Lte High capacity event parameters

Report
Lte High capacity event parameters
Prepared By:
RAJESH KUMAR
Focus areas
•
LTE High Capacity Focus Areas
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. MP Load
•
RRC Connection Setup Intensity
– Due to UE releases by Inactivity
– Due to UE releases by RLC Supervision
•
Incoming Handover Intensity
•
Hardware expansion
5. Connected Users License
• Summary of High Capacity Parameter Settings
Focus areas
•
•
LTE High Capacity Focus Areas
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. MP Load
•
RRC Connection Setup Intensity
– Due to UE releases by Inactivity
– Due to UE releases by RLC Supervision
•
Incoming Handover Intensity
•
Hardware expansion
5. Connected Users License
Summary of High Capacity Parameter Settings
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
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 &TCQI
= 10ms (SR periodicity)
SR
nSF,PUCCH = 10 (# sub-frames for PUCCH)
ncap = 4 (CQI resources/RB pair)
TCQI = 80ms (CQI periodicity)
• 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)
› 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)
› 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)
noOfPucchSrUsers (limited by nCQI.res)=noOfPucchCqiUsers=640
This setting will reduce peak UL throughput
Pucch resources
number of pucch rb-pairs
•
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
› 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
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
Pdcch resources
• PDCCH is used for
adaptive pdcch (1/2)
– 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
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
Focus areas
•
LTE High Capacity Focus Areas
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. MP Load
•
RRC Connection Setup Intensity
– Due to UE releases by Inactivity
– Due to UE releases by RLC Supervision
•
Incoming Handover Intensity
•
Hardware expansion
5. Connected Users License
• Summary of High Capacity Parameter Settings
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
–
•
pmSinrPuschDistr
–
•
The measured Noise and Interference Power on PUCCH, according to 36.214
pmRadioTbsPwrRestricted
–
•
The measured Noise and Interference Power on PUSCH, according to 36.214 of the SINR values
calculated for PUSCH
pmRadioRecInterferencePwrPucch
–
•
Distribution of the SINR values calculated for PUSCH
pmRadioRecInterferencePwr
–
•
Distribution of the SINR values calculated for PUCCH
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
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. MP Load
•
RRC Connection Setup Intensity
– Due to UE releases by Inactivity
– Due to UE releases by RLC Supervision
•
Incoming Handover Intensity
•
Hardware expansion
5. Connected Users License
Summary of High Capacity Parameter Settings
Prb utilization / cell throughput capacity
schedulingalgorithm
•
Current setting schedulingAlgorithm = 3
(PROPORTIONAL_FAIR_MEDIUM),
propose to change to following at high
load
–
–



System Fairness
4 (PROPORTIONAL_FAIR_LOW) or
5 (MAXIMUM_C_OVER_I)
Higher Cell Throughput
Higher TTI utilization
Higher PRB utilization
For PFL or Max C/I, user at cell
edge may have low throughput, as
scheduler has higher weightage for
RF condition
Cell Throughput
•
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
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
•
•
LTE High Capacity Focus Areas
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. MP Load
•
RRC Connection Setup Intensity
– Due to UE releases by Inactivity
– Due to UE releases by RLC Supervision
•
Incoming Handover Intensity
•
Hardware expansion
5. Connected Users License
Summary of High Capacity Parameter Settings
Mp load
mp load control mechanism (new in L13A)
Main contributors (signaling) for MP Load
• RRC Connection Setups
• Incoming Handovers
• Paging Requests
Mp load
1.1 RRC Connection setup intensity
(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
Mp load
1.2 RRC Connection setup intensity
(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
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)
Re-Tx count
#1
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)
…
#8
RLC Failure
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
Mp load
3. hardware expansion
• MP capacity for DUS is higher than MP capacity
on DUL
Mp load
•
pmProcessorLoad
–
•
–
The number of Handover Preparation Failure messages sent by the target eNodeB due to high load (MP Load Ccontrol).
pmHoPrepRejInOverload
–
•
The total number of failed RRC connection establishments due to overload (Procedure Latency Supervision).
pmHoPrepRejInHighLoad
–
•
The total number of failed RRC connection establishments due to high load (MP Load Control).
pmRrcConnEstabFailOverload
–
•
The number of discarded S1AP paging messages not routed to any cell due to high load (MP Load Control).
pmRrcConnEstabFailHighLoad
–
•
This counter counts the number of received S1AP paging messages in the RBS.
pmPagS1Discarded
–
•
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
–
•
The average CPU load on the whole MP system (all the CPU cores).
pmProcessorLoadDistr
–
•
observability
The number of Handover Preparation Failure messages sent by the target eNodeB due to overload (Procedure Latency
Supervision).
Focus areas
• LTE High Capacity Focus Areas
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. 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
› Current Connected Users License is 800 per DUL
› Connected Users license should be topped-up for high traffic sites on demand basis
DUL
Rrc Conn user
DUL21
1500
DUL31
2500
DUL41
3000
Increase Connected Users License may
have impact on signaling load
Connected Users License
check is part of RRC
Setup procedure
Connected users
observability
• pmRrcConnEstabFailLic
– The total number of failed RRC Connection
Establishments due to lack of connected users
license
Focus areas
• LTE High Capacity Focus Areas
1. Control Channel Dimensioning
• PUCCH Resources
• PDCCH Resources
2. UL Noise Rise
3. PRB Utilization / Cell Throughput Capacity
4. MP Load
• RRC Connection Setup Intensity
– Due to UE releases by Inactivity
– Due to UE releases by RLC Supervision
• Incoming Handover Intensity
• Hardware expansion
5. Connected Users License
• Summary of High Capacity Parameter Settings
Parameter
Summary of high cap parameters
Current
Recommended
noOfPucchSrUsers
320
640
Maximize number of allowed SR users
noOfPucchCqiUsers
320
640
Maximize number of allowed CQI users
CFI_AUTO_MAXIMUM
_3
CFI_AUTO_MAXIMUM_3 (no
change)
pZeroNominalPucch
-117
-117 (no change)
pZeroNominalPusch
-96
-103
schedulingAlgorithm
3
(PROPORTIONAL_FAIR
_MEDIUM)
4 (PROPORTIONAL_FAIR_LOW)
or 5 (MAXIMUM_C_OVER_I)
tInactivityTimer
10s
30s
SRB/DRB::dlMaxRetxThreshold
SRB/DRB::ulMaxRetxThreshold
8/8
8/8
8/8 (no change)
8/8 (no change)
45ms/50ms
45ms/50ms
80ms/80ms
80ms/80ms
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
30 (3dB)
50 (5dB) (low priority)
pdcchCfiMode (10MHz)
SRB/DRB::tPollRetransmitDl
SRB/DRB::tPollRetransmitUl
a3Offset
Objective
Recommended setting is already set, just monitor CCE
and CFI usage
Recommended setting is already set
Reduce UL noise rise at high load
Increase cell throughput and PRB utilization
Reduce signaling load
Max # RLC re-Tx in UL/DL (control signaling load).
Recommended setting is already set
Increase poll timer for RLC re-Tx (if no status report
received) to avoid RLC failures, reduce signaling load
Reduce signaling load. Will review feasibility to use
alternative approach on ‘UE Level Oscillating Handover
Minimization’ feature
THNAK YOU

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