E.2 GAN Iu Mode Specific Requirements for Interworking with UTRAN

3GPP44.318Generic Access Network (GAN)Mobile GAN interface layer 3 specificationRelease 17TS

When operating in GAN Iu mode, the GANC emulates a UTRAN RNC to the rest of the network. Therefore, the UTRAN to GAN and GAN to UTRAN handovers are considered to be intra-system (UTRAN-to-UTRAN) handovers. This differs from the GAN A/Gb mode case where UTRAN to GAN and GAN to UTRAN handovers are considered to be inter-system (i.e., inter-RAT) handovers.

In addition to the procedures described in sub-clauses 8a.10 and 8a.11, the following procedures shall be followed with respect to GAN Iu mode handover to and from UTRAN:

1. When a UTRAN to GAN Iu mode to UTRAN handover sequence occurs:

– The GANC shall retain the Chosen Integrity Protection Algorithm (CIPA), Chosen Encryption Algorithm (CEA), Integrity Key (IK), Ciphering Key (CK) and COUNT parameters received from the source RNC. The GAN shall relay these parameters to the target RNC.

– The MS shall store the START values that are in effect when entering GAN Iu mode. The MS shall provide the START values to the GANC (i.e., in the GA-RRC RELOCATION INFORMATION message) and the GANC shall forward the START values with the other parameters (described above) to the target RNC.

2. When a UTRAN to GAN Iu mode handover occurs (i.e., other than described in bullet 1 above):

– The MS shall store the START values that are in effect when entering GAN Iu mode. When the MS transitions to the idle state (i.e., GA-RRC IDLE state for both CS and PS domains) while in GAN Iu mode, then the MS shall compare the START values with THRESHOLD and set the START values and key status as described in TS 25.331 [40] (i.e., behave as if the connection was released in UTRAN).

3. When a GAN Iu mode to UTRAN handover occurs (i.e., other than described in bullet 1 above):

– The GANC relays the RRC message (e.g., Physical Channel Reconfiguration) provided by the target RNC in the Relocation Request Ack message to the MS in the GA-RRC RELOCATION COMMAND. This message includes the Integrity Protection Activation Info which includes the FRESH value.

– The GANC shall include the current settings for the security algorithms and keys (e.g., CIPA, IK, CEA, and CK parameters) in the Source RNC to Target RNC Transparent Container.

– The GANC shall obtain the START value(s) from the MS (i.e., in the GA-RRC RELOCATION INFORMATION message) and include them in the RRC Container sent to the target RNC in the Source RNC to Target RNC Transparent Container parameter.

– The GANC shall initialize the relevant COUNT value(s) to zero and include them in the RRC Container sent to the target RNC in the Source RNC to Target RNC Transparent Container parameter.

Annex F (normative):
3G Cell Identity coding