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.

LTE Reselection Parameters.
  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.

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