8a GA-RRC elementary procedures

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

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

8a.1 GA-RRC connection establishment

The GAN Iu mode GA-RRC CS and PS connections are logical connections between the MS and the GANC. As described in 3GPP TS 43.318, the GA-RRC sub-layer in the MS contains two entities, the CS domain GA-RRC sublayer entity and the PS domain GA-RRC sublayer entity. These entities operate independently and in parallel; e.g., two GA-RRC connections are established in the case of simultaneous CS and PS services, one GA-RRC connection for each domain. Each GA-RRC sub-layer entity in the MS can be in one of two states, GA-RRC-IDLE or GA-RRC-CONNECTED. Figures showing state changes (e.g., from GA-RRC-IDLE to GA-RRC-CONNECTED) in this sub-clause refer to changes for a single GA-RRC sub-layer entity, either CS or PS.

A GA-RRC connection is established when the upper layers in the MS request the establishment of a signalling connection for either CS or PS domain and the GA-RRC sub-layer entity in the MS is in the GA-RRC-IDLE state for that domain; i.e., no GA-RRC connection exists. When a successful response is received from the network, GA-RRC replies to the upper layer that the GA-RRC sub-layer entity in the MS has entered the RRC connected mode (i.e., the GA-RRC-CONNECTED state). The upper layers then have the possibility to request transmission of NAS messages to the network (as described in sub-clause 8a.2).

Note that in the case of a network-initiated CS or PS session, the GA-RRC connection is implicitly established when the MS responds to the GA-RRC PAGING REQUEST message from the GANC with the GA-RRC INITIAL DIRECT TRANSFER message containing the paging response (see sub-clause 8a.3).

Also, in the case of handover from GERAN or UTRAN to GAN Iu mode, the GA-RRC connection is implicitly established when the MS sends the GA-RRC RELOCATION ACK message to the GANC (normal case) or the GA-RRC RELOCATION ACCESS message to the GANC (exception case), as described in sub-clause 8a.10.

Figure 8a.1.1 MS initiation of GA-RRC connection, successful case

Figure 8a.1.2 MS initiation of GA-RRC connection, failure case

8a.1.1 Initiation of GA-RRC connection establishment by the MS

The MS initiates the establishment of the GA-RRC connection when the upper layers in the MS request the establishment of a signalling connection for either CS or PS domain and the GA-RRC sub-layer entity in the MS is in GA-RRC-IDLE state for that domain.

Before initiation of the GA-RRC connection establishment request, the MS shall check for access permission based on Access Control Class bits returned within GA-RC REGISTER ACCEPT message as defined in [12].

If it is allowed for the MS to access the network, the MS shall send a GA-RRC REQUEST message to the GANC on the established TCP connection, including the IE "CN Domain Identity" and the IE "Establishment Cause", and start timer TU5908 for the domain (i.e., the MS may have up to two instances of the TU5908 timer running at the same time, one for each domain).

8a.1.2 Reception of GA-RRC REQUEST by GANC

When the GANC receives the GA-RRC REQUEST message, the GANC may either accept or reject the GA-RRC connection establishment request.

8a.1.2.1 GA-RRC connection establishment request accepted

If the GANC accepts the GA-RRC connection establishment request, it shall send the GA-RRC REQUEST ACCEPT message to the MS including the IE "CN Domain Identity".

8a.1.2.2 GA-RRC connection establishment request rejected

If the GANC rejects the GA-RRC connection establishment request, it shall send the GA-RRC REQUEST REJECT message to the MS including the IE "CN Domain Identity".

8a.1.3 GA-RRC connection establishment response handling in the MS

8a.1.3.1 GA-RRC connection establishment request accepted

When the MS receives the GA-RRC REQUEST ACCEPT message, it shall:

– if timer TU5908 is active for the domain indicated by the IE "CN Domain Identity":

– stop timer TU5908 for that domain,

– move into the GA-RRC-CONNECTED state for that domain,

– indicate to upper layers that GA-RRC has entered the connected state for that domain, and

– send the GA-RRC INITIAL DIRECT TRANSFER message to the network;

– if timer TU5908 is not active for the domain indicated by the IE "CN Domain Identity":

– ignore the GA-RRC REQUEST ACCEPT message, and

– continue with the procedure as if the GA-RRC REQUEST ACCEPT message was not received.

8a.1.3.2 GA-RRC connection establishment request rejected

When the MS receives the GA-RRC REQUEST REJECT message, it shall:

– if timer TU5908 is active for the domain indicated by the IE "CN Domain Identity":

– stop timer TU5908 for that domain,

– remain in the GA-RRC-IDLE state for that domain, and

– indicate to upper layers that GA-RRC was not able to enter the connected state for that domain;

– if timer TU5908 is not active for the domain indicated by the IE "CN Domain Identity":

– ignore the GA-RRC REQUEST REJECT message, and

– continue with the procedure as if the GA-RRC REQUEST REJECT message was not received.

8a.1.4 Failure cases

8a.1.4.1 Timer TU5908 expiry

If timer TU5908 expires in the MS, the GA-RRC sub-layer entity in the MS shall remain in the GA-RRC-IDLE state and indicate to upper layers that GA-RRC was not able to enter the connected state for the domain.

8a.2 Upper layer message transmission

The GA-RRC INITIAL DIRECT TRANSFER message is used to transfer the "initial" upper layer message for the domain (i.e., the first NAS message after GA-RRC connection establishment for the domain) from the MS to the GANC. Receipt of the GA-RRC INITIAL DIRECT TRANSFER message by the GANC triggers the establishment of the signalling connection to the indicated CN domain for the MS. The GA-RRC UPLINK DIRECT TRANSFER message is used to transfer all subsequent upper layer messages for the signalling connection from the MS to the GANC.

The GA-RRC DOWNLINK DIRECT TRANSFER message is used to transfer upper layer messages from the GANC to the MS.

8a.2.1 Initial upper layer message forwarding by the MS

Figure 8a.2.1.1 Initial direct transfer, normal flow

The GA-RRC sub-layer entity in the MS shall initiate the initial direct transfer procedure in the GA-RRC-CONNECTED state when the upper layers request the transfer of the first non-access stratum (NAS) message associated with the signalling connection.

The MS shall include the IE "CN Domain Identity" and the contents of the received NAS message in the L3 Message IE. The MS also includes the Intra Domain NAS Node Selector (IDNNS) IE which may be used by the GANC to route the establishment of a signalling connection to a CN node within the indicated CN domain (i.e., using IuFlex).

8a.2.2 Reception of GA-RRC INITIAL DIRECT TRANSFER by GANC

When the GANC receives the GA-RRC INITIAL DIRECT TRANSFER message from a GA-RRC sub-layer entity in MS in the GA-RRC-CONNECTED state and there is no signalling connection to the indicated CN domain, the GANC shall establish an Iu signalling connection between the GANC and the indicated CN domain and transfer the initial NAS message to the CN.

8a.2.3 Subsequent upper layer message forwarding by the MS

Figure 8a.2.3.1 Uplink direct transfer, normal flow

The GA-RRC sub-layer entity in the MS shall initiate the uplink direct transfer procedure in the GA-RRC-CONNECTED state when the upper layers request the transfer of a subsequent NAS message associated with the signalling connection (i.e., after the initial NAS message).

The MS shall include the IE "CN Domain Identity" and the contents of the received NAS message in the IE "L3 Message".

8a.2.4 Reception of GA-RRC UPLINK DIRECT TRANSFER by GANC

When the GANC receives the GA-RRC UPLINK DIRECT TRANSFER message from a GA-RRC sub-layer entity in the MS in the GA-RRC-CONNECTED state, the GANC shall transfer the NAS message to the CN using the existing signalling connection.

8a.2.5 Upper layer message forwarding by the GANC

Figure 8a.2.5.1 Downlink direct transfer, normal flow

The downlink direct transfer procedure is initiated by the GANC when the GANC receives a NAS message from a CN domain (i.e., after the establishment of the GA-RRC connection to the MS for the domain).

The GANC shall include the IE "CN Domain Identity" and the contents of the received NAS message in the IE "L3 Message".

8a.2.6 Reception of GA-RRC DOWNLINK DIRECT TRANSFER by the MS

When the MS receives the GA-RRC DOWNLINK DIRECT TRANSFER message it shall, using the IE "CN Domain Identity", route the contents of the IE "NAS message" and the value of the IE "CN Domain Identity" to upper layers.

8a.2.6.1 Invalid GA-RRC DOWNLINK DIRECT TRANSFER

If the MS receives a GA-RRC DOWNLINK DIRECT TRANSFER message and GA-RRC sub-layer entity in the MS is not in GA-RRC-CONNECTED state for the indicated domain, the MS shall:

– ignore the contents of the GA-RRC DOWNLINK DIRECT TRANSFER message;

– transmit a GA-RRC STATUS message to the GANC as follows:

– set the IE "GA-RRC Cause" to "Message type not compatible with protocol state"

– include the received message contents in the IE "PDU in Error"

– continue with any ongoing procedure and act as if the GA-RRC DOWNLINK DIRECT TRANSFER message was not received.

8a.3 Paging

The GANC uses the paging procedure to transmit paging information received from the CN to the MS. The procedure also results in GA-RRC connection establishment between the MS and the GANC for the indicated domain.

Figure 8a.3.1 Paging, normal flow

8a.3.1 Initiation of paging

The GANC sends the GA-RRC PAGING REQUEST message to the MS when the GANC receives a PAGING message over the Iu interface from a CN domain. The IMSI of the MS to be paged is identified by the IE "Permanent NAS UE Identity" received in the request from the CN. If the request also includes the (P-)TMSI then the GANC shall include the (P-)TMSI in the IE "Mobile Identity"; else the GANC shall include the IMSI in the IE "Mobile Identity". The GANC also includes the IE "CN Domain Identity" and the IE "GA-RRC Paging Cause", if a cause is received from the CN.

8a.3.2 Reception of GA-RRC PAGING REQUEST by the MS

If the mobile identity in the GA-RRC PAGING REQUEST message matches any of the valid identities of the MS and the GA-RRC sub-layer entity in the MS is in the GA-RRC-IDLE state for the indicated domain, the MS shall:

– if timer TU5908 is not active for the domain and access to the network is allowed:

– indicate reception of paging to upper layers, and

– forward the IE "CN Domain Identity", the IE "Mobile Identity" and the IE "Paging Cause" (if received) to the upper layers;

– Note: The upper layers will request the establishment of a signalling connection and the transmission of the paging response in the initial NAS message. This results in the implicit establishment of the GA-RRC connection (i.e., the GA-RRC sub-layer entity in the MS enters the GA-RRC CONNECTED state) and the transmission of the paging response from the MS to the GANC in the GA-RRC INITIAL DIRECT TRANSFER message, as shown in Figure 8a.3.1.

– if timer TU5908 is active for the domain:

– ignore the GA-RRC PAGING REQUEST message, and

– continue with the ongoing procedure as if the GA-RRC PAGING REQUEST was not received.

8a.3.3 Abnormal Cases

If the MS receives a GA-RRC PAGING REQUEST message and the GA-RRC sublayer entity in the MS is in GA-RRC-CONNECTED state for the indicated domain or the MS is in the GA-RC-REGISTERED state but in GERAN/UTRAN/E-UTRAN mode, the MS shall:

– ignore the GA-RRC PAGING REQUEST message, and

– continue with any ongoing procedure as if the GA-RRC PAGING REQUEST was not received.

If the MS receives a GA-RRC PAGING REQUEST and the mobile identity included in the message does not match any of the valid identities assigned to the MS, the MS shall:

– ignore the GA-RRC PAGING REQUEST message, and

– continue with any ongoing procedure as if the GA-RRC PAGING REQUEST message was not received.

8a.4 Transport channel activation

There are two versions of the transport channel activation procedure, the circuit transport channel (i.e., the "RTP channel") activation procedure and the packet transport channel activation procedure. As illustrated in the following sub-clauses, these two procedures use the same messages and the same basic message flows (as illustrated in the following figure), but differ in the content of the messages.

Figure 8a.4.1 Transport channel activation, normal flow

8a.4.1 Circuit transport channel activation

8a.4.1.1 Initiation of circuit transport channel activation

The following are the possible triggers for initiation of the circuit transport channel (CTC) activation procedure:

– If the MS is in the GA-RRC-CONNECTED state for the CS domain and the GANC receives the RAB Assignment Request message from the MSC;

– If the MS is in the GA-RRC-CONNECTED state for the CS domain and the GANC receives the GA-RRC RELOCATION ACCESS message from the MS during the CS handover to GAN Iu mode process (see sub-clause 8a.10.5).

One or more CTCs may be activated using a single instance of the channel activation procedure; however, it is not possible to activate both circuit and packet transport channels using a single instance of the channel activation procedure.

The GANC begins the activation of the CTC(s) by transmitting the GA-RRC ACTIVATE CHANNEL message to the MS. The message contains the IE "CN Domain Identity" (indicating CS domain) and IE "CTC Activation List" which includes the parameters necessary to describe each circuit transport channel.

8a.4.1.2 Reception of GA-RRC ACTIVATE CHANNEL (CS domain) by the MS

The MS shall act on the received GA-RRC ACTIVATE CHANNEL message indicating the CS domain as follows:

– for each CTC specified in the IE "CTC Activation List":

– store the RAB ID;

– if the IE "RAB Configuration" indicates that the CTC is for AMR or AMR-WB speech, use the format specified in Annex A.1 and Annex D to code and decode the RTP packets;

– if the IE "RAB Configuration" indicates that the CTC is for circuit switched data, use the format specified in Annex A.2 to code and decode the RTP packets;

– use the value indicated by the IE "Sample Size" as the minimum sample size for the coding and decoding of the RTP packets, if the MS is not able to use the indicated value. If the circuit transport channel is for AMR or AMR-WB speech with RTP redundancy, the sample size is defined as the size of the new speech sample in each RTP packet, not including any redundant speech samples;

– configure the uplink RTP packets to be transmitted to the UDP port and IP address identified by the IE "RTP UDP Port" and the IE "GANC IP address", respectively;

– use the Payload Type included in the IE "Payload Type" for the PT field in the RTP header for the RTP packets;

– if received, use the configuration included in the IE "Multi-rate Configuration 2" for the circuit transport channel that is for AMR or AMR-WB speech;

– if received, use the configuration included in the IE "RTP Redundancy Configuration" for the circuit transport channel that is for AMR or AMR-WB speech. The redundancy policy is defined for each of the AMR modes specified in the IE "Multi-rate Configuration 2". The level of redundancy can span from no redundancy to double redundancy. In the same active codec set, a lower codec mode shall not be associated with a lower redundancy level then a higher codec mode. For example, the highest mode in the set is used with no redundancy, the next lower with single redundancy and rest of the modes with double redundancy.

– if received, pass the contents of the NAS Synchronisation Indicator to upper layers.

On completing the above procedure, the MS shall:

– start timer TU5911 for the CS domain;

– transmit a GA-RRC ACTIVATE CHANNEL ACK message including the IE "CN Domain Identity" and the IE "CTC Activation Ack List". For each CTC specified in the IE "CTC Activation Ack List":

– include the IE "RAB ID" for the CTC with the same value as received in the GA-RRC ACTIVATE CHANNEL message in the IE "RAB ID";

– include the IE "GA-RRC Cause" indicating either success (i.e., value ‘0’) or a failure cause value;

– for each CTC that is successfully configured (i.e., GA-RRC Cause value is ‘0’):

– include the allocated UDP port number in the IE "RTP UDP Port" for the downlink RTP packets to be sent from the GANC to the MS;

– include the selected RTP sample size, to be used for uplink and downlink RTP packets, in the IE "Sample Size";

– include the Payload Type in the IE "Payload Type";

– if the IE "RTCP UDP Port" was received in the GA-RRC ACTIVATE CHANNEL message and the MS is capable of supporting RTCP, activate the uplink RTCP stream and include the IE "RTCP UDP Port" for the downlink RTCP packets to be sent from the GANC to the MS.

8a.4.1.3 Reception of GA-RRC ACTIVATE CHANNEL ACK (CS domain) by GANC

On reception of the GA-RRC ACTIVATE CHANNEL ACK message indicating the CS domain, the GANC shall configure itself for transmission of RTP packets to the "RTP UDP Port" indicated in the message and RTCP packets to the "RTCP UDP Port" indicated in the message (if included) for each successfully activated CTC, and transmit a GA-RRC ACTIVATE CHANNEL COMPLETE message to the MS.

To enable downlink quality measurements in the MS, the GANC shall send at least one RTP frame each 480 ms for each active CTC. During periods of discontinuous transmission (DTX), if the CTC is for AMR or AMR-WB speech, each RTP frame transmitted by the GANC shall bear a format in the AMR/AMR-WB payload Table of Contents that either (a) omits all NO_DATA indications and contains only the next AMR speech or SID frame that is available, or (b) includes a single NO_DATA frame should no AMR speech or SID frame become available for 480 ms. The RTP timestamp shall indicate the time of that speech or SID or NO_DATA frame. See Section A.1.2 of Annex A for examples.

8a.4.1.4 Reception of GA-RRC ACTIVATE CHANNEL COMPLETE (CS domain) by MS

On reception of the GA-RRC ACTIVATE CHANNEL COMPLETE message indicating the CS domain, the MS shall stop timer TU5911 for the CS domain and consider the successfully activated CTC(s) to be available for use by upper layers. To enable uplink quality measurements in the GANC, the MS shall send at least one RTP frame each 480 ms for each active CTC. During periods of discontinuous transmission (DTX), each RTP frame transmitted by the MS shall bear a format in the AMR/AMR-WB payload Table of Contents that either (a) omits all NO_DATA indications and contains only the next AMR speech or SID frame that is available, or (b) includes a single NO_DATA frame should no AMR speech or SID frame become available for 480 ms. The RTP timestamp shall indicate the time of that speech or SID or NO_DATA frame. See Section A.1.2 of Annex A for examples.

8a.4.2 Packet transport channel activation

8a.4.2.1 Initiation of packet transport channel activation

The following is the possible trigger for initiation of the packet transport channel activation procedure:

– If the MS is in the GA-RRC-CONNECTED state for the PS domain and the GANC receives the RAB Assignment Request message from the SGSN.

One or more packet transport channels may be activated using a single instance of the channel activation procedure; however, it is not possible to activate both circuit and packet transport channels using a single instance of the channel activation procedure.

The GANC begins the activation of the PTC(s) by transmitting the GA-RRC ACTIVATE CHANNEL message to the MS. The message contains the IE "CN Domain Identity" (indicating PS domain) and IE "PTC Activation List" which includes the parameters necessary to describe each packet transport channel.

8a.4.2.2 Reception of GA-RRC ACTIVATE CHANNEL (PS domain) by the MS

The MS shall act on the received GA-RRC ACTIVATE CHANNEL message indicating the PS domain as follows:

– for each PTC specified in the IE "PTC Activation List":

– store the RAB ID;

– allocate local PTC resources based on the values in the IE "RAB Configuration";

– use the TEID value included in the IE "GANC TEID" for the TEID field in the GA-RRC PDU messages to be sent to the GANC;

– use the TEID value included in the IE "MS TEID" to verify the TEID field in the GA-RRC PDU messages to be received from the GANC;

– configure the uplink GA-RRC PDU messages to be transmitted to the UDP port and IP address identified by the IE "GANC UDP Port" and the IE "GANC IP address", respectively.

On completing the above procedure, the MS shall:

– start timer TU5911 for the PS domain;

– transmit a GA-RRC ACTIVATE CHANNEL ACK message including the IE "CN Domain Identity" and the IE "PTC Activation Ack List". For each PTC specified in the IE "PTC Activation Ack List":

– include the IE "RAB ID" for the PTC with the same value as received in the GA-RRC ACTIVATE CHANNEL message in the IE "RAB ID";

– include the IE "GA-RRC Cause" indicating either success (i.e., value ‘0’) or a failure cause value;

– for each PTC that is successfully configured (i.e., GA-RRC Cause value is ‘0’):

– include the allocated UDP port number in the IE "MS UDP Port" for the downlink GA-RRC PDU messages to be sent from the GANC to the MS.

8a.4.2.3 Reception of GA-RRC ACTIVATE CHANNEL ACK (PS domain) by GANC

On reception of the GA-RRC ACTIVATE CHANNEL ACK message indicating the PS domain, the GANC shall configure itself for transmission of GA-RRC PDU messages to the "MS UDP Port" indicated in the message for each successfully activated PTC, and transmit a GA-RRC ACTIVATE CHANNEL COMPLETE message to the MS.

8a.4.2.4 Reception of GA-RRC ACTIVATE CHANNEL COMPLETE (PS domain) by MS

On reception of the GA-RRC ACTIVATE CHANNEL COMPLETE message indicating the PS domain, the MS shall stop timer TU5911 for the PS domain, and start timer TU4001 for each of the successfully activated PTC(s) which are now available for use by upper layers.

8a.5 GA-RRC connection release

8a.5.1 GA-RRC connection release request by MS

If the MS needs to release the GA-RRC connection and signalling connection to a particular CN domain, it shall send the GA-RRC RELEASE REQUEST message to the GANC and start timer TU5909 for the domain. The MS shall include the IE "CN Domain Identity" and the IE "GA-RRC Cause". The GA-RRC Cause value shall be one of the following:

#40: UE generated signalling connection release

#115: unspecified failure

Figure 8a.5.1.1 GA-RRC connection release request by MS

8a.5.2 Reception of GA-RRC RELEASE REQUEST by GANC

When the GANC receives the GA-RRC RELEASE REQUEST message, it shall request the selected CN domain to release the Iu connection for the MS, including all active RABs for that domain. The GANC selects the CN domain based on the value of the received IE "CN Domain Identity".

8a.5.3 Initiation of GA-RRC connection release by GANC

The GANC initiates the GA-RRC connection release procedure to command the MS to release the GA-RRC connection and any user plane resources for a particular domain and instruct the GA-RRC sub-layer entity of the MS to leave the GA-RRC-CONNECTED state and return to the GA-RRC-IDLE state for the domain. The GANC normally initiates this procedure when it receives the Iu Release Command from the CN; however, the GANC may also initiate this procedure under certain failure conditions.

Figure 8a.5.3.1 GA-RRC connection release, normal flow

The GANC initiates the GA-RRC connection release procedure by sending the GA-RRC RELEASE message to the MS.

The GA-RRC RELEASE message includes the IE "GA-RRC Cause". The GA-RRC Cause value should be one of the following:

#83: normal release; e.g., at the end of a call

#115: unspecified failure

Other values, if received, should be treated as "unspecified failure".

8a.5.4 Reception of GA-RRC RELEASE by MS

When the GA-RRC sublayer entity in the MS receives the GA-RRC RELEASE message, it shall:

– send a GA-RRC RELEASE COMPLETE message to the GANC,

– release the GA-RRC connection and any user plane resources for the indicated domain,

– stop timer TU5002 for the domain (if running) (see sub-clause 8a.8),

– stop timer TU5909 for the domain (if running), and

– enter the GA-RRC-IDLE state for the domain.

8a.5.5 Failure cases

8a.5.5.1 Timer TU5909 expiry

If timer TU5909 expires in the MS, the GA-RRC sublayer entity in the MS shall release the GA-RRC connection and any user plane resources and enter the GA-RRC-IDLE state for the domain associated with the TU5909 timer.

8a.6 Security mode control

The security mode control procedure is used by the network to set the security mode; i.e., the settings for integrity protection and encryption, including the algorithms to use. This information is not used when GA-RRC is the serving entity in the MS, but shall be stored in the MS for possible future use after a handover from GAN Iu mode to UTRAN during the same upper layer transaction (i.e., the UTRAN RRC layer becomes the serving entity during this upper layer transaction).

The security mode control procedure also proves that the MS identity that is authenticated to the GANC is the same as the MS identity authenticated to the core network.

The security mode control procedure applies only for a MS in the GA-RRC-CONNECTED state for either the CS domain or the PS domain.

The security mode control procedure is always triggered by the network.

Figure 8a.6.1 Security mode control, normal flow

8a.6.1 Security mode control initiation

The GANC initiates the security mode control procedure by sending a GA-RRC SECURITY MODE COMMAND message to the MS. This message includes the IE "Selected Integrity Protection Algorithm", the IE "Selected Encryption Algorithm" (optional), and the IE "Random Number". The GANC selects the algorithms based on the permitted algorithms received from the CN and the MS security capabilities indicated in the IE "3G Security Capability" received from the MS in the GA-RC REGISTER REQUEST message.

8a.6.2 Security mode control completion

Whenever the MS receives a valid GA-RRC SECURITY MODE COMMAND message, it shall, if a (U)SIM is present and considered valid and the key set identifier (KSI) stored on the (U)SIM indicates that an integrity key and cipher key are available for the domain indicated in the IE "CN Domain Identity", store the selected integrity protection algorithm and (if received) the selected encryption algorithm for possible future use after a handover from GAN Iu mode to UTRAN during the same upper layer transaction. If handover from GAN Iu mode to UTRAN occurs, encryption is enabled if the IE "Selected Encryption Algorithm" is present in the message and disabled otherwise.

The MS shall also calculate a MAC (Message Authentication Code). The MAC shall be calculated over the following data:

RAND | IMSI

using "HMAC-SHA1-96" algorithm, as specified in [24] with the integrity key (IK) for the domain indicated in the IE "CN Domain Identity" used as the authentication key.

In the formulas above, the "|" character denotes concatenation. RAND is the 16-octet random number received from the GANC in the GA-RRC SECURITY MODE COMMAND message. IMSI is the MS IMSI, in the same format as defined for the Mobile Identity IE as defined in [8]; i.e. as a variable-length sequence of digits in BCD format (e.g. the IMSI "123456789098765" is encoded as the following octets (in hexadecimal): "21 43 65 87 09 89 67 F5"). Network byte order is used.

The IK key is the IK that has been derived during the last authentication for the domain indicated in the IE "CN Domain Identity". The length of the MAC is 12 octets.

When the appropriate action on the GA-RRC SECURITY MODE COMMAND message has been taken, the MS sends a GA-RRC SECURITY MODE COMPLETE message to the GANC. The MS includes the calculated MAC value in the IE "Ciphering Command MAC".

8a.7 Transport channel modification

There are two versions of the transport channel modification procedure, the circuit transport channel modification procedure and the packet transport channel modification procedure. As illustrated in the following sub-clauses, these two procedures use the same messages and the same basic message flows (as illustrated in the following figure), but differ in the content of the messages.

Figure 8a.7.1 Transport channel modification, normal flow

8a.7.1 Circuit transport channel modification

8a.7.1.1 Initiation of circuit transport channel modification

The GANC initiates the circuit transport channel (CTC) modification procedure when it determines that one or more active CTCs require modification; e.g., based on information received from the MSC in the RAB Assignment Request message or based on local GANC logic.

The following CTC parameters may be modified:

– RAB Configuration

– Sample Size

– GANC RTP UDP Port

– GANC IP Address

– Multi-rate Configuration 2

– RTP Redundancy Configuration

– GANC RTCP UDP Port

– NAS Synchronisation Indicator

The GANC only includes the IEs which specify modifications to the existing CTC parameters.

One or more CTCs may be modified using a single instance of the channel modification procedure; however, it is not possible to modify both circuit and packet transport channels using a single instance of the channel modification procedure.

The GANC begins the modification of the CTC(s) by transmitting the GA-RRC MODIFY CHANNEL message to the MS. The message contains the IE "CN Domain Identity" (indicating CS domain) and IE "CTC Modification List" which includes the parameters necessary to describe the modifications to each circuit transport channel.

8a.7.1.2 Reception of GA-RRC MODIFY CHANNEL (CS domain) by the MS

On receipt of the GA-RRC MODIFY CHANNEL message indicating the CS domain, the MS shall process the specified CTC modifications.

On completion of the modification of the CTC(s), the MS shall:

– transmit a GA-RRC MODIFY CHANNEL ACK message including the IE "CN Domain Identity" and the IE "CTC Modification Ack List". For each CTC specified in the IE "CTC Modification Ack List":

– include the IE "RAB ID" for the CTC with the same value as received in the GA-RRC MODIFY CHANNEL message in the IE "RAB ID";

– include the IE "GA-RRC Cause" indicating either success (i.e., value ‘0’) or a failure cause value;

– for each CTC that is successfully modified (i.e., GA-RRC Cause value is ‘0’):

– include the modified parameter values currently used by the MS.

When the MS has sent the GA-RRC MODIFY CHANNEL ACK message, it shall start transmitting RTP packets based on the successful parameter modifications. The MS shall be able to receive RTP packets with the old parameters until the MS determines that the first RTP packet using the new parameters has been received.

8a.7.1.3 Reception of GA-RRC MODIFY CHANNEL ACK (CS domain) by GANC

On reception of the GA-RRC MODIFY CHANNEL ACK message indicating the CS domain, the GANC shall configure itself for transmission of RTP packets to the MS using the new parameter values for the successfully modified CTC(s). The GANC shall be able to receive RTP packets with the old parameters until the GANC determines that the first RTP packet using the new parameters has been received.

8a.7.2 Packet transport channel modification

8a.7.2.1 Initiation of packet transport channel modification

The GANC initiates the packet transport channel (PTC) modification procedure when it determines that one or more active PTCs require modification; e.g., based on information received from the SGSN in the RAB Assignment Request message or based on local GANC logic.

The following PTC parameters may be modified:

– RAB Configuration

– GANC UDP Port

– GANC IP Address

The GANC only includes the IEs which specify modifications to the existing PTC parameters.

One or more PTCs may be modified using a single instance of the channel modification procedure; however, it is not possible to modify both circuit and packet transport channels using a single instance of the channel modification procedure.

The GANC begins the modification of the PTC(s) by transmitting the GA-RRC MODIFY CHANNEL message to the MS. The message contains the IE "CN Domain Identity" (indicating PS domain) and IE "PTC Modification List" which includes the parameters necessary to describe the modifications to each packet transport channel.

8a.7.2.2 Reception of GA-RRC MODIFY CHANNEL (PS domain) by the MS

On receipt of the GA-RRC MODIFY CHANNEL message indicating the PS domain, the MS shall process the specified PTC modifications.

On completion of the modification of the PTC(s), the MS shall:

– transmit a GA-RRC MODIFY CHANNEL ACK message including the IE "CN Domain Identity" and the IE "PTC Modification Ack List". For each PTC specified in the IE "PTC Modification Ack List":

– include the IE "RAB ID" for the PTC with the same value as received in the GA-RRC MODIFY CHANNEL message in the IE "RAB ID";

– include the IE "GA-RRC Cause" indicating either success (i.e., value ‘0’) or a failure cause value;

– for each PTC that is successfully modified (i.e., GA-RRC Cause value is ‘0’):

– include the modified parameter values currently used by the MS.

When the MS has sent the GA-RRC MODIFY CHANNEL ACK message, it shall start transmitting GA-RRC PDU messages based on the successful parameter modifications. The MS shall be able to receive GA-RRC PDU messages with the old parameters until the MS determines that the first GA-RRC PDU message using the new parameters has been received.

8a.7.2.3 Reception of GA-RRC MODIFY CHANNEL ACK (PS domain) by GANC

On reception of the GA-RRC MODIFY CHANNEL ACK message indicating the PS domain, the GANC shall configure itself for transmission of GA-RRC PDU messages to the MS using the new parameter values for the successfully modified PTC(s). The GANC shall be able to receive GA-RRC PDU messages with the old parameters until the GANC determines that the first GA-RRC PDU message using the new parameters has been received.

8a.8 Transport channel deactivation

8a.8.1 Transport channel deactivation request by MS

If the MS needs to deactivate one or more transport channels for a particular domain, it shall send the GA-RRC DEACTIVATE CHANNEL REQUEST message to the GANC and start timer TU5002 for the domain. The MS shall include the IE "CN Domain Identity" and the IE "GA-RRC Cause". The GA-RRC Cause value shall be one of the following:

#0: normal release (e.g., due to inactivity timer timeout)

#115: unspecified failure

Figure 8a.8.1 Transport channel deactivation request by MS

8a.8.2 Reception of GA-RRC DEACTIVATE CHANNEL REQUEST by GANC

When the GANC receives the GA-RRC DEACTIVATE CHANNEL REQUEST message, it shall request the selected CN domain to release the identified RABs associated with the MS. The GANC selects the CN domain based on the value of the received IE "CN Domain Identity". Note that the GANC may also request the selected CN domain to release the Iu connection for the MS in this case, based on local policy settings.

8a.8.3 Initiation of transport channel deactivation by GANC

The GANC normally initiates this procedure when it receives the RAB Assignment message from the CN indicating RAB release; however, the GANC may also initiate this procedure under certain failure conditions.

Figure 8a.8.3 Transport channel deactivation, normal flow

One or more circuit or packet transport channels may be deactivated using a single instance of the channel deactivation procedure; however, it is not possible to deactivate both circuit and packet transport channels using a single instance of the channel deactivation procedure.

The GA-RRC DEACTIVATE CHANNEL message includes the IE "GA-RRC Cause" with value as follows:

#0: normal event, e.g. deactivate due to RAB release request from CN

#115: unspecified failure

#10: relocation cancelled (e.g., the handover procedure is stopped because the call has been cleared)

8a.8.4 Reception of GA-RRC DEACTIVATE CHANNEL by MS

When the MS receives the GA-RRC DEACTIVATE CHANNEL message, it shall:

– deactivate the CTC(s) or PTC(s) identified in the IE "RAB ID List";

– send a GA-RRC DEACTIVATE CHANNEL COMPLETE message to the GANC.

8a.8.5 Failure cases

8a.8.5.1 Timer TU5002 expiry

If timer TU5002 expires in the MS, the MS shall release the associated transport channel(s).

8a.9 PS domain user plane data transfer

When the corresponding GA-RRC PTC has been activated, both the MS and the GANC can transfer PS domain user data using the GA-RRC PDU message as illustrated in the following figure:

Figure 8a.9.1 GA-RRC PS domain user data transfer

8a.9.1 MS initiates uplink PS domain user plane data transfer

Assuming that the GA-RRC PTC associated with the identified RAB has been activated as specified in sub-clause 8a.4.2, the MS is able to immediately forward any uplink PS domain user data packets for the RAB to the GANC using the PTC. Upon request from the upper layers to transfer an uplink PS domain user data packet associated with a RAB to the GANC, the PS domain GA-RRC sublayer entity in the MS shall restart the TU4001 timer for the PTC, encapsulate the complete PS domain user data packet within a GA-RRC PDU message, and send the GA-RRC PDU message to the GANC using the associated GA-RRC PTC.

If sequencing has been activated for the PTC (i.e., Delivery Order is requested in the IE "RAB Configuration" associated with the PTC), the MS shall include GA-RRC PDU sequence number information in the GA-RRC PDU message sent to the GANC using the PTC. The GA-RRC PDU sequence number information handling is specified in sub-clause 11.1.3b.2.

Note: The GTP-U G-PDU messages from the CN may include GTP-U sequence number information even though Delivery Order is not requested in the RAB Assignment (e.g., the GGSN implementation may always include GTP-U sequence number information). However, GTP-U messages from the GANC to the CN may not include sequence number information in this case (i.e., even though sequence number information is included from CN to GANC).

8a.9.2 Processing of the received GA-RRC PDU message by the GANC

Upon receiving the GA-RRC PDU message from the MS, the GANC shall relay the GA-RRC PDU payload within a GTP-U G-PDU message to the SGSN via the Iu-ps interface using the GTP-U protocol as defined in [53].

Note that all uplink GA-RRC PDU messages sent by the MS terminate at the GANC.

8a.9.3 GANC initiates downlink PS domain user plane data transfer

Assuming that the GA-RRC PTC associated with the identified RAB has been activated as specified in sub-clause 8a.4.2, the GANC is able to immediately forward any downlink PS domain user data packets for the RAB to the MS using the PTC. Upon receiving a downlink GTP-U G-PDU message for the MS from the CN, the GANC shall relay the GTP-U G-PDU payload within a GA-RRC PDU message to the MS using the associated GA-RRC PTC.

8a.9.4 Processing of the received GA-RRC PDU message by the MS

Upon receiving the GA-RRC PDU message from the GANC, the MS shall restart the TU4001 timer for the PTC, extract the received PS domain user data packet and forward the contents to the upper layers in the MS via the PDCP SAP as per standard UMTS.

If sequencing has been activated for the PTC, the MS shall increment the expected downlink GA-RRC PDU sequence number for each GA-RRC PDU message received from the GANC using the PTC.

Note that all downlink GA-RRC PDU messages received by the MS are sent from the GANC.

8a.9.5 Abnormal Cases

8a.9.5.1 TU4001 timer expiry

If timer TU4001 expires, the MS shall request deactivation of the PTC as specified in sub-clause 8a.8.1.

8a.9.5.2 GANC receives a GA-RRC PDU message while the GA-RRC PTC activation procedure is in progress

Upon receiving an uplink GA-RRC PDU message while the GA-RRC PTC activation procedure for the PTC is in progress, the GANC will process the request as if the GA-RRC PTC was active.

8a.9.5.3 GANC receives a GA-RRC PDU message and the GA-RRC PTC is not active

Upon receiving an uplink GA-RRC PDU message that is associated with a GA-RRC PTC that does not exist, the GANC shall discard the message and initate PTC deactivation as defined in sub-clause 8a.8.

8a.9.5.4 Handling of out-of-sequence packets

Packets received out-of-sequence by the MS shall be processed as described in sub-clause 11.1.3b.2.

8a.9.5.5 MS receives a GA-RRC PDU message while the GA-RRC PTC activation procedure is in progress

Upon receiving a downlink GA-RRC PDU message before sending the response to a received PTC activation request, the MS shall queue the received GA-RRC PDU message and process the message immediately after completing the PTC activation.

8a.9.5.6 Uplink PS domain user data transfer failed due to lower layer failure

If a lower layer failure is detected while attempting to send an uplink PS domain user data packet, the MS shall declare the procedure as failed and send the corresponding indication to upper layers.

8a.10 Handover to GAN Iu mode

The handover to GAN Iu mode procedure is applicable when the MS is in the GA-RC-REGISTERED state.

The preparation phase of the handover to GAN Iu mode procedure is normally initiated when the GANC sends the GA-RRC RELOCATION REQUEST message to the MS, as illustrated in Figure 8a.10.1.

The exception is when the GANC receives a Relocation Request message that does not include the IMSI parameter from a MSC. This exception case is described in sub-clause 8a.10.5.

Figure 8a.10.1: Handover to GAN Iu mode, successful case

8a.10.1 Reception of GA-RRC RELOCATION REQUEST by the MS

The GA-RRC RELOCATION REQUEST message contains the IE "CN Domains to Handover" indicating the CS domain, the PS domain or both CS and PS domains. If the CS domain or both CS and PS domains is indicated, the message includes the IE "CTC Activation List". If the PS domain or both CS and PS domains is indicated, the message includes the IE "PTC Activation List".

The MS shall act on the received GA-RRC RELOCATION REQUEST message containing the IE "CTC Activation List" as follows:

– for each CTC specified in the IE "CTC Activation List":

– store the RAB ID;

– if the IE "RAB Configuration" indicates that the CTC is for AMR or AMR-WB speech, use the format specified in Annex A.1 and Annex D to code and decode the RTP packets;

– if the IE "RAB Configuration" indicates that the CTC is for circuit switched data, use the format specified in Annex A.2 to code and decode the RTP packets;

– configure the uplink RTP packets to be transmitted to the UDP port and IP address identified by the IE "RTP UDP Port" and the IE "GANC IP address", respectively;

– use the Payload Type included in the IE "Payload Type" for the PT field in the RTP header for the RTP packets;

– if received, use the configuration included in the IE "Multi-rate Configuration 2" for the circuit transport channel that is for AMR or AMR-WB speech;

– if received, pass the contents of the NAS Synchronisation Indicator to upper layers.

The MS shall act on the received GA-RRC RELOCATION REQUEST message containing the IE "PTC Activation List" as follows:

– for each PTC specified in the IE "PTC Activation List":

– store the RAB ID;

– allocate local PTC resources based on the values in the IE "RAB Configuration";

– use the TEID value included in the IE "GANC TEID" for the TEID field in the GA-RRC PDU messages to be sent to the GANC;

– use the TEID value included in the IE "MS TEID" to verify the TEID field in the GA-RRC PDU messages to be received from the GANC;

– configure the uplink GA-RRC PDU messages to be transmitted to the UDP port and IP address identified by the IE "GANC UDP Port" and the IE "GANC IP address", respectively.

On completing the above procedures, the MS shall:

– transmit a GA-RRC RELOCATION REQUEST ACK message including the IE "CN Domains to Handover" with value the same as received in the GA-RRC RELOCATION REQUEST message. If the CS domain or both CS and PS domains is indicated, the message shall include the IE "CTC Activation Ack List". If the PS domain or both CS and PS domains is indicated, the message shall include the IE "PTC Activation Ack List".

– For each CTC specified in the IE "CTC Activation Ack List" (if included):

– include the IE "RAB ID" for the CTC with the same value as received in the GA-RRC RELOCATION REQUEST message in the IE "RAB ID";

– include the IE "GA-RRC Cause" indicating either success (i.e., value ‘0’) or a failure cause value;

– for each CTC that is successfully configured (i.e., GA-RRC Cause value is ‘0’):

– include the allocated UDP port number in the IE "RTP UDP Port" for the downlink RTP packets to be sent from the GANC to the MS;

– include the selected RTP sample size, to be used for uplink and downlink RTP packets, in the IE "Sample Size";

– include the Payload Type in the IE "Payload Type";

– if the IE "RTCP UDP Port" was received in the GA-RRC RELOCATION REQUEST message and the MS is capable of supporting RTCP, activate the uplink RTCP stream and include the IE "RTCP UDP Port" for the downlink RTCP packets to be sent from the GANC to the MS.

– For each PTC specified in the IE "PTC Activation Ack List" (if included):

– include the IE "RAB ID" for the PTC with the same value as received in the GA-RRC RELOCATION REQUEST message in the IE "RAB ID";

– include the IE "GA-RRC Cause" indicating either success (i.e., value ‘0’) or a failure cause value;

– for each PTC that is successfully configured (i.e., GA-RRC Cause value is ‘0’):

– include the allocated UDP port number in the IE "MS UDP Port" for the downlink GA-RRC PDU messages to be sent from the GANC to the MS.

After transmitting the GA-RRC RELOCATION REQUEST ACK message to the GANC, the GA-RRC sub-layer entity (if only one of CS and PS domains is subject to handover) or entities (if both CS and PS domains are subject to handover) in the MS transitions to the GA-RRC CONNECTED state.

8a.10.2 Reception of GA-RRC RELOCATION REQUEST ACK by the GANC

On reception of the GA-RRC RELOCATION REQUEST ACK message, the GANC shall do the following:

– If the IE "CN Domains to Handover" indicates either the CS domain or both domains, the GANC shall configure itself for transmission of RTP packets to the "RTP UDP Port" indicated in the message and RTCP packets to the "RTCP UDP Port" indicated in the message (if included) for each successfully activated CTC.

– If the IE "CN Domains to Handover" indicates either the PS domain or both domains, the GANC shall configure itself for transmission of GA-RRC PDU messages to the "MS UDP Port" indicated in the message for each successfully activated PTC.

– The GANC then continues with the relocation preparation process with the CN.

8a.10.3 Normal execution

The normal execution phase of the handover to GAN Iu mode procedure is initiated when the source radio access technology (e.g. GERAN or UTRAN) orders the MS to handover (GERAN) or relocate (UTRAN) to GAN Iu mode.

– The exception is when the GANC receives a Relocation Request message that does not include the IMSI parameter from a MSC. This exception case is described in sub-clause 8a.10.5.

The execution procedure is applicable when the MS is in the GA-RC-REGISTERED state provided the conditions described in Annex C.2: "(Source-RAT) Measurement Report for Handover and Cell Change Order to GAN Iu mode" are met.

The handover order in GERAN is sent via the INTER SYSTEM TO UTRAN HANDOVER COMMAND message which contains a HANDOVER TO UTRAN message. The handover order in UTRAN is sent via the PHYSICAL CHANNEL RECONFIGURATION message. If the UARFCN and PSC parameters included in either of the HANDOVER TO UTRAN message or the PHYSICAL CHANNEL RECONFIGURATION message (both are specified in [40]) match those of the GAN Iu mode cell, the MS shall:

– send a GA-RRC RELOCATION COMPLETE message to the GANC;

– in the case of PS domain handover, start timer TU4001 for each of the successfully activated PTC(s);

– switch the serving RR to GAN Iu mode; i.e. attach the GA-RRC sub-layer entities to the RR-SAP.

8a.10.4 Reception of GA-RRC RELOCATION COMPLETE by the GANC

On reception of the GA-RRC RELOCATION COMPLETE message, the GANC shall indicate handover detection and completion to the CN.

8a.10.5 Exception case: No IMSI in CS domain Relocation Request

The following exception procedures are applicable if the handover is for the CS domain only and the GANC did not receive the IMSI parameter in the Relocation Request message from the MSC. The procedure is illustrated in Figure 8a.10.5.

Figure 8a.10.5: Handover to GAN Iu mode, exception case

In this case, the MS will not receive the GA-RRC RELOCATION REQUEST message from the GANC before receiving the handover order from the source radio access technology, as described in sub-clause 8a.10.3.

If the UARFCN and PSC parameters included in either of the HANDOVER TO UTRAN message or the PHYSICAL CHANNEL RECONFIGURATION message match those of the GAN Iu mode cell, the GA-RRC CS domain sub-layer entity in the MS shall:

– if the handover is not for a signalling channel only, the MS shall:

– send a GA-RRC RELOCATION ACCESS message to the network including the complete UTRAN RRC handover command message in the IE "UTRAN RRC Message" and enter the GA-RRC-CONNECTED state for the CS domain (Note: The MS shall extract the UTRAN RRC Handover to UTRAN Command message from the GERAN RRC Handover to UTRAN Command IE that is present in the GERAN RRC Inter System to UTRAN Command message);

– start timer TU3920;

– otherwise, the MS shall:

– immediately send a GA-RRC RELOCATION COMPLETE message to the GANC;

– enter the GA-RRC-CONNECTED state for the CS domain;

– switch the serving RR to GAN Iu mode; i.e. attach the GA-RRC sub-layer entities to the RR-SAP.

On receipt of the GA-RRC RELOCATION ACCESS message, the GANC shall initiate CTC activation as specified in sub-clause 8a.4.1.

On receipt of the GA-RRC ACTIVATE CHANNEL COMPLETE message, the MS shall:

– stop timer TU3920;

– send a GA-RRC RELOCATION COMPLETE message to the GANC;

– switch to GAN Iu mode; i.e. attach the GA-RRC sub-layer entities to the RR-SAP.

On reception of the GA-RRC RELOCATION COMPLETE message, the GANC shall indicate handover detection and completion to the CN.

If the CTC activation procedure fails or the timer TU3920 expires before CTC activation is completed, the MS shall:

– terminate the procedure including release of the associated GA-RRC resources;

– resume the connection in the source radio access technology used before the handover;

– indicate the failure to the source radio access technology.

8a.11 Handover from GAN Iu mode

The purpose of this procedure is to transfer, upon request from the MS (and under the control of the GANC), a connection between the MS and the GANC to another radio access technology (e.g. GERAN or UTRAN).

The procedure is applicable when one or both of the GA-RRC sub-layer entities in the MS are in GA-RRC-CONNECTED state.

Figure 8a.11.1: Handover from GAN Iu mode, successful case

Figure 8a.11.2: Handover from GAN Iu mode, failure case

8a.11.1 Initiation

The procedure may be initiated by the MS based on:

– local measurements of GAN coverage signal quality;

– reception of a GA-RRC UPLINK QUALITY INDICATION message indicating poor uplink quality in the UL Quality Indication IE; If the UL Quality Indication IE indicates "Network problem" a handover out to GERAN or UTRAN should be attempted. In case the UL Quality Indication information element shows "Radio problem" or "Undetermined problem" a search for a new access point should be done before the handover out is initiated;

– reception of RTCP packets indicating poor uplink quality (i.e., in the CS case);

– excessive loss or delay in the received RTP packets (i.e., in the CS case).

When the MS decides to trigger the handover from GAN Iu mode, it shall:

– send a GA-RRC RELOCATION INFORMATION message to the GANC including a list of candidate/ target cell identifiers ranked in order of preference which is the most recent list available from the other radio access technology (e.g. GSM RR) and including the received signal strength for each identified GERAN or UTRAN cell. The MS may include GERAN cells, UTRAN cells or both.

8a.11.2 Reception of GA-RRC RELOCATION INFORMATION by the GANC

The GANC should signal the need for handover to the CN.

If the CN grants the handover request, the GANC should send a GA-RRC RELOCATION COMMAND message to the MS.

The GA-RRC RELOCATION COMMAND message should only indicate a target cell which was reported by the MS in the GA-RRC RELOCATION INFORMATION message.

8a.11.3 Reception of GA-RRC RELOCATION COMMAND by the MS

The MS shall:

– suspend all NAS layer signalling transmissions;

– start the connection establishment to the target radio access technology (e.g. GERAN or UTRAN) by using the contents of the IE "UTRAN RRC Message". This message carries information about the candidate/ target cell identifier and radio parameters relevant for the target radio access technology.

A MS with simultaneously active PS and CS sessions in GAN Iu mode shall follow the procedure as outlined in [40] when it switches to the target cell.

NOTE: The requirements concerning the establishment of the radio connection towards the target radio access technology (e.g. GERAN) and the signalling procedure are outside of the scope of this specification.

8a.11.4 Successful completion of the handover from GAN Iu mode

Upon successfully completing the handover from GAN Iu mode, the GANC should:

– release all radio resources associated with the GAN connection.

Upon successfully completing the handover from GAN Iu mode, the MS shall:

– switch to the target radio access technology (e.g. GERAN or UTRAN) mode; i.e. detach the GA-RRC sub-layer entities from the RR-SAP;

– enter the GA-RC-REGISTERED state (but in GERAN/UTRAN mode).

NOTE: The release of the GAN radio resources is initiated from the target RAT. The MS may deregister from the GANC (as defined in sub-clause 6.4) after successfully completing the handover. If the MS chooses to deregister from the GANC, it may do so either immediately after successfully completing the handover or after sending the GA-RRC RELEASE COMPLETE message to the GANC in response to the GA-RRC RELEASE message from the GANC.

8a.11.5 MS fails to complete requested handover

If the MS does not succeed in establishing a connection to the target radio access technology, the MS shall:

– revert back to the GAN Iu mode configuration;

– return a GA-RRC RELOCATION FAILURE message to the GANC and resume normal operation as if the GA-RRC RELOCATION COMMAND message has not been received. The GA-RRC Cause value shall be set to value ‘Relocation Failure In Target CN/RNC Or Target System’ as specified in [52].

8a.11.6 Reception of GA-RRC RELOCATION FAILURE by the GANC

The GANC may initiate the release of resources in the target radio access technology.

8a.11.7 Abnormal Cases

If the GA-RRC RELOCATION COMMAND message instructs the MS:

– to perform a non-supported scenario, or

– to use a non-supported configuration,

the MS shall return a GA-RRC RELOCATION FAILURE message with GA-RRC Cause value set to ‘Unspecified failure’ or other appropriate cause as defined in [52] and resume normal operation as if the GA-RRC RELOCATION COMMAND message has not been received.