6.2.1 Intra-MSC SRNS Relocation

23.1533GPPOut of band transcoder controlRelease 17Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

Figure 6.2/1: Configuration during intra-MSC SRNS Relocation

Figure 6.1/1 shows the configuration during intra-MSC SRNS relocation. After setting up the new I_U interface (towards RNC-A’) until releasing the old one, the original TrFO relation (A⇔B) and the target TrFO relation (A’⇔B) exist in parallel. Within the respective context (TBE) interworking between T1, T2 and T3 is necessary:

T3 will receive initialisation from RNC-A’.

T2 shall hide initialisation performed on I_U,A’ from RNC-B.

If the option to remove the TBE was applied after call setup, the whole context (TBE) needs to be inserted prior to performing SRNS Relocation. Initialisation data need to be available within MGW-A. After Relocation, the context (TBE) may be removed again, i.e. the MGW-A again acts as a pure AAL2 switch.

Figure 6.2/2: Intra-MSC SRNS Relocation and TrFO. Flow chart part 1

Figure 6.2/3: Intra-MSC SRNS Relocation and TrFO. Flow chart part 2

Figure 6.2/3: Intra-MSC enhanced SRNS Relocation and TrFO. Flow chart

RAB Assignment on the new Iu leg:

A RAN side terminations with IuFP property (T3) has to be added to the already seized call context (step 2.) before sending Relocation Request (4.), that contains all the RAB parameters already applied on the Iu leg towards RNC-A.

UP initialisation

RNC-A’ shall accept the requested set of codec modes and is not allowed to puncture out any negotiated mode. The INIT frames shall be according to the RAB parameters received.

At reception of an INIT frame from the new RNC, the termination at MGW-A shall not perform forwarding of the IuFP initialisation. The MGW shall check whether the received RFCI allocations match the stored RFCI allocation. If it does not match, it may re-initialise the IuFP towards RNC-A’ at this point in time.

Removal of TrFO Break Equipment (TBE)

If the MGW supports the removal of TBEs, it shall insert the TBE before seizing the additional termination. It may again remove the TBE after performing RFCI matching and through-connection of the new termination and the termination to the far end party.