8.10 Packet Switched Handover procedure

3GPP44.060General Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocolRelease 17TS

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

8.10.1 General

This procedure is only applicable in packet transfer mode when both the mobile station and the network support PS handover. The support of PS handover procedures requires the support of PFC procedures in both the network and the mobile station. In packet transfer mode, a mobile station that supports PS handover may receive a PS HANDOVER COMMAND message from the BSS indicating the resources to be used in the new cell.

The support of the PS handover procedures is optional for the mobile station and the network and is indicated in the MS Radio Access Capability IE. For an E-UTRAN capable multi-RAT mobile station, the support of PS handover to E-UTRAN is indicated in the "GERAN to E-UTRAN support in GERAN packet transfer mode" field within the MS Radio Access Capability IE (see 3GPP TS 24.008). A mobile station supporting the PS handover procedures shall also support the extended RLC/MAC control message segmentation as defined in 9.1.12a.

8.10.2 Neighbour Cell System Information Distribution

For the case of PS handover from A/Gb mode to A/Gb mode the network shall send the mobile station PACKET NEIGHBOUR CELL DATA messages containing PSI messages (PBCCH allocated in new cell) or SI messages (PBCCH not allocated in new cell) corresponding to the new cell prior to sending it the PS HANDOVER COMMAND message directing it to that cell. PACKET NEIGHBOUR CELL DATA messages are received on PACCH as described in sub-clause 8.8.1. The minimum set of SI and PSI messages to be sent in PACKET NEIGHBOUR CELL DATA messages is as follows:

– If PBCCH is not allocated in the new cell then SI3, SI1 (if present in the new cell) and SI13 shall be sent.

– If PBCCH is allocated in the new cell then PSI1, a consistent set of PSI2 messages and PSI14 shall be sent.

For the case of PS handover from Iu mode to A/Gb mode or from GAN mode to A/Gb mode or from E-UTRAN to A/Gb mode the network shall send the mobile station the same set of PSI messages or SI messages corresponding to the new cell as for the case of PS handover from A/Gb mode to A/Gb mode. In this case the network sends the mobile station the system information corresponding to the new cell within the Handover from UTRAN Command message as described in 3GPP TS 25.331 for the case of PS handover from Iu mode to A/Gb mode or within the GA-PSR HANDOVER COMMAND message as described in 3GPP TS 44.318 [42] for the case of PS handover from GAN mode to A/Gb mode or within the MobilityFromEUTRACommand message as described in 3GPP TS 36.331 [45] for the case of PS handover from E-UTRAN to A/Gb mode.

For the case of PS handover from A/Gb mode to Iu mode or from A/Gb mode to GAN mode or from A/Gb mode to E-UTRAN, system information corresponding to the new cell is sent to the mobile station in the new cell as described in 3GPP TS 25.331 for PS handover to Iu mode or as described in 3GPP TS 44.318 [42] for PS handover to GAN mode or as described in 3GPP TS 36.331 [45] for PS handover to E-UTRAN.

8.10.3 PS Handover at the network side

8.10.3.1 Initiation of PS Handover Procedure

The source BSS may initiate the PS handover procedure as a result of various trigger conditions such as, but not restricted to, the following:

– Upon receiving a measurement report or a PACKET CELL CHANGE NOTIFICATION message from a mobile station operating in A/Gb mode.

– Upon determining that resource limitations exist for the serving cell.

– Upon receiving the Service UTRAN CCO IE from the SGSN indicating that a mobile station operating in A/Gb mode would be better served in a cell supporting a different RAT.

If the mobile station is not already in NC2 then the source BSS may order the mobile station to enter NC2 before initiating the PS handover procedure. For the normal case of PS handover the target RNC/BSS/GANC/eNB receives a network request to allocate resources required to perform a PS handover. For the optimized case of PS handover (applicable only for A/Gb mode to A/Gb mode PS handover – see 3GPP TS 43.129) an SGSN request for the BSS to allocate resources is not required as the resources required to perform a PS handover are allocated autonomously by the BSS (i.e. without SGSN involvement).

8.10.3.2 A/Gb to A/Gb PS Handover

For both the normal and optimized cases of PS handover from A/Gb mode to A/Gb mode the (source) BSS shall impose the following restrictions on RLC/MAC control plane corresponding to a mobile station for which the PS handover procedure is ongoing:

– All mobile station requests to establish new uplink TBFs shall be ignored and no new downlink TBFs shall be established.

– The PS HANDOVER COMMAND message shall be sent using extended RLC/MAC control message segmentation (see sub-clause 9.1.12a) if three or more RLC/MAC control blocks are required to send the complete message.

After sending the PS HANDOVER COMMAND to the MS, the source BSS shall continue to schedule opportunities for the mobile station to transmit an RLC/MAC control message, either by means of an existing uplink TBF, or by means of polling using an existing downlink TBF, for a period of time sufficiently long to allow the mobile station to transmit a PACKET CELL CHANGE FAILURE message (should a PS handover failure occur). During this period, the BSS may allocate fewer transmission opportunities than would otherwise be required according to the QoS requirements of the ongoing PFCs. No TBFs shall be released during this period except on receipt of a DELETE-BSS-PFC PDU from the SGSN.

For both the normal and optimized cases of PS handover from A/Gb mode to A/Gb mode the (target) BSS creates a complete PS HANDOVER COMMAND message that is sent to the mobile station in the old cell:

For the normal case of PS handover the source BSS shall send the Page Mode, Global TFI and Container ID information elements to the target BSS which uses them to create a complete PS HANDOVER COMMAND message (see sub-clause 11.2.43).

For the normal case of PS handover the source BSS receives a complete PS HANDOVER COMMAND message from the target BSS (passed through the SGSN) and then sends it to the mobile station. For the optimized case of PS handover the BSS creates a complete PS HANDOVER COMMAND message and sends it directly to the mobile station.

If the PS HANDOVER COMMAND indicates RLC reset for a TBF allocated in the new cell corresponding to the PFC(s) receiving a PS handover, the target BSS shall initialize one or more new RLC entities to support that TBF. Otherwise, the TBF allocated in the new cell shall be supported using the same set of RLC entities used to support the TBF in the old cell corresponding to the same PFC(s) (i.e. the RLC state machine is maintained across PS handover).

The PS HANDOVER COMMAND message created by the target BSS shall always allocate resources for at least one uplink TBF to ensure that the mobile station can send PS HANDOVER ACCESS messages (if required) and one or more RLC data blocks in the new cell. When only one uplink TBF is allocated by the PS HANDOVER COMMAND message and does not correspond to a PFC, RLC acknowledged mode shall be used.

The PS HANDOVER COMMAND message shall include the PS Handover Radio Resources Info IE if the allocated resources are not required to support any of the features Downlink Dual Carrier, Downlink Multi Carrier, EGPRS2, Fast Ack/Nack Reporting or RTTI configurations. If the allocated resources are required to support Downlink Multi Carrier the network shall include the PS Handover Radio Resources 3 IE in the PS HANDOVER COMMAND message. Otherwise, the network shall include the PS Handover Radio Resources 2 Info IE in the PS HANDOVER COMMAND message.

The PS HANDOVER COMMAND message created by the target BSS shall indicate the PS Handover type with the synchronization indication field, i.e. non-synchronized, synchronized or pre-synchronized PS handover.

The PS HANDOVER COMMAND shall contain the PFI for each TBF being set up if and only if both the network and the mobile station support multiple TBFs. A mobile station which receives a PS HANDOVER COMMAND and which does not support multiple TBFs shall ignore any PFI value(s) received in the PS HANDOVER COMMAND.The target BSS expects one or more PS HANDOVER ACCESS messages from the mobile station whenever Handover Reference information is included in the PS HANDOVER COMMAND message. Handover Reference information shall always be included whenever non-synchronized PS handover is used.

Depending on the type of handover the target BSS shall proceed as follows:

– In case of a synchronized or pre-synchronized PS handover the target BSS shall enable the reception of RLC data blocks on all uplink TBFs allocated by the PS HANDOVER COMMAND message.

– In case of a non-synchronized PS handover the target BSS shall, upon reception of the first PS HANDOVER ACCESS message containing the expected Handover Reference value, send the Packet Physical Information message to the mobile station and then enable the reception of RLC data blocks on all uplink TBFs allocated by the PS HANDOVER COMMAND message.

– The BSS should schedule USFs on at least one uplink TBF in the target cell to minimize the delay incurred by the mobile station waiting for a USF in the target cell.

The target BSS considers the PS handover procedure to be successfully completed upon receiving the first correct uplink RLC block on any of the uplink TBFs allocated to the mobile station in the PS HANDOVER COMMAND message.

If the target BSS supports blind transmission it may begin transmitting downlink data that becomes available prior to determining that the PS handover procedure has been successfully completed. Otherwise, it may discard downlink data that becomes available prior to determining that the PS handover procedure has been successfully completed.

If the target BSS supports network sharing in the target cell and the MS Radio Access Capabilities IE (see 3GPP TS 24.008) indicates a network sharing supporting MS, it shall include in the PS HANDOVER COMMAND message the Selected PLMN Index field (see sub-clause 10.4.27) corresponding to the PLMN received in the Target Cell Identifier IE in the PS HANDOVER REQUEST message (see 3GPP TS 48.018).

8.10.3.3 GERAN A/Gb to Iu/E-UTRAN PS Handover

For the case of PS handover from A/Gb mode to Iu mode or E-UTRAN the source BSS proceeds as described above for the normal case of A/Gb mode to A/Gb mode PS handover except for the following:

– The source BSS shall create a complete PS HANDOVER COMMAND message using local values for the Page Mode, Global TFI and Container ID information elements and therefore shall not send these information elements to the target RNC or eNB.

– For the case of PS handover to Iu mode, the source BSS receives a complete Handover to UTRAN Command message from the target RNC (passed through the SGSN) and sends it to the mobile station within a PS HANDOVER COMMAND message.

– For the case of PS handover to E-UTRAN, the source BSS receives a complete (RRC E-UTRA) HandoverCommand message as defined in 3GPP TS 36.331 [45] from the target eNB (passed through the MME and SGSN) and sends it to the mobile station within a PS HANDOVER COMMAND message.

– The source BSS shall not send the mobile station unsolicited PACKET NEIGHBOUR CELL DATA messages in the old cell as system information corresponding to the new cell is sent to the mobile station in the new cell as described in 3GPP TS 25.331 (for PS handover to Iu mode) or as described in 3GPP TS 36.331 (for PS handover to E-UTRAN).

8.10.3.4 Iu/E-UTRAN to GERAN A/Gb PS Handover

For the case of PS handover from Iu mode or E-UTRAN to A/Gb mode the target BSS proceeds as described above for the normal case of A/Gb mode to A/Gb mode PS handover except that a complete PS HANDOVER COMMAND message is created by the target BSS using local values for the Page Mode, Global TFI and Container ID information elements (i.e. they are not passed to the target BSS from the source RNC or eNB) and the PS HANDOVER COMMAND message shall always indicate RLC reset and non-synchronized PS handover. The PS HANDOVER COMMAND message is sent to the MS as part of the MobilityFromEUTRACommand in E-UTRAN as specified in 3GPP TS 36.331 [45].

8.10.3.5 A/Gb to GAN PS Handover

When the BSS and the mobile station support PS handover to GAN mode the normal case of A/Gb mode to A/Gb mode PS handover is followed as described in sub-clause 8.10.3.2 except for the following:

– The target GANC shall only provide values for the mandatory fields within the PS Handover Radio Resources IE included within the PS HANDOVER COMMAND message it sends back to the source BSS.

– The source BSS will not send the mobile station system information corresponding to the target GAN cell prior to sending it a PS HANDOVER COMMAND message (i.e. the mobile station acquires the system information required for the target GAN cell during GAN registration – see 3GPP TS 44.318 [42]).

8.10.3.6 GAN to A/Gb PS Handover

For the case of PS handover from GAN mode to A/Gb mode the source GANC proceeds as described in 3GPP TS 44.318 [42]. The target BSS proceeds as described in sub-clause 8.10.3.2 for the normal case of A/Gb mode to A/Gb mode PS handover except that a complete PS HANDOVER COMMAND message is created by the target BSS using local values for the Page Mode, Global TFI and Container ID information elements (i.e. they are not passed to the target BSS from the source GANC) and the PS HANDOVER COMMAND message shall always indicate RLC reset for each PFC and non-synchronized PS handover.

8.10.4 PS Handover at the mobile station side

8.10.4.1 A/Gb to A/Gb PS Handover

Upon reception of the PS HANDOVER COMMAND message for PS handover from A/Gb mode to A/Gb mode, the mobile station shall proceed as follows:

– If an RLC/MAC control block containing a part of the PS HANDOVER COMMAND message contains a valid RRBP field or a polling response is outstanding the mobile station shall send a corresponding PACKET CONTROL ACKNOWLEDGMENT message (in the specified uplink radio block) prior to switching to the new cell.

– RLC/MAC control plane signalling shall be suspended except for the signalling needed to complete the PS handover procedure or to signal a failure of the PS handover procedure.

– The mobile station shall suspend the uplink transmission of user plane data.

– Each outstanding request for establishment or reconfiguration of an uplink TBF in the old cell shall be aborted and the corresponding instance of T3168 shall be stopped.

– All timers related to the RLC contexts in the old cell keep running.

– Timers T3180 and T3190 related to the ongoing TBFs in the old cell and which are currently running shall be re-started.

– If the timer T3192 related to a TBF in the old cell expires, the mobile station shall consider the corresponding TBF that was ongoing in the old cell as implicitly released.

– The mobile station shall start timer T3218, move to the new cell and perform the physical channel establishment as described in sub-clause 8.10.4.4.

– The mobile station may receive downlink RLC data blocks in the new cell prior to determining that the PS handover has been successfully completed if the target BSS uses blind transmission. If this occurs the mobile station shall forward the corresponding user data to upper layers if the PS HANDOVER COMMAND message did not include the NAS Container for PS Handover IE. Otherwise, the mobile station may either discard the received RLC data blocks or buffer them until the successful completion of the PS handover procedure at which point the corresponding user data shall be deciphered by the upper layers based on information contained within the NAS Container for PS Handover IE.

NOTE: It is expected that PS Handover procedure will be completed successfully or terminated before the expiry of T3180 or T3190 and therefore that the MS will not release any TBFs due to the expiry of T3180 or T3190 during the PS Handover procedure.The mobile station considers the PS handover procedure to be successfully completed in the following cases:

– Upon receiving a Packet Physical Information message in the new cell in case of a non-synchronized PS handover (see sub-clause 8.10.4.4.3).

– Upon detecting the first USF for any uplink TBF assigned to the MS in the new cell in case of a synchronized and pre-synchronized PS handover (see subclause 8.10.4.4.1 and 8.10.4.4.2).

If the mobile station is waiting for the Packet Physical Information message when it receives a downlink RLC data block in which a valid polling indication is provided, it shall ignore the polling indication.

Upon successfully completing the PS handover procedure the mobile station shall proceed as follows:

– Stop T3216 (if running), consider all TBFs that were ongoing in the old cell as implicitly released and if the NAS Container for PS Handover IE was included in the PS HANDOVER COMMAND message it shall be sent to upper layers.

– If the PS HANDOVER COMMAND indicates RLC reset the mobile station shall initialize new RLC entities to support the allocated TBFs. Otherwise, the TBFs allocated in the new cell shall be supported using the same RLC entities used to support the TBFs in the old cell corresponding to the same PFCs (i.e. the RLC state machines are maintained across PS handover).

– The mobile station shall resume the uplink transmission of user plane data.

– The mobile station shall trigger a cell update or other GMM specific procedures, as appropriate according to the GMM requirements (see 3GPP TS 24.008).

8.10.4.2 A/Gb to Iu/E-UTRAN PS Handover

Upon receiving a PS HANDOVER COMMAND message for PS handover from GERAN A/Gb mode to Iu mode or E-UTRAN, the mobile station shall act on the message if it is able to perform PS handover based on the content of the received message. If the PS HANDOVER COMMAND message is acted on the mobile station shall start the PS handover procedure and proceed as described above for the case of A/Gb mode to A/Gb mode PS handover while in the old cell. Upon moving to the new cell the mobile station shall proceed as described in 3GPP TS 25.331 for handover to Iu mode or as described in 3GPP TS 36.331 for handover to E-UTRAN. Upon successfully completing the PS handover procedure all TBFs that were ongoing in the old cell shall be considered as implicitly released.

8.10.4.3 Iu/E-UTRAN to A/Gb PS Handover

Upon receiving a Handover from UTRAN Command message for PS handover from Iu mode to A/Gb mode or a MobilityFromEUTRACommand message for PS handover from E-UTRAN to A/Gb mode, the mobile station shall act on the message if all of the following conditions are satisfied:

– It is able to perform PS handover based on the content of the received message.

– The Handover from UTRAN Command or MobilityFromEUTRACommand message contains the minimum set of PSI or SI messages required for mobile station to operate in the new cell (see sub-clause 8.10.4.1.).

– The PS HANDOVER COMMAND message carried within the Handover from UTRAN Command or MobilityFromEUTRACommand message provides resources for at least one uplink TBF in the new cell.

If the Handover from UTRAN Command or MobilityFromEUTRACommand message is acted on the mobile station shall start the PS handover procedure and proceed as follows:

– The mobile station shall act as described in 3GPP TS 25.331 (for handover from Iu mode) or as described in 3GPP TS 36.331 (for handover from E-UTRAN) prior to switching to the new cell except for the following:

– It shall ignore the value of the Page Mode, Global TFI and Container ID information elements included in the PS HANDOVER COMMAND message carried within the Handover from UTRAN Command or MobilityFromEUTRACommand message.

– After switching to the new cell the mobile station shall proceed as described above for the case of A/Gb mode to A/Gb mode PS handover except for the following:

– Upon successfully completing the PS handover procedure the mobile station shall stop T3216 (if running), consider all radio bearers that were ongoing in the old cell as implicitly released, send the NAS Container for PS Handover IE to upper layers if it was included in the PS HANDOVER COMMAND message, start an instance of T3180 corresponding to each uplink TBF allocated by the PS HANDOVER COMMAND message and start an instance of T3190 corresponding to each downlink TBF allocated by the PS HANDOVER COMMAND message.

– Upon successfully completing the PS handover procedure the mobile station shall always establish a new RLC entity for each TBF allocated by the PS HANDOVER COMMAND message.

8.10.4.4 Physical channel establishment

8.10.4.4.1 General

Three procedures are defined. The support of them is mandatory in the mobile station.

If the network requests the transmission of the PS HANDOVER ACCESS message it shall be sent with highest transmission priority using either the 8-bit or 11-bit access burst format on the PACCH associated with any uplink TBF allocated in the PS HANDOVER COMMAND message for which the mobile station detects an assigned USF value. Its content consists of the handover reference field. The burst format used shall be that specified by the ACCESS_BURST_TYPE in the system information for the target cell.

Upon detecting the first USF for any uplink TBF assigned to the MS in the new cell, the MS shall stop T3218.

8.10.4.4.2 Synchronized cell case

If the timing advance with the new cell calculated by the mobile station is not out of range, i.e. smaller than or equal to the maximum timing advance that can be coded as specified in 3GPP TS 44.004, or if the new cell does accept out of range timing advance as indicated in the PS HANDOVER COMMAND message, the mobile station acts on the message.

After having switched to the assigned channels, if the Handover Reference information is included within the PS HANDOVER COMMAND message the mobile station shall send four times the PS HANDOVER ACCESS message.

The mobile station activates the channels in sending and receiving mode. The MS may activate the channels in downlink while sending access bursts.

8.10.4.4.3 Pre-synchronized cell case

The details of the use of this procedure are described in 3GPP TS 45.010.

The mobile station activates the channels in sending and receiving mode. The MS may activate the channels in downlink while sending access bursts.

The timing advance value to be used with the new cell is:

– either the value contained in the PS HANDOVER COMMAND message if the timing advance information is included; or

– the default value for pre-synchronized handover as defined in 3GPP TS 45.010, if the timing advance information element is not included in the PS HANDOVER COMMAND message.

8.10.4.4.4 Non synchronized cell case

After having switched to the assigned channels, the mobile station shall send four times the PS HANDOVER ACCESS message. The mobile station shall start timer T3216 at the start point of the timeslot in which the PS HANDOVER ACCESS message is sent the first time on the PACCH.

The mobile station then activates the channels in receiving mode.

Upon reception of the PS HANDOVER ACCESS message containing the expected Handover Reference value, once the network has the RF characteristics that are necessary, it sends a PACKET PHYSICAL INFORMATION message to the mobile station on the PACCH.

When the mobile station receives a PACKET PHYSICAL INFORMATION message, it stops timer T3216, stops sending access bursts and activates the channels in sending and receiving mode.

8.10.4.5 A/Gb to GAN PS Handover

Upon successfully performing a GAN registration (see 3GPP TS 43.129 [43]), a mobile station in packet transfer mode may trigger a PS handover to a GAN cell by sending a Packet Cell Change Notification message (see sub-clause 8.8.3). The mobile station may send the Packet Cell Change Notification message either at the first possible transmission opportunity following GAN registration if GAN mode is preferred or when the GERAN cell becomes sufficiently degraded if GERAN/UTRAN mode is preferred. If the network and the mobile station support PS handover to GAN mode, the network may initiate the PS handover procedure. The mobile station shall then proceed as described in sub-clause 8.10.4.1 for the case of A/Gb mode to A/Gb mode PS handover except for the following:

– Since the mobile station provides an ARFCN and BSIC corresponding to a GAN cell within the PACKET CELL CHANGE NOTIFICATION message it does not expect a valid minimum set of PSI or SI messages prior to receiving a PS Handover Command message directing it to a GAN cell.

– Upon receiving a PS HANDOVER COMMAND message the MS determines that PS handover to a GAN cell has been ordered if the ARFCN and BSIC included within the message matches the corresponding values it included within the PACKET CELL CHANGE NOTIFICATION message.

– After successful PS handover to the GAN cell (see 3GPP TS 44.318 [42]) the mobile station switches to GAN mode and considers all TBFs that were ongoing in the old cell as implicitly released.

8.10.4.6 GAN to A/Gb PS Handover

Upon receiving a GA-PSR Handover Command message for PS handover from GAN mode to A/Gb mode, a mobile station that supports GAN PS handover shall act on the message as described in 3GPP TS 44.318 [42] prior to switching to the new cell. After switching to the new cell the mobile station shall proceed as described in sub-clause 8.10.4.1 for the case of A/Gb mode to A/Gb mode PS handover except for the following:

– None of the actions corresponding to TBFs in the old cell are applicable.

– Upon successful completion of the PS handover procedure the mobile station shall consider the GA-PSR Transport Channel used in the old cell as implicitly released.

– The mobile station shall always establish a new RLC entity for each TBF allocated by the PS HANDOVER COMMAND message (i.e. regardless if an intra-SGSN or an inter-SGSN PS handover was performed).

8.10.5 Abnormal Cases

8.10.5.1 MS Behaviour for A/Gb to A/Gb PS Handover

A mobile station operating in A/Gb mode shall consider the PS handover to A/Gb mode to have failed if the PS HANDOVER COMMAND message:

– contains an invalid Frequency Parameters information element; or

– contains specifying frequencies that are not all in one frequency band; or

– contains a Frequency Parameters information element specifying a frequency that is in a frequency band not supported by the mobile station; or

– does not properly specify an uplink or downlink PDCH or specifies a multislot configuration that the mobile station does not support (see 3GPP TS 45.002); or

– does not provide resources for at least one uplink TBF in the new cell; or

– would result in one or more TBFs with FANR activated and one or more TBFs with FANR not activated for that mobile station; or

– includes an inconsistent RTTI configuration assignment as per the conditions specified in sub-clause 7.1.3.6; or

– contains any other failure.

A mobile station operating in A/Gb mode shall consider the PS handover to A/Gb mode to have failed for the following reasons:

– In the synchronized cell case (see sub-clause 8.10.4.4.1), if the timing advance with the new cell calculated by the mobile station is out of range, i.e. is bigger than the maximum timing advance that can be coded as specified in 3GPP TS 44.004, and if the new cell does not accept out of range timing advance as indicated in the PS HANDOVER COMMAND message.

– If it has not stored a valid minimum set of the following of PSI or SI messages (provided via PACKET NEIGHBOUR CELL DATA messages, see sub-clause 8.8.1) required for mobile station to operate in the new cell: PSI1, a consistent set of PSI2 messages and PSI14 (if PBCCH allocated in the new cell) or SI3, SI1 (if present in the new cell) and SI13 messages (if PBCCH not allocated in the new cell).

– Timer T3218 expires while in the new cell.

– Timer T3216 expires while in the new cell.

A mobile station operating in A/Gb mode when a PS handover to A/Gb mode fails shall proceed as follows:

– If timer T3218 expired it shall return to the cell on which the PS HANDOVER COMMAND message was received.

– If timer T3216 expired it shall return to the cell on which the PS HANDOVER COMMAND message was received.

– Send a Packet Cell Change Failure message with the cause code set to "No response on target cell" if timer T3218 or T3216 expired, otherwise "PS Handover failure-others". The message shall be sent on PACCH.

– The transmission of a Packet Cell Change Failure message terminates the PS handover procedure in the mobile station and after the transmission of this message the mobile station is therefore allowed to request the establishment of additional uplink TBFs.

– After terminating the PS handover procedure the mobile station shall resume all uplink and downlink TBFs that were ongoing in the old cell prior to receiving the PS HANDOVER COMMAND message. Timers T3180 (uplink TBFs) and T3190 (downlink TBFs) corresponding to these TBFs shall be re-started.

– For each TBF that is resumed the corresponding RLC state machine shall reflect its state when the last RLC data block was transmitted for that TBF in the old cell (uplink TBFs) and the last RLC data block was received for that TBF in the old cell (downlink TBFs).

8.10.5.2 MS Behaviour for A/Gb to Iu/E-UTRAN PS Handover

A mobile station operating in A/Gb mode shall consider PS handover to Iu mode or E-UTRAN to have failed if it is unable to perform PS handover for any reason based on the content of the received PS HANDOVER COMMAND message.

A mobile station operating in A/Gb mode when a PS handover to Iu mode or E-UTRAN fails shall proceed as described above for the case where PS handover from A/Gb mode to A/Gb mode fails except that T3216 shall never be running.

8.10.5.3 MS Behaviour for Iu/E-UTRAN to A/Gb PS Handover

A mobile station operating in Iu mode or E-UTRAN shall consider PS handover to A/Gb mode to have failed for the following reasons:

– It is unable to perform PS handover for any reason based on the content of the received Handover from UTRAN Command or MobilityFromEUTRACommand message.

– The Handover from UTRAN Command or MobilityFromEUTRACommand message does not contain the minimum set of PSI or SI messages required for mobile station to operate in the new cell (see sub-clause 8.10.2).

– Timer T3218 expires while in the new cell.

– Timer T3216 expires while in the new cell.

– The PS HANDOVER COMMAND message carried within the Handover from UTRAN Command or MobilityFromEUTRACommand message does not provide resources for at least one uplink TBF in the new cell.

– The PS HANDOVER COMMAND message would result in one or more TBFs with FANR activated and one or more TBFs with FANR not activated for that mobile station.

– The PS HANDOVER COMMAND message includes an inconsistent RTTI configuration assignment as per the conditions specified in sub-clause 7.1.3.6.

A mobile station operating in Iu mode when a PS handover to A/Gb mode fails shall return to the cell it was in prior to receiving the Handover from UTRAN Command message (if T3216 or T3218 expired) and proceed as described in 3GPP TS 25.331.

A mobile station operating in E-UTRAN when a PS handover to A/Gb mode fails shall return to the cell it was in prior to receiving the MobilityFromEUTRACommand message (if T3216 or T3218 expired) and proceed as described in 3GPP TS 36.331.

8.10.5.4 BSS Behaviour for PS Handover from A/Gb

The source BSS shall terminate the PS handover procedure if any of the following events occur:

– All TBFs allocated to the mobile station in the old cell are released at any point prior to sending the PS HANDOVER COMMAND message to the mobile station.

– The source BSS receives a PACKET CELL CHANGE FAILURE message or any other RLC block from the mobile station after sending the final segment of the PS HANDOVER COMMAND message, if the network does not request acknowledgement of receipt of that segment (i.e. does not include in any segment a valid RRBP field requiring the mobile station to send a PACKET CONTROL ACKNOWLEDGEMENT message), or after the receipt of a PACKET CONTROL ACKNOWLEDGEMENT message indicating that the mobile station has received the final segment of the PS HANDOVER COMMAND message.

If the PS handover procedure is terminated for either of the above reasons, the (source) BSS shall resume all uplink and downlink TBFs that were ongoing in the old cell for that MS prior to sending the PS HANDOVER COMMAND message. For normal PS Handover the source BSS shall then indicate the PS handover failure to the SGSN. For optimized PS Handover the source BSS shall then release all resources associated with the new TBFs.

For each TBF that is resumed the corresponding RLC state machine shall reflect its state when the last RLC data block was transmitted for that TBF in the old cell (downlink TBFs) and the last RLC data block was received for that TBF in the old cell (uplink TBFs).

For both the normal and optimized cases of PS Handover, after sending the PS HANDOVER COMMAND to the MS, the source BSS shall continue to schedule transmission opportunities for the mobile station for a period of time sufficiently long to allow the mobile station to transmit a PACKET CELL CHANGE FAILURE message (should a PS handover failure occur).

For normal PS Handover, if the source BSS does not receive any RLC/MAC block from the MS and does not receive (a) DELETE-BSS-PFC PDU(s) from the SGSN for all ongoing PFCs during this time period, the source BSS shall consider radio contact with the MS to be lost and shall release all resources related to the MS and initiate the PS Handover Cancel procedure (see 3GPP TS 48.018), by sending a PS-HANDOVER-CANCEL PDU to the SGSN with cause "Radio contact lost with MS".

For optimized PS Handover, if the BSS does not receive any RLC/MAC block from the MS on any of the old TBFs and does not receive an uplink RLC data block from the MS on any of the new TBFs during this time period, the BSS shall consider the MS to be lost and therefore release all resources associated with the new TBFs and old TBFs.

8.10.5.5 BSS Behaviour for PS Handover to A/Gb

If the (target) BSS expects but does not receive any PS HANDOVER ACCESS messages from the mobile station it considers the PS handover procedure to have failed and shall release all TBFs allocated to the mobile station in the new cell.

If the (target) BSS expects but does not receive the correct Handover Reference value from the mobile station it considers the PS handover procedure to have failed and shall release all TBFs allocated to the mobile station in the new cell.

8.10.5.6 MS Behaviour for A/Gb to GAN PS Handover

Upon receiving a PS Handover Command message in the source cell, if connectivity has been lost on the corresponding GA-PSR Transport Channel the MS shall discard the PS Handover Command message and send the source BSS a Packet Cell Change Failure message with the cause code set to "PS Handover failure".

8.10.5.7 MS Behaviour for GAN to A/Gb PS Handover

See 3GPP 44.318 [42].