5G Radio Network Througput Problem Analysis HCIA.pdf

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5G Radio Network Throughput
Problem Analysis

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Objectives
Upon completion of this course, you will be able to:
Know the key factors for radio peak throughput calculation
Implement radio throughput problem isolation
Implement radio throughput problem optimization

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Throughput Optimization Scenario
Peak throughput test problem: During the peak throughput test, UE can’t reach the target value
Related radio factors:
Channel environment is not ideal
Channel parameters are not optimal
Driver test throughput test problem: During the driver test, the average throughput can’t reach the
target value
Related radio factors:
RF issues (Coverage, interference)
Abnormal event (Service drop, handover failure)
Improper parameters

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Contents
1.NR Radio Peak Throughput Factor Analysis
2.NR Radio Throughput Problem Optimization

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5G Radio Peak Throughput Analysis -Downlink

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Key Parameters for DL Peak Throughput
Description Adviseto peak throughput achievement
SSBperiod Indicatethe SSB transmission
period
Theperiod can be set largest to reduce SSB
overhead, but it will increase access latency
Sib1Period Indicatethe SIB1 transmission
period
For SA, theperiod can be set largest to
reduce SSB overhead, but it will increase
access latency. For NSA, SIB1 can be
disabled
TRSperiod Indicate theTRS period Theperiod can be set largest to reduce SSB
overhead, for it will impact demodulation
performance in mobility scenario
DlDmrsType Indicate PDSCH DMRS type Type2 in recommended asit has less
overhead, but the performance is worse than
type1
DlDmrsMaxLength Indicate the PDSCHDMRS length 1 symbol is recommend for peakthroughput
scenario

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Key Parameters for DL Peak Throughput (Cont.)
Parameter Description Adviseto peak throughput achievement
DlAdditionDmrsPos Indicatethe resource for additional
PDSCH DMRS configuration
Forpeak throughput scenario, it is recommend not
use additional DMRS
SSB rate match
switch
Indicatewhether SSB rate matching
switch is ON or OFF
Forpeak throughput scenario, it is recommend to
enable SSB rate match
CSI-RS rate match
switch
Indicatewhether CSI-RS rate matching
switch is ON or OFF
Forpeak throughput scenario, it is recommend to
enable CSI-RS rate match
TRS rate match
switch
Indicatewhether TRS rate matching
switch is ON or OFF
Forpeak throughput scenario, it is recommend to
disable TRS rate match
PDCCH rate match Indicatewhether PDCCH rate matching
switch is ON or OFF
Forpeak throughput scenario, it is recommend to
enable CSI-RS rate match and also reduce the
PDCCH RB number
OccupiedSymbolNum Indicatethe PDCCH symbol number in
CORESET
1 symbol is recommended
OccupiedRbNum Indicatethe PDCCH RB number in
CORESET
We can reducethe PDCCH RB number, at least
24RB are required. Meanwhile, we should enable
PDCCH rate match function

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5G Radio Peak Throughput Analysis -Uplink

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Key Parameters for UL Peak Throughput
Parameter Description Adviseto peak throughput achievement
Format1Rbnumber/
Format3Rbnumber
Indicatelong format PUCCH RB
nubmer
Choose theleast resource for PUCCH, it will
impact access user number
PRACHConfigurati
onIndex
Indicatetime domain PRACH
occasions
Choose the index with the least PRACH
occasion
PUSCHOccupying
PRACH switch
Indicate thewhether PUSCH can
occupy PRACH resource
Wecan enable the switch to increase peak
throughput, but it will impact new UE random
access

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Channel Environment For Peak Throughput Test
Other remarks:
The distance between the terminal and the AAU must be greater than 20 m to avoid uplink power saturation
The downlink high Rank depends on the surrounding multipath environment. Try to select the area with
reflection of surrounding trees and buildings and ensure the non-direct path between the test point and base
station antenna. In the uplink performance test, the direct path environment is preferred and the test point
with line of sight is the best location
SSB
RSRP
SSBSINRN SSB RSRP Freq
Offset
CSI-RS
RSRP
CSI-RS
SINR
DMRS0~n
SINR
Requirement -
65dBm~-
75dBm
>3dB The RSRP of the
strongest neighboring
cell is at least 6dB
less than of the
serving cell
(-50,50)-
70dBm
~-
80dBm
>30dB >30dB

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Contents
1.NR Radio Peak Throughput Factor Analysis
2.NR Throughput Problem Optimization

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E2E Data Transfer Architecture and Factors
CPE
gNodeBBBU
eNodeBBBU
Switch
Router
HSS
MME/UGW Firewall
APP Server
12. TCP
windows/Thread/RTT
Hardware performance
10. Transmission packet loss/bandwidth
X2
11. QCI/AMBR
6. Alarm
7. Parameter
8. Channel calibration
9. Transmission
packet loss
3. UE capacity
RB/Modulation/Feature
1. TCP windows/Thread/RTT
2. Hardware performance
4. SINR/CQI/RI/SRS
5 Channel condition
Factors 1, 2, 3, 6, 7, 9, 10, 11, and 12 affect the Grant and RB, and factors 4, 5, 6, 7, and 8 affect the MCS, BLER, and rank.

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General Optimization Flow
Step1：Check if AMBR subscription rate is enough
Method: In NSA network, check the SgNBAddition Request message to find the subscription UE-AMBR
Step2: Check if cell status is normal, clean all the alarms that may impact data throughput

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General Optimization Flow (Cont.)
Step 3: UE capability check
Supported bandwidth: Indicate the maximum
bandwidth that supported by UE, for sub 6G, it
should be 100MHz
MIMO layer number: For commercial UE, it should
be 4 layers on downlink, and 2 layers on uplink
Modulation scheme: 256QAM should be
supported

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General Optimization Flow (Cont.)
UE SRS switching capability
If UE supports SRS antenna switching function,
gNodeBcould adopt SRS beaming weighting
mechanism SRS
If UE doesn’t support antenna switching function,
only PMI beamforming weight can be used which
has worse performance than SRS weighting
UE ratemachingcapability:
If UE doesn’t support rate matching, then rate
matching function is not valid for the UE

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The Common Problem for Radio Interface
Radio resource related problem: not enough resource for PDCCH or PDSCH
DL grant number is less: For 4:1 TDD slot configuration, the DL grant number per second should reach
1600 times
RB number is less：Allocation RB number is not enough
Radio environment related problem
Low MCS
Low rank
High PDSCH IBLER

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Radio Interface Factors Analysis
Downlink Key Indicator Breakdown
Counter Name DL Grant/S PDSCH RB Num/Slot AvgDL MCS0/1 IBLER AvgDL Rank
Peak Rate Standard 1600 times
100 MHz bandwidth:
267/slot
80 MHz bandwidth: 213/slot
The difference in the actual
Probe statistics: 1 RB to 2
RBs.
256QAM: 27 orders IBLER: 0%
2T4R: 4; 4T8R: 8
Reasonable Range
in Non-Peak-Rate
Scenarios
1500 to 1600
Theoretical value minus 4
RBs to 6 RBs
N/A 9% to 12% N/A
Observation
Method
1. Probe log; 2. OMT log; 3. U2020Common User monitoring
Affecting Factor
1. AMBR rate limit;
2. Inappropriate PDCP and
RLC parameters
corresponding to QCI;
3. Multi-user scheduling;
4. Missing CCE detection or
CCE allocation failure;
5. Scheduling failure (HARQ
process exhausted);
1. AMBR rate limit
2. Multi-user scheduling;
3. Low RBs due to
insufficient inbound traffic
caused by TCP packet loss
or disorder
1. Coverage and channel environment
2. Absence of CQI reporting because the CSI-RS is not
measured, fixed MCS 4 order scheduling;
3. Parameter settings: CSI-RS port configuration, DMRS
configuration, MCS configuration, IBLER adaptation;
4. Channel calibration failure
1. Parameter settings:
SRS weight, DMRS
configuration, and rank
configuration;
2. Channel calibration
3. External interference
SRS measurement;
4. SRS power
5. Rank adaptive
algorithm;
6. Channel environment
(NLOS and LOS)

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Radio Relevant Parameter Monitor

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DL Grant and RB Problem Analysis –Insufficient Ingress Traffic
Isolation
If the inbound traffic is not enough (packet loss from server to gNodeB), if will definitely impact the
DL grant and RB number. So we can implement MAC padding test to exclude the ingress traffic
problem
MAC padding function: gNodeBsimulate the MAC layer PDU and transmit to particular UE. If the
MAC padding result can’t reach the target data rate, that means the problem occurs on gNodeB
side as well as radio interface

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DL Grant and RB Problem Analysis –Multiple Users Impact
Step 1：Check whether the problem is caused by too many user or not
We can implement real time user static monitoring to check the current user number

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DL Grant and RB Problem Analysis –CCE Detection Failure &
Allocation Failure
For CCE detection failure
Method to check: Implement Cell DT test in U2020 to check whether there is CCE detection failure
Possible causes:
Poor DL coverage that cause UE fail to decode PDCCH, in this case, implement RF optimization
CCE aggregation level is fixed configured: check NRDUCELLRSVDPARAM. RsvdU8Param7, the value should be 0,
which means CCE aggregation level is dynamic
PDCCH IBLER target setting problem: Check NRDUCellPdcch.PdcchBlerTargetparameter, the value should be less
than 2%
–gNodeBwill adjust PDCCH power to meet this target, if the value is too large, it will cause PDCCH demodulation failure

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DL Grant and RB Problem Analysis –CCE Detection Failure &
Allocation Failure (Cont.)
For CCE allocation failure：
Method to check: Implement CCE load monitoring in U2020, if the CCE load is very high, it may cause CCE
allocation failure
Possible cause:
Poor DL coverage that cause large CCE aggregation level allocation in the cell
Two may users in the cell
CCE ratio configuration problem: Check the NRDUCELLPDCCH. UlMaxCcePct, the proper ratio is 50%

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MCS Problem Related Parameters Analysis
ProblemScenario Possible cause Solution
MCS is fixedvalue 1. MCS is fixedconfigured
2. UE doesn’t report CSI, so gNodeB
will use fixed MCS4 for scheduling
1.Check NRDuCellRsvdParam.
RsvdU8Param68, ifthe value is
non-zero,thatmeans DL MCS is
fixed configured
2.Poor SRS quality thatcause CSI-
RS beamforming abnormal
MCS is very low after
handover
Initial MCS setting is too low Check NRDUCellPdsch. DlInitMcs, the
value should be more than 4
DL MCS can’t reach
maximum valueany
time
TRSperiod is too large that cause
large frequency offset
NRDUCellCsirs. TrsPeriod, itshould
not be more than 20ms

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RANK Problem Related Parameters
ProblemScenario Possible cause RelevantParameters
Rank can’t reach
rank4
AAU channel calibration problem Manual execute channel calibration,
STR NRDUCELLCHNCALIB, if it still
failure, then check whether external
interference exists.
CSI-RS port number is less than 4CheckNRDUCellRsvdParam.
RsvdU8Param47, the value should be
equal or more than 2(port number
more than 4)
Maximum MIMOlayer number is less
than 4
CheckNRDUCELLPDSCH.
MaxMimoLayerNumparameter, the
value should be more than 4
Rank is low after
handover
Initial Rank setting is too low Check NRDuCellRsvdParam.
RsvdU8Param67,thevalue can be
increased if the coverage is good after
handover

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High IBLER Problem Related Parameters
ProblemScenario Possible cause RelevantParameters
IBLERis higher than
10%
IBLERtarget is too large Checkthe NRDUCELLPDSCH.
DlTargetIblerparameter, the value can’t
exceed 10%
TRSperiod is too large, that
cause high BLER in mobility
environment
Check NRDUCELLCSIRS. TrsPeriod, the
value shouldn’t be exceed 40ms
PDSCHDMRS is not enough in
high mobility environment
CheckNRDUCELLPDSCH.
DlAdditionalDmrsPos, we can set it to pos1
to increase DMRS resource
Downlinkbeamforming weigh is
fixed configured
SRS-PMIadaptive switch should be turned
on

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Summary
NR radio peak throughput analysis and parameters setting
Radio throughput problem isolation method
MCS/BLER/RANK problem analysis and parameters

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