the channel during setup

No

YES

Both rejectedand follow the Re-transmissionProcess

B

RACH Collisions RACH Collisions


RACH

T3120

Re-transmission

RACH

T3120Rejected

AGCHAGCH

T3120 = 3 - 12,14,16,20,25,32,50 RACH SlotsMaximum Re-transmission = 1,2,4,7For every Re-transmission T3120 is randomly generated

ALOHA ProcessALOHA Process


-- One RACH reaches one does not

RACH

RACH

Both Wait for AGCH


Both tune to SDCCHSABM ( Initial Message )

SABM ( Loc Upd Req ) Initial Message = IMSI

UA ( Initial Message )

UA ( Initial Message )

DROPS ( since IMSI mismatches )

RACH Collision ( B )RACH Collision ( B )


TMSI Reallocation Procedure

Authentication Procedure

Identification Procedure

Ciphering *

IMSI Detach Procedure

* Ciphering is not a MM procedure, but since it is linked with other procedures discussed here , it is covered in this section

MM - Common ProceduresMM - Common Procedures


Loc Upd ( IMSI )

TMSI Allocation

Call Setup ( TMSI )

TMSI Reallocation

TMSI ReallocationTMSI Reallocation


Purpose Provide identity confidentiality

Operational Requirements

TMSI is an unambiguous identity associated with LAI Must be performed at change of Location Areas Initiated in ciphered mode Can also be associated with some other procedure

TMSI REALLOCATIONTMSI REALLOCATION


MSC

T3250

StopsT3250

TMSI Reallocation Command

TMSI Realacation Complete

TMSI Reallocation Command

Location Area Identification

Mobile Identity : TMSI / IMSI

TMSI Reallocation Complete

No Elements

TMSI REALLOCATIONTMSI REALLOCATION


AuthenticationPurpose

-- To verify Subscriber Identity ( IMSI and SIM )-- To provide a new ciphering key to the Mobile Station

Operational Requirement

-- at each registration-- at every call attempt ( MOC & MTC ) ( left to operators , but should be done

for visiting subscribers )-- before performing some supplementary services activation, de-activation, registration or erasure-- required for Location Updating for roaming-- not mandatory prior to IMSI Attach and Detach

Authentication process is always initiated and controlled by the network



A3 A3

Ki KiRAND

RAND

=SRES

SRES

Authentication



Authentication


Ciphering Key Sequence No -- Values ( 0-6 ) , 7 = No keyAuthentication Parameter RAND - 128 bits Random Number


Authentication Parameter SRES -- 32 bits Signed Response

MSC

T3260

StopsT3260





Unsuccessful Authentication

Authentication Reject

Authentication ReqData Request

Authentication Req

BTS BSC MSC

T3260

Data IndicationAuthentication Resp

Authentication Resp

StopsT3260

Invalid SRES

Authentication RejData RequestAuthentication Rej

All MM-Connections Released

RR- Connection Release procedure initiated Sets Authentication Failure Flag

Waits for Connections to be released Delete its TMSI,LAI,Ciphering Key, CKSN Return to IDLE no IMSI state

Authentication Reject

No elements



Abnormal CasesExpiry of timer T3260

MSCAuthentication Request

StartsT3260

T3260 ExpiresAuthentication Request

Re-StartsT3260

T3260 ExpiresAuthentication Reject

RR - Connection Release Procedure initiated



Identity Check

Identity Check ( IMEI )

Sends IMEI

EIRWhite listed / Grey listed / Black listed ?????



Identification

MSC requests the Mobile to send its identity , for verification Identity could be IMSI, TMSI,IMEI IMEI shall only be sent in ciphered mode

Identity Request

Identity type : IMSI / IMEI / TMSI

Identity Response

Mobile Identity

MSC

T3270

StopsT3270

Identity Request

Identity Response



Identification

Abnormal Case

Expiry of timer T3270

MSCIdentification Request

StartsT3270

T3270 ExpiresIdentification Request

Re-StartsT3260

T3270 Expires

Releases RR - Connection



Ciphering

Purpose

-- privacy of speech and data-- privacy of signaling information

Operational Requirements

-- Implementation dependent-- Ciphering should be done before confidential signaling information is passed ( Called Number, Calling Number, TMSI )

* Note : IMSI and IMEI are also confidential signaling information ,but they require physical protection



30

A8

RAND Ki

A5 Ciphering Stream XOR

Information Bits ( 114 )Ciphered Bits

KcFrame No

Ciphering



Ciphering

Cipher Mod CmdEncryption Cmd

Cipher Mod Cmd

BTS BSC MSC

Data IndicationCiph Mod Comp

start decipheringStart ciphering& deciphering

correct L2 framestart ciphering

Cipher Mode Comp

Cipher Mode CommandLayer 3 Header InformationAlgorithm Identifier : No encryption/

A5 / 1Key : Ciphering key

Encryption CommandChannel NumberEncryption Information : Algorithm Identifier KeyL 3 Information

Cipher Mode CommandCipher Mode setting :

No CipheringStart Ciphering

Cipher Mode CompleteNo Elements



NetworkAuthentication Request ( RAND + CKSN )

Authentication Response ( SRES )A3/A8

Ki

FNo

( Kc + CKSN )

( CKSN )

NetworkChannel Request


( stored in SIM )

( stored in MSC/VLR )

Initial Message ( CKSN )

If CKSN Checked , No authentication

Ciphering Key Sequence No ( CKSN )



Purpose

Mobile Station Power down SIM is removed

To mark the Mobile as inactive in the network

Conditions

Operation

If no RR-connection exists, RR-connection will be first established If RR-connection exists, then all MM - connections will be first released If Location Update procedure is On, than it will be finished, then this

procedure will be started

IMSI Detach ProcedureIMSI Detach Procedure


MSC

StartsT3220

IMSI Detach Indication

Wait for RR-Connection ReleaseIf T3220 expires, MS will localy release RR-Connection

IMSI Detach Indication

PD : MMTI : 0MT : IDIMobile Station Classmark 1Mobile Identity

Abnormal Case

RR-Connection cannot be established or RR-Connection is lost before message is sent, then the IMSI detach is aborted by the MS

Marks MS as detached in VLR Will not sent any page

IMSI Detach ProcedureIMSI Detach Procedure


Reduce Paging Load

Resource Planning

L.Area = 1 L.Area = 2 L.Area = 3

Importance of Location AreaImportance of Location Area


MSC should know the Location of the Mobile for paging. Mobile is continuously changing Location Area. Mobile when changes Location Area informs the MSC about its new L.A

Process of informing MSC about new Location Area is Location Update

L.Area = 1 L.Area = 2 L.Area = 3

Location Update

What is Location Update ?What is Location Update ?


IMSI Attach -- Power on in same LAI-- Compliment to Explicit IMSI Detach

Normal Location Update -- Change in LAI due to mobility-- Power on in new LAI -- MS unknown in VLR as a response to Connection establishment request

Periodic Updating-- Expiry of Periodic Update Timer ( T3212 )-- In the event of MS out of Service , on exit, MSC will mark it as Implicit

Detach in the VLR-- Timer is reset to "0" on any Loc Update, first MM message recd , MS

responded to page, on expiry of timer

Location Updating ProcedureLocation Updating Procedure


Location Update is done at VLR or VLR and HLR

Update at VLR

-- When MS roams into a new Location Area-- Periodically

Update at HLR

-- When MS registers in a new VLR-- When MS registers in the same VLR, but MSC Location Area has changed and HLR requires new routing information-- On HLR or VLR Restoration

Location Update ProcedureLocation Update Procedure


MSCBSCBTS

Complete Layer 3 InfoLoc Upd Req ( SABM )


Clear Command

Clear Complete

Channel ReqChannel Reqd

Channel ActivationChan Actvn Ack

Imm Assgn CmdImmediate Assgn

Establish Ind

Auth ReqData Request

Auth RespData Ind



Loc Upd Accept

Location Update Signaling DiagramLocation Update Signaling Diagram


( SABM ) Loc Upd Req Establish Indication ( CR )Comp Layer 3 Info

BTS BSC MSC

StartsT3210

( UA ) Loc Upd Req

MM - Security Procedures


Loc Upd Accept

StopsT3210

Loc Upd Request : MS Identity(IMSI/TMSI), Classmark, and OLD LAI



Abnormal Cases

Location Update Rejection

BTS BSC MSC

Loc Upd RejectData Request

Loc Upd Reject

StopsT3210

Stores the Reject Cause

StartsT3240

Waits for n/w to release RR-Connection Upon release of RR-Connection, take

necessary action based on Reject Cause

Location Update Reject

Reject Cause-- IMSI Unknown-- PLMN not allowed-- LA not allowed-- TMSI not allocated



Abnormal Cases on MS side

Random Access Fails

No response to RACH after max_retransmissions Timer T3213 is started MS goes for a cell reselection, with return to cell inhibited for 5 secs After 5 secs , the MS returns to the cell where Random access failed On expiry, procedure is initiated again



Channel Request

Immediate Assign

Service Request

Authentication

Set Up

Ciphering

Call Proceeding

Assignment

Alerting

Connection

Mobile Originated CallMobile Originated Call


Mobile Originated Call

MS BTS BSC MSC

Channel ReqdChannel Req

Channel Actvn

Imm AssgnImm Assgn

CM Serv Req

CM Service Accept

Authentication

Set Up

Call ProceedingAssgn ReqAssgn CmdAssgn Cmd

Assign Comp Assign Comp Assign Comp

AlertConnect

Connect AckSpeech

Chan Actvn Ack

Establish ind CL3 Informtn

Cipher Mode Setting and TMSI Reallocation

CC - Call Establishment ProceduresCC - Call Establishment Procedures


CM Service Request

PD : MM TI : 1-7 MT : CSRCM Service Type : MOC , Emergency Call, SMS transfer, SS activationCiphering Key Sequence Number : 000 - 111Mobile Station Classmark 2 : Power , Revision , Encryption,Frequency, SMSMobile Identity : IMSI, TMSI , IMEI

--- No Information Elements

Service Request

PD : MM TI : 1-7 MT : CSRCM Service Accept

CM Service Request

MSC

StartsT3230 & T303

CM Service Accept

StopsT3230

CC- Call Establishment ProcedureCC- Call Establishment Procedure


Abnormal Case

CM Service Rejection

Network starts RR connection release

MSC

CM Serv Reject

StopsT3230 CM Service Reject

Reject Cause

#4 : IMSI unknown in VLR#17 : Network Failure#22 : Congestion#32 : Service Option not supported#33 : Requested Service option not subscribed#34 : Service option temporarily out of order#38 : Call cannot be identified

T3230 Expires

-- Mobile aborts the RR connection



SETUP

Setup

PD : CC TI : 1-7 MT : SBearer Capabilities : *Mobile Identity : IMSI, TMSI , IMEICalling Party Sub-Address : X.213 / ISO 8348 AD2 coding , user specifed codingCalled Party Sub-Address : X.213 / ISO 8348 AD2 coding , user specifed codingUser -User : Convey information between the MS & the remote ISDN user. *

Call Proceeding

PD : CC TI : 1-7 MT : CPRepeat Indicator : Used for in-call modification procedureBearer Capabilities : Included if the network has to specify the connection element Progress Indicator : *

* Detailed Information follows

SetupMSC

Call Proceeding

StopsT303 StartsT310



Abnormal CasesInvalid Call Information

Release Complete

PD : CC TI : 1-7 MT : RCCause : See next page

Setup

MSC

Release Complete

StopsT303

Releases the MM connectionReturns to Idle Mode



1 Unassigned ( unallocated) number

3 No route to destination

6 Channel unacceptable

16 Normal clearing

17 User busy

18 No user responding

19 User alerting, no answer

21 Call rejected

22 Number changed

26 Non selected user clearing

27 Destination out of order

28 Invaid num format( incomplete num )

29 Facility Rejected

30 Response to Status Enquiry

31 Normal, unspecifed

34 No circuit / channel available

38 Network out of order

41 Temporary failure

42 Switching equipment congestion

43 Access information discarded

44 requested circuit/chan unavailable

47 Resources unavailable,unspecified

49 Quality of Service unavailable

50 Requested facility not subscribed

57 Bearer Capability not authorized

58 Bearer Capability not presently available63 Service or option not available

65 Beare Service noit implemented

69 Requested facility not implemented

70 Only restricted data capability available

79 Service or option not implemented

81 Invalid transaction identifier value

88 Incompatible destination

91 Invalid transit network selection

95 Invalid message, unspecified

127 Interworking, Unspecified

# 96 - # 101 = Protocol error

102 Recovery on timer expiry



Channel Assignment

MSCAssignment Command

Assignment CompleteTCH

( FACCH )



Assignment Command

PD : RR TI : 0 MT : ACChannel Description

Channel type & TDMA offset

Timeslot Number : 0 - 7TSC : BCC - 0 - 7Hopping Channel : Single , HoppingChannel Selector : For single Channel -- Band Number, ARFCN For Hopping Channel -- MAIO ( 0 - 63 ), HSN ( 0 - Cyclic

1 - 63 = Algorithm )

Power Command : Power Level ( 0 to 31 )Cell Channel Description : Used to decode the Mobile Allocation tableMobile Allocation table

0 0 0 0 1 -- TCH / F 0 0 0 1 T -- TCH / H 0 0 1 T T -- SDCCH/ 4 0 1 T T T -- SDCCH/ 8

T indicates the subchannel

Channel Mode : signaling only, speech full rate, speech half rate Data- 9.6 / 4.8 / 2.4 kbps full Data- 9.6 / 4.8 / 2.4 kbps half



Abnormal Cases

Assignment Failure

PD : RR TI : 0 MT : AFRR Cause : No cell allocation available

Invalid Message Invalid Information element contents Protocol Error

MSCAssignment Command

Assignment CompleteSDCCH

( SDCCH )



MSC

StopsT310

Alerting

Alerting

PD : CC TI : 1 -7 MT : AProgress Indicator :

Coding standard - Q.931 , GSM Location - connected element ( explained earlier ) Progress Indicator - In band information or appropriate pattern ( RBT,BT ) now available

Alerting



Connect

PD : CC TI : 1 -7 MT : CProgress Indicator :

Coding standard - Q.931 , GSM Location - connected element ( explained earlier ) Progress Indicator - In band information or appropriate pattern ( RBT,BT, Connection tone ) now available

PD : CC TI : 1 -7 MT : C ---- no information elements

Call Connection

MSC

Connect

Connect Acknowledge

Connect Acknowledge



-- GSM Specs define ' 112' as emergency number

-- '112' is accessible with or without SIM

-- Without SIM it is sent on the best channel

-- Mobile on sensing '112' sets the establishment cause to emergency call in the RACH

-- Routing of this call can be done to a desired location defined in the Switch.

Emergency CallsEmergency Calls


Emergency Calls

PD : MM TI : 1-7 MT : CSRCM Service Type : Emergency CallCKSN : 000 - 111Mobile Station Classmark 2 : Mobile Identity : IMSI, TMSI , IMEI

CM Serv Request

Service Request

CM Serv Request

MSC

CM Service Accept

Emergency Setup

PD : CC TI : 1-7 MT : CSRBearer Capability : Only significance is for full rate/ half rate speech coding

Emergency Setup

Call Proceeding



Call Re-establishment

Conditions:

Call Re-establishment should be allowed in the cell Occurs only on lower layer failure ( RF Link ) Mobile should be in active mode on TCH New cell should be in the same BSC Re-establishment will occur within 20 secs

CM Re-estb Request

MSC

CM Service Accept

Assignment Command (TCH)



CCCH_ GROUP

BCCH defines the number of PCHN ( timeslots ) supporting CCCH CCCH can be allocated only to TN 0,2,4,6 CCCH will have the same structure on all allocated timeslots ( 9 blocks ) Each PCHN supporting CCCH is alloted a CCCH_Group No ( range : 0 .. 3 ) Each CCCH_Group carries its own group of Mobiles. Mobiles will listen to paging messages and send RACH's only in their specific group

Paging is process by which Mobile receives incoming calls Mobile has to monitor the paging channel to receive paging messages Mobile will not monitor all paging channels, it will monitor the channel specific

to its CCCH_Group and Paging Group

B9 blocks

D C9 blocks

T C9 blocks

T C9 blocks

T

0 1 2 3 4 5 6 7

PagingPaging


Within the CCCH_Group , Mobile listen to paging in specific paging (CCCH) blocks only

The block specific to a mobile is its Paging Group

0 F S B C F S C C F S C C F S C C F S C C I

1 D

2 I S B C I I C C I I C C I I C C I I C C I

3 T


5 T


7 T

TN

CCCH_GROUPPaging Group

Paging GroupPaging Group


How to derive CCCH_Group and Paging Group for a mobile ?

Let us understand some parameters required to achieve this .

1. BS_CC_CHANS : Total No of PCHN supporting CCCH ( Sys Info Type 3 ) Range : 1 - 4

2. BS_AG_BLKS_RES : Blocks reserved for AGCH

3. BS_PA_MFRMS : Multiframe Repetition rate

4. IMSI : 15 digit Mobile Identity

We will now understand 2 & 3

PagingPaging


Each BCCH and CCCH block = 4 Frames CCCH = AGCH + PCH For Non-Combined & B+C, CCCH = 9 For Combined , CCCH = 3

BS_AG_BLKS _RES

51 Frame Multiframe Non-Combined ( B ) structure [ TN 0 ]F S B C F S C C F S C C F S C C F S C C I

F S B C F S C C F S D D F S D D F S A A I

51 Frame Combined ( B + D )Multiframe Structure [ TN 0 ]

I I B C I I C C I I C C I I C C I I C C I

Additional PCHN supporting CCCH ( B+C)

PagingPaging


--- Some CCCH Blocks can be reserved for AGCH

--- This parameter broadcasted on BCCH informs the Mobile about the number of blocks reserved for AGCH

The value for Non-Combined MF structure ranges between 0 - 7For combined MF structure it ranges between 0-2

BS_AG_BLKS _RES

Example

* Each Paging block ( P ) is a paging group

51 Frame Multiframe Non-Combined ( B ) structure [ TN 0 ]F S B C F S C C F S C C F S C C F S C C I

F S B C F S C C F S D D F S D D F S A A I

51 Frame Combined ( B + D )Multiframe Structure [ TN 0 ]

I I B C I I C C I I C C I I C C I I C C I

Additional PCHN supporting CCCH ( B+C)

PagingPaging


Available Paging Blocks = CCCH Blocks -- bs_ag_blks_res

Maximum AGCH Reservation for Non-Combined = 7 Available

Paging Blocks = 2 Maximum AGCH Reservation for Combined = 2

Available Paging Blocks = 1

Mimimum AGCH Reservartion for Non-Combined = 0 Available Paging Blocks = 9Minimum AGCH Reservation for Combined = 0 Available Paging Blocks = 3

No of Paging Blocks will have a range of 1 - 9

Available Paging Blocks on 1 CCCH_Group

PagingPaging


Mobile belonging to Paging Group P0 will remain idle during P1 ,P2,P3

Mobile utilizes power only during PO. This is known as DRX

BS_PA_MFRMS

-- No of Multiframes after which Same Paging Group is repeated-- This Parameter is broadcasted on BCCH-- Ranges between 0 -- 9 Multiframes

F S B A F S A A F S A A F S A A F S P0 P1 I



MF 2

MF 3

PagingPaging


No of Paging Groups = Paging Blocks x Repitition of Paging BLock N = [ CCCH - bs_ag_blks_res ] x bs_pa_mfrms

Minimum Available Paging Groups = Min Pag blocks x Min bs_pa_mfrms = 1 x 1 = 1

Maximum Available Paging Groups = Max Pag blocks x Max bs_pa_mfrms = 9 x 9 = 81

Range of Paging Groups on 1 CCCH_Group

Total No of Paging Groups on 1 CCCH_Group ( N )

PagingPaging


How does a Mobile knows it CCCH_Group Paging Group No ?

Pag Grp No = [ ( IMSI mod 1000 ) mod ( BS_CC_CHANS x N ) ] mod N

N = Total Paging Groups = No of Paging Blocks x bs_pa_mfrms

CCCH_Group = [ ( IMSI mod 1000 ) mod ( BS_CC_CHANS x N ) ] div N

PagingPaging


Calculate the CCCH_Group & Paging group for a Mobile with IMSI 404001234765898 in a cell with 2 PCHN's for CCCH and 7 blocks reserved for AGCH, and paging group repetition is after 5 multiframes ?

C=1 & P=8C=1 & P=8

Would you like to do an exercise ?Would you like to do an exercise ?


Paging Procedures

BTS packs some paging requests and sends them together in Paging Requests messages on Air Interface.

The Mobile on the other hand listens to it corresponding Paging Group On getting a Paging Message belonging to its IMSI/TMSI it sends a response

* Detailed Paging Procedure will be explained with Mobile Terminated Calls

MSC

Paging( IMSI/TMSI, IMSI, LAI )

BSC

Calculates Pag Grp Nofor cells of LAIPaging Command

BTS

( IMSI or TMSI,Pag Grp No)

Pag Req Type1/2/3

PagingPaging


Packing of Paging Requests

Paging Request Type 1 -----> 2 IMSI or 2 TMSI

Paging Request Type 2 -----> 2 TMSI and 1 IMSI or TMSI

Paging Request Type 3 -----> 4 TMSI

Paging Mode

Normal mode : Paging Message is specific Paging Group onlyFull Mode : Paging Message for that group can occur in any Paging BlockExtended : If paging message has more data, it follows in next block

PagingPaging


Channel Request

Immediate Assign

Authentication

Set Up

Ciphering

Call Confirmed

Assignment

Alerting

Connection

Paging

Paging Response

Mobile Terminated CallMobile Terminated Call


MS BTS BSC MSC

AlertConnect

Connect AckSpeech

Channel ReqdChannel Req

Channel Actvn

Imm AssgnImm Assgn

Paging Response

CM Service AcceptSecurity Procedures

Set Up

Call Proceeding

Chan Actvn Ack

Establish ind CL3 Informant

TCH Assignment

PagingPaging CommandPaging Request

Mobile Terminated CallMobile Terminated Call


BTS BSC MSC

PagingPaging Command

Paging Request 1/2/3 StartsT3113

Paging

Message Type : PIMSI : 15 digitsTMSI : ( omitted if not used )Cell Identifier List :

Cell Id Discrimtr - CGI,LAC & CI, CI,LAC, All cells

Paging Command

Channel Number : PAGCHPaging Group :

Paging Request 1

PD : RR TI : 0 MT : PRPage Mode : Normal, Extended

Re-organization, Same as beforeMobile Identity : IMSI, TMSIMobile Identity : IMSI, TMS--------------------------------------------------------------------------------Paging Request 2 Paging Request 3TMSI TMSITMSI TMSIMobile Identity : IMSI, TMSI TMSI

TMSI

PagingPaging


BTS BSC MSC

Paging Request 1/2/3

Channel Request

Immd Assign

Establish Indication( SABM )Paging Response

Paging

StartsT3113

( UA )Paging Response Complete L3 Info

Paging ResponseStopsT3113

PD : RR TI : 0 MT : PRCiphering Key Sequence Number : 000 - 111Mobile Station Classmark 2 : Power , Revision , Encryption,Frequency, SMSMobile Identity : IMSI, TMSI , IMEI

Abnormal CaseT3113 Expires : --- Paging message is retransmitted

--- No of retransmission and the value of T3113 are implementation dependent

Paging ResponsePaging Response


SETUP

PD : CC TI : 1-7 MT : SBearer Capabilities : *Mobile Identity : IMSI, TMSI , IMEICalling Party BCD Number : Number of the calling partyUser -User : Convey information between the MS & the remote ISDN user. *

Call Confirmed

PD : CC TI : 1-7 MT : CPRepeat Indicator : Used for in-call modification procedureBearer Capabilities : Included if the network has to specify the

connection element

* Detailed explained earlier in MOC

Setup

SetupMSC

Call Confirmed



Alerting

PD : CC TI : 1 -7 MT : AProgress Indicator :

Coding standard - Q.931 , GSM Location - connected element ( explained earlier ) Progress Indicator - In band information or appropriate pattern now available

MSCAlerting

Connect

Connect Acknowledge

AlertingAlerting


-- Mobile receives the signal strength of the serving cell-- Mobile transmits-- During the Idle timeslots measures signal strength of neighbor

Measurement Period Available to Mobile

End of Reception to start of Transmission is = 2 Timelsots End of Transmission to start of Reception is = 4 TimeslotsEnd of Transmisson in 25th frame to start = 12 Timelsots of reception in 1st frame in next MF

--- Mobile does measurement of neighbors in last two cases only

Mobile in Active Mode

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 45 6 7 0 1 2 3 4 5 6 7 0 I I I I I I I

BTS 0 I I I I I I I 0 1 2 3 4 5 6 7

Active Mode ProceduresActive Mode Procedures


Measurements are made over each SACCH multiframe .

SACCH multiframe is 104 TDMA frames(480ms) for TCH and 102 TDMA frames (470.8ms) for a SDCCH.

MS shall make a RxLev measurement in every TDMA frame on at least one of the BCCH carriers indicated in the BA one after another .

Measurements on the frame preceding the idle frame may be optionally omitted to allow more time to MS for BCCH synchronization.

If frequency hopping is used and if BCCH carrier is in the hopping sequence and PWRC indicator is set , then the BCCH carrier bursts will not be used in the averaging process for RxLev, but for RxQual it will be used.

Measurements made during the previous recording period are to be discarded.

Measurements in Active ModeMeasurements in Active Mode


Full and SubRxlev_Full & RxQual_Full : Measurements taken over full set of TDMA frames

Full set of TDMA frames : 102 for SDCCH

Full set of TDMA frames : 104 TCH

Rxlev_Sub & RxQual_Sub : Measurements taken over subset of TDMA frames If even one frame is not transmitted in the measurement period,

then it is considered as subset of TDMA frames.

When are sub measurements done practically ?

When DTX used, and the receiver enters the DTX mode , then the measurement is done over all the frames is not valid.

With DTX, if there is completely no speech for 480ms, then still there will be 8 frames of SID and 4 frames of SACCH, these 12 subset frames will be used for sub measurements .

DTX is not used on BCCH carrier (all timeslots) , hence if the call is on a TCH which is on a BCH carrier, then it will always be FULL, and in the measurement report both Sub and Full values will be same.

DTX is not used on the SDCCH also , hence the above clause applies to this also.

On a TCH carrier, when DTX was used by the BTS in the previous 480ms period, measurement is Sub, else it is full.

If Frequency Hopping was used, and BCH carrier was a part of it, and dowlink power control is used, then the measurements for Rx_Lev will always be sub ( since BCH carrier frames are not included in the measurement averaging)

Measurements in Active ModeMeasurements in Active Mode


--- Mobile also has to verify Neighbor ARFCN by decoding BSIC--- BSIC can be decoded by getting SCH of neighboring cells which is on its TS 0--- Mobile uses the Idle time slot to locate TS0 of neighbor

Will the mobile hit SCH on TS0 of neighbor ? --- TCH MF is 26 and CCH MF is 51 ( non-divisible ) --- Sliding Multiframe Cycles helps mobile in getting SCH ( next pg ) --- As seen, Within 11 cycle, idle TS will align with SCH ( about 1.2 seconds ) --- Within 10 secs mobile will be able to decode BSIC of 6 neighbors --- MS shall keep on decoding the BSIC for each carrier at least one in 10s

T T T T T T T T T T T T A T T T T T T T T T T T T I

0 T 2 3 4 5 6 7 0 I I I I I I I

0 25TCH Multiframe

Mobile in Active ModeMobile in Active Mode


T T T T T T T T T T T T A T T T T T T T T T T T T IT T T T T T T T T T T T A T T T T T T T T T T T T

I T T T T T T T T T T T T A T T T T T T T T T T T T

F S B B B B C C C C F S C C C C C C C C F S C C C CC C C C F S C C C C C C C C F S C C C C C C C C I

I T T T T T T T T T T T T A T T T T T T T T T T T

T I T T T T T T T T T T T T A T T T T T T T T T TT I T T T T T T T T T T T T A T T T T T T T T T T T

T T T T T T T T T T T A T T T T T T T T T T T T IT T T T T T T T T T T T A T T T T T T T T T T T T I

T T I T T T T T T T T T T T T A T T T T T T T T TT T I T T T T T T T T T T T T A T T T T T T T T T T

T T T I T T T T T T T T T T T T A T T T T T T T TT T T I T T T T T T T T T T T T A T T T T T T T T T

T T T T I T T T T T T T T T T T T A T T T T T T TT T T T I T T T T T T T T T T T T A T T T T T T T T

T T T T T I T T T T T T T T T T T T A T T T T T TT T T T T I T T T T T T T T T T T T A T T T T T T T

T T T T T T I T T T T T T T T T T T T A T T T T TT T T T T T I T T T T T T T T T T T T A T T T T T T

0

1325

Sliding Multiframe CycleSliding Multiframe Cycle


--- Mobile sends the measurement report to the BTS in every SACCH Frame--- Measurement Report is of 18 octets and takes 4 SACCH bursts--- It takes 480ms to send 1 Measurement Report


0 25TCH Multiframe 1


0 25

120ms

TCH Multiframe 2

Measurement ReportingMeasurement Reporting


Serving Cell

---- BCCH Indicator---- DTX( indicates whether DTX was used by the MS in measurement period)---- RXLEV ( 0 - 63 ) = ( -110dbm to -48dbm )---- RXQUAL ( 0 - 7 ) = ( > 0.2 % to 12.8 % )

Neighbouring Cells ( 6 )

---- No of cells measured---- RXLEV of each cell ( 0 - 63 ) = ( - 110dbm to -48dbm )---- ARFCN of each cell---- BSIC of each ARFCN

The MS has to take at least 32 samples for each measurement

Layer 1 Header

--- MS Tx Power Level --- Timing Advance

SACCH Report From MobileSACCH Report From Mobile


Measurement Result from BTS

--- BS Power

--- Received Signal Strength on Uplink ( --110dbm to -48dbm )

--- Receive Quality on Uplink ( BER >0.2 % to 12.8 % )

--- Layer 3 MS Info ( Measurement Report send by MS )

--- Layer 1 MS Info ( MS Power & Timing Advance )

The BTS has to take at least 32 samples for each measurement of RxLev and RxQual

Measurement on BTSMeasurement on BTS


--- The BSC Averages the Measurement received after a set period ( Hreqave )

--- The averaging could be following types :

Unweighted Average

Weighted Average

Modified Median

Hreqave : Averaging Period for Rxlev,Rxqual & Timing Advance ( In terms of SACCH Frames ( 480ms ). Range : ( 1, 31

)

Measurement AveragingMeasurement Averaging


ReportNumber

Rxqual Rxlev(s) N1 N2 N3 N4 N5 N6 N7 N8 N9

1 2 -98 -100 -98 -97 -90 -94 ---- -102 ---- ----

2 3 -100 -98 -102 -98 -90 -96 ---- ----- -101 ----

3 5 -102 -96 ---- -97 -94 -99 --- -101 -102 -99

4 2 -99 -97 ---- -96 -97 -100 -104 -99 -101 ----

5 6 -105 -100 -100 -99 -99 ---- ---- -97 -98 ----

6 5 -103 -95 --- -96 -99 --- --- -96 -99 -102

7 1 -97 -98 --- -94 -97 --- ---- -94 -98 -100

8 5 -104 -103 -99 -96 -94 ---- ----- -94 -96 ----

9 5 -104 -95 ---- -95 -95 -99 ---- -96 -98 -----

10 5 -105 ---- -94 -96 -98 -100 -97 -98 -----

Result Number

Rxqual Rxlev

1 2 -99

2 2 -97

3 4 -103

4 3 -100

5 5 -103

6 5 -102

7 0 -97

8 4 -102

9 5 -102

10 5 -104

MS --> BTS (SACCH)

BTS

+ BSC

Generate the Measurement Results table at BSC if HREQAVE = 2

( Abis )

Exercise !!!Exercise !!!


AvergNumber

Rxqual Rxlev(s)

1 2.5 -99

2 3.5 -100.5

3 5.5 -104

4 3 -100.5

5 5 -104.5

AvergNumber

N1 N2 N3 N4 N5 N6 N7 N8 N9

1 -99 -100 -97.5 -90 -95 ---- -102 -101 ----

2 -96.5 ---- -96.5 -95.5 -99.5 -104 -100 -101.5 -99

3 -97.5 -100 -97.5 -99 ---- ---- -96.5 -98.5 ----

4 -100.5 --- -95 -95.5 --- ---- -94 -97 -100

5 -95 ---- -94.5 -95.5 -98.5 -100 -96.5 -98 -----

Downlink Measurements

Neighbour Measurements

Result Number

Rxqual Rxlev

1 2 -98

2 3.5 -101.5

3 5 -102.5

4 2 -99.5

5 5 -102.5

Uplink Measurements

AnswerAnswer


MS Power Control

BTS BSCMS Power Control

SACCH

MSMS Power Control

Channel Number :MS Power : Power step 1 to 31

BS Power Control ( optional )

BTS BSCBS Power Control

MSBS Power Control

Channel Number :BS Power : Power step 1 to 31

Power Control ProcedurePower Control Procedure


Cell 1 Cell 2

Handover is a process by which the control/communication of a Mobile is transferred from one cell to another

HandoverHandover


--- Receive Quality (RXQUAL) on Uplink & Downlink.

--- Receive Signal Strength (RXLEV) on Uplink & Downlink.

--- Distance ( Timing Advance ).

--- Interference Level.

--- Power Budget.

Criteria for HandoverCriteria for Handover


Handover between cells of same BTS

C0C0

BTS

SYNCHRONISED

Internal Inter-Cell HandoverInternal Inter-Cell Handover


Non-synchronized

MSC BSC

BTS

BTS

--- This type of Handover takes place if the cell to which which handover is to be done belongs to the same BSC. --- In this the BSC handles everything without involving MSC.--- The MSC will be informed by the BSC after Handover.

Internal Inter-Cell HandoverInternal Inter-Cell Handover


Inter-Cell Handover

CH Actvn

CH Actvn AckDR ( Hand Cmd )

Hand CMD

Hand Access

Hand Detec

Phys Info

Hand Complete

RF CH Release

RF CH Release AckHand Performed

MSBTS(Old)

BSC BTS(New) MSC

DI ( Hand Comp )

StartsT3103

StartsT3124

StopsT3124

StartsT3105 StopsT3105

StopsT3103

Any Correct Frame

Inter-Cell Handover ProcedureInter-Cell Handover Procedure


Handover Command

CH Actvn

CH Actvn AckDR ( Hand Cmd )

Hand CMD

MSBTS(Old)

BSC BTS(New)

StartsT3103

PD : RR TI : 0 MT : HCCell Description :

BA-NO : Band 0 or 1NCC & BCC : BSIC valueARFCN No: 1 - 124

Channel Description --- SDCCH/4,SDCCH/8 or TCH, TN Number or Subchannel No ( SDCCH )

TSC, ARFCN, Single or Hopping, HSN Mobile Allocation Index OffsetHandover Reference --- 0 - 255Power Command --- Power Level ( 0 - 31 )

Synchronization Indication : Non Synchronized / SynchronizedCell Channel Description : CA - table ( ARFCN's ) for hoppingChannel Mode : Signaling,Speech F/H,Date : 9.6,4.8 f/h, 2.4f/hMobile Allocation : MA TableStarting Time : Starting TDMA Frame No , FN Module 42432

Inter-Cell handover ProcedureInter-Cell handover Procedure


BTS(Old) BSC BTS(New) MS

Hand CMDMS Handover AccessHandover Detection

Synchronous

BTS starts transmission on the activated channel with cipheringBTS starts transmission on SACCH alsoMS sends Handover Access burst in four successive slots, immediately starts ciphering & starts sending and receiving information.BTS on receiving the correct Handover Access Burst starts reception on the activated channel

BTS starts transmission on the activated channel with ciphering,but not on SACCHMS starts T3124,sends Handover Access burst continously, activates deciphering, starts receptionBTS sends a Physical Information Message, starts T3105, starts transmission on SACCH , also starts reception on main ch.MS stops T3124 and starts the normal transmission and reception on the main channel

Asynchronous

StopsT3124


Hand CMDMSHandover Access

Handover DetectionPhysical Info

StartsT3124

Correct Frame


Inter-cell Handover ProcedureInter-cell Handover Procedure


Handover Access

Physical Information

PD : RR TI : 0 MT : HCTiming Advance : 0 - 63 bits

Handover Detection

Channel Number : TCH ,SDCCH/4,SDCCH/8 TN No ,Subchannel No (SDCCH )


Hand CMDMSHandover Access

Handover DetectionPhysical Info

StartsT3124

Correct Frame


TB8

SYNCH41

Information36

TB3

GP

8 bitsHandover Reference No BSIC

6 bits( BSIC is XOR with Parity Bits )



Handover Complete

PD : RR TI : 0 MT : HCRR Cause : Normal Release ( of old channels )


Handover CompleteDI (Handover Complete)RF Channel Release

StopsT3103

Handover Performed

MSC

Handover Performed

Message Type : HPCause : Uplink Quality,Uplink Strength

Uplink Strength,Downlink strength Distance, O & M Intervention, Call Control, Better Cell, Equipment Failure,No Resource

Cell Indentifier : * Cell identification discriminator : -- Whole CGI/ LAC&CI / CI only Cell identification 1 : MCC + MNC + LAC + CI Radio Channel Identity : *

Channel Description, MA table, Starting time* Optional



Abnormal Cases


Hand CMDMS Handover Access

Handover Detection StartsT3124

T3124 Expires ( asynchronous ) Lower layer failure occurs

MS Deactivates new channels Activates Old Channels, & sends

Handover Failure

DI (Handover Failure)

MS resumes normal operation( as no handover attempt had occurred )

StopsT3103

Handover Failure

PD : RR TI : 0 MT : HCRR Cause : Abnormal Release ( unspecified ), Channel Unacceptable, timer expired, Invalid Message( unspecified ), No CA available, Protocol errors



MSC

BSC

BSC

BTS

BTS

--- In this type of Handover,the Mobile is handed over to a cell which belongs to another BSC.

--- The MSC is completely involved in this Handover

External Inter-Cell HandoverExternal Inter-Cell Handover


INTER - BSC Handover

MS BSC(Old) BSC(New)MSC

Hand Reqd

Hand Reqst

Hand Reqst AckHand CMD

DI(Hand CMD)

BTS

CH Actvn

CH Actvn Ack

BTS

Hand CMD

Hand Access

Hand Detect

Hand Comp

Hand CompClear CMD

Hand Detection

DI(Hand Comp)

Phy Info

Starts T 7

Stops T 7

External Inter-Cell Handover ProcedureExternal Inter-Cell Handover Procedure


MS BSC(Old) BSC(New)MSC BTSBTS

Hand Access

Hand Detect

Hand Comp

Hand Comp

Hand Detection

DI(Hand Comp)

Phy Info

Handover Command

Message Type : HC

Handover Command

Message Type : HCRR Cause : Normal Release ( old channels ) - Optional



Handover Failure

PD : RR TI : 0 MT : HCRR Cause : Abnormal Release ( unspecified ), Channel Unacceptable, timer expired, Invalid Message( unspecified ), No CA available, Protocol errors

Handover Failure

PD : RR TI : 0 MT : HCCause : Radio Interface Failure , reversion to old channelRR Cause : Abnormal Release ( unspecified ), Channel Unacceptable, timer expired, Invalid Message( unspecified ), No CA available, Protocol errors

BSC(Old) BSC(New)MSC

Handover Failure

MS

Handover FailureClear Command

Abnormal Case

Failure at MS



Handover between channels / timeslots of same cell

BTS

Intra-Cell HandoverIntra-Cell Handover


Handover on Interference is based on RXQUAL & RXLEV

If RXQUAL is poor and RXLEV is good , then Handover takes place

Interference Handover is an Intra-cell Handover

InterferenceInterference


Channel Number : Activation Type : intra cell handoverChannel Mode :Channel Identification :Encryption Information :BS Power, MS Power , Timing Advance:BS & MS Power Parameter :

Channel Activation

Channel Activation

BTS BSC

DR ( Assgn Command)Assignment Command

Assignment Complete DI ( Assgn Complete )

StartsT10

Channel Actvn Ack

StopsT10

Old Channel

New Channel

MS

RF Channel Release

RF Channel Release Ack

Intra-Cell HandoverIntra-Cell Handover


Release of Call

TCH

Disconnect

Release

Release Comp

FACCH

MSC

StartsT305

StopsT305

Disconnect

PD : CC TI:1 -7 MT : DCause : #16 - Normal Clearing

#38 - Network Out of Order

Release

PD : CC TI:1 -7 MT : RCause : Not reqd

PD : CC TI:1 -7 MT : R Cause : Not reqd

Release Complete

Channel Release

Channel Release

PD : RR TI : 0 MT : CRCause : - Normal Release

- Abnormal Release, unspecified - No activity on radio path - Preemptive release - No CA available ( handover ) -

CC - Call ClearingCC - Call Clearing


Radio Link Failure is based on SACCH Messages

It is controlled by the Radio Link Counter ( S )

The max value of ' S ' is broadcasted on BCCH

If Mobile is not able to decode SACCH message

' S ' decreases by 1

If Mobile is able to decode SACCH message

' S ' increases by 2

If ' S ' reaches 0 , Radio Link failure is declared

Radio Link FailureRadio Link Failure


4

3

2

1

0

' S '

SACCH Blocks

BCCH = ' S ' is 4

Radio Link FailureRadio Link Failure


Idle Mode Link Failure depends on the counter DSC

DSC is initialized to the nearest integer of 90 / Bs_pa_mfrms.

For every Paging Message non-decode ( BFI=1), DSC is decreased by 4.

For every successful decode, it is increased by 1.

Once DSC reaches "0", link failure is declared and Mobile does cell reselection.

Radio Link Failure in Idle ModeRadio Link Failure in Idle Mode


LAPDm

RIL3

Rad IntBTS

LAPDm

RIL3

Rad Int

DTAP

RR

MS04.04

04.04

04.08/ 04.10 04.08/ 04.10

Air Interface - L2 SignalingAir Interface - L2 Signaling


LAPDm signaling is done using Frames. LAPDm frames contain Address, Control and L3 information. LAPDm has a window size of 1 ( every frame sent must be

acknowledged before next is sent, in acknowledge mode )

Lapdm frame supports maximum 23 octets only Lapdm frame structure has no flags ( since blocks channels available ).

Lapdm message has two SAPI's ----- SAPI 0 = for DTAP and RR signaling

----- SAPI 3 = for Short Message Service

** SAPI : Service Access Point Identifier

Link Access Protocol on Dm ( LAPDm)Link Access Protocol on Dm ( LAPDm)


Modes of LAPDmAcknowledge : Every frame sent must receive acknowledgementUnacknowledged : No acknowledgement required for the frames sent

Type of LAPDm frames

Information Frames ( I - Frames ) : These convey the actual information ( message ) in acknowledge mode.

Supervisory Frames ( S- Frame ) : These manages the flow of I-frames by acknowledging or requesting retransmission

of I-frames.

Unnumbered Frames ( U - Frame ) : These provide setting up of acknowledge mode and unacknowledged Information ( I - Frame ) transfer.

LAPDm FramesLAPDm Frames


Unnumbered FramesSABM ( Set Asynchronous Balance mode ) : This frame is sent to begin acknowledge mode of information transfer ( I -frame ) Disc ( Disconnect Mode ) : This frame is sent to terminate acknowledge mode of Information TransferUI ( Unnumbered Information ) : This is used for Unacknowledged Information transfer

UA (Unnumbered Acknowledge) : This is used to acknowledge the SABM & DISC framesDM ( Disconnect Mode ) : This indicates the disconnection and SABM could be performed

These frames don't use sequencing [ N(R) & N(S) ]

SABM

UA

DISC

DM ( or UA )

UI

UI

UI

UI

LAPD FramesLAPD Frames


Supervisory FramesRR ( Receive Ready ) : Positive Acknowledgement.RNR ( Receive Not Ready ) : Stop sending messages ( buffer is full ).REJ ( Reject ) : Negative Acknowledgement

These Frames uses Sequencing [ only N ( R ) ]

Information Frames

These frames are used to transfer Layer 3 Information ( RSL,OML,L2M messages ) in sequence,that is is in acknowledged mode.

These frames uses Sequencing

LAPD FramesLAPD Frames


Layer 2

Layer 2

Layer 3

Layer 2

Layer 3

Layer 2

SABM

UA

I - frame ( C )

RR

Disc

I - frame ( R )

DM ( or UA )

RR

Layer 2

Layer 2

Acknowledge Mode

LAPDm Frames FlowLAPDm Frames Flow


Acknowledge Mode ( with window size of 1 ) Unacknowledged mode

Lapdm modes vary on the type of logical channel the information is sent

For SAPI 0 :BCCH UnacknowledgedCCCH UnacknowledgedSDCCH Unacknowledged and AcknowledgedSACCH UnacknowledgedFACCH Unacknowledged and Acknowledged

For SAPI 3 :SDCCH AcknowledgedSACCH (TCH) Acknowledged

Lapdm Modes Lapdm Modes


LAPDm frame forBCCH,RACH,AGCH,PCH

Lapdm frame forSDCCH,SACCH,FACCH

More bit = 1 indicates more information to follow ( in next block ) = 0 indicates end of information ( message )

Link Protocol Discriminator = 00 ( not used for GSM )

Length IndicatorField

Layer 3 Information(RIL 3 Message )

Fill Bits

1 octet 22 Octets

1 octet1 octet1 octet 20 Octets

0 Link ProtocolDiscrmntr

SAPI C/ R Extended Address

1 2 3 2 1

Address Field

ControlField

Length Ind Field

Layer 3 Information( RIL3 Message )

Fill Bits

Lenght Indicator More bit ELI6 1 1

LAPDm Frame StructureLAPDm Frame Structure


N( S )( 7 bits )

P/ F( 1 bit )

N( R )( 7 bits )

( Acknowledge Mode )

Flag Address Control Information FCS FLAG8 16 16 max249oct 16 8

Fixed Bits C / R

( Unacknowledged Mode )

Type Direction C/R Value

Command BS to MS 1

Command MS to BS 0

Response BS to MS 0

Response MS to BS 1

LAPD Frame Structure - Control FieldLAPD Frame Structure - Control Field


Flag Address Control Information FCS FLAG8 16 16 max249oct 16 8

Maximum 249 Octets

LAPD

Length IndicatorField 22 Octets

Information

Address Field

ControlField

LIF 20 OctetsInformation

Address Field

ControlField

LIF 18 OctetsInformation

BCCH & CCCH FACCH & SDCCH SACCH21 Octets

+1 octet for Tim Adv &1 octet for Pwr Control

23 Octets456 bits

Error Coding

Interleaving done over 4 bursts

57 57 5757 5757 57 57 57 26 57

TDMA Burst

23 Octets 23 Octets

LAPDm Message in a BurstLAPDm Message in a Burst

chapter 3

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