5.1 UESBI-Uu signalling flows

23.1953GPPProvision of User Equipment Specific Behaviour Information (UESBI) to network entitiesRelease 5TS

5.1.1 RRC connection establishment (initial and at cell reselection towards UTRAN)

At RRC connection establishment from idle mode, UESBI-Uu information shall be sent directly by the UE to the Serving RNC. This is valid both for the cases where the UE initiates the contact with the network either from RRC idle mode or in the case of a cell reselection from GERAN to UTRAN.

Figure 5.1.1-1: UESBI-Uu transfer at RRC Connection Establishment

The RRC Connection Establishment procedure is defined in TS 25.331 [6]

5.1.2 RR connection establishment

Figure 5.1.2-1: UESBI-Uu transfer at RR Connection Establishment

The UE sends the "Inter RAT Handover Information" which contains the UESBI-Uu to the GERAN BSS. Whether this information is sent immediately at RR connection establishment or this is delayed until just before inter-RAT handover is performed, is controlled by the BSS. Further information is given in TS 25.331 [6] and TS 44.018 [7].

5.1.3 SRNS relocation

UESBI-Uu information is sent from the Serving RNC to the Target RNC in the RRC: SRNS RELOCATION INFO message (specified in 25.331 [6]) which is carried through the CN during SRNS relocation in the RANAP: Source RNC to Target RNC Transparent Container IE ([9]).

This transparent container is:

– put in the RANAP Relocation Required message sent by the Serving RNC to the CN,

– carried from source MSC/SGSN to target MSC/SGSN via E or Gn interface signalling in the case of inter MSC/SGSN SRNS relocation

– sent by the target MSC/SGSN in the RANAP Relocation Request message sent to target RNC.

5.1.4 Inter RAT hand-over

5.1.4.1 3G  2G inter-RAT hand-over

If the UE fails to support properly this kind of Hand-Over, UTRAN can detect it through UESBI information already received from UE or CN, and react accordingly (e.g. avoid this kind of Hand-Over,… ).

5.1.4.2 2G  3G inter-RAT hand-over

UESBI-Uu information is sent from UE to Serving RNC via "Inter RAT Hand-Over" Information transfer.

Figure 5.1.4.2-1 UESBI-Uu transfer at inter-RAT handover

The inter RAT handover information transfer procedure is used by the UE to convey RRC information needed for inter RAT handover to UTRAN. "Inter RAT Hand-Over Information" is prepared by the UE, then sent on the Radio Resource (RR) layer of the source RAT (e.g. RR for GSM) together with Radio classmark information. Further information is given in TS 25.331 [6] and TS 44.018 [7].

At 2G  3G hand-over / SRNS relocation this information is transferred from source BSS to target RNC through the CN via the relevant BSS to RNC transparent containers defined in 48.008 [8] and 25.413 [9].

The target RNC shall use the UESBI-Uu to determine whether the handover can succeed.

In the case that the target RNC believes that the handover can succeed, the target RNC may use the UESBI-Uu to aid the handover procedure.

In the case that the UESBI-Uu indicates to the target RNC that the handover will fail, the target RNC shall reject the handover attempt. The target RNC shall use a specific cause value that causes the source BSS to not attempt further 2G to 3G handovers for that UE, and, causes the source BSS to take appropriate actions, eg to modify the set of neighbouring cells that the UE is measuring.

This requires that the GSM BSS shall include the Response Request IE in the Handover Required message.

Following an inter-BSS handover, the new BSS might attempt a GSM to UMTS handover that is doomed to failure. To avoid this the old BSS shall indicate to the new BSS whether or not the UE has had a handover to UMTS rejected by an RNC "because of the UESBI".