8.3.9 Inter-RAT cell reselection from UTRAN

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

8.3.9.1 General

The purpose of the inter-RAT cell reselection procedure from UTRAN is to transfer, under the control of the UE and to some extent the UTRAN, a connection between the UE and UTRAN to another radio access technology (e.g. GSM/GPRS or E-UTRA).

8.3.9.2 Initiation

This procedure is applicable in states CELL_FACH, CELL_PCH or URA_PCH.

When the UE based on received system information makes a cell reselection to a radio access technology other than UTRAN, e.g. GSM/GPRS or E-UTRA, according to the criteria specified in [4], the UE shall:

1> If the NAS procedures associated with inter-system change specified in [5] require the establishment of a connection:

2> initiate the establishment of a connection to the target radio access technology according to its specifications.

8.3.9.2a Initiation of inter-RAT cell reselection to GERAN Iu mode

When the UE in CELL_PCH or CELL_FACH state performs an inter-RAT cell reselection to GERAN Iu mode, according to the criteria specified in [4], the UE shall:

1> initiate the cell update procedure, setting the U-RNTI in the IE "G-RNTI".

When the UE in URA_PCH state performs an inter-RAT cell reselection to GERAN Iu mode, according to the criteria specified in [4], the UE shall:

1> compare the URA identity which the UE had been assigned to in UTRAN against the GRA identities which are broadcast in the GERAN cell;

1> If the assigned URA identity is not present in the list of GRA identities that are broadcast in the GERAN cell:

2> initiate the GRA update procedure, setting the U-RNTI in the IE "G-RNTI".

8.3.9.3 Successful cell reselection

When the UE has succeeded in reselecting a cell in the target radio access technology, the UE shall:

1> release all UTRAN specific resources.

UTRAN should:

1> release all UE dedicated resources upon indication that the UE has completed a connection establishment to the other radio access technology.

8.3.9.4 UE fails to complete an inter-RAT cell reselection

If the inter-RAT cell reselection fails, the UE shall:

1> resume the connection to UTRAN using the resources used before initiating the inter-RAT cell reselection procedure.