8.4 Network controlled cell reselection procedure

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

A cell reselection is controlled either by the mobile station or by the network. An exception is the case of a mobile station that has enabled PEO in which case cell reselection is only initiated by the mobile station (see 3GPP TS 45.008 [15]).

When the cell reselection is controlled by the mobile station, the mobile station shall apply the cell reselection procedure defined in sub-clause 5.5.1.1 (A/Gb mode).

When a cell reselection is initiated by the network for an individual mobile station, the cell change order procedure is started by sending a PACKET CELL CHANGE ORDER message to the mobile station on the PCCCH or PACCH.

The PACKET CELL CHANGE ORDER message contains:

– The characteristics of the new cell that are necessary to identify it (i.e. BSIC + BCCH frequency);

– The NC measurement parameters valid for the mobile station in the new cell (NETWORK_CONTROL_ORDER and optionally: NC_NON_DRX_PERIOD, NC_REPORTING_PERIOD_I and NC_REPORTING_PERIOD_T);

– The IMMEDIATE_REL parameter;

– The CCN_ACTIVE parameter and optionally the CONTAINER_ID referring to the one included in received instances of the PACKET NEIGHBOUR CELL DATA message.

For a multi-RAT mobile station supporting UTRAN, the PACKET CELL CHANGE ORDER message may contain information on a UTRAN target cell, together with the IMMEDIATE_REL parameter; the establishment of UTRAN channel(s) and subsequent measurement reporting are defined in 3GPP TS 25.331.

For a multi-RAT mobile station supporting "CCN towards E-UTRAN, E-UTRAN Neighbour Cell measurement reporting and Network controlled cell reselection to E-UTRAN", the PACKET CELL CHANGE ORDER message may contain information on an E-UTRAN target cell; in this case, the establishment of channel(s) and subsequent measurement reporting are defined in 3GPP TS 36.331.

Upon receipt of the PACKET CELL CHANGE ORDER message the mobile station shall start timer T3174 and apply the cell reselection procedure defined in sub-clause 5.5.1.1 (A/Gb mode), with the additional rule that an immediate abort of operation in the old cell may be required by the network through the IMMEDIATE_REL field, except for the acknowledgement, by means of a PACKET CONTROL ACKNOWLEDGEMENT message, of a valid RRBP field possibly included in the PACKET CELL CHANGE ORDER message. A UTRAN capable mobile station ordered to a UTRAN cell shall obey the PACKET CELL CHANGE ORDER message irrespective of whether the target cell is known or not known (see 3GPP TS 25.133 and 3GPP TS 25.123); an E-UTRAN capable mobile station ordered to an E-UTRAN cell shall obey the PACKET CELL CHANGE ORDER message irrespective of whether the target cell is known or not known (see 3GPP TS 36.133).

If the timers related to measurement reporting expire while the reselection procedure has not yet been completed, these timers shall be restarted so that the mobile station resumes the measurement reporting procedures once camped on the new cell.

8.4.1 Network controlled cell reselection completion

The mobile station shall regard the network controlled cell reselection procedure as successfully completed when it has performed access and successfully completed contention resolution in the new cell, or the GMM READY timer (see 3GPP TS 24.008) stops running during the execution of the procedure. The mobile station shall then stop timer T3174.

NOTE 1: Access may be performed for the establishment of a dedicated connection or an uplink TBF.

NOTE 2: If the GMM READY timer stops running, the mobile station shall apply the network controlled cell re-selection mode NC0 (i.e., cell re-selection using ‘normal MS control’, see 3GPP TS 45.008).

In case of inter-RAT network controlled cell reselection, the mobile station shall regard the network controlled cell re-selection as successfully completed according to specifications of the target RAT, or when the GMM READY timer (see 3GPP TS 24.008) stops running during the execution of the procedure. The mobile station shall then stop timer T3174.

NOTE 3: In case of network controlled cell reselection to UTRAN, the procedure is regarded as succesfully completed when the mobile station receives an RRC CONNECTION SETUP message in the target cell (see 3GPP TS 25.331). In case of network controlled cell reselection to E-UTRAN, the procedure is regarded as succesfully completed when the mobile station receives an RRCConnectionSetup message in the target cell (see 3GPP TS 36.331).

8.4.1b (void)

8.4.2 Abnormal cases

In the following cases, the mobile station shall determine that the network controlled cell reselection procedure has failed:

– The PACKET CELL CHANGE ORDER message commands the mobile station to a frequency in a frequency band not supported by the mobile station. Cause: "frequency not implemented";

– The PACKET CELL CHANGE ORDER message is received while the mobile station is not in dual transfer mode but a circuit switched connection is on going. Cause: "on-going CS connection";

– In A/Gb mode, the PACKET CELL CHANGE ORDER message is received and the GMM READY timer (see 3GPP TS 24.008) is not running (i.e., mobile station in GMM STAND-BY state). Cause, if the GMM READY timer has a negotiated value equal to zero: "Forced to the Standby State". Cause, if the GMM READY timer has a negotiated value greater than zero: "MS in GMM Standby state";

– Access is denied in the new cell (i.e., the mobile station receives an IMMEDIATE ASSIGNMENT REJECT, a PACKET ASSIGNMENT REJECT or, in a UTRAN cell, an RRC CONNECTION REJECT message or fails to establish an RRC connection in an E-UTRAN cell as specified in 3GPP TS 36.331). Cause: "Immediate Assign Reject or Packet Access Reject on target cell";

– The mobile station is unable to synchronise to the new cell (see 3GPP TS 45.008) or the timer T3174 expires before a successful completion of the network controlled cell reselection procedure. Cause: "No response on target cell";

– Due to any other reason (e.g. unknown or unsupported target cell information). In this case the MS shall set the ARFCN and BSIC fields to the value zero and set the cause to value "frequency not implemented".

If the mobile station determines that the network controlled cell reselection procedure has failed, the mobile station shall stop timer T3174 (if it is still running) and start timer T3176. The mobile station shall return to the old cell, where it may trigger a cell update or other GMM specific procedure. In case the mobile station synchronised and attempted to access the new cell before returning to the old cell, the mobile station shall trigger a cell update or other GMM specific procedure, as appropriate according to the GMM requirements (see 3GPP TS 24.008).

The mobile station shall send a PACKET CELL CHANGE FAILURE message with the appropriate cause value to the network in the old cell and stop timer T3176. The PACKET CELL CHANGE FAILURE message may be sent on PACCH when the mobile station is in packet transfer mode or MAC-Shared state. Alternatively, the mobile station may initiate random access with access type "single block without TBF establishment" (PCCCH) / "single block packet access" (CCCH) and send the PACKET CELL CHANGE FAILURE message using an allocated single uplink block.

A mobile station shall ignore a PACKET CELL CHANGE ORDER message received while in dual transfer mode (refer to in 3GPP TS 44.018).

If a MS which is UTRAN capable is commanded to a 3G-target cell whose description is in contradiction to the UTRAN capabilities of the mobile station, it shall include the UTRAN FDD target cell or UTRAN TDD Target cell IE in the PACKET CELL CHANGE FAILURE message.

If a mobile station which is E-UTRAN capable is commanded to an E-UTRAN target cell whose description is in contradiction to the E-UTRAN capabilities of the mobile station, it shall include the E-UTRAN target cell IE in the PACKET CELL CHANGE FAILURE message. For a mobile station supporting extended EARFCNs, it may instead include the E-UTRAN Target cell with extended EARFCN IE in the PACKET CELL CHANGE FAILURE message.

If a mobile station supporting extended EARFCNs receives a PACKET CELL CHANGE ORDER message with both E-UTRAN target cell IE and E-UTRAN Target cell with extended EARFCN IE included therein, it shall return the E-UTRAN Target cell with extended EARFCN IE in the PACKET CELL CHANGE FAILURE message.

In case the network controlled cell reselection procedure fails and the MS returns to the old cell, the MS shall delete any stored NC measurement parameters and revert to the broadcast parameters. If individual priorities are indicated in the PACKET CELL CHANGE ORDER message, they shall be deleted.

If the mobile station is unable to synchronise to the old cell (see 3GPP TS 45.008), or if timer T3176 expires, the mobile station shall cancel the sending of the PACKET CELL CHANGE FAILURE message and perform an autonomous cell re-selection.