WCDMA: priority based cell reselection

Priority based measurement rules

The UE shall always perform measurements on layers with higher priority than the serving WCDMA cell. The intensity of these measurements may vary depending on whether Srxlev and Squal of the serving cell are above or below the thresholds defined by the parameters sPrioritySearch1 and sPrioritySearch2, see TS 25.133 for more details.

For lower priority layers the need to perform measurements is controlled by the parameters sPrioritySearch1 and sPrioritySearch2 in relation to Srxlev and Squal as specified below:

• If Srxlev > sPrioritySearch1 and Squal > sPrioritySearch2 the UE may choose not to measure on lower priority LTE frequencies.
• If Srxlev <= sPrioritySearch1 and/or Squal <= sPrioritySearch2 the UE is required to perform measurements on lower priority LTE frequencies

Priority based cell reselection criteria

Cell reselection to a higher priority layer is performed by the UE if Srxlev of the cell is greater than threshHigh for a duration of Treselection seconds.

Cell reselection to a lower priority layer is performed by the UE if the following criteria are fulfilled for a duration of Treselection seconds:

• Srxlev of the serving cell < threshServingLow or Squal of the serving cell < 0
• Srxlev of the neighbour cell > threshLow.

For LTE, Srxlev is defined as Srxlev = Qrxlevmeas - qRxLevMin
Qrxlevmeas is the RSRP level of the LTE cell (in dB) measured by the UE.
Parameter qRxLevMin indicates the minimum required RSRP level for camping.

Only LTE cells fulfilling the S-criteria, that is cells with Srxlev > 0, are considered as candidates for cell reselection. If more than one cell meets the cell reselection criteria above, the UE shall reselect the LTE cell with the highest Srxlev level among the cells meeting the criteria on the highest absolute priority layer.