The cell selection criterion S is a pre-condition for suitable cells.
The conditions for E-UTRAN, UTRAN FDD and GSM cells are listed in the figure.
R – CRITERION – CELL RESELECTION
HIGH MOBILITY / MEDIUM MOBILITY / NORMAL MOBILITY:
For faster moving UEs the procedure alters – speed dependent scaling rules are applied. If the number of (different cells) cell reselections during the past time period TCRmax exceeds NCR_H, high mobility has been detected. If the number exceeds NCR_M, and not NCR_H, medium mobility has been detected.
In high/medium-mobility states, a UE:
• multiplies Qhyst by “Speed dependent ScalingFactor for Qhyst for mobility state” if sent.
• multiplies TreselectionRAT by “Speed dependent ScalingFactor for TreselectionRAT for mobility state for RAT cells. (RAT = EUTRAN, UTRAN, GERAN).
Cell reselection evaluation is performed according to the UE internal triggers or if the information on the BCCH used for the cell reselection evaluation procedure has been changed.
FOR INTRA-FREQUENCY AND EQUAL PRIORITY INTER-FREQUENCY CELLS:
(Re-) Selected cell is a suitable cell (e.g. fulfills the S criterion) and is the best ranked cell (has the highest R). The UE shall however reselect the new cell, only if the following conditions are met:
• the new cell is better ranked than the serving cell during a time interval Treselections
• more than 1 second has elapsed since the UE has camped on the current serving cell.
The cell-ranking criterion R is defined as shown below:
s – indicates the serving cell,
n – indicates the candidate cell.
FOR INTER-FREQUENCY AND INTER-RAT NEIGHBOUR CELLS:
If UE camps longer than 1 sec in the serving cell and:
– a higher priority neighbor fulfills (during TreselectionRAT):
SnonServingCell,x > Threshhigh -> reselect neighbor cell.
– no cell fulfills SnonServingCell,x > Threshhigh :
SServingCell < Threshserving,low and SnonServingCell,x > Threshx,low ->reselect neighbor cell.