MIND recommendations
Default Recommended
value
value
NRCELL.totalNumberOfRAPreambles
64
16
NRCELL.prachConfigurationIndex
38
151
Description
For small cells deployment (short preamble formats) it may
be useful to reduce maximum number of preambles per cell
in order to increase re-use distance for root sequence index
(RSI) planning. There is no golden rule though - too low
number of preambles per cell may cause too much collisions
under heavy load.
Applicable for TDD FR1 (Frequency Range 1, below 6GHz):
Given PRACH indices give average capacity for PRACH with
B4 preamble format that on SCS 30kHz (FR1) provides at
maximum around 1.9km cell range.
Other
recommended
values
Environment/
Scenario
32
["Dense urban",
"Small Cell"]
156,157,158,
159,160
["General", "General"]
NRCELL.prachConfigurationIndex
38
94
NRCELL.prachConfigurationIndex
38
148
-104
-104
0
1
NRCELL.initialPreambleReceivedTarg
etPower
NRCELL.actBeamforming
NRCELL.beamSet.basicBeamSet
NRCELLGRP.numberOfTransmittedSs
Blocks
NRCELL.prachConfigurationIndex
NRCELL.initialPreambleReceivedTarg
etPower
1
1
7
Applicable for TDD FR1 (Frequency Range 1, below 6GHz):
Given PRACH indices give high capacity for PRACH with A2
preamble format that on SCS 30kHz (FR1) provides at
maximum around 1km cell range.
Applicable for TDD FR1 (Frequency Range 1, below 6GHz):
Given PRACH indices give low capacity for PRACH with B4
preamble format that on SCS 30kHz (FR1) provides at
maximum around 1.9km cell range.
initialPreambleReceivedTargetPower default value -104
(corresponding to -104dBm) is recommended for FR1.
Recommended value for FR2 is -116 (corresponding to 116dBm) - if NRCELL.nrarfcn is lower or equal to 800 000
then evaluated frequency range is FR1 (Frequency Range 2)
i.e. below 6GHz
102
["High traffic",
"Urban", "Dense
urban", "Small Cell"]
149
["Low traffic",
"General", "Urban",
"Sub-urban"]
["General", "General"]
["General", "General",
"General", "General"]
beamset_6_2 is providing best averaged throughput in
drive tests, beamset_6 and beamset_5_3 are also providing
good performance
to align with basicBeamSet equal to 2
16, 6
["Demo - peak
throughput",
"Demo"]
2
38
161
-104
-116
Applicable for TDD FR1 (Frequency Range 1, below 6GHz):
Given PRACH indices give high capacity for PRACH with B4
preamble format that on SCS 30kHz (FR1) provides at
maximum around 1.9km cell range.
Applicable for TDD FR2 (Frequency Range 2, above 6GHz):
Recommended value for
NRCELL.initialPreambleReceivedTargetPower is -116
(corresponding to -116dBm) for the sites deployed in
frequency range 2 above 6GHz.
["General", "General"]
162
["General", "High
traffic", "Urban",
"Sub-urban"]
["General", "General"]
NRCELL.initialPreambleReceivedTarg
etPower
NRCELL.beamSet.basicBeamSet
-104
1
-116
2
NRCELL.prachConfigurationIndex
38
12
NRCELL.cbraPreamblesPerSsb
64
56
NRCELL.zeroCorrelationZoneConfig
13
14
NRCELL.prachConfigurationIndex
38
90
NRCELL.zeroCorrelationZoneConfig
13
15
NRCELL.initialPreambleReceivedTarg
etPower
-104
-96
NRCELL.prachConfigurationIndex
38
92
initialPreambleReceivedTargetPower default value -104
(corresponding to -104dBm) is recommended for FR1.
Recommended value for FR2 is -116 (corresponding to 116dBm) - if NRCELL.nrarfcn is higher or equal to 2 016 667
then evaluated frequency range is FR2 (Frequency Range 2)
i.e. above 6GHz
peak throughput increased thanks to reduced SSB overhead
with 2 beams
Applicable for FDD (CellTechnology = 0) and FR1 (nrarfcn <=
800000): Mentioned values (12,13, 14) are mean for FDD
deployment and refers to configuration with long preamble
format (0) with maximum supported range of ~14.5km on
SCS=15kHz. It is to be used for FR1 for e.g. LTE refarming
purposes.
value n56 permits to activate contention free RACH during
handover, which leads to better handover success rate
if expected cell size is larger than 871 m in cmW and larger
than 218 m in mmW
Applicable for TDD (CellTechnology = 1) and FR1 (nrarfcn <=
800000): Given PRACH indices give average capacity for
PRACH with A2 preamble format that on SCS 30kHz (FR1)
provides at maximum around 1km cell range.
if expected cell size is larger than 1.3 km in cmW and larger
than 326 m in mmW
["General", "General"]
["Demo - peak
throughput",
"Demo"]
13,14
["General", "General"]
["General", "General"]
["General", "Suburban"]
96, 97
["General", "General"]
["General", "Rural"]
["General", "General"]
Applicable for TDD FR1 (Frequency Range 1, below 6GHz):
Given PRACH indices give low capacity for PRACH with A2
preamble format that on SCS 30kHz (FR1) provides at
maximum around 1km cell range.
93,98
["Low traffic",
"Urban", "Dense
urban", "Small Cell"]
MOC.abbreviation
Parameter name
NRCELLGRP.maxNumOfRrcCGRPSA
Maximum number of RRC connected
users in a New Radio Cell Group for SA
NRCELLGRP.addNumOfNonGBRBearersHo
NRCELL.qRxLevMinOffset
Additional number of non-GBR
capacity for handovers
Offset to the signaled q-RxLevMin
NRCELL.pMax
Maximum output power
NRCELL.maxNumOfUsers
Maximum number of users in a NR cell
for NSA operation
NRCELLGRP.maxNumOfNonGBRBearersCGRPSA Maximum number of non-GBR data
radio bearers in New Radio Cell Group
for SA
NRCELLGRP.numberOfTransmittedSsBlocks
Number of transmitted
Synchronization Signal Blocks
Default
value
Modification
Domain
250
onLine
["Call Blocking Rate", "Capacity",
"Accessibility"]
0
onLine
["Mobility", "Accessibility", "Capacity"]
onLine
["Accessibility", "Cell Coverage"]
Conditional BTS restart
["Throughput", "Critical", "Accessibility",
"Cell Coverage", "Throughput - Average in
DL"]
["Capacity", "Accessibility"]
250
onLine
500
onLine
["Call Blocking Rate", "Accessibility",
"Capacity"]
Conditional BTS restart
onLine
["Throughput", "Throughput - Average in
DL", "Cell Coverage", "Accessibility",
"Throughput - Peak in DL"]
["Call Setup Success Rate", "Accessibility"]
1
NRCELL.rsrpThresholdSSB
RSRP threshold for SSB block selection
NRCELL.prachSequenceType
PRACH sequence type
0
objectLocking
["Accessibility"]
NRCELL.preambleTransMax
6
onLine
3
onLine
["Call Setup Time", "Accessibility", "Call
Setup Success Rate"]
["Capacity", "Accessibility"]
NRCELL.zeroCorrelationZoneConfig
Maximum number of preamble
transmission
Maximum number of secondary cells
for DL carrier aggregation
Zero correlation zone config
13
objectLocking
["Call Setup Success Rate", "Accessibility"]
NRCELL.qQualMinOffset
Offset to the signalled q-QualMin
onLine
["Cell Coverage", "Accessibility"]
NRBTS.maxNumScells
NRCELL.raResponseWindow
NRCELLGRP.maxNumUeDl
NRCELL.cbraPreamblesPerSsb
NRCELLGRP.maxNumOfUsers
Duration of random access response
window
Maximum number of UEs scheduled in
DL TD scheduler
CBRA preambles per SSB
NRCELL.beamSet.basicBeamSet
Maximum number of users in a NR Cell
Group for NSA operation
Minimum required quality level in the
cell
Basic Beam Set
NRCELL.beamSet.nrBtsBeamRefinementP2
NRCELL.qQualMin
onLine
2
BTS restart needed
64
objectLocking
500
onLine
onLine
["Call Setup Success Rate", "Call Setup
Time", "Accessibility"]
["Capacity", "Call Blocking Rate",
"Accessibility"]
["Mobility", "Handover Success Rate",
"Accessibility", "Call Setup Success Rate"]
["Accessibility", "Capacity", "Call Blocking
Rate"]
["Accessibility", "Cell Coverage"]
1
objectLocking
BTS Beam Refinement P2
0
objectLocking
NRCELL.cbPreamblesPerSsb
CBRA preambles per SSB
64
objectLocking
NRCELL.prachRootSequenceIndex
PRACH root sequence index
0
objectLocking
["Accessibility", "Call Setup Success Rate"]
NRCELL.nbrOfSsbPerRachOccasion
Number of SSBs per RACH occasion
3
unmodifiable
["Accessibility", "Call Setup Success Rate"]
NRCELL.dlQam256PowerBackoffSub6
PDSCH Power Back-off for 256QAM
15
onLine
NRCELL.powerRampingStepHighPriorityCfra
Power Ramping Step High Priority
CFRA
Maximum number of users per CPCL
instance
Maximum number of users in a NR cell
for NSA operation
Msg3 Delta Preamble
2
onLine
["Throughput", "Cell Coverage",
"Throughput - Peak in DL", "Accessibility",
"Critical"]
["Call Setup Success Rate", "Accessibility"]
50000
onLine
["Accessibility", "Capacity"]
250
onLine
["Accessibility", "Capacity"]
1
onLine
["Accessibility"]
NRBTS.maxNumOfUsersPerCpCell
NRCELL.maxNumOfUsersPerCell
NRCELL.msg3DeltaPreamble
["Cell Coverage", "Throughput",
"Accessibility"]
["Accessibility", "Throughput", "Cell
Coverage"]
["Handover Success Rate", "Mobility", "Call
Setup Success Rate", "Accessibility"]
NRBTS.maxNumScellsUl
NRCELL.raContentionResolutionTmr
NRBTS.pfaTargetPRACH
NRCELL.msg1FrequencyStart
Maximum number of secondary cells
for UL carrier aggregation
Timer for contention resolution
Probability False Alarm Target for
PRACH
PRACH Frequency start
1
onLine
["Capacity", "Accessibility"]
7
onLine
3
BTS restart needed
["Call Setup Success Rate", "Accessibility",
"Call Setup Time"]
["Accessibility", "Call Setup Success Rate"]
0
objectLocking
["Accessibility", "Call Setup Success Rate"]
KPI ID
KPI Name
Unit
Starting release
NR_5135a
5G Uplink carrier aggregation activated to configured SCell ratio
%
5G18A
NR_5006a
5G Status Transfer failure ratio during SgNB Addition
%
5G18A
NR_5010a
5G Contention free RACH setup attempts
#
5G18A
NR_5014a
5G Radio admission success ratio for NSA user
%
5G18A
NR_5020b
5G Non Stand Alone call accessibility, 5G side
%
5G19
NR_5124a
5G Average number of NSA users
#
5G18A
NR_5125a
5G Maximum number of NSA users
#
5G18A
NR_5013a
5G Contention based RACH setup success ratio
%
5G18A
NR_5130a
5G Downlink carrier aggregation reconfiguration success ratio
%
5G18A
NR_5131a
5G Downlink carrier aggregation reconfiguration attempts
#
5G18A
NR_5134a
5G Downlink carrier aggregation activated to configured SCell ratio
%
5G18A
NR_5011a
5G Contention free RACH setup success ratio
%
5G18A
NR_5015a
5G Number of radio admission requests for NSA user
#
5G18A
NR_5132a
5G Uplink carrier aggregation reconfiguration success ratio
%
5G18A
Related Features
KPI ID
KPI Name
Unit
Starting release
LTE_6420a
E-UTRAN EN-DC X2 Setup Attempts
#
LTE18SP
LTE_6420a
E-UTRAN EN-DC X2 Setup Attempts
#
LTE18SP
LTE_6435a
Average number of UEs capable for EN-DC
#
LTE18SP
LTE_6431a
SCG Addition Preparation Attempts
#
LTE18SP
LTE_6432a
SCG Addition Preparation Failure Ratio due to SgNB Rejection
%
LTE18SP
LTE_6431a
SCG Addition Preparation Attempts
#
LTE18SP
LTE_6432a
SCG Addition Preparation Failure Ratio due to SgNB Rejection
%
LTE18SP
LTE_6419a
E-UTRAN EN-DC X2 Setup Success Ratio
%
LTE18SP
LTE_6430a
E-UTRAN Initial E-RAB Setup Success Ratio for MCG bearer with NR PDCP
%
LTE18SP
LTE_6434a
Maximum number of UEs capable for EN-DC
#
LTE18SP
LTE_6419a
E-UTRAN EN-DC X2 Setup Success Ratio
%
LTE18SP
LTE_6429a
E-UTRAN Initial E-RAB Setup Attempts for MCG bearer with NR PDCP
#
LTE18SP
LTE_6433a
SCG Addition Preparation Failure Ratio due to timer expiry (T_DC_Prep)
%
LTE18SP
LTE_6433a
SCG Addition Preparation Failure Ratio due to timer expiry (T_DC_Prep)
%
LTE18SP
Related Features
MIND recommendations
NRCELL.a3MeasEnabled
Default
value
Recommended
value
0
1
NRCELL.a3MeasSsbRsrp.a3HysteresisSsbRsrp
Environment/Scenario
["General", "General"]
4
2 dB is better to avoid ping pong handover
["General", "General"]
value n56 permits to activate contention
free RACH during handover, which leads to
better handover success rate
["General", "General"]
NRCELL.cbraPreamblesPerSsb
64
56
NRBTS.actDataDuplicationForMobility
0
1
NRCELL.a3MeasSsbRsrp.a3TimeToTriggerSsbRsrp
Description
Other
recommended
values
8
["General", "General"]
320 ms is better to avoid ping pong
handover
["General", "General"]
NRBTS.actIntraFreqInterGnbMobilityNSA3x
0
1
NRBTS.actIntraFreqIntraGnbMobilityNSA
0
1
NRCELL.a3MeasSsbRsrp.a3OffsetSsbRsrp
8
Inter-gNB mobility can be activated to
improve mobility and retainability KPIs
["General", "General"]
["General", "General",
"General", "General"]
["General", "General"]
4 dB A3 offset is better to avoid ping pong
handover
MOC.abbreviation
Parameter name
NRCELL.cbPreamblesPerSsb
CBRA preambles per SSB
NRHOIF.a5MeasSsbRsrq.a5HysteresisSsbRsrq
A5 Hysteresis Ssb Rsrq
NRHOIF.a3MeasEnabled
A3 Measurement Configuration Enabled
NRHOIF.a5MeasSsbRsrq.a5TimeToTriggerSsbRsrq
Default
value
Modification
Domain
64
objectLocking
["Handover Success Rate", "Call Setup
Success Rate", "Mobility", "Accessibility"]
onLine
["Mobility"]
onLine
["Mobility"]
A5 Time To Trigger Ssb Rsrq
onLine
["Mobility"]
NRCELL.sMeasConfigSsbRsrp
s-Measure Configuration Ssb Rsrp
onLine
["Mobility"]
NRREL.cellIndividualSsbRsrqOffset
onLine
["Mobility"]
NRCELL.a3MeasSsbRsrq.a3OffsetSsbRsrq
Cell individual SSB RSRQ offset of related
neighbor cell
a3 Offset Ssb Rsrq
onLine
["Mobility", "Handover Success Rate"]
NRHOIF.a5MeasSsbRsrq.a5Threshold2SsbRsrq
a5 Threshold2 Ssb Rsrq
onLine
["Mobility"]
NRHOIF.a3MeasSsbRsrp.a3HysteresisSsbRsrp
a3 Hysteresis Ssb Rsrp
onLine
["Mobility"]
NRCELL.cbraPreamblesPerSsb
CBRA preambles per SSB
NRHOIF.a3MeasSsbRsrq.a3OffsetSsbRsrq
a3 Offset Ssb Rsrq
NRCELL.a5MeasEnabled
a5 Measurement Configuration Enabled
0
24
64
0
objectLocking
onLine
["Accessibility", "Call Setup Success Rate",
"Handover Success Rate", "Mobility"]
["Mobility"]
onLine
["Mobility", "Handover Success Rate"]
NRHOIF.a3MeasSsbRsrp.a3OffsetSsbRsrp
a3 Offset Ssb Rsrp
onLine
["Mobility"]
NRCELL.filterCoeffSsbRsrq
Filter Coefficient Ssb Rsrq
onLine
["Handover Success Rate", "Mobility"]
NRHOIF.a5MeasSsbRsrq.a5Threshold1SsbRsrq
a5 Threshold1 Ssb Rsrq
onLine
["Mobility"]
NRCELL.cellIndividualSsbRsrpOffset
Cell Individual SSB RSRP Offset
onLine
["Handover Success Rate", "Mobility"]
NRHOIF.a3MeasSsbRsrp.a3TimeToTriggerSsbRsrp
a3 Time To Trigger Ssb Rsrp
onLine
["Mobility"]
NRHOIF.a5MeasSsbRsrp.a5Threshold2SsbRsrp
a5 Threshold2 Ssb Rsrp
onLine
["Mobility"]
NRBTS.actDataDuplicationForSAMobility
Activate data duplication for SA mobility
onLine
["Mobility", "Handover Success Rate"]
NRCELL.a3MeasSsbRsrp.a3HysteresisSsbRsrp
a3 Hysteresis Ssb Rsrp
onLine
["Mobility", "Handover Success Rate"]
NRCELLGRP.addNumOfHoUsers
0
onLine
NRCELL.a3MeasEnabled
Additional number of user capacity for
handovers
a3 Measurement Configuration Enabled
0
onLine
["Handover Success Rate", "Accessibility",
"Capacity", "Mobility"]
["Mobility", "Handover Success Rate"]
NRHOIF.a5MeasSsbRsrp.a5Threshold1SsbRsrp
a5 Threshold1 Ssb Rsrp
onLine
["Mobility"]
NRHOIF.a5MeasSsbRsrp.a5HysteresisSsbRsrp
A5 Hysteresis Ssb Rsrp
onLine
["Mobility"]
NRBTS.actIntraMeNBMobility
Activate intra MeNB mobility
0
onLine
["Mobility"]
NRCELL.filterCoeffSsbRsrp
Filter Coefficient Ssb Rsrp
4
onLine
["Mobility", "Handover Success Rate"]
NRHOIF.a5MeasEnabled
A5 Measurement Configuration Enabled
0
onLine
["Mobility"]
NRREL.cellIndividualSsbRsrpOffset
Cell individual SSB RSRP offset of related
neighbor cell
A5 Time To Trigger Ssb Rsrp
24
onLine
["Mobility"]
onLine
["Mobility"]
NRBTS.actIntraFreqIntraGnbMobilityNSA
Activate intra-frequency intra-gNB mobility
NSA
0
onLine
NRBTS.actDataDuplicationForMobility
Activate data duplication for mobility
0
onLine
["Throughput", "Throughput - Average in
UL", "Mobility", "Handover Success Rate",
"Throughput - Average in DL"]
["Mobility", "Handover Success Rate"]
NRCELL.a3MeasSsbRsrp.a3OffsetSsbRsrp
a3 Offset Ssb Rsrp
onLine
["Handover Success Rate", "Mobility"]
NRCELL.cellIndividualSsbRsrqOffset
Cell Individual SSB RSRQ Offset
onLine
["Handover Success Rate", "Mobility"]
NRHOIF.a5MeasSsbRsrp.a5TimeToTriggerSsbRsrp
4
24
0
24
NRBTS.actIntraFreqInterGnbMobilityNSA3x
Activate intra-frequency inter-gNB mobility
NSA 3x
NRCELL.a3MeasSsbRsrq.a3HysteresisSsbRsrq
a3 Hysteresis Ssb Rsrq
NRCELLGRP.addNumOfNonGBRBearersHo
NRCELL.a3MeasSsbRsrq.a3TimeToTriggerSsbRsrq
Additional number of non-GBR capacity for
handovers
a3 Time To Trigger Ssb Rsrq
NRCELL.a3MeasSsbRsrp.a3TimeToTriggerSsbRsrp
0
onLine
onLine
["Mobility", "Throughput - Average in DL",
"Throughput", "Throughput - Average in
UL"]
["Mobility", "Handover Success Rate"]
onLine
["Mobility", "Capacity", "Accessibility"]
onLine
["Mobility", "Handover Success Rate"]
a3 Time To Trigger Ssb Rsrp
onLine
["Handover Success Rate", "Mobility"]
NRHOIF.a3MeasSsbRsrq.a3HysteresisSsbRsrq
a3 Hysteresis Ssb Rsrq
onLine
["Mobility"]
NRHOIF.a3MeasSsbRsrq.a3TimeToTriggerSsbRsrq
a3 Time To Trigger Ssb Rsrq
onLine
["Mobility"]
0
KPI ID
KPI Name
Unit
Starting release
NR_5044a
5G Average duration of executed intra gNB intra frequency PSCell changes
ms
5G18A
NR_5040a
5G Intra gNB intra frequency PSCell change preparation attempts
#
5G18A
NR_5043a
5G Intra gNB intra frequency PSCell change total failure ratio
%
5G18A
NR_5041a
5G Intra gNB intra frequency PSCell change preparation success ratio
%
5G18A
NR_5042a
5G Intra gNB intra frequency PSCell change total success ratio
%
5G18A
Related Features
Other
recommended
values
Default
value
Recommended
value
NRBTS.tRLFindForDU
0
8
To avoid too sensitive RLF detection
["General", "General"]
NRBTS.drbRlcAmDefProf.dlMaxRetxThreshold
16
32
To avoid too sensitive RLC max retransmission
["General", "General"]
NRBTS.rlcProf4.maxRetxThreshold
6
7
["General", "General"]
NRBTS.rlcProf4.maxRetxThreshold
6
32
["General", "General"]
NRBTS.actInactDetNSAUe
0
1
NRBTS.drbRlcAmDefProf.ulMaxRetxThreshold
16
32
["General", "General",
"General", "General"]
["General", "General"]
MIND recommendations
Description
To avoid too sensitive RLC max retransmission
Environment/Scenario
NRBTS.tRLFindForDU
0
8
MOC.abbreviation
Parameter name
NRBTS.srb1RlcAmProf.ulMaxRetxThreshold
Maximum retransmission threshold UL
NRBTS.rlcProf1.maxRetxThreshold
["General", "General"]
Default
value
Modification
Domain
4
BTS restart needed
["Retainability", "Radio Link Failure"]
Maximum retransmission threshold
6
BTS restart needed
["Radio Link Failure", "Retainability"]
NRBTS.srb1RlcAmProf.dlMaxRetxThreshold
Maximum retransmission threshold DL
4
BTS restart needed
["Retainability", "Radio Link Failure"]
NRBTS.srb2RlcAmProf.ulMaxRetxThreshold
Maximum retransmission threshold UL
4
BTS restart needed
["Retainability", "Radio Link Failure"]
NRBTS.n311
Number n311
1
onLine
["Radio Link Failure", "Retainability"]
NRBTS.drbRlcAmDefProf.dlMaxRetxThreshold
Maximum retransmission threshold DL
16
onLine
NRBTS.rlcProf2.maxRetxThreshold
Maximum retransmission threshold
6
BTS restart needed
["Radio Link Failure", "Retainability",
"Throughput"]
["Radio Link Failure", "Retainability"]
NRBTS.nsaInactivityTimer
Non Stand Alone inactivity timer
10
onLine
["Retainability", "Radio Link Failure"]
NRBTS.actUeInitRlf
Activate UE initiated RLF
1
BTS restart needed
["Radio Link Failure", "Retainability"]
NRBTS.t310
Timer t310
6
onLine
NRBTS.rlcProf4.maxRetxThreshold
Maximum retransmission threshold
6
onLine
NRBTS.n310
Number n310
10
onLine
["Retainability", "Radio Link Failure", "Call
Drop Rate"]
["Retainability", "Throughput", "Radio Link
Failure"]
["Radio Link Failure", "Retainability"]
NRBTS.actNbInitRlf
Activate gNB initiated RLF
1
BTS restart needed
["Radio Link Failure", "Retainability"]
NRBTS.tRLFindForDU
RLF indication timer for DU
0
onLine
["Radio Link Failure", "Retainability"]
NRBTS.srb2RlcAmProf.dlMaxRetxThreshold
Maximum retransmission threshold DL
4
BTS restart needed
["Radio Link Failure", "Retainability"]
NRBTS.drbRlcAmDefProf.ulMaxRetxThreshold
Maximum retransmission threshold UL
16
onLine
NRBTS.tWaitingRlRecover
Waiting RL Recovery timer
3
onLine
["Retainability", "Radio Link Failure",
"Throughput"]
["Retainability", "Radio Link Failure"]
NRBTS.srb3RlcAmProf.dlMaxRetxThreshold
Maximum retransmission threshold DL
4
BTS restart needed
["Radio Link Failure", "Retainability"]
NRBTS.timerF1UeProcGuard
F1AP UE Proc Guard Timer
onLine
["Retainability", "Radio Link Failure"]
2500
NRBTS.rlcProf3.maxRetxThreshold
Maximum retransmission threshold
6
BTS restart needed
["Retainability", "Radio Link Failure"]
NRBTS.actInactDetNSAUe
Activate inactivity detection for NSA UE
0
onLine
["Retainability", "Radio Link Failure"]
NRBTS.srb3RlcAmProf.ulMaxRetxThreshold
Maximum retransmission threshold UL
4
BTS restart needed
["Retainability", "Radio Link Failure"]
NRBTS.actGnbInitRlf
Activate gNB initiated RLF
1
BTS restart needed
["Retainability", "Radio Link Failure"]
KPI ID
KPI Name
Unit
Starting release
NR_5030a
5G SgNB triggered normal release ratio
%
5G18A
NR_5031a
5G Total number of releases on SgNB side
#
5G18A
NR_5036b
5G Number of UE releases due to radio link failure
#
5G19
NR_5035a
5G Number of MeNB initiated SgNB releases
#
5G18A
NR_7a
5G SgNB release success ratio due to user inactivity
%
5G18A
NR_5036a
5G Number of UE radio link failures
#
5G18A
NR_6a
5G Number of SgNB initiated releases due to user inactivity
#
5G18A
Related Features
5GC000479
5GC000479
Other
recommanded
values
Default
value
Recommended
value
-300
-15
["General", "General"]
NRBTS.rlcProf4.tStatusProhibit
3
4
["General", "General"]
NRBTS.rlcProf4.tStatusProhibit
3
2
["General", "General"]
150
10
To allow OLLA room to adjust MCS
1
7
beamset_6_2 is providing best averaged
throughput in drive tests, beamset_6
and beamset_5_3 are also providing
good performance
MIND recommendations
NRCELL.ullaDeltaSinrMin
NRCELL.ullaDeltaSinrMax
NRCELL.beamSet.basicBeamSet
Description
Environment/Scenario
["General", "General"]
16, 6
["General", "General"]
NRBTS.qciTab6Nsa3x.dlFlowControlAlgo
0
1
NRCELL.dlMimoMode
30
60
["General", "General"]
NRCELLGRP.csiReportPeriodicity
320
40
["Low Latency", "General"]
NRCELL.actBeamforming
0
1
NRCELL.tddFrameStructure.ulDlDataSlotRatio
2
5
NRBTS.actIntraFreqIntraGnbMobilityNSA
0
1
NRBTS.fiveQiTab6.dlFlowControlAlgo
0
1
NRCELL.dlMimoMode
30
60
["General", "General"]
NRBTS.qciTab9Nsa3x.dlFlowControlAlgo
0
1
["General", "General"]
NRBTS.rlcProf4.maxRetxThreshold
6
32
["General", "General"]
NRBTS.rlcProf4.ulPollByte
13
11
["General", "General"]
NRBTS.actNonGbrServiceDiff
0
TRUE
NRCELL.ulPowerControlCommon.p0NominalPucch
-108
-90
NRCELL.dllaDeltaCqiMin
-150
-15
0
1
["General", "General"]
255
1
["General", "General"]
NRCELL.actDl256Qam
0
1
NRBTS.drbRlcAmDefProf.ulMaxRetxThreshold
16
32
NRBTS.fiveQiTab9.dlFlowControlAlgo
NRCELL.dlDMRSAdditionalPosition
Only example for QCI tab 6 shown. Can
also be QCI 7, 8, 9, 69 or 70 (any of these
is OK)
semistatic 1/4 is better for peak
throughput demo, if regulations allows
it.
["General", "General"]
["General", "General", "General",
"General"]
["Demo - peak throughput",
"Demo"]
["General", "General", "General",
"General"]
["General", "General"]
It is recommended, that 5GC000776
Non-GBR service differentiation should
be activated, to allow gNB to take into
account service type in scheduling
process.
Increase allowed OLLA range due to
optimistic CQI reporting from UE
Enabled 256QAM on cmWave for better
throughput
To avoid too sensitive RLC max
retransmission
["General", "General"]
["General", "General", "General",
"General"]
["General", "General"]
["General", "General"]
["General", "General"]
NRCELLGRP.csiReportPeriodicity
320
160
["General", "General"]
NRBTS.qciTab8Nsa3x.dlFlowControlAlgo
0
1
["General", "General"]
NRBTS.fiveQiTab7.dlFlowControlAlgo
0
1
["General", "General"]
NRBTS.drbRlcAmDefProf.dlMaxRetxThreshold
16
32
NRBTS.actIntraFreqInterGnbMobilityNSA3x
0
1
-72
-96
NRCELL.ulPowerControlCommon.p0NominalPusch
To avoid too sensitive RLC max
retransmission
Inter-gNB mobility can be activated to
improve mobility and retainability KPIs
["General", "General"]
["General", "General"]
["General", "General"]
Default
value
MOC.abbreviation
Parameter name
Modification
NRCELL.dlMimoMode
Downlink MIMO Mode
NRBTS.qciTab8Nsa3x.numSduDiscard
Number of SDUs to discard
NRCELL.ulDMRSAdditionalPosition
Uplink DMRS additional position
NRBTS.qciTab6Nsa3x.numSduDiscard
Number of SDUs to discard
1 onLine
["Throughput - Average in UL",
"Throughput", "Throughput - Peak in UL"]
["Critical", "Throughput"]
NRBTS.fiveQiTab9.numSduDiscard
Number of SDUs to discard
1 onLine
["Throughput", "Critical"]
NRCELL.rloPathLossThreshold
Radio link outage path loss threshold
NRCELL.csirsForTracking.csirsTrackingPeriod
CSI-RS Tracking Period
80 objectLocking
NRCELLGRP.ullaDeltaSinrMin
Delta SINR minimum of UL OLLA
NRBTS.actNonGbrServiceDiff
Activate non-GBR service differentiation
-30 BTS restart
needed
0 onLine
NRCELL.actDlMuMimo
Activate DL MU-MIMO
30 Conditional BTS
restart
1 onLine
255 objectLocking
130 onLine
0 objectLocking
Domain
["Throughput", "Throughput - Peak in
DL"]
["Critical", "Throughput"]
["Throughput - Average in UL",
"Throughput"]
["Throughput"]
["Throughput", "MCS Usage"]
["Throughput"]
["Throughput - Peak in DL",
"Throughput", "Throughput - Average in
DL"]
NRCELLGRP.dllaDeltaCqiMin
Delta CQI minimum of DL OLLA
-30 BTS restart
needed
15 objectLocking
NRCELLGRP.pucchF2MaxCodeRate
Pucch F2 Max Code Rate
NRBTS.fiveQiTab6.queuingDelayDiscardEnabled
Queue delay SDU discard enabled
NRBTS.qciTab6Nsa3x.ulDataSplitThreshold
UL Data Split threshold
100 onLine
NRBTS.qciTab8Nsa3x.sduDiscardIntervalTmr
SDU discard interval timer
100 onLine
NRBTS.fiveQiTab7.dlFlowControlAlgo
DL flow control algorithm
0 onLine
NRBTS.fiveQiTab8.numSduDiscard
Number of SDUs to discard
1 onLine
["Critical", "Throughput - Average in DL",
"Throughput"]
["Critical", "Throughput"]
NRCELL.ullaIniMcs
Initial MCS for UL Transmission
0 onLine
["Throughput", "MCS Usage"]
NRCELLGRP.ullaBlerTarget
BLER target for UL transmission
NRBTS.drbRlcAmDefProf.ulTPollRetr
Timer poll retransmit UL
NRBTS.pdcpProf2.pdcpBufDiscardEnabled
PDCP Buffer Discarding Enabled
1 onLine
["Throughput"]
NRBTS.mcsDeactSCellUl
UL MCS for SCell deactivation
3 onLine
["Throughput", "MCS Usage"]
NRBTS.qciTab8Nsa3x.ulDataSplitThreshold
UL Data Split threshold
100 onLine
NRCELL.tddFrameStructure
TDD frame structure
NRBTS.pdcpProf2.tReorderingUL
Timer reordering
Conditional BTS
restart
100 onLine
NRBTS.qciTab6Nsa3x.dlFlowControlAlgo
DL flow control algorithm
0 onLine
NRBTS.qciTab6Nsa3x.initialDLTrafficRouting
Default DL traffic routing
1 onLine
NRCELL.ulPowerControlCommon.p0NominalSrs
P0 nominal SRS
NRCELL.sulConf.ullaIniMcsSUL
Initial MCS for UL Transmission on
supplemental UL carrier
1 onLine
10 BTS restart
needed
45 onLine
-72 onLine
0 onLine
["Throughput", "MCS Usage"]
["Throughput - Average in DL",
"Capacity", "Throughput"]
["Critical", "Throughput"]
["Critical", "Throughput - Average in UL",
"Throughput"]
["Throughput", "Critical"]
["Throughput", "MCS Usage"]
["Throughput"]
["Throughput - Average in UL", "Critical",
"Throughput"]
["Throughput"]
["Throughput"]
["Throughput - Average in DL", "Critical",
"Throughput"]
["Throughput - Average in DL", "Critical",
"Throughput"]
["Throughput", "MCS Usage", "Critical"]
["MCS Usage", "Throughput"]
NRCELL.rlResumeSinrThreshold
Radio link resume SINR threshold
NRCELL.dllaIniMcs
Initial MCS for DL transmission
NRCELL.pMaxNROwnCell
Maximum UL transmit power on own cell
NRCELL.drxProfile1
DRX Profile 1
-30 onLine
3 onLine
20 onLine
onLine
KPI ID
KPI Name
Unit
Starting
release
NR_5057a
5G Residual BLER in PUSCH using 64QAM MCS table
%
5G18A
NR_5063a
5G Average UE related SINR for PUSCH in Rank 2
dB
5G18A
NR_5091a
5G Active cell MAC PDU throughput on PUSCH on initial HARQ transmissions
Mbit/s
5G18A
NR_5121a
5G Average number of active UEs with data in the buffer for DRBs in UL
#
5G18A
NR_5141a
5G F1 data split ratio in uplink
%
5G18A
NR_5065a
5G Average UE related SINR for PUCCH
dB
5G18A
NR_5083a
5G MAC SDU data volume received in UL on DTCH
MB
5G18A
NR_5084a
5G NSA PDCP SDU throughput (without repetitions) in DL
Mbit/s
5G18A
NR_5085a
5G NSA PDCP SDU throughput (without repetitions) in UL
Mbit/s
5G18A
NR_5088a
5G MAC PDU Cell throughput on active PDSCH data slots on initial HARQ transmissions
Mbit/s
5G18A
NR_5114a
5G PRB utilization for PDSCH
%
5G18A
NR_5120a
5G Average number of active UEs with data in the buffer for DRBs in DL
#
5G18A
NR_5140b
5G F1 data split ratio in downlink
%
5G19
NR_5063b
5G Average UE related SINR for PUSCH in Rank 2
dB
5G19
NR_5064a
5G Average UE related RSSI for PUSCH
dBm
5G18A
NR_5123a
5G Maximum number of active UEs with data in the buffer for DRBs in UL
#
5G18A
NR_5140a
5G F1 data split ratio in downlink
%
5G18A
NR_5060a
5G Average wideband CQI, 64QAM table
#
5G18A
NR_5061a
5G Average wideband CQI, 256QAM table
#
5G18A
NR_5080a
5G PDCP SDU data volume transmitted without repetitions in DL
MB
5G18A
["Throughput - Average in UL",
"Throughput"]
["MCS Usage", "Throughput"]
["Critical", "Throughput"]
["Throughput", "Throughput - Average in
DL", "Packet Delay"]
Related Features
NR_5081a
5G PDCP SDU data volume received without repetitions in UL
MB
5G18A
NR_5100a
5G Average MAC layer user throughput in downlink
Mbit/s
5G18A
NR_5101a
5G Average MAC layer user throughput in uplink
Mbit/s
5G18A
NR_5110a
5G Usage ratio of PDSCH data slots over all DL data slots
%
5G18A
NR_5115a
5G PRB utilization for PUSCH
%
5G18A
NR_5141b
5G F1 data split ratio in uplink
%
5G19
NR_5054a
5G Initial BLER in downlink transmissions in PDSCH
%
5G18A
NR_5055a
5G Residual Block Error Ratio (BLER) for PDSCH
%
5G18A
NR_5056a
5G Initial BLER in PUSCH using 64QAM MCS table
%
5G18A
NR_5062a
5G Average UE related SINR for PUSCH in Rank 1
dB
5G18A
NR_5062b
5G Average UE related SINR for PUSCH in Rank 1
dB
5G19
NR_5066a
5G Average UE related RSSI for PUCCH
dBm
5G18A
NR_5082a
5G MAC SDU data volume transmitted in DL on DTCH
MB
5G18A
NR_5089a
Mbit/s
5G18A
NR_5090a
5G MAC PDU Cell throughput on active PUSCH data slots using 64QAM table on initial
HARQ transmissions
5G Active cell MAC PDU throughput on PDSCH on initial HARQ transmissions
Mbit/s
5G18A
NR_5111a
5G Usage ratio of PUSCH data slots over all UL data slots
%
5G18A
NR_5122a
5G Maximum number of active UEs with data in the buffer for DRBs in DL
#
5G18A
Other
recommended
values
Default
value
Recommended
value
320
80
0
1
320
40
NRCELLGRP.actProactUlScheduling
0
1
NRCELLGRP.ulSchedTimeInterval
40
200
["General", "Demo - peak throughput", "Low
Latency", "General"]
["General", "Demo - peak throughput"]
NRCELLGRP.csiReportPeriodicity
320
160
["General", "General"]
MIND recommendations
NRCELLGRP.csiReportPeriodicity
NRCELL.actCDrx
NRCELLGRP.csiReportPeriodicity
Description
Environment/Scenario
["General", "Demo - peak throughput"]
["General", "General"]
["General", "Low Latency"]
MOC.abbreviation
Parameter name
NRCELL.drxWactUlEnabled
DRX scheduling weight for UL enabled
NRCELL.drxWactDlEnabled
Default
value
Modification
Domain
0
onLine
DRX scheduling weight for DL enabled
0
onLine
NRCELL.drxProfile1.drxRetransTimerDl
DRX Retransmission Timer for Downlink
24
onLine
NRCELLGRP.ulSchedTimeInterval
UL scheduling time interval
40
NRCELL.drxProfile1.drxInactivityTimer
DRX Inactivity Timer
4
Conditional
BTS restart
onLine
["Throughput", "Throughput - Average in UL", "Packet
Delay"]
["Throughput - Average in DL", "Packet Delay",
"Throughput"]
["Packet Delay", "Throughput - Average in DL",
"Throughput"]
["Packet Delay", "Usage"]
NRCELL.drxProfile1.drxOnDurationTimer
DRX On Duration Timer
7
onLine
NRCELL.actCDrx
Activate connected DRX
0
onLine
["Throughput - Average in DL", "Packet Delay",
"Throughput"]
["Packet Delay", "Critical"]
NRCELLGRP.csiReportPeriodicity
CSI Reporting Periodicity
320
objectLocking
["Usage", "Packet Delay", "Throughput"]
NRCELL.drxProfile1.drxLongCycle
DRX Long Cycle
onLine
NRCELL.drxProfile1
DRX Profile 1
NRCELLGRP.actProactUlScheduling
Activate UL proactive scheduling
["Throughput", "Throughput - Average in DL", "Packet
Delay"]
["Throughput - Average in DL", "Packet Delay",
"Throughput"]
["Packet Delay", "Usage", "Throughput"]
3
onLine
0
Conditional
BTS restart
["Packet Delay", "Throughput"]
KPI ID
KPI Name
Unit
Starting release
R_5051a
5G Average estimated X2 round trip delay between CU and MAC eNB
ms
5G18A
NR_5050a
5G Average estimated F1 round trip delay between CU and MAC DU
ms
5G18A
Related Features
5G19A Accessibility
The objective of this section is to describe the parameters and KPIs related to accessibility
optimisation
Back to Parameter Overview
Introduction :
Accessibility is one of the most important procedures in Radio Optimisation since no access means
no service. In 5G, it starts from when UE exits idle/fly mode till the success of 5G RACH procedure
including RRC establishment in LTE (for NSA Case).
This section consists in finding a way to tune and gives recommendation on accessibility related
parameters based on listed degraded KPIs (will be listed later)
Three major sub-areas can be identified for the accessibility domain :
•
Coverage
•
Random Access (RACH)
•
Radio Admission Control
Radio admission control
High Load leads to high usage, the purpose of admission control is to manage the use of radio
resources by accepting or rejecting requests, based on the following basic thresholds :
•
Number of active UEs operating in NSA mode 3x per 5G cell group
NRCELLGRP:maxNumOfUsers
•
Number of active UEs operating in NSA mode 3x per 5G cell NRCELL:maxNumOfUsersPerCell
•
Number of non-GBR DRBs of active UEs operating in NSA mode 3x per 5G cell group
NRCELLGRP:maxNumOfNonGBRBearers
While receiving X2: SgNB Addition Request/modification gNB perform the below check to admit or
reject the connection :
For Handover part additional number of NSA UEs and non-GBR DRBs in the Cell Group level are
needed introduced by the parameter NRCELLGRP:addNumOfHoUsers and
NRCELLGRP:addNumOfNonGBRBearersHo
Since Admission control is performed at the reception of X2: SgNB Addition Request/modification
the starting point for performances monitoring will be the below KPIs: :
•
5G SgNB addition preparation success ratio [%] Id: NR_5004b
•
5G SgNB modification preparation success ratio [%] Id: NR_496b
When will be faced a degradation on the above mentioned KPIs, the radio admission control
performance can be checked using following KPIs :
•
5G Radio admission success ratio for NSA user [%] Id: NR_5014a and the related cause of
rejection
•
5G Radio admission success ratio for NSA user in handover [%] Id: NR_50a
•
5G Non-GBR DRB radio admissions success ratio for NSA user in handover [%] Id: NR_51a
Call Setup Phase rejection causes
1. Lack of CP-UE capacity :
5G Radio admission rejection ratio per cause lack of CP-UE capacity [%]Id: NR_272a
It is the rejection ratio of radio admission requests for NSA user due to lack of CP -UE capacity.
2. Lack of non-GBR capacity :
KPI "5G Radio admission rejection ratio per cause lack of non-GBR capacity [%]Id: NR_273a "
represents the rejection ratio of radio admission requests for NSA user due to lack of non-GBR
capacity. To reduce this kind of rejection, it may be possible to increase the value of parameter
NRCELLGRP:maxNumOfNonGBRBearers if it isn't at its max value (500)
3. Lack of NSA user capacity :
KPI "5G Radio admission rejection ratio per cause lack of NSA user capacity [%]Id: NR_274a "
represents the rejection ratio of radio admission requests for NSA user due to lack of NSA user
capacity. To reduce this kind of rejection, it may be possible to increase the value of parameter
NRCELL:maxNumOfUsersPerCell if it isn't at its max value (250)
Note :in term of KPI target the maximum will be 33 for TDD and 100 for FDD duplex mode .
4. Lack of PUCCH capacity :
M55115C00005 indicates The number of unsuccessful radio admissions for NSA users [due to no
PUCCH capacity] based on that we can create like this SGNB_DU_NSA_ADMISSION_NO_PUCCH /
SGNB_DU_NSA_ADMISSION_REQ
The admission control will check if there is enough PUCCH capacity to send the CSI reports from the
UEs to the BTS. Depending on the setting of the csiReportPeriodicity parameter
Additional KPIs need to be monitored to check the amount of average and Max NSA users are
needed :
•
NR_5124a 5G Average number of NSA users
•
NR_5125a 5G Maximum number of NSA users
Handover Phase rejection causes
1. Lack of non-GBR capacity :
This can be monitored through KPI "5G Non-GBR DRB radio admissions success ratio for NSA user
in handover [%] Id: NR_51a" which represents the rejection ratio of radio admission requests for
NSA user due to lack of non-GBR capacity in the handover phase. It can be improved by increasing
the value of parameter NRCELLGRP:addNumOfNonGBRBearersHo .
2. Lack of NSA user capacity :
This can be monitored through KPI "5G Radio admission success ratio for NSA user in handover [%]
Id: NR_50a", which represents the rejection ratio of radio admission requests for NSA user due to
lack of NSA user capacity in the handover phase. It can be improved by increasing the value of
parameter NRCELLGRP:addNumOfHoUser.
Carrier Aggregation Case
Additional number of user are needed for UE at S-Cell controlled by the parameter
NRCELL:maxNumOfSCellAlloc
The KPI 5G SCell Radio admission success ratio for NSA user per DU [%]Id: NR_455a shows the
ratio of successful radio admissions for the SCell
Random Access
The UE requests the connection to the network using the Random Access Procedure via common
uplink resources. In NSA mode, based on the RRC Connection Reconfiguration message, UE detects
PSS, SSS and PBCH of NR gNB. Once it successfully detects PSS, SSS, PBCH of NR gNB, it performs
RACH procedure to PSCell of the gNB.
The main purpose of RACH procedure is to:
•
Obtain the resources for Msg3
•
Initial L1 synchronization (Timing and power)
Random access procedure is needed in the following cases (NSA and SA cases):
•
Initial access / SgNB addition
•
Loss of UL synchronization
•
Handover / RRC Conn. Re-estab.
•
Beam recovery request / Request for other SI
•
Transition from RRC_INACTIVE
•
Time alignment at Scell addition
KPI and counters
The monitoring of the Random Access procedure is done with:
NR_5010a - that counts the 5G Contention free RACH setup attempts.
M55306C20001 – M55306C20064 RA setup att. for dedicated preambles corresponding to SSB beam
ID {0-63}
NR_5011a - that measures the 5G Contention free RACH setup success ratio
M55306C05001 RA setup completions for dedicated preambles (When gNB transmits a RA response
message for dedicated RA preamble.)
The Contention Free Random Access procedure is used in case of NRCell handover. For initial access,
the CFRA procedure is triggered if the MeNB forwards the measResultSSB-Index to SgNb. In Nokia
eNb, it requires feature LTE5667 available from SRAN20C.
NR_5012a - that counts 5G Contention based RACH setup attempts
M55306C00001 – M55306C00064 RA setup att. for contention based preambles grp A
corresponding to SSB beam ID {0-63}
and NR_5013a - that measures 5G Contention based RACH setup success ratio
M55306C6001 RA Msg3 receptions for contention based RACH procedure
NR_971a - that measures the 5G Abnormal release ratio due to issues in RACH
NR_971a = 100 * Sum([rlf_initiated_ue_rach_fail] + [rlf_initiated_ue_scg_chge_fail]) /
Sum([x2_sgnb_rel_required_sent] + [x2_sgnb_rel_req_received])
In case the Rach setup success ratio is low, it should be considered to use an alternative formula
that excludes the possible ghost preambles.
NR_5022a - that measures the 5G Active RACH setup success ratio
The NR_5022a = 100 * Sum(ra_msg3_recep) / Sum(ra_msg3_recep + rlf_initiated_ue_rach_fail
+rlf_initiated_ue_scg_chge_fail) considers only the UEs that have requested the SgNB addition or
modification. Thus, if there's a lot of ghost preambles, the KPI NR_5022a will provide more realistic
view of the accessibility success ratio.
NR_5022a formula with counters IDs:
NR_5022a =M55306C06001/(M55306C06001+M55116C00009+M55116C00012)
If the success ratio with this alternative KPI remains low, then it must be check if UEs that are out of
the cell range are trying to connect.
The 5G timing advance distribution counters M55307C01001..32 : Timing advance during the RACH
procedure (based on preamble TA) and M55307C02001..32 : Timing advance during the connection
(based on PUSCH / PUCCH TA) provide the information on how far away from the cell antenna that
the terminals are on average. Higher values on the higher bin could show that UE out of cell range
are trying to connect.
To avoid such UE to attempt a connection, the antenna can be downtilted or some parameters that
configured the RACH must be analyzed and then tuned.
parameter: NRBTS.pfaTargetPRACH
Parameter pfaTargetPRACH indicates the probability False Alarm Target for PRACH. It is needed to
determine the DTX threshold for PRACH. The sensitivity of the receiver can be lowered with this
parameter to decrease the number of PRACH false detection.
parameter: MRBTS.NRBTS.NRCELL.rsrpThresholdSSB
Parameter rsrpThresholdSSB is used by the UE to find beams that are suitable for preamble (PRACH)
transmission. Whenever beam RSRP is higher than configured value, this beam is potential candidate
for the UE to be used for preamble transmission
In case of dynamic trigger of EN-DC, this parameter should take a value that is consistent with the
value of 4G parameter LNBTS.NRDCDPR.nrDcMeasConfig.b1ThresholdNrRsrp.
A higher value of these parameters will provide stronger radio link to the UE and could increase the
success ratio of the RACH procedure.
parameter: MRBTS.NRBTS.NRCELL.zeroCorrelationZoneConfig is used for msg1
Parameter zeroCorrelationZoneConfig associated with preamble format determines the number of
Cyclic shifts possible per root sequence. This parameter determines the cell range.
parameter: MRBTS.NRBTS.NRCELL.prachConfigurationIndex is used for msg1
Parameter prachConfigurationIndex determines the location of PRACH in time domain (subframe
number, starting symbol, number of Prach slots within a subframe, number of time -domain Prach
occasion within a Rach slot, Prach duration) and the Preamble format. It has an impact on the Prach
capacity.
parameter: MRBTS.NRBTS.NRCELL.msg1FrequencyStart
Parameter msg1FrequencyStart is used to position first PRACH occasion in frequency domain. Giving
a different value of this parameter for neighbour cell separates the PRACH occasions in the
frequency domain and could thus avoid RSI collisions.
These parameters are planning parameters that position the PRACH slot in time and frequency in the
frame and configure the cell range. They can be tuned when the UEs located too far from the
antennas are still trying to connect to the cell. The cell range can be reduced.
parameter: MRBTS.NRBTS.NRCELL.msg3DeltaPreamble
The parameter msg3DeltaPreamble determines This parameter defines the power offset between
msg3 and RACH preamble transmission in steps of 1dB. If the Msg3 are not received by the gNB,
then the value can be increased (default value is 1 dB).
parameter: NRBTS.NRCELL.initialPreambleReceivedTargetPower used for msg1
The parameter initialPreambleReceivedTargetPower determines initial preamble power expected
at gNB side. Based on the value of this parameter UE computes own transmission power to fit
requirement given by this parameter
parameter: MRBTS.NRBTS.NRCELL.preambleTransMax
The parameter preambleTransMax specifies maximum number of Msg1 transmissions before
reporting Random Access problem to upper layers.
parameter: MRBTS.NRBTS.NRCELL.powerRampingStep used in msg1
Parameter powerRampingStep determines by how much UE should increase power for Msg1
transmission whenever previous transmission of Msg1 was not successful.
This parameter values can be increased when the number of attempts seems too low.
msg1-SubcarrierSpacing (30kHz for below 6GHz, 120kHz for above 6GHz) is used in msg1.
parameter: MRBTS.NRBTS.NRCELL.prachRootSequenceIndex is used in msg1.
Parameter prachRootSequenceIndex defines starting Root Sequence Index (RSI) and is crucial from
PRACH planning perspective. Neighboring cells shouldn’t have overlapping preamble pools to avoid
collisions
parameter: MRBTS.NRBTS.NRCELL.raContentionResolutionTmr
The parameter raContentionResolutionTmr supervises reception of Msg4 (Contention Resolution).
Timer starts with Msg3 transmission (and is restarted with every Msg3 retransmission). Once timer
expires, UE needs to start Random Access Procedure from the scratch.
parameter MRBTS.NRBTS.NRCELL.totalNumberOfRAPreambles is used in msg1
Lowering value of parameter totalNumberOfRAPreambles (from default 64) will increase freedom
during PRACH planning (more resources - RSI) however will impact PRACH capacity of the cell
parameter:MRBTS.NRBTS.NRCELL.raResponseWindow
The parameter raResponseWindow supervises reception of Msg2 (Random Access Response). Once
timer is exceeded, UE determines next possible PRACH occasion and retries Msg1 transmission
(timer is restarted).
Coverage
Typical coverage issues and related KPI
Coverage optimisation is needed when the actual measurements are different from expectations
based on link budget (theoretical) calculation.
When the link budget is below expectations i.e. when a target service is not satisfied at cell edge
conditions, there is a coverage gap. The cell coverage can be limited either in UL or in DL. In 5G,
generally, UL is the limiting path as UE Tx power is shared between LTE and NR.
When there is excessive coverage (vs. target footprint, vs. target load), inter-cell and/or inter-beam
interference can occur. Power and thus energy is also wasted. The coverage can be reduced via e.g.
power reduction, mechanical and/or electrical tilting, re-azimuthing, antenna opening reduction.
Most significant DL coverage quality indicators are:
NR_5060a 5G Average wideband CQI, 64QAM table
NR_5061a 5G Average wideband CQI, 256QAM table
The set of counters M55324C0040x ACTUAL_TX_POWER_BEAM_ID_x provides actual transmitted
power with beam ID x
In case those indicators are low, the following set of KPI will also be impacted due to poor DL quality
NR_296a 5G Average MCS used for PDSCH Rank1 with 64QAM table
NR_297a 5G Average MCS used for PDSCH Rank2 with 64QAM table
NR_298a 5G Average MCS used for PDSCH Rank3 with 64QAM table
NR_299a 5G Average MCS used for PDSCH Rank4 with 64QAM table
NR_300a 5G Average MCS used for PDSCH Rank1 with 256QAM table
NR_301a 5G Average MCS used for PDSCH Rank2 with 256QAM table
NR_302a 5G Average MCS used for PDSCH Rank3 with 256QAM table
NR_303a 5G Average MCS used for PDSCH Rank4 with 256QAM table
NR_85a 5G Ratio of PDSCH transmissions in Rank 1 (with 64QAM MCS table)
NR_86a 5G Ratio of PDSCH transmissions in Rank 2 (with 64QAM MCS table)
NR_87a 5G Ratio of PDSCH transmissions in Rank 3 (with 64QAM MCS table)
NR_88a 5G Ratio of PDSCH transmissions in Rank 4 (with 64QAM MCS table)
NR_304a 5G Ratio of PDSCH transmissions in Rank 1 with 256QAM MCS
NR_305a 5G Ratio of PDSCH transmissions in Rank 2 with 256QAM MCS
NR_306a 5G Ratio of PDSCH transmissions in Rank 3 with 256QAM MCS
NR_307a 5G Ratio of PDSCH transmissions in Rank 4 with 256QAM MCS
NR_89a 5G Usage of 2Tx transmission in PDSCH
NR_90a 5G Usage of 4Tx transmission in PDSCH
NR_184a 5G Initial BLER in downlink transmissions using 64QAM MCS table
NR_185a 5G Residual BLER in downlink transmissions using 64QAM MCS table
NR_289a 5G Initial BLER in downlink transmissions using 256QAM MCS table
NR_176a 5G Residual Block Error Ratio (BLER) for PDSCH using 256QAM MCS table
Most significant UL coverage level and quality indicators are:
NR_5062a 5G Average UE related SINR for PUSCH in Rank 1
NR_5063a 5G Average UE related SINR for PUSCH in Rank 2
NR_5065a 5G Average UE related SINR for PUCCH
NR_5064a 5G Average UE related RSSI for PUSCH
NR_5066a 5G Average UE related RSSI for PUCCH
NR_106a 5G Average received UE signal power for PUSCH
M55303C11001 PUCCH_FORMAT0_DTX
M55303C12001 PUCCH_FORMAT0_NON_DTX
M55303C15001 PUCCH_FORMAT2_DTX
M55303C16001 PUCCH_FORMAT2_NON_DTX
By dividing DTX over {DTX and non DTX}, the ratio of DTX in UL can be derived.
In case those indicators are low, the following set of KPI will also be impacted due to poor UL quality
NR_292a 5G Average MCS used for PUSCH CP-OFDMA Rank1 with 64QAM table
NR_293a 5G Average MCS used for PUSCH CP-OFDMA Rank2 with 64QAM table
NR_294a 5G Ratio of PUSCH transmissions in Rank 1 (with 64QAM MCS)
NR_295a 5G Ratio of PUSCH transmissions in Rank 2 (with 64QAM MCS)
NR_5056a 5G Initial BLER in PUSCH using 64QAM MCS table
NR_5057a 5G Residual BLER in PUSCH using 64QAM MCS table
Additionally, cell distance through TA (Timing Advance) commands distribution can be checked to
verify min/av/max distance of UE to the cell.
5G Average Timing Advance index in RACH setup
5G Average Timing Advance index during RRC connected
Beamforming
Feature 5GC000535 introduces Analog Beamforming for frequencies above 6 GHz (28GHz/39GHz);
feature 5GC000533 introduces Digital Beamforming in time domain for RUs connected via CPRI to
BBU for frequencies below 6GHz. A Grid of Beams (GoB) is used and selection of beams is based on
UE feedback.
NRCELL.actBeamforming = True (1) to activate beamforming
NRCELL.beamSet.basicBeamSet defines the basic set of beams consisting of SS/PBCH beams and
refined beams on gNB side. To provide the best coverage, the basicBeamSet shall be chosen
according to the geographical topology.
In analog beamforming, the GoB is made of 32 directions, selected by basicBeamSet
(beamSetAbf_1A, beamSetAbf_32A, beamSetAbf_32B, beamSetAbf_32C).
1 - beamSetAbf_32A provides narrower beams to the cell-edge user compared to near-cell user so well designed for longcell
2 - beamSetAbf_32B is well designed for tall and narrow cell
In digital beamforming, up to 8 SSB beams (coarse beams) can be used for synchro (sweeping
principle) and for traffic. SSB beams corresponds to the parameter
NRCELLGRP.numberOfTransmittedSsBlocks. Azimuth opening angles corresponds to the parameters
NRCELL.beamSet.leftEdgeAngle/NRCELL.beamSet.rightEdgeAngle.
3 - Example of coverage with AEQD HW using beamSet_6_2 based on UE traces.
Power parameters
MRBTS.NRBTS.NRCELL.pMax is the power per Trx. The minimum and maximum range of pMax
depends on Radio Unit.
•
Total output power can be derived with the following formula: Total output power is = Pmax
+ 10*LOG(#TRX). [#TRX is 64 for AEQD, 2 for AEUA.]
•
Maximum output power per cross beam = Pmax + 10*LOG(#TRX)
•
Maximum output power per polarization beam = Pmax + 10*LOG(#TRX/2)
•
MRBTS.NRBTS.NRCELL.ssPbchBlockPower defines the SS and PBCH powers in terms of EPRE.
To increase the Cell Coverage this parameter can be increased e.g when set to 10 dBm (instead of
default 0 dBm), the RSRP measured by the UE is 10dB higher. However it must satisfy some rules
w.r.t to pMax. See MIND and Golden SCF, and must be carefully increased such that it does not
interfer that much with DL data.
SS/PBCH block power setting is managed by NRCELL:ssPbchBlockPower parameter that should
follow this rule:
For beamforming case:
NRCELL:ssPbchBlockPower ≤ NRCELL:pMax + 10 log (no. TRX per polarization) – 10*log (nb_re)
Typical ssPbchBlockPower value for beamforming case for AEQD is between 11 and 16 dBm (note
that the 3GPP value signalled over RRC is 3dB higher to account for polarisation)
For non beamforming case:
NRCELL:ssPbchBlockPower ≤ NRCELL:pMax – 10*log (nb_re)
(note that the 3GPP value signalled over RRC in case of 4x4 MIMO is 6dB higher to account for 4
transmit paths)
For calculation, see Golden SCF (tab mMIMO ssPbchBlockPower for BF case and tab RRH
ssPbchBlockPower for non BF case)
Some RU are not suitable for indoor trials (even with pMax set at min value). However it is possible,
in the scope of an indoor demo, by applying R&D scripts at RU or ABIL Loner, to decrease the TX
output power and the gains. Both contributes to significantly reduce the RF-EMF.
When DL 256QAM is used, the maximum DL transmission power needs to be restricted in order to
guarantee that the PA operates in its linear region. This is controlled by parameter
MRBTS.NRBTS.NRCELL.dlQam256PowerBackoffSub6 or
MRBTS.NRBTS.NRCELL.dlQam256PowerBackoffAbove6. This decreases the coverage of the cell.
5G19A Mobility
The objective of this section is to describe parameters and KPI related to mobility optimisation.
Back to Parameter Overview
Mobility scenarios and related KPIs
In NSA mode, there are several mobility scenarios involving both LTE and NR cells, as UE may be
moving from one NR cell to a neighbour NR cell, or from one LTE cell to a neighbour LTE cell.
Mobility scenarios are described in following picture :
1 - 5G19A Mobility Scenarios
In 5G19A, both intra-frequency intra-gNB and inter-gNb mobility are supported. Inter-frequency
mobility is not supported.
With L19A, during LTE mobility, NR cell is removed from source cell and re-established in target cell,
thus leading to NR traffic interruption during handover. With L19B (together with 5G19A), it is
possible to perform LTE handover without SgNb change thanks to feature LTE4281.
It is recommended to activate both intra-gNb and inter-gNB mobility with following settings :
NRBTS.actIntraFreqIntraGnbMobilityNSA = True (1)
NRBTS.actIntraFreqInterGnbMobilityNSA3x = True (1)
NRBTS.actIntraMeNBMobility = True (1)
On LTE side, following parameters should be activated :
MRBTS.LNBTS.actHoWoSnChg = intraEnbHoEnabled (1) (L19B only)
It is also recommended to activate data duplication for mobility with following parameter :
NRBTS.actDataDuplicationForMobility = True (1)
Note that some issues were observed, both in 5G19 and 5G19A, with UDP DL mobility (PR489231:
5G19A,, B - Major,[5G19A][classical][IWK][L19A][AEQD]Handover failed, due to source MeNB not
sending SN Status Transfer to target MeNB). It could be linked to the lack of configuration of object
DSCPTOQMAP, in the case when qosClassificationCriteria = ‘dscp’. DSCPTOQMAP allows to map
DSCP value to the different transport QoS Priorities. DSCP corresponding to C-plane (cPlaneDscp)
and M-plane (mPlaneDscp), among other DSCP, should have higher priorities.
For example, if cPlaneDscp = 46 and mPlaneDscp = 34:
TNLSVC.TNL.ETHSVC.L2SWI.DSCPTOQMAP.queueForDscp34 = EF (0)
TNLSVC.TNL.ETHSVC.L2SWI.DSCPTOQMAP.queueForDscp46 = EF (0)
It is also recommended to activate contention free RACH access during handover with following
parameter :
NRBTS.NRCELL.cbraPreamblesPerSsb = n56 (56)
It will be mainly useful to secure handover success rate in loaded network by reserving PRACH
preambles for handover procedure, but note that full benefit of the feature will be available only
when eNB will support LTE feature LTE5667 - "Extended B1 measurement report for NR” currently
planned in SRAN20C (IE candidateCellInfoListMN will then be supported in event b1)
This section is not covering intra-cell mobility related to beamforming. Please consult Accessibility
section for more details on beamforming.
Handover success rate can be monitored through following KPIs :
NR_5042b - 5G Intra gNB intra frequency PSCell change total success ratio
NR_5074a - 5G Inter gNB intra frequency PSCell change total success ratio on target gNB
In case of degradation, preparation and execution success ratios can be monitored through following
KPIs :
NR_5041b - 5G Intra gNB intra frequency PSCell change preparation success ratio
NR_5071a - 5G Inter gNB intra frequency PSCell change preparation success ratio on target gNB
NR_5048a - 5G Intra frequency intra DU PSCell change execution success ratio
NR_5073a - 5G Inter gNB intra frequency PSCell change execution success ratio on target gNB
Failures during preparation may be due to admission control rejections (see accessibility section for
related parameters) or X2 issues (check X2 alarms)
Failures during execution may be due to radio conditions, either because of w rong neighbouring
selection or too late handover trigger. For this last reason, mobility measurements and handover
parameters may be tuned as described hereafter. Neighbouring optimisation is also briefly described
in last section.
Mobility Measurements
Mobility measurements are based on RSRP/RSRQ like in LTE. However, there is no Cell Reference
Signal (CRS) like in LTE, but several reference signals (SS, CSI, SRS) with different measurements.
In 5G19A, RSRP, RSRQ and SINR are based based on Synchronisation Signal (SS) only
SS-RSRP is defined as the linear average over the power contributions (in [W]) of the resource
elements that carry Secondary Synchronization Signal (SSS).
Reference points:
•
For frequency range below 6 GHz - antenna connector of the UE
•
For frequency range above 6 GHz - SS-RSRP is measured based on the combined signal from
antenna elements corresponding to a given receiver branch
Mapping of SS-RSRP values on dBm values is shown below and is useful to define A3 thresholds as
they are defined in "coded" value.
SS-RSRQ is specified as the ratio N × "SS-RSRP" /"NR carrier RSSI"
Where:
•
N - the number of resource blocks in the NR carrier RSSI measurement bandwidth.
•
NR carrier Received Signal Strength Indicator (NR carrier RSSI), comprises the linear
average of the total received power (in [W]) observed only in certain OFDM symbols of
measurement time resource(s) (confined within SS/PBCH Block (SSB) Measurement Time
Configuration (SMTC) window duration), in the measurement bandwidth, over N numb er of
resource blocks from all sources (including co-channel serving and non-serving cells,
adjacent channel interference, thermal noise etc.)
Reference points:
•
For frequency range below 6 GHz - antenna connector of the UE
•
For frequency range above 6 GHz - SS-RSRQ is measured based on the combined signal from
antenna elements corresponding to a given receiver branch
Mapping of SS-RSRQ values on dB values is shown below and is useful to define A3 thresholds as
they are defined in "coded" value.
SS signal-to-noise and interference ratio (SS-SINR), is defined as the linear average over the power
contribution (in [W]) of the resource elements carrying secondary synchronisation signals divided by
the linear average of the noise and interference power contribution (in [W]) over the resource
elements carrying secondary synchronisation signals within the same frequency bandwidth. The
measurement time resource(s) for SS-SINR are confined within SS/PBCH Block Measurement Time
Configuration (SMTC) window duration.
If higher-layers indicate certain SS/PBCH blocks for performing SS-SINR measurements, then SS-SINR
is measured only from the indicated set of SS/PBCH block(s).
Reference points:
•
For frequency range below 6 GHz - antenna connector of the UE
•
For frequency range above 6 GHz - SS-RSRQ is measured based on the combined signal from
antenna elements corresponding to a given receiver branch
Handover Preparation Optimisation
The handover preparation phase is subject to Radio Admission Control as any new call setup. Th e
rejection of handover at admission control can be monitored through following KPI :
1. Lack of non-GBR capacity :
This can be monitored through KPI "5G Non-GBR DRB radio admissions success ratio for NSA user
in handover [%] Id: NR_51a" which represents the rejection ratio of radio admission requests for
NSA user due to lack of non-GBR capacity in the handover phase. It can be improved by increasing
the value of parameter NRBTS.NRCELLGRP.addNumOfNonGBRBearersHo .
2. Lack of NSA user capacity :
This can be monitored through KPI "5G Radio admission success ratio for NSA user in handover [%]
Id: NR_50a", which represents the rejection ratio of radio admission requests for NSA user due to
lack of NSA user capacity in the handover phase. It can be improved by increasing the value of
parameter NRBTS.NRCELLGRP.addNumOfHoUsers.
Handover Execution Optimisation
Handovers between 5G cells are possible based on event A3 or event A5 radio conditions measured
in RSRP/RSRQ domain
Which measurement option is effectively in use depends not only on configured thresholds
(RSRP/RSRQ based) but also on the setting of two parameters:
•
NRCELL:a3MeasEnabled = none (0), rsrp (1), rsrq (2), rsrpAndRsrq (3), rsrpCombined (4),
rsrqCombined (5)
•
NRCELL:a5MeasEnabled = none (0), rsrp (1), rsrq (2), rsrpAndRsrq (3), rsrpCombined (4),
rsrqCombined (5)
It is recommended to configure only event A3 for intra-frequency handover, in order to trigger
handover as soon as a neighbor cell becomes better than serving cell. Event A5 is not useful for
intra-frequency handover, so not recommended for activation
For both parameters, possible values mean:
•
none (0) even if the thresholds for RSRP and RSRQ are configured in SgNB database no
measurement configuration is provided to the UE terminal
•
rsrp (1) even if the thresholds for RSRP and RSRQ are configured in SgNB database, only
RSRP based measurement configuration is provided to the UE terminal. HO preparation
phase is triggered after receiving Measurement Report for this RSRP based event
•
rsrq (2) even if the thresholds for RSRP and RSRQ are configured in SgNB database, only
RSRQ based measurement configuration is provided to the UE terminal. HO preparation
phase is triggered after receiving Measurement Report for this RSRQ based event
•
rsrpAndRsrq (3) thresholds for RSRP and RSRQ are configured and both measurement
configuration are provided to the UE terminal as separate measurements. HO preparation
phase is triggered after receiving Measurement Report for this event either RSRP or RSRQ
based
•
rsrpCombined (4) even if the thresholds for RSRP and RSRQ are configured only RSRP based
measurement configuration is provided to the UE terminal. After detection by the UE
terminal radio conditions for event A3/A5 in RSRP domain and reporting it by Measurement
Report, the SgNB takes into account also reported RSRQ levels of serving and target cell. HO
preparation phase may be triggered if also reported RSRQ levels meet the radio conditions
for event A3/A5 defined in SgNB database by RSRQ related thresholds.
•
rsrqCombined (5) even if the thresholds for RSRP and RSRQ are configured only RSRQ based
measurement configuration is provided to the UE terminal; after detection by the UE
terminal radio conditions for event A3/A5 in RSRQ domain and reporting it by Measurement
Report the SgNB takes into account also reported RSRP levels of serving and target cell; HO
preparation phase may be triggered if also reported RSRP levels meet the radio conditions
for event A3/A5 defined in SgNB database by RSRP related thresholds.
It is recommended to configure event A3 with « rsrp » for nominal intra-frequency handover as
follows :
NRBTS.NRCELL.a3MeasEnabled = rsrp (1)
Event A3 parameters (eg TimeToTrigger and Offset/Hysteresis) need to be optimized according to
radio environment : low values are good for fast moving UEs but can create too many ping-pong
Handovers.
In 5G19A first networks deployment with both intra-gNB and inter-gNB mobility, mainly in city
centres, A3 parameters have been increased to reduce ping pong between cells. Current
recommendations are as follows :
NRBTS.NRCELL.a3MeasSsbRsrp.a3HysteresisSsbRsrp = 4 (4) (i.e. 2 dB)
NRBTS.NRCELL.a3MeasSsbRsrp.a3OffsetSsbRsrp = 8 (8) (i.e. 4 dB)
NRBTS.NRCELL.a3MeasSsbRsrp.a3TimeToTriggerSsbRsrp = ms320 (8)
Note that a3HysteresisSsbRsrp and a3OffsetSsbRsrp are defined as signalled to the UE, so real value
in dB is half of GUI value (eg 8 means 4 dB).
It is also recommended to keep filter coefficient for RSRP equal to default value fc4.
NRBTS.NRCELL.filterCoeffSsbRsrp = fc4 (4)
There are no N-KPIs to monitor too early, too late or ping pong handover, so optimisation should be
done only based on handover execution ratio monitoring. Retainability and throughput KPIs should
also be checked when doing mobility optimisation.
2 - Handover based on A3 event RSRQ
For loaded networks, it may be better to configure A3 events as "rsrpCombined" in order to take into
account RSRQ measurements on top of RSRP.
NRBTS.NRCELL.a3MeasEnabled = rsrpCombined (4)
In such case, RSRQ parameters should be set as follows :
NRBTS.NRCELL.a3MeasSsbRsrq.a3HysteresisSsbRsrq = 2 (2) (i.e. 1 dB)
MRBTS.NRBTS.NRCELL.a3MeasSsbRsrq.a3OffsetSsbRsrq = 4 (4) (i.e. 2 dB)
NRBTS.NRCELL.a3MeasSsbRsrq.a3TimeToTriggerSsbRsrq = ms320 (8)
NRBTS.NRCELL.filterCoeffSsbRsrq = fc4 (4)
Same as for RSRP parameters, offset and hysteresis are defined as signalled to the UE, and real value
in dB is half of GUI value.
As mentioned above, it is not recommended to activate event A5 in 5G19A for intra-frequency
measurements.
NRBTS.NRCELL.a5MeasEnabled = none (0)
However, even if a5MeasEnabled is set to 0, in case the A5 RSRP structure is present
(NRBTS.NRCELL.a5MeasSsbRsrp), the gNb will configure A2 event and release SgNb in case RSRP falls
below A5 threshold according to feature 5CC001954. It is thus required to completely remove
NRBTS.NRCELL.a5MeasSsbRsrp structure if event A2 is not planned to be used.
The criterion to activate event A2 without event A5 is the following :
•
If NRBTS.NRCELL.a5MeasSsbRsrp.a5Threshold1SsbRsrp is configured, A2 based SgNB release
is enabled. The effective A2 threshold configured to the UE is equal to
NRBTS.NRCELL.a5MeasSsbRsrp.a5Threshold1SsbRsrp - 5 dB (fixed offset).
•
If NRBTS.NRCELL.a5MeasSsbRsrp.a5Threshold1SsbRsrp is not configured, A2 based SgNB
release is disabled.
It is usually not recommended to release NR cell based on A2 event as this will likely reduce 5G
footprint which is already considered as being too small... 5G NR release will then be triggered based
on radio link failure detection by UE or gNB. This is the recommended scenario for "General" and
"5G - High Coverage" use cases.
However, in case operator does not want to keep NR cell in bad radio conditions, it is possible to
configure event A2 but it is then mandatory to set event A2 threshold to a lower value than event B1
threshold used to setup SgNb. Otherwise, this will lead to ping pong between NR release due to A2
and SgNb setup due to b1.
The following recommendations are proposed for the "5G - High Retainability" use case :
NRBTS.NRCELL.a5MeasEnabled = none (0)
NRBTS.NRCELL.a5MeasSsbRsrp.a5Threshold1SsbRsrp = 41 (41) (i.e. -105 - 5 = -110 dBm)
MRBTS.LNBTS.NRDCDPR.nrDcMeasConfig.b1ThresholdNrRsrp = -100 dBm (56)
MRBTS.NRBTS.NRCELL.rsrpThresholdSSB = -100 dBm (56)
NRBTS.NRCELL.a5MeasSsbRsrp.a5HysteresisSsbRsrp = 4 (4) (i.e. 2 dB)
NRBTS.NRCELL.a5MeasSsbRsrp.a5TimeToTriggerSsbRsrp = ms320 (8)
Reversely, for "5G - High Coverage" use case, following recommendations are proposed :
MRBTS.LNBTS.NRDCDPR.nrDcMeasConfig.b1ThresholdNrRsrp = -120 dBm (36)
MRBTS.NRBTS.NRCELL.rsrpThresholdSSB = -120 dBm (36)
Neighbour Cell Declaration
Neighbor relations between 5G cells are using NRREL object class (MRBTS/NRBTS/NRCELL)
•
The neighbor relations from a given 5G cell are possible only for cells for which the NRREL
objects are defined in the NRCELL object relevant to the source cell
•
Up to 256 NRREL objects can be created per 5G NRCELL object (1 radio cell – can be multiple
NRCELLs per DU)
3 - Neighbour cell declaration model
There is no ANR algorithm in 5G19A to automatically add all required 5G neighbour cells, so all
additions need to be done manually. It is possible to use Eden net application to identify required 5G
neighbour cells (for instance based on distance) and to prepare plans for Netact import. Note that
5G neighbour cells should also be added in LTE cells in order to allow inter-site EN-DC setup (ie
possibility to setup EN-DC call with 5G cell which is not necessarily co-located with LTE cell).
It is possible to tune cell individual offset for serving cell and each neighbour cell in order to speed
up or delay handover, through following parameters :
NRBTS.NRCELL.cellIndividualSsbRsrpOffset = 0 dB
NRBTS.NRCELL.NRREL.cellIndividualSsbRsrpOffset = 0 dB
NRBTS.NRCELL.cellIndividualSsbRsrqOffset = 0 dB
NRBTS.NRCELL.NRREL.cellIndividualSsbRsrqOffset = 0 dB
To speed up handover towards a neighbour cell, NRREL offset should be set to positive value (eg +1
to +3 dB), and reversely to negative value (-1 to -3 dB) to delay handover.
In case all handovers from serving cell should be advanced, NRCELL offset should be set to negative
value, and reversely to positive value to delay handover.
Other Mobility Parameters
Parameters related to NRHOIF objects are listed in Mobility domain, but are not used in 5G19A.
Indeed, they are related to inter-frequency mobility and Standalone (SA) configuration, which will be
available in 5G19B only.
Also some A5 event parameters are listed in Mobility domain, although they are not used in 5G19A.
References Studies
Inter-gNb mobility has been validated in 5G19A Orange project, with some optimisation of A3
parameters, see here.
5G19A Retainability
Back to Parameter Overview
Introduction
Call drop ratio is one of the most important metrics used to assess network performance
•
Radio Link Failure (RLF) is one of the most often reasons of call drops.
Whenever call (voice or data) is cut off before parties had finished, Radio Link Failure is in place.
There are 2 kinds of RLF:
•
UE Initiated RLF Handling
•
SgNB Initiated RLF Handling
Note : UE Inactivity Handling is not considered as a RLF : release due to user inactivity is considered
as "a normal release". However, it is still part of retainability category.
Those 3 items are detailed hereafter, with insight on how to monitor them (counters/KPI) and
associated parameters.
1/ Radio Link Failure – UE Initiated RLF
Parameter:
•
Activation flag: NRBTS.actUeInitRlf=true (1)
Reasons for UE initiated Radio Link Failure on 5G side:
•
1-A/ Random Access Procedure Failure
•
1-B/ DL out-of-sync (OOS)
•
1-C/ Radio Link Control (RLC) failure – maximum number of retransmissions is reached
•
1-D/ SCG reconfig & SRB3 integrity failure (from 5G19A)
UE initiated RLF call flow:
Upon RLF detection, UE informs MeNB (ScgFailureInformation msg), which passes information to
SgNB. Within “SCGFailureInformation”, the cause of detected RLF is present:
After receiving SCGFailureInformation, MeNB makes a decision i f SgNB change (ie PScell change) or
SgNB release will happen.
In case of PSCell change, MeNB forwards information to SgNB via SgNB Modification Request over
X2 interface.
•
When receiving SgNB Modification Request, PSCell change procedure is started.
•
Radio Link recover timer is set (NRBTS.tWaitingRlRecover).
•
During the waiting RL recover timer, the UE data is switched to LTE leg.
•
The SgNB sends in SgNB Modification Request Ack message (SgNB-CU confirms that it is
aware UE detected RLF)
If NRBTS.tWaitingRlRecover expires before PScell is changed, SgNB will release the UE context, by
sending a “SgNB release Required” with the cause: ‘Radio Connection with UE lost’ to MeNB.
If PSCell change procedure is failed, SgNB release is triggered too: “SgNB Release Required” msg is
sent by SgNB to MeNB (with release cause ‘RNL Radio Connection with UE Lost’).
Note: if activation flag: NRBTS: actUeInitRlf is set to false(0) – which is not recommended- “SgNB
Modification Request Reject” message is sent. The UE may then drop the 5G (tbc).
Parameter:
•
NRBTS.tWaitingRlRecover
-
Default = recommended = 500ms(3).
-
In deployment scenario (in Feb 2020), default value 500ms(3) represents 69% of
sites. Other value is observed: 0ms(0) (~ 31% of sites)
Counters and KPIs:
•
M55116C00006(RLF_INITIATED_UE_PSCELL_CHN_F): in case PS-Cell Change was triggered
but could not be completed successfully. “SgNB Release Required” msg sent by SgNB to the
MeNB with the release cause "RNL Radio Connection with UE Lost". One of the counters
related to detailed cause (M55116C0008 to M55116C00013) is pegged too. They will be
described further in this document.
•
M55116C00007(RLF_INITIATED_UE_PSCELL_CHANGE): in case PS-Cell changes completed
successfully
•
M55112C00503 (SGNB_MOD_REQUEST) is pegged when msg “SGNB Modification Request”
is received
1-A/ Random Access Failure
For this section, please also check the Random Access part in accessibility section.
If the RAR (Msg2) is not received within a specific time window (NRCELL: raResponseWindow + 3
slots), the UE will retransmit preamble (Msg1) with power ramped up.
Preamble (Msg1) can be retransmitted up to NRCELL.preambleTransMax. When it’s reached,
“Random Access Problem Indication” is sent to UE higher layers and Random Access Procedure is
started from scratch.
When Msg3 is retransmitted too many times (more than NRCELLGRP: maxHarqMsg3Tx and if
NRCELL: preambleTransMax is reached); RLF is declared.
Parameters:
•
NRCELL.raResponseWindow
a. No default value. Recommended values are sl20 in cm wave (or digital
beamforming) and sl80(7) in mm wave (or analog beamforming).
b. Deployment scenario is not meaningful, as value depends on type of beamforming.
•
•
NRCELL.preambleTransMax
-
Default = recommended = n10(6).
-
In deployment scenario (in Feb 2020), default value represents 52% of sites. Other
values are observed: n20(7) (~ 43% of sites) and n5(2) (~ 3% of sites)
NRCELLGRP.maxHarqMsg3Tx
-
Default = recommended = 5(5).
-
In deployment scenario (in Feb 2020), default value represents 98% of sites. Oher
values are observed: 20(7) (~ 43% of sites) and 5(2) (~ 3% of sites)
Counters & KPIs:
•
M55116C00009(RLF_INITIATED_UE_RACH_FAIL): Number of UEs released due to RL failure
initiated by UE with the root cause Random Access Problem
•
Warning: for some UE (eg seen in the past for Samsung S10) : in case of RACH failure,
M55116C00012(RLF_INITIATED_UE_SCG_CHGE_FAIL) is updated (cause
synchReconfigFailureSCG).
•
Due to this, KPI related to fraction of UE release (such as “NR_40a(5G UE release ratio due to
RLF initiated by UE with cause Random Access Problem) or NR_40b are not accurate).
Possible counter issue:
The share of 5G releases due to radio link failures is depending on the RSRP value of LTE
measurement report B1. If a low B1 threshold is selected, such that SgNB additions are attempted in
very bad 5G RSRP areas, there is naturally a higher risk that the 5G radio link will soon be terminated
due to radio link failure.
(B1 = “Inter RAT neighbor becomes better than threshold”, ie B1 is the RSRP threshold for
establishing 5G radio links in Dual Connectivity Mode. Associated LTE parameter is
mrbts.lnbts.nrdcpr.nrDcMeasConfig.b1ThresholdNrRsrp).
From counter perspective, the 5G radio connection is seen as established when the gNB has received
the SgNB Reconfiguration Complete message from the eNB. Note that this message comes before
the 5G RACH procedure has been completed, i.e. a failure in the RACH procedure is regarded as a
dropped call rather than a failed call establishment.
1-B/ Radio Link Failure – UE Initiated RLF – DL Out of Sync
UE monitors "out-of-sync" and "in-sync" indications from layer 1. Upon receiving NRBTS.N310
consecutive "out-of-sync" indications, UE starts timer NRBTS.T310. NRBTS:T310 is stopped upon
receiving NRBTS.N311 consecutive "in-sync" indications. As a result, connection is continued without
any dedicated signaling exchange.
If NRBTS:T310 expires (no or less than N311 "in-sync" indications), radio link failure is detected and
SCGFailureInformation is sent by UE to MeNB
Parameters:
•
•
•
NRBTS.n310
-
Default = recommended = n10(10).
-
In deployment scenario (in Feb 2020), default value n10 represents 97% of sites.
Other value n20(20) is observed (~ 3% of site)
NRBTS.T310
-
Default = recommended = 2000 ms(6).
-
In deployment scenario (in Feb 2020), default value 2000ms represents 54% of sites.
Other values are observed: 1000ms(5) (~ 30% of sites) and 6000ms(8) (~ 15% of site)
-
Mitigation : same comment as the one for maxRetxThreshold. Quick RLF may be
looked for "on purpose", e.g. to quickly drop a bad 5G radio connection to preserve
good throughput (if there is another 5G site nearby where a new connection can be
set up, higher throughput can then be observed when decreasing the t310
parameter so 5G drops happen faster).
NRBTS.n311
-
Default = recommended = n1(1).
-
In deployment scenario (in Feb 2020), only default value n1(1) is observed (in Feb
2020)
Counters & KPI:
•
M55116C00008(RLF_INITIATED_UE_T310_EXPIRY) : Number of UEs released due to radio
link failure initiated by UE with the root cause T310 expiry
•
NR_39b(5G UE release ratio due to RLF initiated by UE with cause T310 expiry) : Fraction of
UEs releases initiated by the UE with the root cause T310 expiry
1-C/ Radio Link Failure – UE Initiated RLF – RLC Failure
Radio link failure can be triggered by UE if maximum number of RLC retransmissions is reached
(NRBTS.rlcProf4.maxRetxThreshold in 5G19A, passed to UE via RRCConnectionReconfiguration
message)
In case of RLC failure, UE reports radio link failure to the MeNB via SCGFailureInformation.
Parameter:
•
NRBTS.rlcProf4.maxRetxThreshold
-
Default = t16(6), Recommended = t32(7)
-
In deployment scenario (in Feb 2020), default value represents 37% of sites. Other
value t32(7) is observed (~ 63% of site).
-
Mitigation : in theory, t32 (vs t16) allows to reduce the number of RLF drops.
However, it may actually be a benefit to choose a smaller value than t32, to quickly
drop a bad 5G radio connection (especially if inter-gNB handover is not enabled and
the 5G uses a narrow bandwidth such as 10 MHz) and then hope there is another 5G
site nearby where a new connection can be set up.
Counters or KPIs:
•
M55116C00010(RLF_INITIATED_UE_MAX_RLC_RETX) : Number of UEs released due to radio
link failure initiated by UE with the root cause Max RLC retransmission
•
NR_41b(5G UE release ratio due to RLF initiated by UE with cause Max RLC retransmission) :
Fraction of UEs releases initiated by the UE with the root cause Max RLC retransmission
1-D/ Radio Link Failure – UE Initiated RLF – other causes (SGC change, SCG reconfig & SRB3
integrity failure (from 5G19A))
In all 3 cases below, UE sends ‘SCGFailureInformation” msg towards MeNB :
1. SCG change failure: if UE can’t complete PSCell change (e.g. UE can’t access target
SgNB). Warning, SCGFailureInformation (cause “synchReconfigFailureSCG”) is also sent for
some UE (eg seen in the past for Samsung S10) in case of RACH failure.
2. SCG reconfiguration failure: if UE is unable to comply with (part of) the configuration
included in the RRC Reconfiguration message received over SRB3 (UE sends SCG failure
information to report error).
3. SRB3 integrity failure: whenever integrity check for SRB3 is not passed.
Counters & KPIs:
When UE is released due to RLF initiated by UE, in case PS-Cell Change could not be triggered (“SgNB
Release Required” msg is sent by SgNB to MeNB, with release cause ‘RNL Radio Connection with UE
Lost’), several causes are possible :
•
Root cause is srb3-IntegrityFailure: M55116C00011(RLF_INITIATED_UE_SRB_INTGRTY_F)
•
Root cause synchReconfigFailure-SCG: M55116C00012(RLF_INITIATED_UE_SCG_CHGE_FAIL)
•
Root cause scg-reconfigFailure: M55116C00013(RLF_INITIATED_UE_SCG_RECNF_F)
Note: SgNB received faulty measurements, M55116C00005(RLF_INITIATED_UE_MEAS_FAULTY) is
not supposed to be involved in RLF. Typically, this case is already included in maxRLC subcase (or
other subcases).
Similarly, in fraction:
•
Root cause is srb3-IntegrityFailure: NR_257b (5G UE release ratio due to RLF initiated by UE
with cause SRB3 integrity failure)
•
Root cause synchReconfigFailure-SCG: NR_44b (5G UE release ratio due to RLF initiated by
UE with cause SCG change failure), but this KPI is not useable (as root cause may be linked
with RACH failure)
•
Root cause scg-reconfigFailure: NR_45b(5G UE release ratio due to RLF initiated by UE with
cause SCG reconfig failure)
Note: SgNB received faulty measurements: NR_290a (5G UE release ratio due to RLF ini tiated by UE
because gNB received faulty measurements), but this KPI is not useable for RLF (see above note for
associated counter).
Summary Counters diagram for RLF detection, UE initiated in 5G19A:
The following diagram shows call flow and RLF counters pegging (in 5G19, chart extracted from
here):
SGNB_MOD_REQUEST is Incremented when SGNB MODIFICATION REQUEST message is received
due to failure types :
•
t310expiry,
•
randomAccessProblem,
•
rlc-MaxNumRetx,
•
synchReconfigFailure-SCG,
•
srb3-IntegrityFailure,
•
scg-reconfigFailure
SGNB_REL_SN_REQ_UE_LOST: Incremented when SGNB RELEASE REQUIRED message is sent to LTE
eNB with cause equal to Radio Connection With UE lost.
SGNB_REL_SN_SUCC_UE_LOST: Incremented when SGNB RELEASE CONFIRM message is received
from LTE eNB for a release request with cause UE lost.
Note: MeNB sends to SgNB the X2AP: SgNB Modification Request message which contains the "RRC:
SCG Failure information" message from UE. This message is decoded only if RLF feature is activated.
2/ Radio Link Failure – SgNB Initiated RLF
Activation flag NRBTS.actGnbInitRlf = true (1).
SgNB detects RLF for 5G link based on:
•
2-A/ DTX detection for requested DL HARQ feedback on PUCCH
•
2-B/ DTX detection of CSI reports on PUCCH
•
2-C/ Radio Link Control (RLC) failure – maximum number of retransmissions is reached
Note: in early loads of 5G19A (MP0.1), SgNB initiated RLF was not recommended to be activated, as
DTX detection of CSI reports on PUCCH, would be triggered too often (in medium or bad RF) and
caused SgNB release, therefore reducing the coverage. In further load 5G19A (MP1.0), this is no
longer the case (because hardcoded triggering conditions for ”DTX detection of CSI reports on
PUCCH” has been set to different value, so that this is no more triggered), we recommend
actGnbInitRlf = true.
2-D/ Common call Flow (whatever the type of RLF detected by SgNB), SgNB initiates “release of the
UE context”:
•
SgNB declares an RLF on the PSCell: a control timer (NRBTS: tWaitingRlRecover) is
set. During the waiting time, the data is switched to LTE leg of the split bearer (PDCP
switching to LTE can happen only if NRBTS:dlDataSplitMode= dlOverF1UX2U).
•
After timer expiry, SgNB will release the UE context by sending an SgNB initiated SgNB
release with the cause: ‘Radio Connection with UE lost’ to MeNB
•
And in turn, the MeNB starts procedure of UE Context Release procedure on 5G side.
In the following paragraphs, we will describe first 3 types of SgNB initiated RLF detection (2A/, 2B/
and 2C/ cases) and their associated parameters. And then, describe common SgNB release & UE
context release procedure, together with their associated parameters & counters.
2-A / Radio Link Failure – SgNB Initiated RLF -DTX For DL HARQ Feedback
SgNB counts the number of consecutive DTX detection for requested DL HARQ feedback (Radio link
problem detection is done per carrier, so only DL HARQ feedback received for the current carrier is
evaluated (even if DL HARQ feedback is sent jointly for several DL carriers via single PUCCH)).
If number of consecutive DTX exceeds 35 (value defined by R&D parameter, it was 100 before,
changed by PR417980), SgNB starts RLF guard timer NRBTS:tRLFindForDU. If RLF guard timer will
expire, gNB-DU will inform gNB-CU about RLF by sending UE Context Modification Required over F1
link.
If the number of consecutively received non DTX for DL HARQ feedback exceeds 5 (value defined by
R&D parameter) the radio link is assumed to be recovered.
Parameters:
•
•
NRBTS.tRLFindForDU
-
Default = 300ms(0), Recommended in 5G19A = 2000ms(8)
-
In deployment scenario (in Feb 2020), default value 300ms represents 61% of sites.
Other values 3000ms (36%) and 2000ms (3%) are observe.)
-
Tips: a large value of tRLFindForDU makes it possible for the radio link to recover.
Other parameters are R&D parameters.
Counters or KPIs:
•
There is no dedicated counter for SgNB initiated RLF detection, with RLF due to “DTX For DL
HARQ Feedback”.
•
Counter M55116C00004(RLF_INITIATED_RNL) is updated (cause Radio Network Layer - RL
failure others). But warning, this counter is also pegged in case of user inactivity (pegging
M55112C02001(SGNB_RELEASE_REQ_UE_INACT) too)
2-B/ Radio Link Failure – SgNB Initiated RLF – DTX of CSI on PUCCH
For each UE, CSI reports are evaluated to detect radio link problems (Radio link problem detection is
done per carrier, only CSI reports for the current carrier are evaluated even if they are received in
other carrier). If the number of consecutively received DTX for CSI reports exceeds 75 in 5G19A,
radio link problem is detected.
Note that this value 75 is defined by R&D parameter rdRlpDetCsiBsi ; it was 10 before 5G19A,
changed in 5G19A to 75 by PR448933, and then in 5G19B, RLF detection upon CSI DTX is deactivated
(tbc) with PR498017.
in case such RLF is detected, SgNB starts RLF guard timer NRBTS: tRLFindForDU (same timer used for
DL HARQ DTX).
If RLF guard timer will expire, SgNB DU will inform gNB CU about RLF by sending UE Context
Modification Required over F1 link.
If the number of consecutively received non DTX for CSI reports exceeds 2, a radio link is recovered.
Parameters (same as for “Radio Link Failure – SgNB Initiated RLF -DTX For DL HARQ Feedback”)
•
•
NRBTS.tRLFindForDU
-
Default = 300ms(0), Recommended in 5G19A = 2000ms(8)
-
In deployment scenario (in Feb 2020), default value 300ms represents 61% of sites.
Other values 3000ms (36%) and 2000ms (3%) are observed.
-
Tips: a large value of tRLFindForDU makes it possible for the radio link to recover.
Other parameters are R&D parameters.
Counters or KPIs:
•
There is no dedicated counter for this type of SgNB initiated RLF detection (RLF – DTX of CSI
on PUCCH)
•
Counter M55116C00004(RLF_INITIATED_RNL) is updated (cause Radio Network Layer - RL
failure others). But warning, this counter is also pegged in case of user inactivity (pegging
M55112C02001 (SGNB_RELEASE_REQ_UE_INACT) too).
Parameters:
•
NRBTS.rlcProf4.maxRetxThreshold
-
Default = t16(6), Recommended in 5G19A = t32(7)
-
In deployment scenario (in Feb 2020), default value t16 represents 65% of sites.
Other value t32 (35%) is observed.
-
Tips: a large value of maxRetxThreshold makes it possible for the radio link to
recover.
Counters or KPIs:
•
Counter M55113C01006(NF1CC_UECTXT_MOD_REQRECD) is “Number of UE Context
Modification Required” received in gNB-CU due to Cause: “rl-failure-rlc”.
•
Counter M55117C01006(NF1CD_UECTXT_MOD_REQSENT) is “Number of UE Context
Modification required” sent from gNB-DU due to Cause: “rl-failure-rlc”.
•
In classical configuration (gNB-CU = gNB-DU), both counters should give similar values (tbc)
2-D/ Common call Flow (whatever the type of RLF detected by SgNB), SgNB initiates “release of
the UE context”:
Parameters:
•
Radio Link recover timer (NRBTS:tWaitingRlRecover) is the same as for UE initiated RLF
detection case.
•
Two timers supervise SgNB release and UE context cleaning on 5G:
-
NRBTS.timerX2UeProcGuard (default = recommended =5000ms(5000)). In
deployment scenario (in Feb 2020), default value 5000ms represents 75% of sites.
Other value 2000ms (25%) is observed
-
NRBTS.timerF1UeProcGuard (default = recommended =
2500ms(2500)). Deployment scenario is not available with significant volume of
data.
Counters & KPIs for RLF SgNB initiated (TBC):
•
Contrary to RLF UE initiated (where we can get the details of the cause, eg. T310, maxRLC
etc…), for RLF SgNB initiated, we don’t have the details per cause. Note: there was a
customer request for getting details (cause “DL HARQ or CSI reporting” or “Max RLC
retransmission “), but it was rejected (https://jira3.int.net.nokia.com/browse/FGCR-3462 ).
•
Today, RLF SgNB initiated are pegging the 2 following counters (which are not mutually
exclusive, ie both can happen during tWaitingRlRecover) :
•
-
M55116C00004(RLF_INITIATED_RNL), pegged at msg “UE Context Modification
Required” with cause Radio Network Layer - RL failure others
-
M55113C01006(NF1CC_UECTXT_MOD_REQRECD), at msg “UE Context Modification
Required” with cause rlf-rlc
There is no 1 to 1 mapping between M55112C00007 (X2_SGNB_REL_REQUIRED_SENT) and
M55116C00004 (RLF_INITIATED_RNL) + M55113C01006 (NF1CC_UECTXT_MOD_REQRECD),
as
-
Not every RLF_INITIATED_RNL, NF1CC_UECTXT_MOD_REQRECD will lead to 5G call
release: if RLF recovers before tWaitingRlRecover expires, 5G call will not be
released,
-
Multiple pegging of M55116C00004 (RLF_INITIATED_RNL) or M55113C01006
(NF1CC_UECTXT_MOD_REQRECD) is possible before tWaitingRlRecover expires.
•
Note1: the recovery may be successful, so even if RLF_INITIATED_RNL or
NF1CC_UECTXT_MOD_REQRECD are pegged, it does not mean that
SGNB_REL_SN_REQ_UE_LOST is pegged
•
Note2: it can happen that UE Inactivity also pegs M55116C00004 (RLF_INITIATED_RNL)
•
Note3 : in case of RLF SgNB initiated cause “Radio Network Layer - RL failure others” , it may
happen that M55112C00007 (X2_SGNB_REL_REQUIRED_SENT) is NOT pegged (RLF recovers
before timer twaitingRlRecover expiry, no msg “SgNB release required” is sent)
•
NR_5032a (5G SgNB triggered abnormal release ratio) is the main retainability KPI (starting
from 5G19A). This KPI indicates SgNB initiated abnormal Release Ratio for SCG split bearers.
MeNB initiated releases are considered as normal releases.
3/ User Inactivity
User Inactivity handling is considered as a normal release, but to be taken into account when
speaking about retainability.
Like RLF (UE initiated or SgNB initiated), it leads to “SgNB initiated UE context release” msg.
In NSA deployment scenario, UE inactivity can be detected by SgNB only if NRBTS: actInactDetNSAUe
= true. SgNB will treat UE as inactive if there is no DL/UL data received and no data in the buffer for
a given time period (UL & DL inactivity timers are independent):
•
NRBTS.nsaInactivityTimer + 1s; at the time of bearer set up
•
NRBTS.nsaInactivityTimer after the reception of the first DL PDCP SDU or UL PDCP PDU
After the inactivity detection, the SgNB sends “SgNB Release Required” message to the MeNB with
the cause value ‘User Inactivity’.
Parameters:
•
NRBTS.actInactDetNSAUe, activates inactivity detection for NSA UE. Default =false(0).
Recommended = true(1). In deployment scenario, 100% of sites have value=true(1).
•
NRBTS.nsaInactivityTimer. Default = recommended = 10s(10). In deployment scenario, 94%
of sites have default value (10s), 3% of sites have value 20s, 2% have value 15s.
Note : effect of nrbts.nsalactivityTimer' s value : it is a compromise between
1. releasing the connection quickly and thereby using less resources from admission control
perspective (especially PUCCH capacity) and less UE battery power
2. keeping the connection longer and thereby avoid the need for doing another SgNB addition
if more packets are arriving.
The inactivity timer value also impacts the value of many of the drop ratio formulas. With a long
inactivity timer, it is more likely that the radio connection will drop before the connection is released
due to inactivity; if the timer is decreased, there is higher chance that it will be released instead of
dropping. For the end-user, it doesn’t matter if an idle connection is released due to inactivity or due
to radio link failure but the KPI formula values for retainability will be impacted.
•
NRBTS.timerX2UeProcGuard. See previous paragraph (2-D/ SgNB initiates “release of the UE
context”)
Counters & KPIs for User Inactivity:
•
M55112C00007 (X2_SGNB_REL_REQUIRED_SENT) is pegged
•
M55112C02001 (SGNB_RELEASE_REQ_UE_INACT) is pegged (SGNB RELEASE REQUIRED sent
to eNB with cause “User inactivity”)
•
M55112C00502 (SGNB_REL_SN_REQ_UE_LOST) is NOT pegged (SGNB RELEASE REQUIRED
sent to eNB with cause “Radio Connection with UE lost”)
•
Warning: in some cases, for User Inactivity, M55116C00004 (RLF_INITIATED_RNL) is pegged
Indeed, number of SGNB RELEASE REQUIRED is splitted into 2 sub-categories:
1. cause “Radio Connection with UE lost”: Counter M55112C00502
(SGNB_REL_SN_REQ_UE_LOST) and if SgNB Release procedure is successful M55112C00501
(SGNB_REL_SN_SUCC_UE_LOST)
2. cause “User inactivity”: Counter M55112C02001 (SGNB_RELEASE_REQ_UE_INACT) and if
procedure is successful (msg “SgNB Release Confirm” is received from MeNB for a release
request with cause User inactivity): M55112C02002 (SGNB_RELEASE_SUCC_UE_INACT)
Note: in 5G19B, we will have a 3rd counter sub-category “A2 based SgNB release”, introduced with
5GC002177 : M55112C05001 (X2_SGNB_REL_REQUIRED_SENT_A2)
4/ Other Retainability issues
The following items will cause retainability issue too:
•
gNB release because of A2 release as 5G RSRP becomes bad.
-
In 5G19A, the 5GC001954: Introduction of A2 based SgNB release feature makes it
possible to release the 5G radio link when the 5G RSRP becomes lower than a
certain threshold. Full implementation (including proper parameters and PM
counters) comes with 5GC002177: A2 based SgNB release in 5G19B.
•
gNB reset
•
4G radio link failure
•
4G HO failures if 5G is not supported
5G19A Throughput
The objective of this section is to describe the parameters that may influence the Throughput
domain.
Back to Parameter Overview
When focusing on the Throughput domain, the first step is to identify the typical peak rates at
physical layer from other projects and compare with the peak rates possible with one ’s current
parameter database. For this, a tool exist at the following link: http://5gtables.eecloud.dynamic.nsnnet.net/nrTput.php (note that it is possible to import directly an SCF database into the tool). A
concatenation of the best performances obtained in several projects is available at this link.
The list of parameters impacting the theoretical peak throughput are (in bold the ones we may 'play'
with).
NRCELL.nrarfcn
NRCELL.cellTechnology
NRCELL.chBw
NRCELL.tddFrameStructure
NRCELL.actDl256Qam
NRCELL.dlMimoMode
NRCELL.ulMimoMode
NRCELL.prachConfigurationIndex
NRCELLGRP.ssBurstSetPeriod
NRCELL.csirsForTracking.csirsTrackingPeriod
NRCELL.dlDMRSAdditionalPosition
NRCELL.ulDMRSAdditionalPosition
NRCELL.actBeamforming
NRCELLGRP.numberOfTransmittedSsBlocks
An example of the peak throughput expectations is shown below (for VDF Spain):
In case the throughput performance is far from the expectations, the second step is to confirm that
all parameters in the database are running with the recommended values - only then, further
parameter tuning can be considered in order to reach better performances.
All parameters which may impact the throughput are listed in the Parameter Overview – table
“Throughput parameters” of this section, with their corresponding sub-domain (DL or UL throughput
related, for example) and with their default values. The parameters for which specific
recommendations apply are listed in the Parameter Overview – table “Throughput
recommendations” of this section, with their corresponding scenario (Demo, General, for example).
The most important and relevant parameters are further described below.
Thus, the main purpose of the Throughput section consists in proposing parameter
recommendations and tuning that shall mitigate possible observed throughput performance
degradations, as reflected in the degradation of the KPIs listed in this section, in Parameter (& KPI)
Overview.
Typically, in Downlink:
•
Low MAC throughput, NR_5100a (5G Average MAC layer user throughput in downlink),
could be linked to different reasons, such as:
-
Low rank, e.g. low rate of rank4 in Near Cell, which may be confirmed with NR_307a
(5G Ratio of PDSCH transmissions in Rank 4 with 256QAM MCS). Some of the hints in
5G19A are:
◦
Decreasing ssPbchBlockPower (implementation of CNI-46722 has increased
the coverage of SSB by 6dB, allowing therefore a decrease of parameter
ssPbchBlockPower by the same amount in 5G19A).
◦
Activate the additional DMRS, dlDMRSAdditionalPosition. Although
impacting negatively the theoretical max, it should in practice overall allow
for better DL throughput, especially in mobility conditions (but also in static).
-
Modulation or MIMO order used is not optimal: in 5G19A, it is possible to use
256QAM (actDl256Qam = true) together with MIMO 4x4 (dlMimoMode = 4x4 or
4x2 Open Loop Spatial Multiplexing)
-
Low CQI, as shown by NR_5060a (5G Average wideband CQI, 64QAM table) or
NR_5061a (5G Average wideband CQI, 256QAM table) reflects bad DL radio
conditions. This in some cases could be improved by optimizing the beamset:
◦
•
basicBeamSet: new beamSet_6_2 is now preferred to beamSet_6 in order
to have better performances both near and far from the cell center.
NR_5065a (5G Average UE related SINR for PUCCH) and NR_5066a (5G Average UE related
RSSI for PUCCH) can give a hint on the quality of the PUCCH, which may impact the DL
throughput since it carries the ACK/NACK of the DL packets
-
UE may be forced to transmit at higher or lower power on the PUCCH, depending on
the value configured for p0NominalPucch. Looking at the NR_5065a and NR_5066a ,
we may figure out if the PUCCH power is at a usual level.
-
PUCCH Format0 and Format2 are the only formats supported in 5G19A. They are
known to be not optimal compared to Long PUCCH. One way to improve the PUCCH
Format2 (carrying ACK/NACK+CSI) is to set the pucchF2MaxCodeRate to zeroDot08
(instead of the default value zeroDot15). Improvements in this area are available
from 5G19A MP2.0.1 for the cell edge DL throughput performances.
Note that NR_5100a (5G Average MAC layer user throughput in downlink) as well as NR_5088a (5G
Active cell MAC PDU throughput on PDSCH data slots on initial HARQ transmissions) are not as
accurate as NR_578a (5G MAC PDU Cell throughput on PDSCH considering the accumulated time of
frames with data slots used for PDSCH), since in the first two KPIs calculation, we consider all slots as
potential DL slots.
Another throughput KPI, which could be used is NR_5090a (5G Active cell MAC PDU throughput on
PDSCH on initial HARQ transmissions), which is the cell MAC throughput average over all the OFDM
symbols used for PDSCH.
NR_5084a (NSA PDCP SDU thp tx w/o rep DL) shows the PDCP throughput. There could be a big
difference between MAC throughput for initial HARQ and PDCP throughput if the overall BLER is
important. The PDCP / RLC / HARQ configuration or Link Adaptation parameters could be tuned for
improvement in this domain.
The UL throughput is mostly influenced by the required quality of the received signal; in order to
reach the required quality the UE adjusts its power of PUSCH channel transmission and eventually
gnb forces lower MCS and number of PRBs to have better chance to succeed decoding the
transmission.
•
Low MAC throughput, NR_5101a (5G Average MAC layer user throughput in uplink), could
be linked to reasons such as:
-
-
High UL BLER, as shown by NR_5056a (5G Initial BLER in PUSCH using 64QAM MCS
table) and NR_5057a (5G Residual BLER in PUSCH using 64QAM MCS table). One
area of tuning here is the uplink Link Adaptation:
◦
NR_5056a should be close to parameter ullaBlerTarget. Higher initial BLER
should only be possible in very bad radio conditions with MCS already at 0.
Lower initial BLER should only be possible in very good radio conditions with
MCS already at its max.
◦
Speeding the Link Adaptation is possible, for example by increasing
ullaDeltaSinrStepdown from 0.25 to 0.5.
◦
Activating the second UL DMRS, ulDMRSAdditionalPosition, should also be
considered as an improvement to the UL BLER. Although impacting
negatively the theoretical max, it should in practice overall allow for better
UL throughput.
Low UL SINR, as shown by NR_5062b (5G Average UE related SINR for PUSCH in Rank
1) and NR_5063b (5G Average UE related SINR for PUSCH in Rank 2). NR_5064a (5G
Average UE related RSSI for PUSCH) could also be monitored: if it has increased, this
could be the sign of increased interference.
Note that NR_5101a (5G Average MAC layer user throughput in uplink) as well as NR_5089a (5G
Active cell MAC PDU throughput on PUSCH data slots using 64QAM table on initial HARQ
transmissions) are not as accurate as NR_579a (5G MAC PDU Cell throughput on PUSCH considering
the accumulated time of frames with data slots used for PUSCH), since in the first two KPIs
calculation, we consider all slots as potential UL slots.
Another throughput KPI, which could be used is NR_5091a (5G Active cell MAC PDU throughput on
PUSCH on initial HARQ transmissions), which is the cell MAC throughput average over all the OFDM
symbols used for PUSCH.
NR_5085a (NSA PDCP SDU thp tx w/o rep UL) shows the PDCP throughput. There could be a big
difference between MAC throughput for initial HARQ and PDCP throughput if the overall BLER is
important. The PDCP / RLC / HARQ configuration or Link Adaptation parameters could be tuned for
improvement in this domain.
Overall, main functional areas in 5G19A which can improve the DL and/or UL throughputs are:
•
Additional DMRS
•
SSB power: ssPbchBlockPower
•
Basic beamset
•
Inter-gNB Mobility (on top of 5G19 intra-gNB mobility)
•
SU-MIMO
•
256QAM modulation
•
Link Adaptation
•
Split bearer:
-
Data forwarding at split bearer setup and release
-
X2 Flow control for established split bearer
•
PDCP / RLC / HARQ configuration
•
UL:DL ratio & Frame structure
•
UL MIMO1x1 versus UL MMO2x2 with Single UE Tx
•
SSB burst & CSI RS Tracking periodicities
Additional DMRS
An additional DMRS can be configured, separately for downlink and uplink by setting
dlDMRSAdditionalPosition and ulDMRSAdditionalPosition.
Supported values are:
•
0: no additional DMRS
•
1: one additional DMRS
•
Automatic: indicates additional DMRS position is controlled by the gNB, it equals 1
additional DMRS when PTRS is off and 0 when PTRS is ON (default)
When additional DMRS are configured, system performance is improved with the cost of higher
reference signal overhead. The performance improvement comes from better channel estimation
and frequency offset estimation.
Additional DMRS will mainly benefit to moving UEs, if UE is not moving and has no big frequency
offset, the additional DMRS would reduce throughput due to higher reference signal overhead (up to
14%, depending on the slot configuration).
When comparing same rank and same MCS, the additional DMRS will reduce the peak throughput
(8%-14%) since it blocks one more complete OFDM symbol
Drive tests in the field has shown that the feature brings clear benefit on throughout in DL. The
average MCS also increases and the usage of 256QAM is higher when additional DMRS is configured.
In UL, it was not proven yet that the feature enhances the throughput.
It is then recommended to configure additional DMRS in DL only.
SSB power: ssPbchBlockPower
ssPbchBlockPower defines the SS and PBCH powers in terms of EPRE.
To increase the Cell Coverage this parameter can be increased. E.g when set to 10 dBm (instead of
default 0 dBm), the RSRP measured by the UE is 10dB higher.
However it must satisfy some rules w.r.t to pMax. See MIND and Golden SCF, and must be carefully
increased such that it does not interfer that much with DL data.
Starting 5G19A, an increase in the RSRP measured by the UE has been observed with the same
ssPbchBlockPower value.
It was also noticed that when activating 256QAM feature, the average reported rank indicator has
decreased. A decrease of ssPbchBlockPower helped overcome this issue and increase the
throughput.
Then we recommend to carefully set this parameter and not set it too high as it may cause
interference and degrade the performance.
Basic beamset
The beamset used, configured with parameter basicBeamSet, may have a big impact on the
throughput:
•
The increasing number of beams in the beamset has a negative impact on the DL max
theoretical throughput, since the more beams used, the more slots are needed for beam
sweeping (1 slot / 2 beams, in cmW), and thus the less slots available for DL data.
•
It may have a positive impact on the near cell throughput, both in DL and in UL, if more than
one row of beams are used, since some rows are downtilted, hence bringing better coverage
in near cell area, often accompanied by better SINR, MCS and Rank.
In 5G19A, the following beamsets are supported in cmW on AEQD (others may be present and
selectable, but currently not supported yet):
-
beamSet_1
-
beamSet_2
-
beamSet_4
-
beamSet_6
-
beamSet_8
-
beamSet_4_4
-
beamSet_5_3
-
beamSet_6_2
-
beamSet_3_3_2
-
beamSet_2_2_2_2
The general recommendation in 5G19A is to use beamSet_6_2, especially (but not only) if two rows
of beams are targeted. It has shown good results over the whole cell area (2dB or more average
RSRP gain over the cell from beamSet_6 to beamSet_6_2, while same level of SINR were observed:
see different beamSets testing results from LDO UAE in 5G19A Field Performances AEQD, du
UAE.pptx), and has been optimized by Radio team. However, when only one row of beams is
sufficient, beamSet_6 may also be used in order to show higher DL max throughput. And other
beamsets may also be used and tested depending on the radio environment.
Note that, depending on the number of beams used, parameter numberOfTransmittedSsBlocks
must be configured consequently.
Impact of Mobility
Lack of 5G mobility may have a negative impact on the throughput. 5G Radio conditions may be
degraded in serving 5NR cell due to interference from better neighboring NR cell, leading to bad
throughputs. Without 5G mobility, the situation will only get better after Radio Link Failure
procedure or 4G mobility, which will trigger the selection of the new best 5G cell.
More information about the configuration of the mobility (A3 offset, hysteresis, time-to-trigger, etc.)
may be found in the Mobility section.
SU-MIMO
DL SU-MIMO 2x2 and 4x4 principles :
2 streams per user in case of DL 2x2 MIMO : 1 beam, made of 2 polarizations, per user
4 streams per user in case of DL 4x4 MIMO : 2 beams, each made of 2 polarizations, per user
Beams selection for DL SU MIMO operation :
Analog beamforming (mmW):
•
For DL MIMO 2x2 : use the SSB-beam available from PRACH procedure.
•
No DL MIMO 4x4
Digital beamforming (cmW) without beam refinement (NRCELL.beamSet.nrBtsBeamRefinementP2 =
False)
•
For DL MIMO 2x2 : Use the SSB beam available from the PRACH procedure
•
For DL MIMO 4x4 : Use in addition the second best SSB beam reported by the UE.
Digital beamforming (cmW) with beam refinement (NRCELL.beamSet.nrBtsBeamRefinementP2 =
True)
•
For DL MIMO 2x2 : Use the best refined beam reported by the UE
•
For DL MIMO 4x4 : Use in addition the second best refined beam reported by the UE. Could
be from same 'parent' SSB beam or from another one.
Highest DL peak throughput is achieved if the streams are orthogonal with each other.
The cross-pol beam by nature offers two streams perfectly orthogonal (MIMO 2x2)
But it is much more difficult to achieve orthogonality with two cross-pol beams (MIMO 4x4).
Reflexion (multipath) may help (urban area). Ideally it is better if the second best beam is not
contiguous with the best beam (less interferences between them), but it is hard to have control on
this !
Refined beams available from 5G19A should help getting higher DL SINR, so higher DL throughput
(less bler, ....). Hopefully the refined beams may favor the rank 4 opportunities in the field, but this is
to be confirmed through drive tests.
A mobile issue regarding refined beams is that some UE not capable of refined beams report
however to be capable, leading to gnb configuring them with refined beams, leading ultimately to
UE crash. Before enabling the feature we must ensure that such faulty UEs are not present in the
field. Finally, be aware that Qualcomm supports the refined beams from SDX55 chipsets (not SDX50).
DL MIMO Mode
The DL MIMO mode is configured with NRCELL.dlMimoMode
• 30 : 2x2 Closed Loop Spatial Multiplexing (DEFAULT VALUE)
• 40: 4x4 or 4x2 Closed Loop Spatial Multiplexing
• 50: 2x2 Open Loop Spatial Multiplexing
• 60: 4x4 or 4x2 Open Loop Spatial Multiplexing
For cmW with digital beamforming with more than 1 beam configured, the recommended value is
'4x4 or 4x2 Open Loop Spatial Multiplexing'. In other cases value 2x2 Closed Loop Spatial
Multiplexing or 2x2 Open Loop Spatial Multiplexing can be used.
Closed Loop mode :
This modes uses the UE’s feedback Rank, PMI, CQI. This mode requires that the gNB transmits the
CSI-RS (Channel State Information Reference Signal) and that the UE measures it and sends feedback
accordingly.
Open Loop :
In this mode, gNB uses only UE's feedback Rank and CQI.
It is recommended to use Closed Loop mode when available. However for the time being Closed
Loop mode is only available for MIMO 2x2. Therefore, for MIMO 4x4, Open Loop mode shall be used.
Layer mapping : Only one codeword shall be considered and will be mapped from 1 to 4 layers. A
2nd codeword is defined only for more than 4 layers, which is out of scope currently.
1 - DL SU-MIMO : streams versus 4 streams
2 - Layer mapping up to 4 layers
256QAM modulation
DL 256QAM is available since 5G19:
•
Two MCS tables, table1 and table2, are defined (see pictures). The scheduler will use one or
the other depending on the UE capabilities and the feature activation.
-
actDl256Qam = False : the scheduler always uses the table1
-
actDl256Qam = True : The scheduler uses the table1 if the UE is not 256QAM
capable.The scheduler uses the table2 if the UE is 256QAM capable.
•
Contrary to 5G19, it is possible and even recommended for better throughput to activate DL
256QAM with DL MIMO4x4, since it leads to better performance than with DL64QAM + DL
MIMO4x4.
•
The 3GPP TBS values are given by following R&D link: http://5gtables.eecloud.dynamic.nsnnet.net/
•
Finally, a power back-off is implemented with 256QAM in order to comply with 3GPP Error
Vector Magnitude (EVM) at transmitter side: amount of back-off is a trade-off between the
overall throughput and the coverage at cell edge.
-
dlQam256PowerBackoffSub6 for cmW
-
dlQam256PowerBackoffAbove6 for mmW
The recommended power backoff depends on the Radio Module, it is given in the GMC excel file,
sheet dlQam256PowerBackoff. One may also adapt this recommendation to its own case, typically
when pMax is set to a lower value than the max achievable by the Radio Unit, one may consider set
power backoff to 0.
3 - 3GPP TS 38.214 Table 5.1.3.1-1: MCS index table 1 for PDSCH
4 - 3GPP TS 38.214 Table 5.1.3.1-2: MCS index table 2 for PDSCH
Link Adaptation
The DL/UL Link adaptation is a mandatory feature, which is always active. The L1 measurements,
which are the basis for the DL/UL MCS selection, are:
1.
•
For DL MCS: the CQI reports provided by the UE
•
For UL MCS: the UL SINR measurements evaluated by the gNB
DL MCS selection
DL MCS is taken from a CQI-To-MCS mapping table.
Separate mapping tables are implemented depending on the MCS index table (64QAM MCS index
table /256QAM MCS index table), the applied rank (Rank1 / Rank2 / Rank3 / Rank4), and the band
(below 6GHz / above 6GHz).
A CQI correction based on UE’s HARQ feedback may be applied in order to stay close to the
configured DL bler target dllaBlerTarget (default: 10%).
The CQI correction is bounded by dllaDeltaCqiMin (default: -15.0) and dllaDeltaCqiMax (default:
15.0)
The CQI step down (in case of UE’s NACK) is configured through dllaDeltaCqiStepDown.
The CQI step up (in case of UE’s ACK) is dllaDeltaCqiStepDown x [dllaBlerTarget/(1- dllaBlerTarget)].
The default MCS dllaIniMcs is applied as long as CQI reports are missing or when the CQI reports are
outdated, or if DL Link Adaptation is not implemented.
2.
UL MCS Selection
UL MCS is taken from a SINR-To-MCS mapping table.
Separate SINR-to-MCS mapping tables depending on the number of layers used for spatial
multiplexing (Rank1 / Rank2), the supported slot types (10 PUSCH symbols / 11 PUSCH symbols), and
the band (below 6GHz / above 6GHz)
The measured SINR is eventually corrected based on the received power headroom reports (PHR) to
eliminate any bias influencing the measured SINR due to restricted UL transmission power.
A SINR correction based on gNB HARQ may be applied in order to stay close to the configured UL
bler target ullaBlerTarget.
The SINR correction is bounded by ullaDeltaSinrMin and ullaDeltaSinrMax.
The SINR step down (in case of gNB’s NACK) is configured through ullaDeltaSinrStepdown.
The SINR step up (in case of gNb’s ACK) is ullaDeltaSinrStepDown x [ullaBlerTarget/(1ullaBlerTarget)].
The default MCS ullaIniMcs is applied as long as long as SINR reports are missing or when the SINR
reports are outdated or when the UL LA is not implemented.
In order to reach highest UL throughputs in very good radio conditions, the recommendation is to
use ullaBlerTarget = 3%. ullaDeltaSinrMin and ullaDeltaSinrMax could be set respectively to –15.0
and 10.0.
However, in a commercial network, higher values of ullaBlerTarget could be used, such as 5% or
even 10%, depending on the results of the field tests.
Split Bearer
1.
Data forwarding at split bearer setup and release:
Data Forwarding (4G->5G) over X2 at Split Bearer setup is activated through parameter
actDlDataForwardingX2 on 5G gNB (SgNB indicates it to the Menb in the X2AP: SGNB ADDITION
REQUEST ACKNOWLEDGE)
•
If actDlDataForwardingX2 = False, there isn’t “continuous DL data transmission”: UL/DL data
transmission over 5G radio starts when data is received from SGW or UE.
•
If actDlDataForwardingX2 = True, there is “continuous DL data transmission”, using X2-U.
The 4G NB forwards DL data over X2-U, indicates end of forwarding over X2-U interface.
UL/DL data transmission over 5G radio continues when data is received from SGW or UE.
The best setting for throughput performance is actDlDataForwardingX2 = True
Data Forwarding (5G->4G) over X2 at Split Bearer release happens upon reception of the X2AP:
SGNB RELEASE REQUEST (whatever the trigger): the SgNB suspends the transmission over 5G radio
and forwards the data to MeNb. The parameter actDlDataForwardingX2Limit activates/deactivates
DL data forwarding limitation over X2 towards the MeNB to protect LTE's PDCP buffer overrun. It can
only be set to true if actDlDataForwardingX2 = True.
•
actDlDataForwardingX2Limit should only be set to True in case of Nokia 4G equipment:
-
•
2.
Due to current lower 4G throughput observed in case of EN-DC, it is recommended
however to keep the parameter to False.
actDlDataForwardingX2Limit should be set to False in case of other vendor 4G equipment.
X2 Flow control for established split bearer
When the split bearer is up and running between the S-GW and the 5G gNB, the X2 Flow Control
takes place.
On the DL part:
•
DL data path is based on dlDataSplitMode
-
0: dlOverF1U => DL Data is all sent to 5G DU
-
1: dlOverX2U => DL Data is all sent to 4G eNb
-
2: dlOverF1UX2U => DL Data is sent on both 4G & 5G legs, depending on flow
control output
Choose dlOverF1UX2U for increased throughput and DL traffic continuity.
•
The flow control configured can be Nokia prioprietary or 3GPP, based on dlFlowControlAlgo.
It is recommended to use 3ggp (as it seems to give better results).
The flow control is tuned with:
-
dlDataSplitGainThreshold: 5 -> 3, and can even be set to 1 to make sure X2U PDU
are in anyway forwarded.
-
minThFlowCtrlX2: 1Mbps -> 20Mbps, to make sure no low throughput during
calibration phase, although this period is quite small based on dddsPeriodX2 of
10ms.
-
maxTransferDelayX2: 20ms -> 100ms, to be above the QCI delay (can be optimized
later to lower values 80ms/60ms).
On the UL part:
•
UL data path is based on ulDataPath
-
0: ulOverLte
-
1: ulOverNr
-
2: ulOverLteNr.
If ulOverLteNr, then UE performs the split based on ulDataSplitThreshold (number of bits in the UE
buffer above which it starts sending data on the second path).
Choose ulOverLte if you want to favor UL coverage.
Choose ulOverNr or ulOverLteNr if you want to favor UL peak throughput.
Note that UE may not be capable of 'ulOverLteNr'. In such case, the gNb forces ulDataSplitThreshold
to infinity.
UL Dynamic data split
The dynamic uplink data split mode feature introduces an uplink measurement based switching
between the modes:
•
uplink NR only transmission
•
uplink LTE only transmission
•
uplink LTE + NR transmission.
The feature is activated by setting : NRCELL.actDynUlDataSplitMode = True
Switching NR UL data transmission to "LTE only" increases the NR UL data coverage.
When NR UL data transmission is switched to "LTE only“, the only data packets remaining on the NR
PUSCH are the NR DL data related control packets (RLC Ack/Nack and Status PDUs).
It is expected that Cell edge UE performance is improved, the NR PUSCH coverage is extended and
the NR DL range is further utilized for high DL user throughput.
The switching criteria are UL SINR and UL Pathloss.
Operator configurable uplink thresholds are defined in order to control the change between the
modes.
UL radio link outage (RLO) is detected in the NR cell (PCell of a UE) based on the following combined
conditions:
•
The averaged UL SINR < NRCELL:rloSinrThreshold
•
The UL pathloss > NRCELL:rloPathLossThreshold
UL radio link Resume (RLS) is detected in the NR cell (PCell of a UE) based on the following 2
combined conditions:
•
The averaged UL SINR > NRCELL:rlResumeSinrThreshold
•
The UL pathloss < NRCELL:rlResumePathLossThreshold
In order to define the correct setting for a given network, drive tests should be performed to
compare UL performances between UL over NR only (feature disabled) and UL switching between
LTE and NR (feature enabled ideally with different sets of parameter). Switching point should be
where UL LTE throughout starts to be higher than UL NR throughput.
Results will also depend on the available bandwidth on LTE side. If LTE bandwidth is equal to 20MHz
then it could be worth having an agressive setting to favor switching UL to LTE.
Here are some examples of validated settings:
5G BW: 80Mhz (tdLTE)
4G BW: 5MHz
PDCP / RLC / HARQ configuration:
For L1 HARQ, consider in particular:
•
maxDlHarqTx (default = 5)
•
maxUlHarqTx (default = 5)
For RLC, consider in particular :
•
MRBTS.NRBTS.rlcProf4.maxRetxThreshold (default t16)
It might be beneficial to increase to max value t32 for NSA call retainability.
RLC timers have also been optimized to following shorter values:
•
MRBTS.NRBTS.rlcProf4.tReassembly = 15ms
•
MRBTS.NRBTS.rlcProf4.tStatusProhibit = 15ms
•
MRBTS.NRBTS.rlcProf4.tPollRetr = 45ms
For PDCP, consider in particular:
•
MRBTS.NRBTS.pdcpProf2.tReordering (default ms100).
Note that trying a very short value (ms1) had dramatic negative impact on FTP throughput.
UL:DL ratio & Frame structure
Parameter ulDlDataSlotRatio is introduced by feature 5GC000542-B.
With new frame structure types (5GC001116 ad 5GC001208) available, the parameter
frameStructureType is used to set the frame structure:
•
semiStatic = standardized by 3gpp, supported ulDlDataSlotRatio = 1/4, 3/7, supported
guardPeriodLength = 2, 4, 6 OFDM symbols
•
tdLte = standardized by 3gpp and compatible with LTE TDD frame structure.
ulDlDataSlotRatio is not configurable. lteToNrFrameShift can be 0ms or 3ms.
•
flexible = vendor specific, supported ulDlDataSlotRatio = 1/9, 2/8, 3/7, 5/5. Not
recommended for use as no longer maintained by R&D
The same UL:DL ratio shall be configured in all cells of the network to avoid interference , probably
also need to coordinate with other networks in same region. That is why it is likely that the
operators will not use ‘flexible’ for deployment, but rather 'semiStatic' or 'tdLte'. Anyway, value
'flexible' should not be used any more as it is not maintained.
•
•
Regarding the guardPeriodLength:
-
Only value 2 and 4 are supported for semiStatic frame structure (recommendation i s
to use 4 symbols of GP with more than 7 kms of cell range).
-
Only value 4 and 6 are supported for tdLte frame structure. However, since traffic is
not possible in the special slots in tdLte in 5G19, it does not matter which value is
used in that case.
Regarding lteToNrFrameShift:
-
0ms can be used if numberOfTransmittedSsBlocks ≤ 6 beams (and if no alignment
with any other network is required)
-
3ms is to be used if numberOfTransmittedSsBlocks > 6 beams
◦
In this case, note that manualFrameTimingAdjustment needs to be set to
3000µs, if a time shift of 3 ms is desired. See Yammer post and slides for
more details.
The peak throughput depends on the chosen frame structure and UL:DL ratio. Refer to the 5G
throughput tool for detailed computation: http://5gtables.eecloud.dynamic.nsn-net.net/nrTput.php.
•
Although tdLte frame structure should lead to higher DL throughput compared to semiStatic
due to lower number of special slots in tdLte, it is the contrary in 5G19A, since traffic is not
possible in special slots in tdLTE. Therefore, ceteris paribus, we should expect about 3%
lower throughput with tdLte.
•
The statement above is however not always true (and therefore, DL throughput provided by
the 5gtables tool is not correct in that case) and depends on the value of
csiReportPeriodicity and the size of the CSI report in the UL.
csiReportPeriodicity impacts not only latency & capacity (see section "Usage: Packet Delay"), but
also throughput.
•
In 5G19, by default, CSI reports sent by the UE cannot be multiplexed with UL ACK/NACK:
the gNB avoids scheduling in DL if the corresponding UL ACK/NACK would fall in the same
slot as a CSI report.
•
This may have a high impact (up to 8-9%) on DL throughput, depending on the value
of csiReportPeriodicity (i.e. on the number of times CSI reports need to be sent).
However, FGCR-2650 - Support of mux-SR-HARQ-ACK-CSI-PUCCH-sameSymbol was added in late
5G19, and allows now the multiplexing of SR, ACK/NACK and CSI report on the same PUCCH
symbol.
•
It needs to be enabled by swconfig.txt file with following flag: 0x10003E=1 (and possibly
0x460181=1)
Even if FGCR-2650 is enabled, DL scheduling can still be impacted, due to “PR474594: New Problem
Reported (5G19,, B - Major,[5G19][classical][AEQD]DL Throughput falls down by around 8% when
csiReportPeriodicity = slots40)”.
•
FGCR-2650 was not correctly coded, and multiplexing of SR, ACK/NACK and CSI report is
possible only if the number of bits is below 11 (in case of 1 beam and/or MIMO 2x2 - i.e.
small size of CSI report - , it should be fine). Correction to PR474594 will not be added in
5G19 as it is not a TOP BLOCKER.
In 5G19A, FGCR-2650 will not be needed any more since other implementation of PUCCH will be
available.
UL MIMO1x1 versus UL MMO2x2 with Single UE Tx
Note that most (if not all) of the UEs currently available in the market, as of February 2020, have
only one single 5G Tx, meaning that they have only one transmitted antenna for 5G (and usually
another common one for 4G/3G/2G).
These UEs cannot perform UL MIMO2x2, and will be limited to UL MIMO1x2 (1 Tx at UE side + 2 Rx
at gNB side)
Be careful though not to confuse single UE Tx and UL MIMO1x1.
It is possible at gNB side to configure the UE to perform only UL MIMO 1x1 via swconfig.txt file
(rdULRank: 0x460019=1).
The corresponding UL throughput is then given in the 5Gtables tool
(http://5gtables.eecloud.dynamic.nsn-net.net/nrTput.php), selecting the option: Uplink Layers = 1x1
MIMO (5GC000532).
However, this is not optimal, since we lose, among other things, the Rx diversity at gNB side.
Therefore, the recommendation is still to use UL MIMO 2x2, even if the UE is limited to 1 single 5G
Tx. The corresponding UL throughput is obtained by dividing by two the UL throughput obtained in
the 5Gtables tool, selecting the option: Uplink Layers = 2x2 MIMO.
SSB burst & CSI RS Tracking periodicities
SSB burst periodicity is configured with parameter ssBurstSetPeriod.
•
The lower the SSB burst periodicity, the higher the number of SSB slots and thus the lower
the number of slots which can be used for DL scheduling, leading to lower throughput
(below an example of scheduling with 10ms periodicity on the left and 20ms on the right).
The higher the SSB burst periodicity, the slowlier will be the acquisition of the 5G signal and/or the
detection of the best 5G beam.
5 - ssBurstSetPeriod = 10ms
6 - ssBurstSetPeriod = 20ms
CSI RS Tracking period is configured with parameter csirsTrackingPeriod.
•
The lower the CSI RS Tracking period, the higher the number of CSI RS Tracking slots (see the
two green colored slots above with csirsTrackingPeriod = 80ms, i.e. 160 slots).
•
The higher the CSI RS Tracking period, the less updated the CSI information available to UE
(and indirectly to gNB).
Current recommendation is to use csirsTrackingPeriod = 80ms and ssBurstSetPeriod = 20ms.
5G19A Latency
Introduction
There is a clear motivation to minimize latency in the 5G mobile networks : low latency improves
end-to-end performance and enables number of new applications.
So low latency is one of the main targets in of 5G networks and therefore parameters and KPIs
managing it are described below.
The proactive scheduling
•
Improves the Latency
•
Does not degrade the capacity (no impact on the number of RRC-connected Ues)
•
Does not impact the multi-UE uplink throughput but degrades the mono-UE (1with traffic +x
UEs connected without traffic) uplink throughput
•
It is also likely to create more uplink interferences which could have negative effect for the
uplink throughput by degrading the uplink SINR.
→ Recommendation : Activate the proactive scheduling. Consider deactivate it when the live
network becomes loaded. Choose a proactive scheduling interval consistent with your need: use a
medium interval for live networks (ulSchedTimeInterval = 20ms), use small interval for special events
requiring low latency (e.g gaming). If possible also activate the release upon inactivity.
Proactive scheduling functionality shall be controlled by feature activation flag
actProactUlScheduling (“TRUE” to activate the feature, “FALSE” to deactivate).
Proactive UL Resource Assignment provides the possibility to demonstrate very low ping response
times in lab and low load field environments.
NB: with DRX feature activated (actCDrx set to “True”), proactive scheduling can be not or less
efficient if occurring during DRX active state.
REM: DRX feature (5GC000772) is released for a UE when all DRBs are released or a voice DRB is
setup or a measurement gap is setup.
Two timers shall be handled for each 5GUE :
•
ulSchedTimeInterval: This parameter indicates the targeted time interval for proactive UL
resource assignment for each connected user.
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•
Default value: 4 ; unit is ms; value range: 0.2…1000; stepsize = 0.2.
csiReportPeriodicity: This parameter defines the CSI reporting periodicity
◦
Default value: 320; value range: slot20, slot40, slot80, slot160 and slot320.
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The CSI report periodicity
•
Also drives the Scheduling Request opportunities (a unic parameter for both). So a low value
improves the Latency for network without proactive scheduling.
•
It is directly related with the capacity as the CSI reports are sent over PUCCH, the
‘dimensioning’ channel in term of capacity. So a high value improves the capacity, a low
value significantly degrades the capacity.
•
A high value may have side effects on the downlink throughput stability by changing the
behavior of Link Adaptation and Beam tracking as reports from UE come less often
→ Recommendation : Set the CSI report periodicity to its maximum value if you need capacity
(csiReportPeriodicity = slot320). Set it to an intermediate value if you don’t need maximal capacity
and if you want to favor Latency or Throughput (csiReportPeriodicity = slot40 or slot80).
The chosen value for these parameters has adverse effects on the KPIs : a given value would enable
high Capacity but degrade the Latency, and conversely.
This is a trade-off between capacity, latency and uplink user throughput.
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Proactive scheduling : Latency versus uplink throughput
The Proactive Scheduling (actProactUlScheduling = True) significantely improves the latency.
1 - Lab test : example for Ping RTT in cmW, single UE, as a function of proactive scheduling Time Interval
Single UE, or single UE + 8 UEs connected inactive, or single UE + 8 Ues connected active : the
proactive scheduling improves the latency in all cases.
2 - Lab test : example for Ping RTT in cmW, without and with proactive scheduling.
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csiReportPeriodicity : Latency versus Capacity
For non-pre-scheduled Ues (actProactUlScheduling = False), the latency mainly depends on the
occasions for Scheduling Requests (SR) (csiReportPeriodicity).
The more frequent are the SR occasions, the best is the latency. But the capacity is dramatically
reduced.
3 - Field test : example for Ping RTT (ms) in cmW as a function of SR periodicity
The capacity figures are extracted from the capacity tool located here, considering the following
configuration :
-
Frame structure 5GC001116_3ms
-
numberOfTransmittedSsBlocks = 8
-
ssBurstSetPeriod [ms] = 20ms
-
prachConfigurationIndex = 98
-
csirsTrackingPeriod [ms] = 80
Those figures should be taken for illustration only; use the ones corresponding to your configuration.
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