ETSI TS 101 346 V7.2.0 (1999-11)
Technical Specification Digital cellular telecommunications system (Phase 2+);
General Packet Radio Service (GPRS); Serving GPRS Support Node (SGSN) - Visitors Location
Register (VLR);
Gs interface layer 3 specification
(GSM 09.18 version 7.2.0 Release 1998)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
Reference
RTS/SMG-030918Q7R1(cgo03io3.PDF)
Keywords
Digital cellular telecommunications system,
Global System for Mobile communications
(GSM), GPRS, Packet Radio, Phase2+
ETSI
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? European Telecommunications Standards Institute 1999.
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Contents
Intellectual Property Rights (7)
Foreword (7)
Introduction (7)
1Scope (8)
2References (8)
2.1Normative references (8)
2.2Informative references (9)
3Definitions, symbols and abbreviations (11)
4Description of the association between a VLR and an SGSN (11)
4.1Association at the VLR (12)
4.1.1States at the VLR (12)
4.2Association at the SGSN (13)
4.2.1MM context variables at the SGSN (13)
4.2.2States at the SGSN (13)
5Paging for non-GPRS services procedure (14)
5.1General description (14)
5.2Procedures in the VLR (14)
5.2.1Paging Initiation (14)
5.2.2Paging Response (15)
5.2.3Paging Failure (15)
5.2.4MS unreachable (15)
5.3Procedures in the SGSN (15)
6Location Update for non-GPRS services procedure (16)
6.1General description (16)
6.2Procedures in the SGSN (17)
6.2.1Location Update Initiation (17)
6.2.2Location Update Response (18)
6.2.3Location Update Failure (18)
6.2.4Abnormal cases (18)
6.3Procedures in the VLR (18)
6.3.1Location Update Response (18)
6.3.2Location Update Failure (19)
6.3.3TMSI reallocation procedure (19)
6.3.4Abnormal cases (19)
7Non-GPRS alert procedure (20)
7.1General description (20)
7.2Procedures in the VLR (20)
7.2.1Alert Initiation (20)
7.2.2Alert Response (20)
7.2.3Alert failure (20)
7.2.4Alert Indication (20)
7.2.5Abnormal cases (20)
7.3Procedures in the SGSN (21)
7.3.1Alert response (21)
7.3.2Alert failure (21)
7.3.3Alert indication (21)
8Explicit IMSI detach from GPRS services procedure (21)
8.1General description (21)
8.2Procedures in the SGSN (21)
8.2.1Explicit GPRS detach initiation (21)
8.2.3Abnormal cases (22)
8.3Procedures in the VLR (22)
9Explicit IMSI detach from non-GPRS services procedure (22)
9.1General description (22)
9.2Procedures in the SGSN (23)
9.2.1Explicit IMSI detach initiation (23)
9.2.2Explicit IMSI detach Response (23)
9.2.3Abnormal cases (23)
9.3Procedures in the VLR (23)
10Implicit IMSI detach from non-GPRS services procedure (23)
10.1General description (23)
10.2Procedures in the SGSN (24)
10.3Procedures in the VLR (24)
11VLR failure procedure (24)
11.1General description (24)
11.2Procedures in the VLR (24)
11.2.1VLR Reset Initiation (24)
11.2.2VLR Reset Response (24)
11.2.3Abnormal cases (25)
11.3Procedures in the SGSN (25)
12SGSN failure procedure (25)
12.1General description (25)
12.2Procedures in the SGSN (25)
12.2.1SGSN Reset Initiation (25)
12.2.2SGSN Reset Response (25)
12.2.3Abnormal cases (26)
12.3Procedures in the VLR (26)
13HLR failure (26)
13.1General description (26)
13.2Procedures in the SGSN (26)
14MS Information procedure (26)
14.1General description (26)
14.2Procedures in the VLR (27)
14.3Procedures in the SGSN (27)
15MM information procedure (27)
15.1General description (27)
15.2Procedures in the VLR (27)
15.3Procedures in the SGSN (27)
16Error Handling and Future Compatibility (28)
16.1General (28)
16.2Message too short (28)
16.3Unknown or unforeseen message type (28)
16.4Missing mandatory information element (28)
16.5IEs unknown or unforeseen in the message (28)
16.6Out of sequence IEs (29)
16.7Repeated IEs (29)
16.8Syntactically incorrect mandatory IE (29)
16.9Syntactically incorrect optional IEs (29)
16.10Conditional IE errors (29)
16.11IEs with semantically incorrect contents (29)
17Message functional definitions and contents (29)
17.1Message Contents (29)
17.1.1BSSAP+-ALERT-ACK message (29)
17.1.2BSSAP+-ALERT-REJECT message (30)
17.1.3BSSAP+-ALERT-REQUEST message (30)
17.1.4BSSAP+-GPRS-DETACH-ACK message (30)
17.1.5BSSAP+-GPRS-DETACH-INDICATION message (30)
17.1.5.1Cell global identity (31)
17.1.6BSSAP+-IMSI-DETACH-ACK message (31)
17.1.7BSSAP+-IMSI-DETACH-INDICATION message (31)
17.1.7.1Cell global identity (31)
17.1.7.2Location information age (32)
17.1.8BSSAP+-LOCATION-UPDATE-ACCEPT message (32)
17.1.8.1New TMSI, or IMSI (32)
17.1.9BSSAP+-LOCATION-UPDATE-REJECT message (32)
17.1.10BSSAP+-LOCATION-UPDATE-REQUEST message (32)
17.1.10.1Old location area identifier (33)
17.1.10.2New cell global identity (33)
17.1.10.3TMSI status (33)
17.1.11BSSAP+-MM-INFORMATION-REQUEST (33)
17.1.11.1MM information (33)
17.1.12BSSAP+-MOBILE-STATUS message (33)
17.1.12.1IMSI (34)
17.1.13BSSAP+-MS-ACTIVITY-INDICATION message (34)
17.1.13.1Cell global identity (34)
17.1.14BSSAP+-MS-INFORMATION-REQUEST message (34)
17.1.15BSSAP+-MS-INFORMATION-RESPONSE message (34)
17.1.15.1IMEI (35)
17.1.15.2IMIESV (35)
17.1.15.3Cell global identity (35)
17.1.15.4Location information age (35)
17.1.15.5Mobile station state (35)
17.1.15.6TMSI (35)
17.1.16BSSAP+-MS-UNREACHABLE message (35)
17.1.16.1Gs Cause (36)
17.1.17BSSAP+-PAGING-REJECT message (36)
17.1.18BSSAP+-PAGING-REQUEST message (36)
17.1.18.1TMSI (36)
17.1.18.2Location area identifier (37)
17.1.18.3Channel needed (37)
17.1.18.4eMLPP priority (37)
17.1.19BSSAP+-RESET-ACK message (37)
17.1.19.1SGSN number (37)
17.1.19.2VLR number (37)
17.1.20BSSAP+-RESET-INDICATION message (37)
17.1.20.1SGSN number (38)
17.1.20.2VLR number (38)
17.1.21BSSAP+-TMSI-REALLOCATION-COMPLETE message (38)
17.1.21.1Cell global identity (38)
18Message format and information element coding (38)
18.1Overview (38)
18.2Message type (38)
18.3Information Element Identifiers (40)
18.4Information elements (40)
18.4.1Cell global identity (40)
18.4.2Channel needed (41)
18.4.3eMLPP Priority (41)
18.4.4Erroneous message (41)
18.4.5GPRS location update type (41)
18.4.6Gs cause (42)
18.4.7IMEI (43)
18.4.8IMEISV (43)
18.4.9IMSI (43)
18.4.10IMSI detach from GPRS service type (44)
18.4.11IMSI detach from non-GPRS service type (44)
18.4.12Information requested (45)
18.4.13Location area identifier (45)
18.4.14Location information age (46)
18.4.15MM information (46)
18.4.16Mobile identity (46)
18.4.17Mobile station classmark 1 (47)
18.4.18Mobile station state (47)
18.4.19PTMSI (47)
18.4.20Reject cause (48)
18.4.21SGSN number (48)
18.4.22TMSI (48)
18.4.23TMSI status (48)
18.4.24VLR number (49)
19List of system variables (49)
19.1Timers (49)
19.2Retry counters (50)
Annex A (informative):Document Change Request History (51)
History (52)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (https://www.sodocs.net/doc/078429862.html,/ipr).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by the Special Mobile Group (SMG).
The present document specifies procedures used between the Serving GPRS Support Node (SGSN) and the Visitors Location Register (VLR) for co-ordination between GSM circuit switched services and GSM packet data services within the digital cellular telecommunications system (Phase 2+).
The contents of the present document are subject to continuing work within SMG and may change following formal SMG approval. Should SMG modify the contents of the present document it will then be republished by ETSI with an identifying change of release date and an increase in version number as follows:
Version 7.x.y
where:
7GSM Phase 2+ Release 1998.
x the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc.
y the third digit is incremented when editorial only changes have been incorporated in the specification.
Introduction
The present document specifies or references the procedures to provide co-ordination between the GSM circuit switched services controlled at the Visitors Location Register (VLR) and the GSM packet switched services controlled at the Serving GPRS Support Node (SGSN). The procedures specified in the present document are intended to optimise the use of the resources when an MS supports both GSM circuit switched services and GSM packet switched services.
1Scope
The present document specifies or references procedures used on the Serving GPRS Support Node (SGSN) to Visitors Location Register (VLR) interface for interoperability between GSM circuit switched services and GSM packet data services.
The present document specifies the layer 3 messages and procedures on the Gs interface to allow coordination between databases and to relay certain messages related to GSM circuit switched services over the GPRS subsystem.
The functional split between VLR and SGSN is defined in GSM 03.60. The required procedures between VLR and SGSN are defined in detail in the present document.
2References
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
?References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
?For a specific reference, subsequent revisions do not apply.
?For a non-specific reference, the latest version applies.
? A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number.
?For this Release 1998 document, references to GSM documents are for Release 1998 versions (version 7.x.y). 2.1Normative references
[1]GSM 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and
acronyms".
[2]GSM 02.06: "Digital cellular telecommunications system (Phase 2+); Types of Mobile Stations
(MS)".
[3]GSM 02.07: "Digital cellular telecommunications system (Phase 2+); Mobile Station (MS)
features".
[4]GSM 02.60: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Service description; Stage 1".
[5]GSM 03.03: "Digital cellular telecommunications system (Phase 2+); Numbering, addressing and
identification".
[6]GSM 03.07: "Digital cellular telecommunications system (Phase 2+); Restoration procedures".
[7]GSM 03.22: "Digital cellular telecommunications system (Phase 2+); Functions related to Mobile
Station (MS) in idle mode and group receive mode".
[8]GSM 03.60: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Service description; Stage 2".
[9]GSM 03.64: "Digital cellular telecommunications system (Phase 2+); Overall description of the
General Packet Radio Service (GPRS) Radio interface; Stage 2".
[10]GSM 04.07: "Digital cellular telecommunications system (Phase 2+); Mobile radio interface
signalling layer 3; General aspects".
3 specification".
[12]GSM 04.64: "Digital cellular telecommunications system (Phase 2+), General Packet Radio
Service (GPRS); Logical Link Control (LLC)".
[13]GSM 04.65: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Subnetwork Dependent Convergence Protocol (SNDCP)".
[14]GSM 08.08: "Digital cellular telecommunications system (Phase 2+); Mobile Switching Centre -
Base Station System (MSC - BSS) interface: Layer 3 specification".
[15]GSM 08.18: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Serving GPRS Support Node (SGSN) - Base Station System (BSS): BSS GPRS
Protocol (BSSGP)".
[16]GSM 08.60: "Digital cellular telecommunications system (Phase 2+); Inband control of remote
transcoders and rate adaptors for Enhanced Full Rate (EFR) and full rate traffic channels."
[17]GSM 09.02: "Digital cellular telecommunications system (Phase 2+); Mobile Application Part
(MAP) specification".
[18]GSM 09.08: "Digital cellular telecommunications system (Phase 2+); Application of Base Station
System Application Part (BSSAP) on the E-interface".
[19]GSM 09.10: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Serving GPRS Support Node (SGSN) - Visitors Location Register (VLR): Gs
interface Layer 2 specification".
[20]GSM 09.16: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Serving GPRS Support Node (SGSN) - Visitors Location Register (VLR): Gs
interface Layer 2 specification".
[21]CCITT Recommendation E.164: "Numbering plan for the ISDN era".
2.2Informative references
[22]GSM 01.61: "Digital cellular telecommunications system (Phase 2+); GPRS ciphering algorithm
requirements".
[23]GSM 02.01: "Digital cellular telecommunications system (Phase 2+); Principles of
telecommunication services supported by a GSM Public Land Mobile Network (PLMN)".
[24]GSM 02.02: "Digital cellular telecommunications system (Phase 2+); Bearer Services (BS)
supported by a GSM Public Land Mobile Network (PLMN)".
[25]GSM 02.03: "Digital cellular telecommunications system (Phase 2+); Teleservices supported by a
GSM Public Land Mobile Network (PLMN)".
[26]GSM 02.08: "Digital cellular telecommunications system (Phase 2+); Quality of service".
[27]GSM 02.09: "Digital cellular telecommunications system (Phase 2+); Security aspects".
[28]GSM 02.11: "Digital cellular telecommunications system (Phase 2+); Service accessibility".
[29]GSM 02.16: "Digital cellular telecommunications system (Phase 2+); International Mobile station
Equipment Identities (IMEI)".
[30]GSM 02.17: "Digital cellular telecommunications system (Phase 2+); Subscriber identity modules
Functional characteristics".
[31]GSM 02.30: "Digital cellular telecommunications system (Phase 2+); Man-Machine Interface
(MMI) of the Mobile Station (MS)".
Service (GPRS); Point to Multipoint Multicast Service Description; Stage 2".
[33]GSM 03.62: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Point to Multipoint Group Call Service Description; Stage 2".
[34]GSM 04.01: "Digital cellular telecommunications system (Phase 2+); Mobile Station - Base
Station System (MS - BSS) interface General aspects and principles".
[35]GSM 04.02: "Digital cellular telecommunications system (Phase 2+); GSM Public Land Mobile
Network (PLMN) access reference configuration".
[36]GSM 04.03: "Digital cellular telecommunications system (Phase 2+); Mobile Station - Base
Station System (MS - BSS) interface Channel structures and access capabilities".
[37]GSM 04.04: "Digital cellular telecommunications system (Phase 2+); layer 1 General
requirements".
[38]GSM 04.05: "Digital cellular telecommunications system (Phase 2+); Data Link (DL) layer
General aspects".
[39]GSM 04.06: "Digital cellular telecommunications system (Phase 2+); Mobile Station - Base
Station System (MS - BSS) interface Data Link (DL) layer specification".
[40]GSM 04.11: "Digital cellular telecommunications system (Phase 2+); Point-to-Point (PP) Short
Message Service (SMS) support on mobile radio interface".
[41]GSM 04.22: "Digital cellular telecommunications system (Phase 2+); Radio Link Protocol (RLP)
for data and telematic services on the Mobile Station - Base Station System (MS - BSS) interface
and the Base Station System - Mobile-services Switching Centre (BSS - MSC) interface".
[42]GSM 07.60: "Digital cellular telecommunications system (Phase 2+), Mobile Station (MS)
supporting GPRS".
[43]GSM 08.06: "Digital cellular telecommunications system (Phase 2+); Signalling transport
mechanism specification for the Base Station System - Mobile Switching Centre (BSS - MSC)
interface".
[44]GSM 08.14: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Serving GPRS Support Node (SGSN) - Base Station System (BSS): Gb interface
layer 1".
[45]GSM 08.16: "Digital cellular telecommunications system (Phase 2+); General Packet Radio
Service (GPRS); Serving GPRS Support Node (SGSN) - Base Station System (BSS): Network
Service".
[46]GSM 09.60: "Digital cellular telecommunications system (Phase 2+), General Packet Radio
Service (GPRS); GPRS Tunnelling Protocol (GTP) across the Gn and Gp Interface".
[47]GSM 09.61: "Digital cellular telecommunications system (Phase 2+), General requirements on
interworking between the Public Land Mobile Network (PLMN) supporting General Packet Radio
Service (GPRS) and Packet Data Networks (PDN)".
[48]GSM 12.00 (ETS 300 612-1): "Digital cellular telecommunications system (Phase 2+); Objectives
and structure of Network Management (NM)".
[49]GSM 12.01 (ETS 300 612-2): "Digital cellular telecommunications system (Phase 2+); Common
aspects of GSM Network Management (NM)".
[50]GSM 12.02: "Digital cellular telecommunications system (Phase 2+); Subscriber, Mobile
Equipment (ME) and services data administration".
[51]GSM 12.03: "Digital cellular telecommunications system (Phase 2+); Security management".
services Switching Centre (MSC)".
[53]GSM 12.14: "Digital cellular telecommunications system (Phase 2+); Maintenance of location
registers".
[54]GSM 12.20: "Digital cellular telecommunications system (Phase 2+); Network Management (NM)
procedures and messages".
[55]GSM 12.22: "Digital cellular telecommunications system (Phase 2+); Interworking of GSM
Network Management (NM) procedures and messages at the Base Station Controller (BSC)".
[56]CCITT Recommendations I.130: "General modelling methods - Method for the characterisation of
telecommunication services supported by an ISDN and network capabilities of an ISDN".
[57]CCITT Recommendation Q.65: "Methodology - Stage 2 of the method for the characterization of
services supported by an ISDN".
[58]CCITT Recommendation Q.702: "Specifications of Signalling System No. 7 - Signalling data
link".
[59]CCITT Recommendation Q.703: "Signalling link".
[60]CCITT Recommendation Q.704: "Signalling network functions and messages".
[61]CCITT Recommendation Q.711 (3/93): "Functional description of the signalling connection
control part".
[62]CCITT Recommendation Q.712 (3/93): "Definition and function of SCCP messages".
[63]CCITT Recommendation Q.713 (3/93): "SCCP formats and codes".
[64]CCITT Recommendation Q.714 (3/93): "Signalling connection control part procedures".
[65]ANSI Recommendation T1.111 (1996): “Signalling System 7 (SS7) Message Transfer Part
(MTP)”.
[66]ANSI Recommendation T1.112 (1996): “Signalling System 7 (SS7) Signalling Connection
Control Part (SCCP)”.
3Definitions, symbols and abbreviations
Unless listed below, the definitions, symbols and abbreviations are listed in GSM 01.04 or GSM 03.60.
4Description of the association between a VLR and an SGSN
The Gs interface connects the databases in the MSC/VLR and the SGSN. The procedures described in this technical specification are used to co-ordinate the location information of MSs that are IMSI attached to both GPRS and non-GPRS services. The Gs interface is also used to convey some circuit switched related procedures via the SGSN.
The basis for the interworking between a VLR and an SGSN is the existence of an association between those entities per MS. An association consists of the SGSN storing the number of the VLR serving the MS for circuit switched services and the VLR storing the number of the SGSN serving the MS for packet switched services. The association is only applicable to MSs in class-A mode of operation and MSs in class-B mode of operation.
All the messages described in this TS use the SCCP class 0 connectionless service.
When the return option in SCCP is used and the sender receives an N_NOTICE indication from SCCP, the sending entity shall report to the Operation and Maintenance system (see ITU-T Q.714).
The behaviour of the VLR and the SGSN entities related to the Gs interface are defined by the state of the association for an MS. Individual states per association, i.e. per MS in class-A mode of operation and MS in class-B mode of operation, are held at both the VLR and the SGSN.
4.1Association at the VLR
The states associated to the Gs interface in the VLR are specified in this subclause. The state diagram at the VLR is shown in figure 4.1. The state diagram does not include the message error handling specified in clause 16.
4.1.1
States at the VLR
Gs-NULL
There is no association with an SGSN for the MS and therefore the VLR considers that the MS is IMSI detached for GPRS services. In this state no BSSAP+-MS-INFORMATION-REQUEST or BSSAP+-MM-INFORMATION-REQUEST messages are sent to the SGSN. The VLR may initiate paging on the Gs interface if the ‘Confirmed by Radio Contact ’ restoration indicator in the VLR is set to ‘false ’ (see GSM 03.07). Any message from the SGSN is ignored apart from the BSSAP+-LOCATION-UPDATE-REQUEST https://www.sodocs.net/doc/078429862.html,-UPDATE PRESENT
The VLR has received a BSSAP+-LOCATION-UPDATE-REQUEST message from the SGSN. In this state the VLR may be waiting for the outcome of the Update Location procedure from the HLR. The VLR shall send BSSAP+-PAGING-REQUEST messages to MSs in class-A and MSs in class-B mode of operation via only the Gs interface.Gs-ASSOCIATED
The VLR considers that the MS is attached to both GPRS and non-GPRS services. In this state the VLR sends BSSAP+-PAGING-REQUEST messages to MSs in class-A mode of operation and and MSs in class-B mode of operation via only the Gs interface. The VLR can perform the MS Identification procedure and the MM information procedure.
TMSI Reallocation received
VLR failure
Reset received from the SGSN
Send Paging
Send Paging
Detach indication received from the SGSN or the MS Location Area Update Request received from the MS via the A interface
From one of the three States (at the VLR)
Paging failure received
Gs-NULL
Gs-ASSOCIATED
BSSAP+-MS-UNREACHABLE
message received
LA-UPDATE Present
Send Paging
Location Area Update Request received from the SGSN
Paging Failure or
Alert Failure received
Location Area Update Request received from the SGSN
Send Location Area Update Accept
Send
Location Area Update Reject
Figure 4.1/GSM 09.18: State diagram at the VLR
4.2Association at the SGSN
The states and MM context variables associated to the Gs interface in the SGSN are specified in this subsection. The state diagram at the SGSN is shown in figure 4.2. The state diagram does not include the message error handling specified in section 16.
4.2.1MM context variables at the SGSN
VLR-Reliable:Boolean
Set to ‘false’ when the SGSN has received a reset indication from the VLR. The SGSN shall request to the MS, upon reception of the next routeing area update (either routeing area update only or combined routeing and location area update) procedure, to re-attach to non-GPRS services if the MS is still IMSI attached to non-GPRS services.
SGSN-Reset:Boolean
Set to ‘true’ when the SGSN restarts after a failure. The ‘SGSN-Reset’ variable is unique within an SGSN and it applies to all the MM context stored in the SGSN.
4.2.2States at the SGSN
Gs-NULL
There is no association with a VLR for the MS and therefore the SGSN considers that the MS is IMSI detached of non-GPRS services. In this state the SGSN accepts BSSAP+-PAGING-REQUEST messages to MSs only if the ‘SGSN-Reset’ restoration indicator in the SGSN is set to ‘true’.
LA-UPDATE Requested
The SGSN has sent a BSSAP+-LOCATION-UPDATE-REQUEST message to the VLR. In this state the SGSN waits for the outcome of the Location Update for non-GPRS procedure at the VLR before sending the response to the MS. In this state the SGSN accepts BSSAP+-PAGING-REQUEST messages.
Gs-ASSOCIATED
The SGSN stores an association for that MS. In this state the SGSN performs the Location Update for non-GPRS services procedure towards the VLR for MSs in class-A and MSs in class-B mode of operation when the MS moves to a new LA.
SGSN failure Send any detach indication (to the VLR)
Paging received
Paging received
Reset received
From one of the three States (at the SGSN)
Gs-NULL
Send
BSSAP+-MS-UNREACHABLE
message
LA-UPDATE Requested
Paging received
Send Location Area Update Request (to the VLR )
Location Area Update Accept received
Combined Routing Area received from the MS
Location Area Update Reject received
(non-combined) Routing Area Update Request received from the MS
Set VLR_reliable=true
(whether SGSN_reset=true or not)
Send TMSI Reallocation
Combined Routing Area Update Request received from the MS
With:
LA has changed ;SGSN has changed ;VLR_reliable = false ; or IMSI Attach indicated.
(Any other cases)
Gs-ASSOCIATED
Figure 4.2/GSM 09.18: State diagram at the SGSN
5
Paging for non-GPRS services procedure
5.1
General description
This procedure is used by the VLR to send a BSSAP+-PAGING-REQUEST message to an MS via the GPRS service.This procedure applies to MSs that are simultaneously IMSI attached for GPRS services and non-GPRS services. The procedure can be performed simultaneously with any other procedure at the Gs interface.
5.2Procedures in the VLR
The VLR shall handle the timers, queuing and retransmission for sending the BSSAP+-PAGING-REQUEST message on the Gs interface in the same way that it handles the sending of a PAGING message on the A interface.
5.2.1Paging Initiation
When a VLR has to page a GPRS MS it shall check whether the MSC has an SCCP connection for that MS. If no SCCP connection exists the VLR checks the state of the association to an SGSN and the value of the restoration indicators for that MS. The VLR sends BSSAP+-PAGING-REQUEST messages to the SGSN if the state of the association for the MS is Gs-ASSOCIATED, LA-UPDATE-PRESENT or if the state of the association is Gs-NULL and the ‘Confirmed by Radio Contact ’ restoration indicator is set to ‘false ’. The sending of the BSSAP+-PAGING-REQUEST message does not change the state of the association with the SGSN.
If the ‘Confirmed by Radio Contact ’ restoration indicator is set to ‘true ’, the VLR shall include the Location area identifier IE into the BSSAP+-PAGING-REQUEST message, otherwise (i.e. after a VLR failure) the Location area identifier IE shall not be included. When sending the BSSAP+-PAGING-REQUEST message, the VLR shall start timer T5.
If the state of the association is Gs-NULL and the restoration indicator ‘Confirmed by Radio Contact’ is set to ‘false’, the VLR shall also perform a search procedure as specified in GSM 03.18.
5.2.2Paging Response
The VLR stops the paging procedure on expiry of timer T5 or on receipt of an SCCP connection establishment containing the Initial L3 message from the MS via the A interface.
5.2.3Paging Failure
On receipt of a BSSAP+-PAGING-REJECT message before the timer T5 expires, the VLR stops timer T5, the association is moved to the Gs-NULL state and within this state the association is marked with the contents of the Gs Cause IE.
5.2.4MS unreachable
On receipt of a BSSAP+-MS-UNREACHABLE message before the timer T5 expires, the VLR stops timer T5 and the paging procedure for that paging request towards the SGSN is stopped. The state of the association at the VLR is not changed.
5.3Procedures in the SGSN
The SGSN accepts BSSAP+-PAGING-REQUEST messages in any state of the association apart from Gs-NULL. Nevertheless the SGSN also accepts BSSAP+-PAGING-REQUEST messages in the Gs-NULL state if the ‘SGSN-Reset’ restoration indicator at the SGSN is set to ‘true’. When an SGSN receives a BSSAP+-PAGING-REQUEST message from a VLR, the SGSN shall first check if the MS is known by the SGSN. The handling of the paging request depends on the state of the association and the MM context variables at the SGSN:
a)The MS is known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘false’:
-If the MS is considered to be IMSI attached for GPRS and non-GPRS services (i.e. the association is not in the state Gs-NULL), the SGSN shall page the MS based on the location information stored in the SGSN.
-If the MS is marked as IMSI detached for GPRS services or IMSI (implicitly or explicitly) detached for non-GPRS services (i.e. the state of the association is Gs-NULL), the SGSN shall return a BSSAP+-PAGING-REJECT message to that VLR indicating in the Gs Cause IE the detach circumstance (‘IMSI detached for GPRS services’, ‘IMSI detached for non-GPRS services’ or ‘IMSI implicitly detached for non-GPRS services’).
-If the MS is marked as unreachable (i.e. the PPF flag is set to ‘false’) the SGSN shall return a BSSAP+-MS-UNREACHABLE message to that VLR indicating in the Gs Cause IE ‘MS unreachable’. The state of the association does not change at the SGSN.
b)The MS is known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘true’:
-If the BSSAP+-PAGING-REQUEST message includes the Location area identifier IE, the SGSN shall page the MS in all the routeing areas served by the SGSN that are included in the location area indicated in the Location area identifier IE.
-If the BSSAP+-PAGING-REQUEST message does not include the Location area identifier IE, the SGSN may page in all the routeing areas served by the SGSN that are also served by the sending VLR.
c)The MS is not known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘false’:
-The SGSN shall return a BSSAP+-PAGING-REJECT message to that VLR indicating in the Gs Cause IE ‘IMSI unknown’.
d)The MS is not known and the restoration indicator ‘SGSN-Reset’ at the SGSN is set to ‘true’:
-If the VLR provides the Location area identifier IE, the SGSN shall page within the location area indicated by the VLR. Otherwise the SGSN may page in all the routeing areas served by the SGSN that are also served by the sending VLR.
If the SGSN accepts the paging request, the SGSN shall process the BSSAP+-PAGING-REQUEST message before sending the message on the Gb interface. The result of the processing on the BSSAP+-PAGING-REQUEST message is the PAGING CS message (see GSM 08.18) sent on the Gb interface.
The SGSN shall not retransmit the PAGING CS message.
If within a location area there are cells that do not support GPRS services, the SGSN shall group these cells under a ‘null RA’. The SGSN will perform the paging procedure described above within both the RA(s) derived from the location information and the ‘null RA(s)’ of the corresponding location area(s) (see GSM 04.08).
Note: the eMLPP priority information element relates to relative priorities within the paged MS and not to the priority in the sending of PAGING CS messages by the BSS.
6Location Update for non-GPRS services procedure 6.1General description
The location update for non-GPRS services procedure is a general procedure used by MSs in class-A mode of operation and MSs in class-B mode of operation. This procedure allows MSs and network to perform:
-Combined IMSI attach for GPRS and non-GPRS services.
-IMSI attach for non-GPRS services if the MS is already IMSI attached for GPRS services.
-IMSI attach for GPRS services indication to the VLR if the MS is already IMSI attached for non-GPRS services -Normal Location Update procedure to the VLR if the MS is IMSI attached for both GPRS and non-GPRS services.
-Reallocation of TMSI to an MS.
The Location Update for non-GPRS services procedures in the Gs interface is always started as a consequence of a direct action by the MS. The combined routeing area update procedure is further specified in GSM 03.60 and 04.08. The Location Update for non-GPRS services procedure is used by the SGSN to forward to the VLR those parts of the combined routeing area update or IMSI attach procedure which belong to the non-GPRS services. This means that non-GPRS related requests which are included in the combined request, are sent from the SGSN to the VLR. The procedure is also used by the SGSN to indicate to the VLR when an IMSI attach to GPRS services has been performed by an MS that was already IMSI attached to non-GPRS services. The SGSN may also forward a BSSAP+-TMSI-REALLOCATION-COMPLETE message from the MS to the VLR.
The VLR shall acknowledge the BSSAP+-LOCATION-UPDATE-REQUEST message. When the VLR processes the request it does not perform authentication because it relies on the SGSN’s security functions.
When an MS is IMSI attached for GPRS and non-GPRS services, any implicit detach timer in the VLR shall be stopped. Instead the Paging Proceed Flag in the SGSN is used to determine the likely availability of the MS to the network. The SGSN does not report to the VLR upon reception of the periodic Routeing Area Update message. When the MS performs a detach only from the GPRS system the GPRS detach indication to the VLR shall cause the VLR’s implicit detach timer to be restarted from its initial value.
If the SGSN performs an implicit detach for both GPRS and non-GPRS traffic, then the SGSN shall indicate to the VLR a BSSAP+-IMSI-DETACH-INDICATION message with cause ‘Implicit SGSN initiated IMSI detach from non-GPRS service’, as further described in section ‘Implicit IMSI detach from non-GPRS service procedure’ (the implicit IMSI detach message indicates that the MS is unavailable for both GPRS and non-GPRS services).
The IMSI attach for GPRS services to the VLR, when the MS is already IMSI attached for non-GPRS services, is requested by the MS sending a combined IMSI attach for GPRS and non-GPRS services message to the SGSN, as further specified in GSM 03.60 and 04.08.
6.2Procedures in the SGSN
The Location Update for non-GPRS services is initiated with a routeing area update procedure or a IMSI/GPRS attach procedure. On receipt of a Routeing Area Update message, the SGSN shall handle the GPRS related request as specified in GSM 04.08. The Location Update for non-GPRS services procedure may be handled by the SGSN in parallel to the Update Location procedure to the HLR. The SGSN shall wait for the outcome of both location update procedures towards the VLR and the HLR before sending the response message to the MS (see GSM 04.08).
6.2.1Location Update Initiation
If timer T6-1 is not running, the SGSN shall start the Location Update for non-GPRS service procedure when it receives from the MS:
-An Attach request indicating combined IMSI and GPRS attach ;
-An Attach request indicating IMSI only attach ;
- A Routeing Area Update request indicating that the Location Area has changed ; or
- A Routeing Area Update request when the SGSN serving the MS has changed.
The number of the VLR is derived from the RAI where the MS is camping. The SGSN starts Timer T6-1. The BSSAP+-LOCATION-UPDATE-REQUEST message includes the old Location Area Identifier received from the MS. The SGSN shall also include the new Location Area Identifier where the MS is currently camping. The new LAI is derived from the RAI.
The BSSAP+-LOCATION-UPDATE-REQUEST message includes the type of location update performed by the MS in the GPRS location update type IE. If the MS has performed an attach request, the SGSN indicates ‘IMSI attach’, otherwise the SGSN indicates ‘Normal location update’.
The BSSAP+-LOCATION-UPDATE-REQUEST message shall include the TMSI status if received from the MS.
If timer T6-1 is running:
If the SGSN receives from the MS:
-An Attach request indicating combined IMSI and GPRS attach ;
-An Attach request indicating IMSI only attach ; or
- A Routeing Area Update request indicating that the Location Area has changed.
Then:
-If the new LAI is the same as in the outstanding request, the SGSN shall not process this new request and shall wait for the VLR’s response to the ongoing procedure ; or
-If the new LAI is different but is in the same VLR as the outstanding request:
-any response from the VLR to the oustanding request is ignored ;
-Timer T6-1 shall stopped and reset ; and
-The SGSN shall start the Location Update for non-GPRS service procedure ;or -If the new LAI is different, and is in a different VLR to the outstanding request:
-Any response from the previously addressed VLR to the oustanding request is ignored ;
-Timer T6-1 shall stopped and reset ; and
-the SGSN shall start the Location Update for non-GPRS service procedure.
When the SGSN receives from the MS a Routeing Area Update request and the SGSN serving the MS has changed, the SGSN shall stop and reset timer T6-1.
6.2.2Location Update Response
If the SGSN receives a BSSAP+-LOCATION-UPDATE-ACCEPT message from the VLR, the SGSN shall: stop timer T6-1 and
-Move the state of the association to Gs-ASSOCIATED ;
-Set the the MM context variable ‘VLR-Reliable’ to ‘true’ ; and
-Indicate to the MS the acceptance of the VLR to the Location Update procedure. The message to the MS includes the Routeing Area Identity, from which the MS is able to extract the location area identity for which the location update procedure succeeded (see GSM 04.08).
The SGSN shall wait for the outcome of the Location Update for non-GPRS service procedure towards the VLR before sending a response to location update procedure to the MS. Any Reject cause that needs to be reported to the MS is specified in GSM 04.08
If the VLR included the Mobile Identity IE in the BSSAP+-LOCATION-UPDATE-ACCEPT message, the SGSN shall forward the information received to the MS. If the Mobile Identity IE contains a new TMSI it will cause the MS to perform a TMSI reallocation procedure, while an IMSI causes the MS to deallocate its TMSI. In case a new TMSI was allocated for the MS, the SGSN shall send to the VLR the BSSAP+-TMSI-REALLOCATION-COMPLETE message when the SGSN receives the Attach Complete or the Routeing Area Complete message from the MS.
6.2.3Location Update Failure
If the SGSN receives a BSSAP+-LOCATION-UPDATE-REJECT message from the VLR, the SGSN shall: -Stop timer T6-1 ;
-Move the state of the association to Gs-NULL ; and
-Indicate to the MS the rejection of the VLR of the Location Update procedure as specified in GSM 04.08. The Reject cause value sent by the VLR shall be forwarded to the MS.
6.2.4Abnormal cases
If timer T6-1 expires, the SGSN shall abort the Location Update for non-GPRS service procedure and indicate this to the MS with the Reject cause value ‘Service option temporarily out of order’. The state of the association to the VLR shall be Gs-NULL.
If the SGSN receives a BSSAP+LOCATION-UPDATE-ACCEPT message and timer T6-1 is not running then: -If timer T8 is running (see section 8), the message shall be ignored ;
-If timer T9 is running (see section 9), the message shall be ignored ; or
-If timers T8 and T9 are not running:
-If the state of the association to the VLR is GS-ASSOCIATED, the message shall be ignored ; or
-If the state of the association to the VLR is different than GS-ASSOCIATED, the message shall be treated as
a message incompatible with the protocol state of the SGSN (see section 16.3).
6.3Procedures in the VLR
When a VLR receives a BSSAP+-LOCATION-UPDATE-REQUEST message it shall check whether the IMSI is known. If the IMSI is not known the VLR shall retrieve the MM context of the MS from the HLR.
6.3.1Location Update Response
If the Location Update is accepted by the VLR and, if necessary by the HLR, the VLR shall:
-Move the association to the Gs-ASSOCIATED state ;
-Set the restoration indicator ‘Confirmed by Radio Contact’ to ‘true’ ;
-Update the association by storing the SGSN number included in the BSSAP+-LOCATION-UPDATE-REQUEST message ; and
-Send a BSSAP+-LOCATION-UPDATE-ACCEPT message to the sending SGSN. This message includes the Location Area Identification received in the new Location Area Identification IE in the previous BSSAP+-LOCATION-UPDATE-REQUEST message.
6.3.2Location Update Failure
If the Location Update is rejected by the VLR it shall:
-Send a BSSAP+-LOCATION-UPDATE-REJECT message to the SGSN with the appropriate reject cause as indicated in GSM 04.08; and
-Move the association from any state to Gs-NULL.
6.3.3TMSI reallocation procedure
If the VLR decides to reallocate the TMSI to the MS it shall include the new TMSI in the BSSAP+-LOCATION-UPDATE-ACCEPT message. If the VLR decides to deallocate the TMSI of the MS it shall include the IMSI of the MS in the BSSAP+-LOCATION-UPDATE-ACCEPT message with a new TMSI. After sending the BSSAP+-LOCATION-UPDATE-ACCEPT message the VLR starts timer T6-2.
NOTE:In the BSSAP+-LOCATION-UPDATE-REQUEST the SGSN may indicate, that there is no valid TMSI available in the MS. This information may be used by the VLR to decide whether to reallocate a new
TMSI to the MS.
Upon receipt of the BSSAP+-TMSI-REALLOCATION-COMPLETE message, the VLR stops the timer T6-2 and considers the new TMSI as valid.I
If an IMSI was sent to the MS, the VLR considers the old TMSI as deleted.
If no BSSAP+-TMSI-REALLOCATION-COMPLETE message is received by the VLR before the timer T6-2 expires, the VLR aborts the TMSI reallocation procedure. The VLR may still perform the TMSI reallocation procedure via the A interface. The outcome of the TMSI reallocation procedure does not change the state of the association. The VLR uses the IMSI or the new TMSI for paging.
6.3.4Abnormal cases
i)MM signalling via A interface
If the VLR receives a Location Update request or an IMSI detach indication from the MS by the A interface when the state of the association in the VLR is not Gs-NULL, the VLR shall move the state of the association to Gs-NULL.
ii)Additional Location Update Request
If the state of the association in the VLR is in the LA-UPDATE PRESENT state and a BSSAP+-LOCATION-UPDATE-REQUEST message is received, then:
-If the message is from the same SGSN and indicates the same New Location Area as the outstanding location update request, then this additional BSSAP+-LOCATION-UPDATE-REQUEST message shall be ignored ;
-If the message is from the same SGSN but indicates a different New Location Area to the outstanding location update request, then this additional BSSAP+-LOCATION-UPDATE-REQUEST message shall be treated and the VLR shall not send any response to the previous BSSAP+-LOCATION-UPDATE-REQUEST message ; or
-If the message is from a different SGSN (indicating either the same or different New Location Area) to the outstanding location update request, then this additional BSSAP+-LOCATION-UPDATE-REQUEST message shall be treated and the VLR shall not send any response to the previous BSSAP+-LOCATION-UPDATE-REQUEST message.
iii)Detach signalling from SGSN
If the state of the association in the VLR is in the LA-UPDATE PRESENT state and either a BSSAP+-GPRS-DETACH-INDICATION or a BSSAP+-IMSI-DETACH-INDICATION message is received, then, the Location Update for non-GPRS services procedure shall be abandoned in the VLR ( neither a BSSAP+LOCATION-UPDATE-ACCEPT nor a BSSAP+LOCATION-UPDATE-REJECT messages is sent) and the further actions described in sections 8 or 9 or 10 are followed.
7Non-GPRS alert procedure
7.1General description
This procedure is used by the VLR to request from an SGSN an indication when activity (either signalling or data transmission) from an MS is detected. This procedure can be invoked at any time by the VLR. The BSSAP+-ALERT-REQUEST message shall be acknowledged by the SGSN.
7.2Procedures in the VLR
7.2.1Alert Initiation
The VLR may start the Non-GPRS alert procedure at any time. When the VLR wants to request to an SGSN that further activity from an MS shall reported by the SGSN, the VLR shall send an BSSAP+-ALERT-REQUEST message to that SGSN. The VLR starts timer T7 when the BSSAP+-ALERT-REQUEST message is sent.
7.2.2Alert Response
When a BSSAP+-ALERT-ACK message is received, the VLR shall stop the timer T7. The state of the association is not changed.
7.2.3Alert failure
If a BSSAP+-ALERT-REJECT message is received, the VLR shall stop the timer T7, move the state of the association to Gs-NULL and within this state the association is marked with the contents of the Gs Cause IE.
7.2.4Alert Indication
The VLR shall not change the state of the association upon reception of an BSSAP+-MS-ACTIVITY-INDICATION message.
7.2.5Abnormal cases
If no BSSAP+-ALERT-ACK message is received before the timer T7 expires, the VLR shall retransmit the BSSAP+-ALERT-REQUEST message a maximum of N7 times. If no BSSAP+-ALERT-ACK message is received after that, a report shall be made to the O&M system. The state of the association is not changed.