LTE Reselection Parameters.

Reselection parameters in LTE networks help determine when a UE should switch from one cell to another. Following is list of LTE reselection parameters with explanations:

Start Reselection.

SIntraSearch:

• It is a Signal threshold for starting intra-frequency reselection.
• Its Range is 29×2=−58dBm to 31.
• A higher value encourages the UE to start reselection earlier when the signal is weak.

sNonIntraSearch:

• It is a Signal threshold for starting inter-frequency or inter-RAT reselection.
• Its Range is 2 to 5.
• Higher values discourage reselection to other RATs (Radio Access Technologies) like GSM or WCDMA.
• Example Calculation is −114+5×2 = −104dBm.

TcrMaxConnMode:

• It is a Maximum time for mobility calculations in connected mode.
• Its Range is T_CRMAX_30S to T_CRMAX_60S.
• Longer times discourage reselection but improve precision in mobility calculations (celResTiF, sIntrasearch, sNonIntrsearch).

High Mobility Scaling:

• Scaling factor for high mobility scenarios.
• Its Range is QHystSfHigh DB0_Q_HYST_SF_HIGH(0dB) to DB_2_Q_HYST_SF_HIGH.
• Higher values discourage reselection during high mobility.
• Offset (qRxLevMinOffset): 0 to 2.

TreselectionRAT:

• It is a time to trigger reselection to another RAT.
• Increasing this time decreases the likelihood of reselection.
• Example Value is TreselectionRAT = 7sec.

Reselection Decision.

IdleQhyst1s:

• It is a hysteresis for staying with the current cell in idle mode.
• If we make range 4 to 2. Lower values discourage sticking to the current cell.

Cell Offset (qOffsetCellEUtran, qOffsetCell, qOffCell):

• Offset applied to the cell’s signal strength.

CellReselPriority:

• It is simple Priority for cell reselection.
• It’s Range is 0 to 2 for high priority.
• Function: Lower values discourage reselection.
• Priority Values: cellReselectionPriority 5 to 3.
• Related: threshXHighHrpd, tReselectionEutra 2 to 4, tReselectionEutraSfHigh 3 to 2.

NcellReselectionHigh:

• It is a threshold for entering high mobility state.
• Range: 16 to 10.
• Function: Lower values make the UE enter high mobility state earlier.
• Related Parameters: threshXHigh, threshXLow, tReselectionEutraSfHigh, threshServingLow 62, sPrioritySearch1, , interFrqThrH, tResEutSF, eutResTiFHM, celResTiFHM, cellReSelPrio 3 to 0 will discourage, mobStateParamNCelChgHgh mobStateParamTEval, qRxLevMinOffset 0 to 2dB, q-RxLevMin, spStResPars, qHystSfHigh, tReselEutr, timeToTriggerSfMedium, tResUtra, tResUtraSF, utrResTiFHM.

Qrxlevmeas.

1. Tevaluation:

• It is time period for evaluating reselection.
• Its Range is 30 to 60s.

1. T320:

• Definition: Timer for UE attach procedure.
• Related Timers:
  • T3410 (UE): Timer for UE attach.
  • T3450 (eNodeB): Timer for eNodeB attach.

System Information Messages (SIB)

• SIB1: Contains information about access and message scheduling, and reselection criteria.
• SIB2: Provides UE timers, common/shared channel configurations, and uplink resource blocks (RBs).
• SIB3: Contains intra-frequency reselection information.
• SIB4: Provides information about intra-frequency neighbors.
• SIB5: Contains inter-frequency neighbor information.
• SIB6: Provides reselection information to WCDMA.
• SIB7: Contains reselection information to GSM.
• SIB8: Provides reselection information to CDMA.
• Sib3Period: RF16 to RF32 – Less resource usage but might cause access delays.

Related Parameters:

• maxCrSibDl: Maximum cell radius for SIB.
• si4Periodicity: Periodicity for System Information 4.

These parameters are crucial for managing the cell reselection process, ensuring that UEs maintain optimal connections while balancing network load and performance.