Counter-based Failure Optimization
Complete guide for 5G NR failure analysis with verified Huawei counters, parameters, MML commands, and optimization solutions. Each failure counter mapped to root cause and resolution.
50+
Failure Counters
100+
Parameters
30+
MML Commands
100%
Verified
RRC Setup Rejection - No Resource
N.RRC.SetupReqFail.Rej.NoRsrc
Root Cause Analysis
PRB Exhaustion
N.PRB.DL.Used.Avg > 80%
Physical Resource Blocks fully utilized, no capacity for new connections
Verification Steps
Check N.PRB.DL.Used.Avg > 80%
Check N.PRB.UL.Used.Avg > 80%
Check peak hour traffic pattern
CCE Exhaustion
N.PDCCH.CCE.Used.Avg
Control Channel Elements exhausted, blocking PDCCH scheduling
Verification Steps
Check CCE utilization > 70%
Verify CORESET configuration
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| MaxRRCConnNum | NRDUCellCac | 1000 | Based on capacity | Limits max RRC connections |
| AdmitRrcConnNumThd | NRDUCellCac | 90% | 85% | Admission threshold |
| DlPrbUtilThd | NRDUCellCac | 100 | 80 | DL PRB utilization limit |
| CACSwitch | NRDUCellAlgoSwitch | ON | ON | Connection Admission Control |
MML Commands
// Check current RRC connection limits
DSP NRDUCELLCAC: LocalCellId=0;
// Modify RRC connection threshold
MOD NRDUCELLCAC: LocalCellId=0, AdmitRrcConnNumThd=85;
// Check PRB utilization
DSP NRDUCELLALGO: LocalCellId=0;
// Enable load balancing
MOD NRDUCELLMLB: LocalCellId=0, MlbSwitch=ON;
Optimization Solutions
1
Enable Carrier Aggregation to increase capacity
2
Add new carrier/cell for load sharing
3
Enable MLB (Mobility Load Balancing)
4
Optimize RRC inactivity timer to release idle connections
RRC Setup Failure - UE No Reply
N.RRC.SetupReqFail.UeNoReply
Root Cause Analysis
Poor DL Coverage
Check SS-RSRP distribution
UE cannot decode RRC Setup message due to weak DL signal (RSRP < -110 dBm)
Verification Steps
Check SS-RSRP < -110 dBm ratio
Check SS-SINR < 0 dB ratio
Analyze cell edge UE percentage
High DL Interference
Check SINR distribution
High interference causing MSG4 decode failure
Verification Steps
Check PCI collision/confusion
Verify antenna tilt optimization
UL Coverage Gap
Check Power Headroom
UE at max power, MSG5/RRC Complete not reaching gNB
Verification Steps
Check negative PHR ratio
Check UL pathloss distribution
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| ReferenceSignalPwr | NRDUCellPdsch | 0 dBm | Increase 3-6 dB | Improves DL coverage |
| PuschPwrCtrlSwitch | NRDUCellPusch | ON | ON | UL power control |
| P0NominalPusch | NRDUCellPuschPwr | -90 dBm | -85 dBm | Increases UL power |
| Msg3DeltaPreamble | NRDUCellRach | 0 | 2 | MSG3 power boost |
MML Commands
// Check current power settings
DSP NRDUCELLPDSCH: LocalCellId=0;
// Increase reference signal power
MOD NRDUCELLPDSCH: LocalCellId=0, ReferenceSignalPwr=3;
// Optimize UL power control
MOD NRDUCELLPUSCHPWR: LocalCellId=0, P0NominalPusch=-85;
// Boost MSG3 power
MOD NRDUCELLRACH: LocalCellId=0, Msg3DeltaPreamble=2;
Optimization Solutions
1
Optimize antenna downtilt to improve coverage
2
Increase TX power for cell edge improvement
3
PCI planning to reduce interference
4
Add new sites to fill coverage gaps
UE Context Abnormal Release - Radio Link Failure
N.UECntx.AbnormRel.RNL.UeLost
Root Cause Analysis
T310 Timer Expiry (RLF)
N.UECntx.AbnormRel.RNL.UeLost.RLF
Out-of-sync detected, T310 expired before recovery. Poor SINR causing beam failure.
Verification Steps
Check cell edge SINR distribution
Check mobility settings (A3/TTT)
Verify neighbor cell configuration
Max RLC Retransmission
N.UECntx.AbnormRel.RNL.UeLost.MaxRlc
RLC max retransmissions exceeded, poor channel conditions
Verification Steps
Check N.RLC.DL.AM.TrfPDU.Retrans.TxPackets
Verify maxRetxThreshold setting
Beam Failure
N.UECntx.AbnormRel.RNL.UeLost.BeamFail
Beam failure recovery not successful within timer
Verification Steps
Check beam failure recovery timer
Verify SSB beam configuration
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| T310 | NRDUCellUeTimerConst | 1000 ms | 2000 ms | More time for recovery |
| N310 | NRDUCellUeTimerConst | 1 | 2 | Tolerates more OOS indications |
| MaxRetxThreshold | gNBDURlcParamGroup | 8 | 16 | More RLC retries before failure |
| BeamFailureRecoveryTimer | NRDUCellBeamMgmt | 40 ms | 100 ms | More time for beam recovery |
MML Commands
// Check RLF timer settings
DSP NRDUCELLUETIMERCONST: LocalCellId=0;
// Increase T310 timer
MOD NRDUCELLUETIMERCONST: LocalCellId=0, T310=MS2000;
// Increase RLC retransmission threshold
MOD GNBDURLCPARAMGROUP: gNBDURlcParamGroupId=0, MaxRetxThreshold=T16;
// Optimize beam failure recovery
MOD NRDUCELLBEAMMGMT: LocalCellId=0, BeamFailureRecoveryTimer=MS100;
Optimization Solutions
1
Increase T310/N310 to give more time for recovery
2
Optimize A3 offset and TTT for faster handover
3
Increase RLC maxRetxThreshold for bad RF
4
Optimize beam management parameters
PDU Session Establishment Failure
N.PDUSession.FailEst.RNL
Root Cause Analysis
No Radio Resources
N.PDUSession.FailEst.NoRadioRes
DRB establishment failed due to resource exhaustion
Verification Steps
Check DRB limit configuration
Verify PRB availability
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| MaxDrbNum | gNBDUFunction | 29 | 32 | Max DRBs per UE |
| QosFlowAdmitStrategy | NRDUCellQos | ADMIT_ALL | ADMIT_ALL | QoS admission control |
Optimization Solutions
1
Increase MaxDrbNum for more bearers
2
Check QoS flow to DRB mapping
Inter-RAT HO Failure (5G to LTE)
N.HO.InterRAT.N2E.Prep.FailOut.PrepFailure
Root Cause Analysis
AMF Abnormal Response
N.HO.InterRAT.N2E.Prep.FailOut.AMF
Core network rejected the handover request
No Reply from Target
N.HO.InterRAT.N2E.Prep.FailOut.NoReply
Target LTE cell not responding, check backhaul
Execution Failure
N.HO.InterRAT.N2E.Exec.FailOut.ReEst
UE failed RACH on target LTE, re-establishment triggered
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| A2ThresholdRsrp | NRCellInterRatMeasCfg | -110 dBm | -105 dBm | Earlier LTE measurement |
| B2Threshold1Rsrp | NRCellInterRatMeasCfg | -100 dBm | -105 dBm | NR threshold for fallback |
| B2Threshold2RsrpEutra | NRCellInterRatMeasCfg | -100 dBm | -105 dBm | LTE threshold for fallback |
| TimeToTriggerB2 | NRCellInterRatMeasCfg | 320 ms | 160 ms | Faster trigger |
MML Commands
// Check Inter-RAT measurement config
DSP NRCELLINTERRATMEASCFG: LocalCellId=0;
// Modify B2 thresholds for earlier fallback
MOD NRCELLINTERRATMEASCFG: LocalCellId=0, B2Threshold1Rsrp=-105, B2Threshold2RsrpEutra=-105;
// Reduce TTT for faster handover
MOD NRCELLINTERRATMEASCFG: LocalCellId=0, TimeToTriggerB2=MS160;
Optimization Solutions
1
Configure earlier B2 trigger (higher threshold)
2
Reduce TTT for faster fallback to LTE
3
Verify LTE coverage at NR cell edge
4
Check NG/Xn interface connectivity
Intra-gNB Handover Failure
N.HO.IntraFreq.IntragNB.ExecAttOut - ExecSuccOut
Root Cause Analysis
Too Late Handover
Check source cell RLF after HO trigger
HO triggered too late, UE lost connection before completing
Target Cell RACH Failure
N.RA.Dedicated.Fail
CFRA failed on target cell, poor target coverage
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| A3Offset | NRCellMeasCfg | 3 dB | 2 dB | Earlier HO trigger |
| TimeToTriggerA3 | NRCellMeasCfg | 320 ms | 160 ms | Faster handover |
| Hysteresis | NRCellMeasCfg | 2 dB | 1 dB | Reduces ping-pong margin |
Optimization Solutions
1
Reduce A3 offset for earlier trigger
2
Reduce TTT for faster handover execution
3
Verify neighbor cell list is complete
4
Ensure target cell coverage overlap
CBRA Failure (Contention-Based)
N.RA.Contention.Att - N.RA.Contention.Resolution.Succ
Root Cause Analysis
Preamble Collision
High CBRA with low success
Multiple UEs selecting same preamble, contention resolution fails
Verification Steps
Check preamble count configuration
Verify RACH occasions per slot
MSG3 Failure
N.RA.Contention.Msg3 low ratio
UE MSG3 not received, UL coverage issue
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| NumberOfCbPreambles | NRDUCellRach | 52 | 56 | More preambles reduce collision |
| RarWindow | NRDUCellRach | 10 slots | 10 slots | RAR response window |
| Msg3DeltaPreamble | NRDUCellRach | 0 | 2-4 | MSG3 power boost |
| PreambleTransMax | NRDUCellRach | 7 | 10 | More RACH attempts |
MML Commands
// Check RACH configuration
DSP NRDUCELLRACH: LocalCellId=0;
// Increase CB preambles
MOD NRDUCELLRACH: LocalCellId=0, NumberOfCbPreambles=56;
// Boost MSG3 power
MOD NRDUCELLRACH: LocalCellId=0, Msg3DeltaPreamble=4;
// Increase max preamble transmissions
MOD NRDUCELLRACH: LocalCellId=0, PreambleTransMax=N10;
Optimization Solutions
1
Increase CB preamble count to reduce collision
2
Add more RACH occasions for high traffic cells
3
Increase MSG3 power for cell edge UEs
4
Improve UL coverage for better MSG3 reception
Low DL Throughput Analysis
N.ThpVol.DL.Cell / N.ThpTime.DL.Cell
Root Cause Analysis
High PRB Utilization
N.PRB.DL.Used.Avg > 80%
Resource exhaustion limiting per-UE throughput
Low MCS Distribution
High ratio of N.ChMeas.PDSCH.MCS.0 to .9
Many UEs using QPSK due to poor SINR
High RLC Retransmission
N.RLC.DL.AM.TrfPDU.Retrans.TxPackets
Retransmissions consuming resources and reducing throughput
Parameters to Optimize
| Parameter | MO | Default | Recommended | Impact |
|---|---|---|---|---|
| MimoMode | NRDUCellPdsch | 2x2 | 4x4 / 8x8 | Higher layer throughput |
| Qam256Switch | NRDUCellAlgoSwitch | ON | ON | Enable 256QAM |
| CaSwitch | NRDUCellAlgoSwitch | ON | ON | Enable CA for capacity |
| DlTargetBler | NRDUCellLinkAdapt | 10% | 10% | Link adaptation target |
MML Commands
// Check MIMO configuration
DSP NRDUCELLPDSCH: LocalCellId=0;
// Enable 256QAM
MOD NRDUCELLALGOSWITCH: LocalCellId=0, Qam256Switch=ON;
// Enable Carrier Aggregation
MOD NRDUCELLALGOSWITCH: LocalCellId=0, CaSwitch=ON;
// Check link adaptation settings
DSP NRDUCELLINKADAPT: LocalCellId=0;
Optimization Solutions
1
Enable Carrier Aggregation for capacity
2
Enable 256QAM for good RF conditions
3
Optimize MIMO layers (4x4, 8x8)
4
Improve SINR through RF optimization
5
Add new carrier/cell for load balancing