In LTE networks, the Minimum RX Level parameter (Qrxlevmin) is a important parameter under the Cell Selection (CellSel) category. It defines the minimum received signal strength (in dBm) a UE requires to select a cell. Optimizing this parameter ensures balanced network accessibility, prevents coverage gaps, and maintains efficient load distribution among cells.
Parameter Overview
- Parameter ID: Qrxlevmin
- Network Element: eNodeB
- MML Command: MOD CELLSEL
- Default Value: -64 dBm
- Recommended Value: -64 dBm
- Value Range: -140 dBm to -44 dBm
- Unit: 2 dBm intervals
- Feature Specification: 3GPP R8
Function and Impact on Cell Selection
The minimum RX level contributes to the cell selection criterion S, which is calculated as:
S=Qrxlevmeas−QrxlevminS = Qrxlevmeas – Qrxlevmin
Where:
- Qrxlevmeas is the measured signal strength of the cell
- Qrxlevmin is the configured minimum RX level
For a UE to select a cell, S must be ≥ 0. If Qrxlevmin is set too high, UEs may struggle to find a suitable cell, leading to increased call setup failures and poor accessibility. Conversely, if it’s too low, UEs might attach to weak cells, causing service degradation and higher drop rates.
Optimization Strategy
- Coverage Analysis:
- Evaluate coverage maps and UE measurements (RSRP/RSRQ) to understand current signal strength patterns.
- Parameter Adjustment:
- In weak coverage areas, consider reducing Qrxlevmin to improve accessibility.
- In high-interference zones or overlapping cells, increase Qrxlevmin to prevent UEs from latching onto poor-quality cells.
- Idle Mode Behavior:
- Since changes in this parameter affect idle mode cell selection and reselection, ensure modifications align with handover and reselection thresholds.
- Validation:
- Monitor Call Setup Success Rate (CSSR), Call Drop Rate (CDR), and Handover Success Rate (HOSR) after tuning to verify the improvements.
Practical Example
Scenario: A cluster shows high call setup failures and low accessibility.
- Current Setting: Qrxlevmin = -64 dBm
- RSRP Analysis: Average RSRP in weak areas = -118 dBm
- Optimization: Set Qrxlevmin to -62 dBm to allow UEs in weak areas to attach to stronger cells.
- Result: CSSR increased by 5%, and call drops reduced by 3%.
Conclusion
The Minimum RX Level (Qrxlevmin) parameter is vital for LTE network performance and optimization. By carefully balancing this parameter, you ensure optimal cell selection, better accessibility, and improved service quality. Continuous monitoring and adjustment based on field measurements will out the best optimization results.