Cell Reselection scenarios

The Cell Reselection process is described in the following stages:

The Cell Reselection process is run when:

  • When the cell on which it is camping is no longer suitable.
  • When the UE, in ”camped normally” state, has found a better neighbouring cell than the cell on which it is camping.
  • When the UE is in limited service state on an acceptable cell.
  • Measurements on intra-frequency cells are performed if Srxlev ≤ SIntraSearchP or Squal ≤ SIntraSearchQ for the serving cell.
  • If Srxlev >SIntraSearchP and Squal > SIntraSearchQ, the UE does not need to perform these measurements.

where Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset) – Pcompensation

Squal = Qqualmeas – (Qqualmin + Qqualminoffset)

  • Measurements on E-UTRA cells on inter-frequency carriers and cells on inter-RAT frequencies with higher cell reselection priority than the current frequency are always performed.
  • Measurements on E-UTRA cells on inter-frequency carriers and cells on inter-RAT frequencies with equal or lower cell reselection priority than the current frequency are performed if Srxlev ≤ SNonIntraSearchP or Squal ≤ SNonIntraSearchQ for the serving cell. If Srxlev > SNonIntraSearchP and Squal > SNonIntraSearchQ, the UE does not need to perform these measurements

Intra frequency and Equal priority cell reselection

 

For equal priority Cell Reselection process is described in the following stages:

  • When camped on an E-UTRA cell, the UE performs a ranking of neighbor E-UTRA cells on the same frequency and other frequencies with equal cell reselection priority, taking into account the cells satisfying the cell selection criteria.
  • The cell ranking is based on the RSRP measurement quantities of the serving cell (Qmeas,s) and the neighbor cells (Qmeas,n).
  • The UE applies the cell ranking criterion Rs on the serving cell and the cell ranking criterion Rn on the intra-frequency and equal priority cells

Rs = Qmeas,s + Qhyst

Rn = Qmeas,n – Qoffset

 

  • Qhyst is a hysteresis value preventing too-frequent reselection back and forth between cells of nearly equal rank.
  • QOffset is an offset in the cell ranking criterion of neighbour E-UTRA cells. It consists of a cell individual part and a frequency specific part. The frequency specific part applies to equal priority inter-frequency cells only.
  • When a neighbor cell is ranked as better than the serving cell (Rn > Rs) during a time interval TreselectionEUTRA, the UE performs a cell reselection to the better-ranked cell.

 

LTE to WCDMA cell reselection

 

From High Priority LTE Cell to Lower Priority WCDMA Cell

 

  • Measurement Criteria (From High Priority LTE Cell to Lower Priority WCDMA Cell): When LTE cell has higher priority than WCDMA, it would stay in LTE cell but it performs measurement for the low priority WCDMA if UE is under the following condition :

Srxlev of the serving cell < sNonIntraSearch (SIB3),

If we express this using dB/dBm, Srxlev of the serving cell < (2 x sNonIntraSearch (SIB3))

where Srxlev = Qrxlevmeas – qRxLevMin (SIB3),

 

  • Reselection Criteria (From High Priority LTE Cell to Lower Priority WCDMA Cell): If UE in LTE cell is under the following condition with the duration longer than tReselectionUtra (SIB6), it should reselect to WCDMA cell.

Srxlev of LTE cell (serving cell)  < threshServingLow (SIB3),

where Srxlev = Qrxlevmeas – qRxLevMin (SIB3),

where Qrxlevemeas = measured RSRP level, qRxLevMin = minimum RSRP level for camping

Srxlev of WCDMA cell  > threshXLowP (SIB6),

where Srxlev = Qrxlevmeas – qRxLevMin (SIB3),

Check Also

TEMS™ Pocket 21.3

TEMS Pocket 21.3 released

Infovista released the latest version of TEMS Pocket 21.3 TEMS™ Pocket 21.3 New Devices added: …

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close