ts_125331v120300p

3GPP TS 25.331 version 12.3.0 Release 12
2157
ETSI TS 125 331 V12.3.0 (2014-10)
B.3.5
States and Transitions for Cell Reselection in URA_PCH,
CELL_PCH, and CELL_FACH
See Idle Mode figure in
3GPP TS 25.304
Cell Selection
when leaving
connected
mode
Camped
Normally
go here
from
idle
mode
return to
idle mode
UTRA RRC
Connected
Mode
trigger
suitable
cell
selected
no suitable
cell found
Initial Cell
Reselection
trigger
suitable cell
selected
Cell
Reselection
no suitable
cell found
suitable cell
in other RAT found
Figure B.3.5-1: UTRA RRC Connected mode cell reselection for URA_PCH, CELL_PCH, and
CELL_FACH
In some states the UE performs cell reselection procedures. The UE selects a suitable cell (defined in [4]) and radio
access technology based on connected mode radio measurements and cell reselection criteria.
Figure B.3.5-1 shows the states and procedures in the cell reselection process in connected mode.
When a cell reselection is triggered, the UE evaluates the cell reselection criteria based on radio measurements, and if a
better cell is found that cell is selected, procedure Cell reselection (see [4]). If the change of cell implies a change of
radio access technology, the RRC connection is released, and the UE enters idle mode of the other RAT. If no suitable
cell is found in the cell reselection procedure, the UE eventually enters idle mode.
When an Initial cell reselection is triggered, the UE shall use the Initial cell reselection procedure (see [4]) to find a
suitable cell. One example where this procedure is triggered is at radio link failure, where the UE may trigger an initial
cell reselection in order to request re-establishment of the RRC connection. If the UE is unable to find a suitable cell,
the UE eventually enters idle mode.
B.4 Inter-RAT handover with CS domain services
When using CS domain services, UTRAN is using an Inter-Radio access system Handover Procedure and GSM is using
a Handover procedure for the transition from UTRA RRC Connected Mode to GSM Connected Mode.
ETSI