3GPP43.129Packet-switched handover for GERAN A/Gb modeRelease 16Stage 2TS
The target BSS/GANC may reject the use of the PS Handover procedure in case none of the PFCs To Be Set Up in the PS Handover Request message could be granted the requested QoS, or, in case of a non-critical PS handover, if at least one of the PFCs To Be Set Up in the PS Handover Request message could not be granted the requested QoS. In this case no MS context will be established in the target BSS/GANC and no resources will be allocated. The target BSS/GANC will send a PS Handover Request Negative Acknowledge message to the new SGSN causing the new SGSN to release any allocated resources (e.g. P-TMSI, MS associated contexts) related to the specific MS. The signalling procedure for the Inter-SGSN HO Reject is shown in clause 5.4.2 for the case where PS handover is attempted to a target BSS/GANC. Similar procedures are used in the other handover cases.
5.4.2 Inter-SGSN HO Reject; Signalling procedure
Figure 19: PS Handover Reject; Inter-SGSN case (GERAN A/Gb mode GERAN A/Gb mode)
1. The first four steps in the flow are identical to the ones in clause 126.96.36.199.
2. In case the target BSS/GANC fails to allocate any resources for any of the requested PFCs it sends a PS Handover Request Negative Acknowledge (Cause, Source Cell Identifier, Target Cell Identifier) message to the new SGSN.
3. When the new SGSN receives the PS Handover Request Negative Acknowledge message it clears any reserved resources (e.g. PDP context, P-TMSI) for this mobile and sends the Forward Relocation Response (Cause, SGSN Address for control plane) message to the old SGSN.
4. When the old SGSN receives the Forward Relocation Response message it sends a PS Handover Required Negative Acknowledge (Old TLLI, Cause, Source Cell Identifier, Target Cell Identifier) message to the source BSS.