Gsm Call Scenarios at a Glance

Title Version Author Ref:

GSM Call Scenarios V1.0 Praveen Devarmani

Recommended Viewer List GPS OAM , BSS Teams

Legend Call Flow:- MS to Network Side Call Flow:- Network to MS side

Publication History V1.0 09w32 Creation

Mobile is Switched On Network Attachment Network Attachment

Network attachment is the process of selecting an appropriate cell (radio frequency) by the mobile station to provide the available services, and making its location known to the network. The process starts when the mobile station is switched on, and ends when the mobile station enters the idle mode

The network attachment process consists of the followintasks: Step 1 Cell identification When a mobile station is switched on, it attempts to make contact with a GSM PLMN by performing the following actions: 1)Measure the BCCH channels 2)Search for a suitable cell The mobile station measures the signal strength of the BCCH (Broadcast Control Channel) channels received. It stores in list information about 30 of these BCCH channels, such as the signal strength and the frequency corresponding to these BCCH channels Step 2 PLMN selection(Selects GSM PLMN) A suitable PLMN is chosen. PLMN selection mechanism The particular PLMN to be contacted can be selected either in one of the following modes: · Automatic mode In automatic mode, the mobile station will choose which PLMNs to try all by itself. The automatic mode is based on the existence of the preferred list, which is stored in a nonvolatile memory in the SIM. This list includes a number of PLMN identities in order of preference and is under control of the user. The most preferred is usually the home PLMN. The list is filled in by the user through a mechanism to be specified by the mobile station manufacturer. · Manual mode In manual mode, the user is presented a list containing all found PLMNs. The user chooses one of the PLMNs from the list.

Step 3 CELL selection(Selects Suitable ARFCN) Cell selection is the process of selecting an appropriate cell (radio frequency) by the mobile station to provide the available services. Cell selection criteria The mobile station attempts to find a suitable cell by passing through the list in descending order of received signal strength; the first BCCH channel which satisfies a set of requirements is selected. The requirements that a cell must satisfy before a mobile station can provide service from it, are: · It should be a cell of the selected PLMN The mobile station checks whether the cell is part of the selected PLMN. · It should not be "barred" The PLMN operator may decide not to allow mobile stations to access certain cells. These cells may, for example, only be used for handover traffic. Barred cell information is broadcast on the BCCH to instruct mobile stations not to access these cells. · The radio path loss between the mobile station and the selected BTS must be below a threshold set by the PLMN operator Step 4 Location Update In order to initiate a call or to receive a call, the mobile station tunes to the control channel (BCCH plus CCCH) of the chosen cell. Then, it registers its presence in this cell (registration process) by means of a location updating procedure. If No suitable cell found after cell selection process(MS enters Step 5 into Emergency Call Mode If the mobile station is unable to find a suitable cell to access, it attempts to access a cell irrespective of the PLMN identity, and enters a "limited service" state in which it can only attempt to make emergency calls.

Mobile in Idle Mode Idle mode is the node in which mobile station does not have a traffic channel allocated to it for make or receive a call, but the Public Land Mobile Network (PLMN) is aware of the existence of the mobile station within the chosen cell.

PLMN area A Public-Land-Mobile-Network (PLMN) area is the geographical area in which a particular PLMN operator provides land mobile communication services to the public. From any position within a PLMN area, the mobile user can set up calls to another user of the same network, or to a user of another network. The other network may be a fixed network, another GSM PLMN, or another type of PLMN. Other network users, and users of other networks, can also call a mobile user who is active in the PLMN area. When there are several PLMN operators, the geographical areas covered by their networks may overlap. National borders normally limit the extent of a PLMN area.

Location area identity Every radio transmitter in the PLMN broadcasts, via a control channel, a Location Area Identity (LAI) code to identify the location area that it serves. When an MS is not engaged in a call, it automatically scans the control channel broadcasts transmitted by the base stations in the locality and selects the channel that is delivering the strongest signal. The LAI code broadcast by the selected channel identifies the location area in which the MS is currently situated. This LAI code is stored in the Subscriber Identity Module (SIM) of the mobile equipment. As the MS moves through the network area the signal received from the selected control channel gradually diminishes in strength until it is no longer the strongest. At this point the MS re-tunes to the channel that has become dominant and examines the LAI code that it is broadcasting. If the received LAI code differs from that stored on the SIM, then the MS has entered another location area and initiates a location update procedure to report the change to the MSC. At the end of the procedure the LAI code in the SIM is also updated.Location area identity format

Mobile Originating Call MS

BTS RADIO RESOURCE ALLOCATION

BSC RADIO RESOURCE ALLOCATION

MS to BTS(RACH) CHANNEL REQUEST(RACH CCCH) Reason(MOC) [Establisment Cause] Random Reference Number

BTS to BSC CHANNEL REQUIRED Channel Req (Reason, Rand ref Num) Timing Advance Frame Number Channel Number BSC to BTS CHANNEL ACTIVATE Channel number Activation Type Channel Mode (DTX??) Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC CHANNEL ACTIVATE ACK Frame Number Channel number BSC to BTS IMM_ASS_CMD Channel Number Timing Advance Frame Number Random Reference [Full Imm. Assign Info]

BTS to MS(AGCH)SDCCH is Assigned IMM_ASS_CMD Channel Number Timing Advance Frame Number Reference [Full Imm. Assign Info]

MSC RADIO RESOURCE ALLOCATION

G-MSC

PLMN

LAYER 2 ESTABLISHMENT(LAPDm) [Data Link Layer]

LAYER 2 ESTABLISHMENT(LAPDm)


MS to BTS(SDCCH) CM_SERV_REQUEST(SABM) CM_SERV_REQ MS data CM service type Ciphering key sequence Number Mobile station classmark Mobile identity

BTS to MS CM_SERV_REQUEST(UA)

BTS to BSC(EST_INDICATION) CM_SERV_REQ CM_SERV_REQ MS data CM service type Ciphering key sequence Number Mobile station classmark Mobile identity BSC to MSC CM_SERV_REQUEST Adds LAC to CM_SERV_REQ Adds CI to CM_SERV_REQ Sends SCCP Connection request to MSC

MSC to BSC CONNECTION CONFIRMED SCCP Connection Established

AUTHENTICATION

AUTHENTICATION

BTS to MS AUTH_REQ(SDCCH) Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type

BSC to BTS AUTH_REQ Auth. Parameter -RAND Cipher Key Sequence Number

AUTHENTICATION MSC to BSC AUTH_REQ Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type

Auth. Request Message Type

MS to BTS(SDCCH) AUTH_RES(RESPONSE) Authentication Parameter [SRES] Auth Response message type

BTS to BSC(SDCCH) AUTH_RES(RESPONSE) Authentication Parameter [SRES] Auth Response message type

BSC to MSC(SDCCH) AUTH_RES(RESPONSE) Authentication Parameter [SRES]

Auth Response message type

BTS to MS CM_SER_ACCEPT CM Service Accept message type

BSC to BTS CM_SER_ACCEPT CM Service Accept message type

MSC to BSC CM_SER_ACCEPT CM Service Accept message type

CIPHERING

CIPHERING

BSC to BTS BTS to MS CIPHER_MODE_CMD(SDCCH) A5/X information

ENCR_CMD(SDCCH) KC (Ciphering Key) CIPHER_MODE_CMD

CIPHERING MSC to BSC CIPHER_MODE_CMD(SDCCH) KC (Ciphering Key) A5/X Algorithm info(Encryption Info)

MS to BTS(SDCCH) CIP_MODE_COMPLETE Cipher mode complete Message type Mobile equipment identity

BTS to BSC(SDCCH) CIP_MODE_COMPLETE Cipher mode complete Message type Mobile equipment identity

IMEI CHECK

BTS to MS IDENT_REQUEST(SDCCH)

IMEI CHECK

BSC to BTS IDENT_REQUEST(SDCCH) Identity Request message type Identity type(IMEI)

BSC to MSC (SDCCH) CIP_MODE_COMPLETE Cipher mode complete Message type Mobile equipment identity IMEI CHECK MSC to BSC IDENT_REQUEST(SDCCH) Identity Request message type Identity type(IMEI)

Identity Request message type Identity type(IMEI) MS to BTS(SDCCH) IDENT_RSP BTS to BSC(SDCCH) IDENT_RSP Mobile Identity(IMEI)

Mobile Identity(IMEI)

TMSI REALLOCATION

BSC to MSC(SDCCH) IDENT_RSP Mobile Identity(IMEI)

TMSI REALLOCATION

TMSI REALLOCATION MSC to BSC

BSC to BTS BTS to MS TMSI_REAL_CMD(SDCCH) TMSI Number LAI Mobile Identity

TMSI_REAL_CMD(SDCCH) TMSI Number LAI Mobile Identity

MS to BTS(SDCCH) TMSI_REAL_COMPLETE BTS to BSC(SDCCH) TMSI_REAL_COMPLETE


BSC to MSC(SDCCH) TMSI_REAL_COMPLETE

SETUP

SETUP

SETUP

MS to BTS(SDCCH) SETUP Bearer Capablities Calling party sub- address Called party BCD number

BTS to BSC(SDCCH) SETUP BSC to MSC(SDCCH)

Bearer Capablities Calling party sub- address Called party BCD number

Called party sub-address

Called party sub-address

SETUP

MSC to G-MSC

Bearer Capablities Calling party sub- address

INITIAL ADDRESS MESSAGE

Called party BCD number Called party sub-address

MSC to BSC CALL_PROCEEDING(SDCCH) BTS to MS

BSC to BTS CALL_PROCEEDING(SDCCH)

CALL_PROCEEDING(SDCCH) Connecting…Dispalyed in Mobile TCH ALLOCATION

TCH ALLOCATION

BSC to BTS PHY_CONTEXT_REQ Query for Situation on Air Interface BTS to BSC(SDCCH) PHY_CONTEXT_CONF Send MS Power to BSC Sends BTS Power to BSC Sends TA info to BSC

Activation Type Channel Mode Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC(SDCCH) CHAN_ACT_ACK Channel Number Frame Number

MSC to BSC ASSIGNMENT_REQUEST(SDCCH) Channel type Layer 3 header information Priority Circuit identity code Downlink DTX flag Interference band to be used Classmark information 2

BSC to BTS CHANNEL_ACTIVATATION

TCH ALLOCATION

G-MSC to ISDN/Other PLMN INITIAL ADDRESS MESSAGE

BTS to MS ASSIGNMENT_CMD(SDCCH) Data of the TCH [TRX Info, Time Slot] TCH ALLOCATED HERE for MS

BSC to BTS ASSIGNMENT_CMD(SDCCH) Data of the TCH [TRX Info, Time Slot]

LAYER 2 ESTABLISHMENT(LAPDm) MS to BTS(FACCH) FACCH/SABM Request for Lapdm layer2 connection BTS to MS



BTS to BSC EST_IND Channel Number (which TCH Time Slt) Link Identifier (C1 & C2) L3 Information

(UA)(FACCH) MS to BTS ASSIGNMENT_COMPLETE

RR cause Cell identifier Chosen channel Chosen encryption algorithm

BTS to BSC ASSIGNMENT_COMPLETE

Indicates Signalling Link is Estb Successfully

RR cause etc…

BSC to MSC ASSIGNMENT_COMPLETE RR cause etc…

SDCCH RELEASE

SDCCH RELEASE

SDCCH RELEASE BSC to BTS

RF_CHAN_RELEASE Channel number [to be released] BTS to BSC RF_CHAN_RELEASE_ACK Channel number [released] ALERT

ALERT

PSTN/Other PLMN to G-MSC Address Complete Message

ALERT MSC to BSC BSC to BTS

BTS to MS ALERT/PROGRESS Alerting Messge type Facility User -User Progress indicator

ALERT/PROGRESS Alerting Messge type Facility User -User Progress indicator

G-MSC to MSC Address Complete Message


PSTN/Other PLMN to G-MSC ANM(Answer Message) G-MSC to MSC ANM(Answer Message) MSC to BSC BSC to BTS BTS to MS CONNECT BOTH USERS START CONVERSATION

MS to BTS

CONNECT

CONNECT Connect message type Facility Progress indicator Connected number Connected subaddress User-user

CONNECT_ACKNOWLEDGE Indicates call is going on and charges Applies

BTS to BSC CONNECT_ACKNOWLEDGE BSC to MSC CONNECT_ACKNOWLEDGE

CALL RELEASE

CALL RELEASE

MS to BTS DISC Disconnect message type Cause(Normal Clearing Examlple)-Reason Facility Progress indicator User-user MS side user Releases the call

CALL RELEASE

BTS to BSC DISC BSC to MSC DISC

MSC to G-MSC Release(REL)-Reason

G-MSC to PSTN/PLMN Release(REL)-Reason

MSC to BSC BSC to BTS BTS to MS REL(RELEASE)

REL(RELEASE) Release Cause

REL(RELEASE) Release Cause

Release Cause MS to BTS RELEASE COMPLETE Release Cause

BTS to BSC RELEASE COMPLETE Release Cause

Traffic Channel RELEASE (by MS)

PSTN/PLMN to G-MSC REL(RELEASE COMPLETE) G-MSC to MSC REL(RELEASE COMPLETE)

BSC to MSC RELEASE COMPLETE Release Cause

Traffic Channel RELEASE

Traffic Channel RELEASE MSC to BSC BSC to BTS

BTS to MS CHANNEL_RELEASE Release Cause

CHANNEL_RELEASE Release Cause

CLEAR_COMMAND Layer 3 header information Release Cause

BSC to BTS DEACTIVATE_SACCH MS to BTS FACCH/DISC (LAPDm)

Channel number

Request for Layer 2 connection Release BTS to MS FACCH/UA (LAPDm) Confirmation of Layer 2 Connnection Release

Radio Channel RELEASE (TRX)

BTS to BSC RELEASE_INDICATION Channel number Link Identifier Release of Air Interface connection Radio Channel RELEASE (TRX) BSC to BTS RF_CHN_RELEASE Channel number (to be released)

BSC to MSC CLEAR_COMPLETE Radio Channel RELEASE (TRX)

BSC requests to BTS for TRX release on air Interface

MSC to BSC

BTS to BSC

RLSD

RF_CHN_RELEASE_ACK

MSC requests BSC to release SCCP resources

TRX release acknowledge Channel number ( which is released)

BSC to MSC RLC Release Cause SCCP Release Acknowledge

MS to MS (Within PLMN)

Mobile Terminating Call MS

BTS

PAGING

MSC to BSC PAGING_REQUEST Paging request type Message type Page mode Channels needed for Mobiles Mobile identities P3 rest octets TMSI IMSI CELL Ids Response to Paging Request RADIO RESOURCE ALLOCATION

PAGING

MSC to BSC PAGING_CMD Paging request type Message type Page mode Channels needed for Mobiles Mobile identities P3 rest octets TMSI IMSI CELL Ids

RADIO RESOURCE ALLOCATION

MS to BTS(RACH) CHANNEL REQUEST(RACH CCCH) Reason(MOC) [Establisment Cause] Random Reference Number

BTS to BSC CHANNEL REQUIRED Channel Req (Reason, Rand ref Num) Timing Advance Frame Number Channel Number BSC to BTS CHANNEL ACTIVATE Channel number Activation Type Channel Mode (DTX??) Channel Identification Encryption information Handover Reference

BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC CHANNEL ACTIVATE ACK Frame Number Channel number BSC to BTS IMM_ASS_CMD Channel Number Timing Advance Frame Number Random Reference [Full Imm. Assign Info] BTS to MS(AGCH)SDCCH is Assigned IMM_ASS_CMD Channel Number Timing Advance Frame Number Reference [Full Imm. Assign Info] LAYER 2 ESTABLISHMENT(LAPDm)


MS to BTS(SDCCH) PAGING_RESPONSE(SABM) MS data Request for Lapdm layer2 connection

BTS to MS PAGING_RESPONSE(UA)

BTS to BSC(EST_INDICATION) PAGING_RESPONSE Paging response message type Ciphering key sequence Number Spare half octet Mobile Stattion ClassMark Mobile Identity

AUTHENTICATION

AUTHENTICATION

AUTH_REQ(SDCCH)

BSC to BTS AUTH_REQ Auth. Parameter -RAND Cipher Key Sequence Number

BTS to MS

Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type

Auth. Request Message Type


CIPHERING


CIPHERING

BSC to BTS BTS to MS CIPHER_MODE_CMD(SDCCH) A5/X information MS to BTS(SDCCH) CIP_MODE_COMPLETE Cipher mode complete Message type Mobile equipment identity

IMEI CHECK

BTS to MS IDENT_REQUEST(SDCCH) Identity Request message type Identity type(IMEI) MS to BTS(SDCCH) IDENT_RSP Mobile Identity(IMEI)


IMEI CHECK

BSC to BTS IDENT_REQUEST(SDCCH) Identity Request message type Identity type(IMEI)

BTS to BSC(SDCCH) IDENT_RSP Mobile Identity(IMEI)

TMSI REALLOCATION

BTS to MS TMSI_REAL_CMD(SDCCH) TMSI Number


TMSI REALLOCATION

BSC to BTS TMSI_REAL_CMD(SDCCH) TMSI Number LAI

LAI Mobile Identity

Mobile Identity

MS to BTS(SDCCH) TMSI_REAL_COMPLETE BTS to BSC(SDCCH) TMSI_REAL_COMPLETE

SETUP

SETUP

BTS to MS(SDCCH) BSC to BTS(SDCCH)

BTS to MS SETUP Bearer Capablities Calling party sub- address Called party BCD number Called party sub-address

SETUP Bearer Capablities Calling party sub- address Called party BCD number Called party sub-address

MS to BTS(SDCCH) CALL_CONF Call confirmed message type Repeat Indicator Bearer capability Bearer capability Cause CC Capabilities

TCH ALLOCATION

BTS to BSC(SDCCH) CALL_CONF

TCH ALLOCATION

BSC to BTS PHY_CONTEXT_REQ Query for Situation on Air Interface BTS to BSC(SDCCH) PHY_CONTEXT_CONF Send MS Power to BSC Sends BTS Power to BSC Sends TA info to BSC BSC to BTS CHANNEL_ACTIVATATION Activation Type Channel Mode Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information

BTS to BSC(SDCCH) CHAN_ACT_ACK Channel Number Frame Number

BTS to MS ASSIGNMENT_CMD(SDCCH) Data of the TCH [TRX Info, Time Slot] TCH ALLOCATED HERE for MS LAYER 2 ESTABLISHMENT(LAPDm) MS to BTS(FACCH) FACCH/SABM Request for Lapdm layer2 connection BTS to MS

BSC to BTS ASSIGNMENT_CMD(SDCCH) Data of the TCH [TRX Info, Time Slot]

LAYER 2 ESTABLISHMENT(LAPDm) BTS to BSC EST_IND Channel Number (which TCH Time Slt) Link Identifier (C1 & C2) L3 Information

(UA)(FACCH) MS to BTS ASSIGNMENT_COMPLETE

RR cause Cell identifier Chosen channel Chosen encryption algorithm

BTS to BSC ASSIGNMENT_COMPLETE

Indicates Signalling Link is Estb Successfully

RR cause etc…

SDCCH RELEASE

SDCCH RELEASE BSC to BTS RF_CHAN_RELEASE Channel number [to be released] BTS to BSC RF_CHAN_RELEASE_ACK Channel number [released]

ALERT

ALERT BTS to MS


BSC to BTS

BTS to MS CONNECT Connect message type Facility Progress indicator Connected number Connected subaddress User-user MS to BTS

ALERT/PROGRESS Alerting Messge type Facility User -User Progress indicator BSC to BTS CONNECT

CONNECT_ACKNOWLEDGE Indicates call is going on and charges Applies

CALL RELEASE

BTS to BSC CONNECT_ACKNOWLEDGE Indicates call is going on and charges Applies

CALL RELEASE

BTS to BSC DISC MS to BTS DISC

MS to BTS REL(RELEASE) Release Cause

BTS to BSC REL(RELEASE) Release Cause

BTS to BSC RELEASE COMPLETE Reason

MS to BTS RELEASE COMPLETE Reason Traffic Channel RELEASE (by MS)


BSC to BTS BTS to MS CHANNEL_RELEASE Release Cause

CHANNEL_RELEASE Release Cause BSC to BTS

MS to BTS FACCH/DISC (LAPDm) Request for Layer 2 connection Release BTS to MS FACCH/UA (LAPDm) Confirmation of Layer 2 Connnection Release


DEACTIVATE_SACCH Channel number

BTS to BSC RELEASE_INDICATION Channel number Link Identifier Release of Air Interface connection Radio Channel RELEASE (TRX) BSC to BTS RF_CHN_RELEASE Channel number (to be released) BSC requests to BTS for TRX release on air Interface

BTS to BSC RF_CHN_RELEASE_ACK TRX release acknowledge Channel number ( which is released)

BSC

MSC VLR

HLR

HLR to VLR UDT/BEGIN(Provide roamining number) VLR to HLR UDT/END(Provide roamining number)

G-MSC to MSC E-Interface (Initial Address Message)

PAGING MSC to BSC PAGING Paging request type Message type Page mode Channels needed for Mobiles Mobile identities P3 rest octets TMSI IMSI CELL Ids



BSC to MSC PAGING_RESPONSE Adds LAC to Paging Response Adds CI to Paging Response Sends SCCP Connection request to MSC

MSC to BSC CONNECTION CONFIRMED SCCP Connection Established Now onwards Logical Conn exist betn MS-MSC

AUTHENTICATION MSC to BSC AUTH_REQ Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type

BSC to MSC(SDCCH) AUTH_RES(RESPONSE) Authentication Parameter [SRES] Auth Response message type



BSC to MSC(SDCCH) IDENT_RSP Mobile Identity(IMEI) TMSI REALLOCATION MSC to BSC TMSI_REAL_CMD(SDCCH) TMSI Number LAI Mobile Identity

BSC to MSC(SDCCH) TMSI_REAL_COMPLETE SETUP MSC to BSC(SDCCH) SETUP Bearer Capablities

BSC to MSC(SDCCH) CALL_CONF

TCH ALLOCATION MSC to BSC ASSIGNMENT_REQUEST(SDCCH) Channel type Layer 3 header information Priority Circuit identity code Downlink DTX flag Interference band to be used Classmark information 2


BSC to MSC ASSIGNMENT_COMPLETE RR cause etc…

SDCCH RELEASE

ALERT

MSC to BSC ALERT/PROGRESS Alerting Messge type Facility User -User Progress indicator MSC to BSC CONNECT BOTH USERS START CONVERSATION

MSC to G-MSC ADDRESS COMPLETE MESSAGE

MSC to G-MSC ISUP(ANSWER MESSAGE)

BSC to MSC CONNECT_ACKNOWLEDGE Indicates call is going on and charges Applies CALL RELEASE BSC to MSC DISC Disconnect message type Cause(Normal Clearing Examlple)-Reason Facility Progress indicator User-user

ISDN to G-MSC to MSC ISUP(RELEASE)

BSC to MSC REL(RELEASE) Release Cause

MSC to G-MSC to ISDN ISUP(RELEASE COMPLETE)

BSC to MSC RELEASE COMPLETE Reason

Traffic Channel RELEASE MSC to BSC CLEAR_COMMAND Layer 3 header information Release Cause


MSC to BSC

RLSD MSC requests BSC to release SCCP resources BSC to MSC RLC Release Cause SCCP Release Acknowledge

G-MSC

ISDN

ISDN to G-MSC IAM(ISUP) G-MSC to HLR UDT/BEGIN(Send Routing Info)

HLR to G-MSC UDT/END(Send Routing Info)

G-MSC to ISDN ADDRESS COMPLETE MESSAGE

G-MSC to ISDN ISUP(ANSWER MESSAGE)

LOCATION UPDATE SCENARIO WHERE VLR CHANGES AND HLR IS INVOLVED MS

BTS RADIO RESOURCE ALLOCATION

BSC RADIO RESOURCE ALLOCATION

MS to BTS(RACH) CHANNEL REQUEST(RACH CCCH) Reason(Location Update) [Establisment Cause] Random Reference Number

BTS to BSC CHANNEL REQUIRED Channel Req (Reason, Rand ref Num) Timing Advance Frame Number Channel Number BSC to BTS CHANNEL ACTIVATE Channel number Activation Type Channel Mode (DTX??) Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC CHANNEL ACTIVATE ACK Frame Number Channel number BSC to BTS IMM_ASS_CMD Channel Number Timing Advance Frame Number Random Reference [Full Imm. Assign Info]

BTS to MS(AGCH)SDCCH is Assigned IMM_ASS_CMD Channel Number Timing Advance Frame Number Reference [Full Imm. Assign Info]


NEW MSC VLR

HLR

NEW MSC VLR

Location Update Request



MS to BTS(SDCCH) LOC_UPDATE_REQUEST(SABM) Ciphering key sequence Number Mobile station classmark Mobile identity Location area identification Locatio Updating request Message type OLD LAC Info BTS to MS LOC_UPDATE_REQUEST(UA)

BTS to BSC(EST_INDICATION) LOC_UPDATE_REQUEST Ciphering key sequence Number Mobile station classmark Mobile identity Location area identification Locatio Updating request Message type OLD LAC Info

BSC to MSC LOC_UPDATE_REQUEST Adds LAC to CM_SERV_REQ Adds CI to CM_SERV_REQ Sends SCCP Connection request to MSC

MSC to BSC CONNECTION CONFIRMED SCCP Connection Established

AUTHENTICATION

AUTHENTICATION

AUTHENTICATION

BSC to BTS BTS to MS AUTH_REQ(SDCCH) Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type

AUTH_REQ Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type

MSC to BSC AUTH_REQ Auth. Parameter -RAND Cipher Key Sequence Number Auth. Request Message Type



BSC to MSC(SDCCH) AUTH_RES(RESPONSE) Authentication Parameter [SRES] Auth Response message type

NEW VLR to OLDVLR UDT/BEGIN(UNIT DATA) SENDS IDENTIFICATION DATA TMSI

NEW VLR to OLDVLR UDT/BEGIN

NEW VLR to OLDVLR UDT/END

NEW VLR to OLDVLR UDT/END

CIPHERING

CIPHERING

BSC to BTS BTS to MS CIPHER_MODE_CMD(SDCCH) A5/X information MS to BTS(SDCCH) CIP_MODE_COMPLETE Cipher mode complete Message type Mobile equipment identity

IMEI CHECK



IMEI CHECK

BSC to BTS BTS to MS IDENT_REQUEST(SDCCH) Identity Request message type Identity type(IMEI) MS to BTS(SDCCH) IDENT_RSP Mobile Identity(IMEI)

IDENT_REQUEST(SDCCH) Identity Request message type Identity type(IMEI)

BTS to BSC(SDCCH) IDENT_RSP Mobile Identity(IMEI)

TMSI REALLOCATION



BSC to MSC(SDCCH) IDENT_RSP Mobile Identity(IMEI)

TMSI REALLOCATION

TMSI REALLOCATION MSC to BSC

BSC to BTS BTS to MS TMSI_REAL_CMD(SDCCH) TMSI Number LAI Mobile Identity



MS to BTS(SDCCH) TMSI_REAL_COMPLETE BTS to BSC(SDCCH) TMSI_REAL_COMPLETE BSC to MSC(SDCCH) TMSI_REAL_COMPLETE

LOCATION UPDATE ACCEPT

BTS to MS LOCATION UPDATE ACCEPT(SDCCH) TMSI Number LAI Mobile Identity Location Updating Accept message type


BSC to BTS LOCATION UPDATE ACCEPT(SDCCH) TMSI Number LAI Mobile Identity Location Updating Accept message type

LOCATION UPDATE ACCEPT MSC to BSC LOCATION UPDATE ACCEPT(SDCCH) TMSI Number LAI Mobile Identity Location Updating Accept message type

LOCATION UPDATE ACCEPT NEW VLR to HLR UDT/BEGIN(Update Location) IMSI LMSI


Traffic Channel RELEASE MSC to BSC BSC to BTS

BTS to MS CHANNEL_RELEASE Release Cause


CLEAR_COMMAND Layer 3 header information Release Cause

BSC to BTS MS to BTS FACCH/DISC (LAPDm) Request for Layer 2 connection Release BTS to MS FACCH/UA (LAPDm) Confirmation of Layer 2 Connnection Release


DEACTIVATE_SACCH Channel number

BTS to BSC RELEASE_INDICATION Channel number Link Identifier Release of Air Interface connection Radio Channel RELEASE (TRX)


BSC to BTS RF_CHN_RELEASE Channel number (to be released) BSC requests to BTS for TRX release on air Interface BTS to BSC RF_CHN_RELEASE_ACK TRX release acknowledge Channel number ( which is released)

MSC to BSC RLSD MSC requests BSC to release SCCP resources BSC to MSC RLC Release Cause SCCP Release Acknowledge

HLR to OLD VLR UDT/BEGIN(Cancel Location) IMSI OLD VLR to HLR

HLR to NEW VLR UDT/CON(Insert Subscriber data) Insert Subscriber data SS DATA MSISDN Subscriber State HLR to NEW VLR UDT/CON(Insert Subscriber data) NEW VLR to HLR UDT/END(Cancel Location)



UDT/END(Cancel Location) IMSI

INTRA BTS HANDOVER :MS CHANGES ONE CELL to OTHER WITHIN ONE BTS In intra-BTS handover, a new channel in the same BTS is assigned to the MS.The intra-BTS handover does not distinguish whether the new channel is just on another timeslot in the same TRX (frequency) or whether the TRX changes as well.

MS

NEW BTS

Active Phase of call going on using old channel

BSC Active Phase of call going on using old channel BSC to BTS CHANNEL ACTIVATE Channel number Activation Type Channel Mode (DTX??) Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC CHANNEL ACTIVATE ACK Frame Number Channel number BSC to BTS HND_CMD/ASS_CMD

BTS to MS HND_CMD/ASS_CMD(FACCH) Hand Over Reference Data of the TCH [TRX Info, Time Slot]

OR HND_CMD/ASS_CMD Hand Over Reference Data of the TCH [TRX Info, Time Slot]

MSC Active Phase of call going on using old channel

Handover Access

Handover Access

Handover Access

MS to BTS HND_ACCESS hand Over reference MS to BTS HND_ACCESS Max. 4 times not after ASS_CMD only after HND_CMD

hand Over reference MS to BTS HND_ACCESS hand Over reference MS to BTS HND_ACCESS hand Over reference MS to BTS SABM(FACCH)

MS to BTS ESTABLISH_INDICATION BTS to MS

UA(FACCH) MS to BTS HND_COMPLETE OR ASSIGNMENT_COMPLETE Handover complete message type RR cause Mobile observed time difference

BTS to BSC HND_COMPLETE

PREVOUSLY OCCUPIED RESOURCE FREE


OR ASSIGNMENT_COMPLETE

BSC to MSC HND_PERFORMED Cause Cell identifier Chosen channel Chosen encryption algorithm PREVOUSLY OCCUPIED RESOURCE FREE

BSC to BTS RF_CHAN_RELEASE

BTS to MSC RF_CHAN_RELEASE_ACK

Active Phase of call strarts using new channel



INTRA BSC HANDOVER: MS CHANGES from ONE BTS to ANOTHER BTS WITHIN ONE BSC

MS

BTS

BSC

Active Phase of call going on using old channel of old BTS The measurement results on the currently used traffic channel suggest an intra-BTS handover. The decision is made by the BSC. BSC to BTS CHANNEL ACTIVATE to New BTS Channel number Activation Type Channel Mode (DTX??) Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC CHANNEL ACTIVATE ACK from New BTS Frame Number Channel number

BTS to MS HND_CMD(FACCH) to OLD BTS Hand Over Reference Data of the TCH [TRX Info, Time Slot]

BSC to BTS HND_CMD to OLD BTS Hand Over Reference Data of the TCH [TRX Info, Time Slot]

NEW MSC VLR

Handover Access

Handover Access

Handover Access

MS to BTS HND_ACCESS hand Over reference BTS TO MS PHYSICAL_INFO(New Timing Advance Value) MS to BTS HND_ACCESS hand Over reference BTS TO MS PHYSICAL_INFO(New Timing Advance Value)

MS to BTS SABM(FACCH)

MS to BTS ESTABLISH_INDICATION BTS to MS

UA(FACCH) MS to BTS HND_COMPLETE Handover complete message type RR cause Mobile observed time difference


BTS to BSC HND_COMPLETE

PREVOUSLY OCCUPIED RESOURCE FREE BSC to BTS RF_CHAN_RELEASE

BTS to MSC RF_CHAN_RELEASE_ACK

Active Phase of call strarts using new channel of New BTS

BSC to MSC HND_PERFORMED Cause Cell identifier Chosen channel Chosen encryption algorithm PREVOUSLY OCCUPIED RESOURCE FREE

INTRA MSC HANDOVER -MS CHANGES BTS FROM ONE BSC TO BTS OF ANOTHER BSC(EXTERNAL HANDOVER) MS READ THE NOTE FIRST OLD/NEW NEW BTS BSC Active phase of the call using the old BTS/BSC

OLD BSC

MSC

OLD BSC to MSC HND_REQUIRED Details of Target BTS Handover Reason Circuit Pool List Preferred Cell List Current Channel Info OLD BSC to MSC HND_REQUIRED OLD BSC to MSC HND_REQUIRED

NEW BSC to NEW BTS CHANNEL ACTIVATE to New BTS Channel number BS Power MS Power Channel Mode (DTX??)

NEW BTS to NEW BSC CHAN_ACT_ACKG Frame Number Channel number

MSC to NEW BSC HND_REQUEST HND_REQUEST Channel type Encryption information

Cell identifier (target BTS) Interference band to be used

Circuit identity code Current Channel Info Classmark information 1 Handover Cause Classmark information 2 Cell identifier (Current BTS) Classmark information 3 NEW BSC to MSC Connection Confirmed(SCCP connection is established)

NEW BSC to MSC HND_REQUEST_ACK(HANDOVER_COMMAND) Layer 3 information Chosen encryption algorithm Chosen channel Circuit pool

NEW BSC to NEW BTS HND_CMD

OLD BSC to OLD BTS(FACCH) HND_CMD

Handover Reference Channel Information Layer 3 information

Handover Reference Channel Information OLD BTS to MS

(FACCH)

Target Frequecy Time Slot

HND_CMD Handover Reference Channel Information Target Frequecy Time Slot Handover Access

Handover Access

Handover Access

Handover Access

MS to NEW BTS HND_ACCESS hand Over reference NEW BTS TO MS PHYSICAL_INFO(New Timing Advance Value) MS to NEW BTS HND_ACCESS hand Over reference

NEW BTS to NEW BSC HANDOVER_DETECT

NEW BTS TO MS PHYSICAL_INFO (New Timing Advance Value)

MS to NEW BTS SABM(FACCH)

NEW BTS to NEW BSC HANDOVER_DETECT

NEW BTS to NEW BSC ESTABLISH_INDICATION

NEW BTS to MS UA(FACCH) MS to NEW BTS HND_COMPLETE Handover complete message type RR cause Mobile observed time diff


OLD BTS to MS CHANNEL_RELEASE

NEW BTS to NEW BSC HND_COMPLETE


OLD BSC to OLD BTS CHANNEL_RELEASE Release Cause

NEW BSC to MSC HND_COMPLETE Cause Cell identifier Chosen channel Chosen encryption algorithm Traffic Channel RELEASE

Traffic Channel RELEASE MSC to OLD BSC CLEAR_COMMAND Layer 3 header information Release Cause

Release Cause

MS to OLD BTS FACCH/DISC (LAPDm) Request for Layer 2 connection Release OLD BTS to MS FACCH/UA (LAPDm) Confirmation of Layer 2 Connnection Release


OLD BSC to OLD BTS DEACTIVATE_SACCH Channel number

OLD BTS to OLD BSC RELEASE_INDICATION Channel number Link Identifier Release of Air Interface connection Radio Channel RELEASE (TRX)

OLD BSC to MSC CLEAR_COMPLETE Radio Channel RELEASE (TRX)


OLD BSC to OLD BTS RF_CHN_RELEASE Channel number (to be released) BSC requests to BTS for TRX release on air Interface

MSC to OLD BSC

OLD BTS to OLD BSC

RLSD

RF_CHN_RELEASE_ACK TRX release acknowledge Channel number ( which is released)

MSC requests BSC to release SCCP resources

OLD BSC to MSC RLC Release Cause SCCP Release Acknowledge

INTRA MSC HANDOVER -MS CHANGES BTS,BSC FROM ONE MSC TO BTS,BSC OF ANOTHER MSC MS

READ THE NOTE FIRST

BTS

A BSC Active phase of the call using the old BTS/BSC BSC A to MSC A HND_REQUIRED

A MSC

B MSC

B BSC

E Interface MSC A to MSC B HND_REQUEST MSC B to BSC B HND_REQUEST BSC B to MSC B CONNECTION CONFIRMED

BSC B to MSC B HND_REQUEST_ACK (HND_CMD)

MSC B to MSC A HND_REQUEST_ACK (HND_CMD)

MSC A to BSC A (HND_CMD)

Channel type Encryption information Circuit identity code Classmark information 1 Classmark information 2 Classmark information 3 Cell identifier (target BTS) Interference band to be used Current Channel Info Handover Cause Cell identifier (Current BTS)

Channel type Encryption information Circuit identity code Classmark information 1 Classmark information 2 Classmark information 3 Cell identifier (target BTS) Interference band to be used Current Channel Info Handover Cause Cell identifier (Current BTS)

BSC to BTS CHANNEL ACTIVATE to New BTS Channel number Activation Type Channel Mode (DTX??) Channel Identification Encryption information Handover Reference BS Power MS Power Timing Advance BS Power Parameters MS Power Parameters Physical Context SACCH Information BTS to BSC CHANNEL ACTIVATE ACK from New BTS Frame Number Channel number

BTS to MS HND_CMD(FACCH) to OLD BTS Hand Over Reference Data of the TCH [TRX Info, Time Slot]

BSC to BTS HND_CMD to OLD BTS Hand Over Reference Data of the TCH [TRX Info, Time Slot]

MSC A to MSC B ISUP(IAM) MSC B to MSC A ISUP(ACM) BSC B to MSC B HND_DETECT MSC B to MSC A HND_DETECT(Process Access Signalling)

MSC B to MSC A ISUP(ANM)

Handover Access

Handover Access

Handover Access

MS to BTS HND_ACCESS hand Over reference BTS TO MS PHYSICAL_INFO(New Timing Advance Value) MS to BTS HND_ACCESS hand Over reference BTS TO MS PHYSICAL_INFO(New Timing Advance Value)

MS to BTS SABM(FACCH)

MS to BTS ESTABLISH_INDICATION

BTS to MS UA(FACCH) Active connection after Inter-MSC handover from BSS A MSC A⇔MSC B⇔BSS B⇔MS

MS to BTS HND_COMPLETE BTS to BSC HND_COMPLETE Handover complete message type

BSC to MSC HND_PERFORMED Cause

RR cause Mobile observed time difference



Cell identifier Chosen channel Chosen encryption algorithm Traffic Channel RELEASE MSC to BSC CLEAR_COMMAND


BSC to BTS BTS to MS CHANNEL_RELEASE Release Cause

Layer 3 header information Release Cause

BSC B to MSC B HND_COMPLETE MSC B to MSC A HND_COMPLETE

MS to BTS FACCH/DISC (LAPDm) Request for Layer 2 connection Release BTS to MS FACCH/UA (LAPDm) Confirmation of Layer 2 Connnection Release

BSC to BTS DEACTIVATE_SACCH Channel number

BTS to BSC RELEASE_INDICATION Channel number Link Identifier Release of Air Interface connection

BSC to MSC CLEAR_COMPLETE




BSC to BTS RF_CHN_RELEASE Channel number (to be released) BSC requests to BTS for TRX release on air Interface BTS to BSC RF_CHN_RELEASE_ACK TRX release acknowledge Channel number ( which is released)

MSC to BSC RLSD MSC requests BSC to release SCCP resources

BSC to MSC RLC Release Cause SCCP Release Acknowledge

SL No:-

Reference

1 2 3 4 5 6

GSM_Messages.pdf GSM_Book-Gunnar_Heine.pdf

Links \\netapp1\proptima\Presentations\GSM_Presentations\Reference_Docs_PPT's\G SM_Messages.pdf \\netapp1\repo-nmcgps\Presentations\GSM_Book-Gunnar_Heine.pdf

Gsm Call Scenarios at a Glance

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