6.15 Signalling procedures

23.2213GPPArchitectural requirementsRelease 17TS

6.15.1 Idle mode procedures

The signalling procedures shown in the following clauses do not represent the complete set of possibilities, nor do they mandate this kind of operation. This document specifies a set of elementary procedures for each interface, which can be combined in different ways in an implementation. Therefore these sequences are merely examples of a typical implementation. By default the combined procedures as defined in TS 23.060 [2] or TS 23.272 [30] are also applicable when using Gs or SGs.

The list of parameters should be regarded as examples of possible information carried by the messages and not as a complete list.

6.15.1.1 Location Area update

Figure 6.8 shows location registration when changing LA including change of 3G-MSC/VLR and when the UE is in MM idle state towards the 3G_MSC/VLR.

The illustrated transfer of MM signalling to/from the UE uses an established RRC connection. This RRC connection can have been established beforehand due to ongoing interwork between UE and 3G-SGSN or be established only for this location registration procedure towards the 3G_MSC/VLR.

For each indicated MM message sent in this case to/from UE, the CN discriminator indicates 3G_MSC/VLR.

Figure 6.8: Interface information transfer for location update when changing VLR area

1 The RRC connection is established, if not already done. The UE sends the initial message LA Update Request (old TMSI, old LAI, etc.) to the new 3G_MSC/VLR. The old TMSI and LAI are those that were assigned to the UE. The SRNS transfers the message to the 3G_MSC/VLR

NOTE: The sending of this message to 3G_MSC/VLR also implies establishment of a signalling connection between SRNS and 3G_MSC/VLR for the concerned UE.

The RAN shall add the RAC and the LAC of the cell where the message was received before passing the message to the MSC.

2. The new 3G_MSC/VLR sends an Send Identification Request (old TMSI) to the old 3G_MSC/VLR to get the IMSI for the UE. (The old LAI received from UE is used to derive the old 3G_MSC/VLR identity/address.) The old 3G_MSC/VLR responds with Send Identification Ack. (IMSI and Authentication triplets).

3. Security functions may be executed.

4. The new 3G_MSC/VLR inform the HLR of the change of 3G_MSC/VLR by sending Update Location (IMSI, MSC address, VLR number) to the HLR.

5. The HLR cancels the context in the old 3G_MSC/VLR by sending Cancel Location (IMSI). The old 3G_MSC/VLR removes the context and acknowledges with Cancel Location Ack.

6. The HLR sends Insert Subscriber Data (IMSI, subscription data) to the new 3G_MSC/VLR. The new 3G_MSC/VLR acknowledges with Insert Subscriber Data Ack.

7. The HLR acknowledges the Update Location by sending Update Location Ack. to the new 3G_MSC/VLR.

8. The new 3G_MSC/VLR validates the UE presence in the new LA. If due to regional, national or international restrictions the UE is not allowed to attach in the LA or subscription checking fails, then the new 3G_MSC/VLR rejects the LA update with an appropriate cause. If all checks are successful, then the new 3G_MSC/VLR responds to the UE with LA Update Accept (new TMSI, new LAI).

9. The UE acknowledges the new TMSI with a TMSI reallocation Complete. (TMSI can optionally be reallocated with the TMSI reallocation procedure).

10. When the location registration procedure is finished, the 3G_MSC/VLR can release the signalling connection towards the SRNS for the concerned UE. The SRNS shall then release the RRC connection if there is no signalling connection between 3G_SGSN and SRNS for the UE.

6.15.1.2 Routing Area Update

The routing area update procedure is detailed in TS 23.060 [2].

6.15.1.2A Tracking Area Update

The tracking area update procedure is detailed in TS 23.401 [27].

6.15.1.3 Periodic registration towards both CN nodes without use of Gs or SGs

Periodic registration for the CS domain is specified in TS 23.012 [3]. Periodic registration for the PS domain is covered in TS 23.060 [2] and in TS 23.401 [27].

6.15.1.4 Periodic registration with use of Gs or SGs

Periodic registration for the PS domain with use of Gs or SGs is covered in TS 23.060 [2] or in TS 23.272 [30]. Only TA/RA Updates are required from the UE to the SGSN or MME.

6.15.1.5 UE initiated combined detach procedure when using Gs or SGs

UE initiated Combined Detach Procedure when using Gs or SGs is specified in TS 23.060 [2] or in TS 23.272 [30]. The UE indicates which form of detach is required, i.e., PS Detach only, CS Detach only or combined Detach.

6.15.1.6 Forbidden LA/RA

The CN (SGSN and MSC/VLR) shall not send the COMMON Id message with SNA information to the UTRAN when the attach request, LA update, or RA update are rejected.

6.15.2 SRNS Relocation

SRNS relocation is UTRAN related functionality covered in TS 25.413 [9] and TS 23.060 [2].

NOTE: Examples of RAN signalling are given in TR 25.931 [15].