Lte Capacity Troubleshooting

Mp load
2. incoming handovers intensity
Current setting for handover is
ReportConfigEUtraBestCell::a3offset = 3dB
ReportConfigEUtraBestCell:: hysteresisA3 = 1dB
ReportConfigEUtraBestCell:: timeToTriggerA3 = 40ms

Propose to change a3offset to 5dB (handover margin increased to 6dB) for high capacity cells to reduce signaling load. a3offsetAnrDelta remains unchanged

Increase handover margin reduces handovers and may impact retainability
Will review feasibility to use alternative approach on 'UE Level Oscillating Handover Minimization' feature
Ul noise rise
pzeronominalpucch, pzeronominalpusch
pZeroNominalPucch and pZeroNominalPusch can be used to adjust power control target, trade off between coverage and capacity
Current setting
pZeroNominalPucch = -117dBm
pZeroNominalPusch = -96dBm (should be reduced to default -103dBm to reduce UL interference peaks at high load)
Ul noise rise
observability
pmSinrPucchDistr
Distribution of the SINR values calculated for PUCCH

pmSinrPuschDistr
Distribution of the SINR values calculated for PUSCH

pmRadioRecInterferencePwr
The measured Noise and Interference Power on PUSCH, according to 36.214 of the SINR values calculated for PUSCH

pmRadioRecInterferencePwrPucch
The measured Noise and Interference Power on PUCCH, according to 36.214

pmRadioTbsPwrRestricted
The number of Transport Blocks on MAC level scheduled in uplink where the UE was considered to be power limited.

pmRadioTbsPwrUnrestricted
The number of Transport Blocks on MAC level scheduled in uplink where the UE was NOT considered to be power limited.

Focus areas
LTE High Capacity Focus Areas
Control Channel Dimensioning
PUCCH Resources
PDCCH Resources
UL Noise Rise
PRB Utilization / Cell Throughput Capacity
MP Load
RRC Connection Setup Intensity
Due to UE releases by Inactivity
Due to UE releases by RLC Supervision
Incoming Handover Intensity
Hardware expansion
Connected Users License
Summary of High Capacity Parameter Settings

Prb utilization / cell throughput capacity
schedulingalgorithm
System Fairness
Cell Throughput
Current setting schedulingAlgorithm = 3 (PROPORTIONAL_FAIR_MEDIUM), propose to change to following at high load
4 (PROPORTIONAL_FAIR_LOW) or
5 (MAXIMUM_C_OVER_I)
Higher Cell Throughput
Higher TTI utilization
Higher PRB utilization

Performance comparison between different schedulers
Best cell throughput (from lowest to highest)
RR < ER < PFH < PFM < PFL < MCI
System fairness (from lowest to highest)
MCI < PFL < PFM < PFL < ER < RR

For PFL or Max C/I, user at cell edge may have low throughput, as scheduler has higher weightage for RF condition
Focus areas
PUCCH Resources
PDCCH Resources
UL Noise Rise
MP Load
Hardware expansion

Pdcch resources
observability
pmPdcchCceUtil
PDF of % of CCEs utilized compared with total CCEs available (at the maximum CFI permitted by pdcchCfiMode) each subframe, considering bandwidth and antenna configuration.

pmPdcchCfiUtil
PDF of number of subframes each CFI value was assigned
Pdcch resources
adaptive pdcch (1/2)
PDCCH is used for
UL/DL scheduling assignments, e.g. PUSCH/PDSCH resource indication, transport format indication, HARQ info and PUCCH/PUSCH PC commands
Number of OFDM symbols available for PDCCH in a sub-frame is CFI. Max OFDM symbols, limited by pdcchCfiMode, is not exceeded

Recommended setting:
Bandwidth =< 10MHz : CFI_AUTO_MAXIMUM_3 (current setting), to handle peaks of PDCCH load
Bandwidth > 10MHz : CFI_AUTO_MAXIMUM_2, since higher number of symbols for PDCCH can increase RB pairs for PUCCH, which leads to reduced UL peak rate
Pucch resources
intro
PUCCH is used for transmitting
SR, HARQ ACK/NACK (PUCCH Format 1)
CQI, RI (PUCCH Format 2)
UE is allocated SR and CQI resources during setup procedure, and the resources are kept as long as UE is UL synchronized.
UE is not allowed to connect to a cell if there's no free SR resources
noOfPucchSrUsers and noOfPucchCqiUsers determine number of resources for SR and CQI per cell
PUCCH is allocated by
2 RB at the band edges (RB-pair)
Time domain sharing, each PUCCH is assigned to
a UE with a periodicity deciding which sub-frame
UE can access PUCCH (default periodicity for CQI
is 80ms, SR is 10ms)
Current setting
noOfPucchSrUsers, noOfPucchCqiUsers = 320

Pucch resources
highest pucch resources for sr & CQI
noOfPucchSrUsers (limited by nCQI.res)=noOfPucchCqiUsers=640
This setting will reduce peak UL throughput
3rd attempt (nRB,format1 = 6, nRB,format2 = 2)
nSR,res = (36*6-44)*10*10/10 = 1720 (>810)
nCQI,res = 2*4*80*10/10 = 640 (<880)
TSR = 10ms (SR periodicity)
nSF,PUCCH = 10 (# sub-frames for PUCCH)
ncap = 4 (CQI resources/RB pair)
TCQI = 80ms (CQI periodicity)
2nd attempt (nRB,format1 = 5, nRB,format2 = 3)
nSR,res = (36*5-44)*10*10/10 = 1360 (>810)
nCQI,res = 3*4*80*10/10 = 960 (>880)
1st attempt (nRB,format1 = nRB,format2 = 4)
nSR,res = (36*4-44)*10*10/10 = 1000 (>810)
nCQI,res = 4*4*80*10/10 = 1280 (>880)
Pucch resources
number of pucch rb-pairs
Recommended setting (noOfPucchSrUsers = noOfPucchCqiUsers = 640)
nPUCCH,SR = [640/10 * 10/10] = 64
nRB,Format1 = [(64+44)/36] = 3
nRB,Format2 = [640/(4*80) * 10/10] = 2
nRB,PUCCH = 3 + 2 = 5 (even 6, < max RB pair per DU)

Odd number will leave 1 RB-pair unused by PUCCH and PUSCH
Current setting (noOfPucchSrUsers = noOfPucchCqiUsers = 320)
nPUCCH,SR = [320/10 * 10/10] = 32
nRB,Format1 = [(32+44)/36] = 3
nRB,Format2 = [320/(4*80) * 10/10] = 1
nRB,PUCCH = 3 + 1 = 4
Pucch resources
observability
pmPucchSrCqiResCongCqi
The number of times a PUCCH allocation request for CQI resource(s) could not be granted

pmPucchSrCqiResCongSr
The number of times a PUCCH allocation request for SR resource(s) could not be granted

Prb utilization / cell throughput capacity
observability
Average Cell Throughput UL = pmUeThpVolUl/(pmSchedActivityCellUl/1000)
Average Cell Throughput DL = pmPdcpVolDlDrb/(pmSchedActivityCellDl/1000)

pmPrbUtilUl
A distribution that shows the uplink Physical Resource Block (PRB) pair utilization (total number of used PRB pairs by available PRB pairs) on the Physical Uplink Shared Channel (PUSCH)
pmPrbUtilDl
A distribution that shows the downlink Physical Resource Block (PRB) pair utilization (total number of used PRB pairs by available PRB pairs) on the Physical Downlink Shared Channel (PDSCH)

Average # Simultaneous Active UE UL = pmActiveUeUlSum/pmSchedActivityCellUl
Average # Simultaneous Active UE DL = pmActiveUeDlSum/pmSchedActivityCellDl

Focus areas
PUCCH Resources
PDCCH Resources
UL Noise Rise
MP Load
Hardware expansion

Mp load
mp load control mechanism (new in L13A)
Main contributors (signaling) for MP Load
RRC Connection Setups
Incoming Handovers
Paging Requests

Connected users
observability
pmRrcConnEstabFailLic
The total number of failed RRC Connection Establishments due to lack of connected users license
Connected users license
Current Connected Users License is 800 per DUL
Connected Users license should be topped-up for high traffic sites on demand basis
Increase Connected Users License may have impact on signaling load

Connected Users License check is part of RRC Setup procedure
DUL
Rrc Conn user
DUL21
1500
DUL31
2500
DUL41
3000
Focus areas
PUCCH Resources
PDCCH Resources
UL Noise Rise
MP Load
Hardware expansion

Mp load
observability
pmProcessorLoad
The average CPU load on the whole MP system (all the CPU cores).
pmProcessorLoadDistr
A distribution of the CPU load of the MP corresponding to the definition of the CPU load used by MP Load Management.
This counter also includes CPU load consumption from execution on priorities below traffic priority. This includes CPU load from performance management and some O&M tasks.

pmPagS1Received
This counter counts the number of received S1AP paging messages in the RBS.
pmPagS1Discarded
The number of discarded S1AP paging messages not routed to any cell due to high load (MP Load Control).

pmRrcConnEstabFailHighLoad
The total number of failed RRC connection establishments due to high load (MP Load Control).
pmRrcConnEstabFailOverload
The total number of failed RRC connection establishments due to overload (Procedure Latency Supervision).

pmHoPrepRejInHighLoad
The number of Handover Preparation Failure messages sent by the target eNodeB due to high load (MP Load Ccontrol).
pmHoPrepRejInOverload
The number of Handover Preparation Failure messages sent by the target eNodeB due to overload (Procedure Latency Supervision).

Focus areas
PUCCH Resources
PDCCH Resources
UL Noise Rise
MP Load
Hardware expansion

Summary of high cap parameters
Parameter
Current
Recommended
Objective
noOfPucchSrUsers
320
640
Maximize number of allowed SR users
noOfPucchCqiUsers
320
640
Maximize number of allowed CQI users
pdcchCfiMode (10MHz)
CFI_AUTO_MAXIMUM_3
CFI_AUTO_MAXIMUM_3 (no change)
Recommended setting is already set, just monitor CCE and CFI usage
pZeroNominalPucch
-117
-117 (no change)
Recommended setting is already set
pZeroNominalPusch
-96
-103
Reduce UL noise rise at high load
schedulingAlgorithm
3 (PROPORTIONAL_FAIR_MEDIUM)
4 (PROPORTIONAL_FAIR_LOW) or 5 (MAXIMUM_C_OVER_I)
Increase cell throughput and PRB utilization
tInactivityTimer
10s
30s
Reduce signaling load
SRB/DRB::dlMaxRetxThreshold
SRB/DRB::ulMaxRetxThreshold
8/8
8/8
8/8 (no change)
8/8 (no change)
Max # RLC re-Tx in UL/DL (control signaling load). Recommended setting is already set
SRB/DRB::tPollRetransmitDl
SRB/DRB::tPollRetransmitUl
45ms/50ms
45ms/50ms
80ms/80ms
80ms/80ms
Increase poll timer for RLC re-Tx (if no status report received) to avoid RLC failures, reduce signaling load
T310 / T311
20 / 1
20 / 1 (no change)
Recommended setting is already set, for RLC supervision
N310 / N311
2s / 3s
2s / 3s (no change)
Recommended setting is already set, for RLC supervision
a3Offset
30 (3dB)
50 (5dB) (low priority)
Reduce signaling load. Will review feasibility to use alternative approach on 'UE Level Oscillating Handover Minimization' feature
THNAK YOU
Mp load
1.2 RRC Connection setup intensity
(due to UE releases by rLC Supervision)
RLC re-transmissions are controlled by
Max # RLC re-transmissions before stopping and indicating to RRC max RLC re-tx reached
SRB/DRB :: dlMaxRetxThreshold (Current setting: 8/8, recommended, no change)
SRB/DRB :: ulMaxRetxThreshold (Current setting: 8/8, recommended, no change)
Poll timer for RLC re-Tx (if no status report received)
SRB/DRB :: tPollRetransmitDl (Current: 45ms/50ms, recommend 80ms/80ms)
SRB/DRB :: tPollRetransmitUl (Current: 45ms/50ms, recommend 80ms/80ms)

Increase Poll timer may reduce SE/TTI usage for re-Tx and free SE/TTI for traffic, but re-Tx time is extended from 360-400ms to 640ms (80ms x 8)

Re-Tx count
#1
…
#8
RLC Failure
Mp load
(due to UE releases by rLC Supervision) – cont'

As part of Radio Connection Supervision, RLC failures are caused by
T310 expiry
Max RLC re-transmissions reached
T310 is controlled by
After receiving N310 consecutive "out-of-sync" indications, start timer T310
After receiving N311 consecutive "in-sync" indications, stop timer T310
After T310 expired Radio Link Failure
Current settings:
N310 = 20 (recommended, no change)
N311 = 1 (recommended, no change)
T310 = 2s (recommended, no change)
UE is released after T310 (2s) + T311 (3s)
Mp load
(due to UE releases by inactivity)
The time a UE can be inactive before it is released is controlled by tInactivityTimer
Current setting for tInactivityTimer is 10s, requirement from UE vendor
Recommend to change to 30s to reduce signaling load for high capacity cells
For tInactivityTimer set to 30s,
E-RAB drop rate will increase due to the E-RAB drops only consider the abnormal E-RAB Releases if there was data in buffer (i.e. active).

Number of UEs stay in RRC_Connected state will be larger, thus lowering the number of available Connected Users License for new users
Control channel resources
UL Control Channel Resources
PUCCH
nRB,PUCCH depends on number of SR and CQI resources Focus Area for High Capacity Parameters
PRACH
nRB,PRACH in 1 radio frame is independent of bandwidth and is fixed for different cell range
DL Control Channel Resources
PDCCH
nRE,PDCCH depends on CFI Focus Area for High Capacity Parameters
PCFICH
nRE,PCFICH in 1 radio frame is 160, independent of bandwidth and # of antenna ports
PHICH
nRE,PHICH in 1 radio frame depends on bandwidth and is fixed for different bandwidth
PBCH
nRE,PBCH in 1 radio frame is 240, independent of bandwidth and # of antenna ports
Focus areas
PUCCH Resources
PDCCH Resources
UL Noise Rise
MP Load
Hardware expansion

Focus areas
PUCCH Resources
PDCCH Resources
UL Noise Rise
MP Load
Hardware expansion

Mp load
3. hardware expansion
MP capacity for DUS is higher than MP capacity on DUL

Lte High capacity event parameters
Prepared By:
RAJESH KUMAR
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Lte Capacity Troubleshooting

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