UMTS Reselection Parameters

General parameters with typical network values of the three types of reselection in UMTS is presented below:

3G to 3G

• qrxlevmin = -109 dBm     (min acceptable threshold of cell RSCP)
• qqualmin = -18 dB           (min acceptable threshold of cell quality EcNo)

• sintersearch =  10 dB   (f1,f2 case)
• sintrasearch =  14 dB    (same frequency)

3G to 2G

• ssearchrat = 2dB            (indicates when to trigger measurements on GSM cells, increasing this value quickens while decreasing it delays the process)
• treselect = 2s
• qoffset1sn = 7dB for gsmrelation; 0 dB for utranrelation                                                       (Source and target signal offset when reselection strategy is RSCP)
• qoffset2sn = 0 dB                 (Source and target signal offset when reselection strategy is EcNo)

2G to 3G

• FDDqRSCPmin = -102 dBm
• FDDqmin = -12 dB

Equation

The equations on which the decision is made using these parameters are:

For EcNo based reselection:

Squal <= sintrasearch     OR        sintersearch           OR            ssearchrat

where Squal = qmeasured  -    qqualmin

Thus the equation becomes:

qmeas - qqualmin <= sintrasearch

qmeas  <= qqualmin + sintrasearch

Similarly, EcNo values can be replaced with RSCP for the RSCP based reselection.

Candidate Cell Priority (HO Priority) - CDR Alcatel-Lucent

Improvement in Quality and reduction in Call Drops can be achieved in Alcatel-Lucent (B11, B10) by proper adjustment of Candidate Cell Priority (HO Priority Level).

Parameter:

• Candidate_Cell_Priority

Target Cells: Radio Drops, HO Drops, Bad UL/DL Quality

Theory: 

• This parameter decides the priority of target cells for each source cell during Handover
• One standard approach is use highest priority for DCS neighbors (0), 2nd highest (1) for less interfered and 3rd highest (2) for others

Repeated SACCH/FACCH - CDR Alcatel-Lucent

Call Drops can be reduced to a great extent in the equipment of Alcatel-Lucent (B11, B10) by using the feature of repeated SACCH/FACCH frames.

Parameter:

• EN_REP_DL_FACCH
• EN_REP_SACCH

Target Cells: Radio Drops, HO Drops

Theory: 

• Each DLFACCH frame is sent twice by enabling this parameter thereby improving handover reliability in AMR Calls reducing call drop rate
• If a SACCH is not decoded correctly by MS, the BTS will resend it that enhances coverage and decreases drops (SACCH is used for transmission of radio measurement data such as TA, Power Control Info, SMS during call etc)