Document Code
Product Name
5G RAN
Intended Audience
INTERNAL
Version
5G RAN V100R002
Prepared By
5G&SRAN I&V Dept, WN
Document Version
V1.0.0
5G Troubleshooting Guide – NSA Access
Prepared By
Xue Ruiqi and Cui Qingxia
Date
2018-9
Reviewed By
Qi Haofeng, Qian Jin, and Qin Yan
Date
2018-9
Approved By
Qi Haofeng
Date
2018-9
Huawei Technologies Co., Ltd.
All Rights Reserved.
5G Troubleshooting Guide – NSA Access
INTERNAL
Change History
Date
Version
2019-04
2019-06
2019-10
2023-05-02
Description
Author
V1.0
Completed the draft.
Xue Ruiqi and Cui Qingxia
V1.1
Added the contention Msg4
analysis method.
Cui Qingxia
V1.2
Section

Added the VIP
complaint handling
method.

Added the analysis
guidance when a UE
fails to measure cells
and synchronization
fails due to RF causes.
Cui Qingxia
Huawei confidential. No spreading without permission.
ii
5G Troubleshooting Guide – NSA Access
INTERNAL
About This Document
Overview
This document describes the user access process and common fault demarcation methods,
helping users to preliminarily isolate and troubleshoot user access problems.
Precautions
When using this guide to quickly troubleshoot problems, some user data such as Internet
Protocol (IP) addresses may be used. You are obligated to take considerable measures, in
compliance with the laws of the countries concerned and the user privacy policies of your
company, to ensure that the personal data of users is fully protected.
You are advised to abide by local laws and regulations to execute the task and take measures
to fully protect personal data. For example, delete the folder for saving tracing records after
the processing.
Intended Audience
This document is intended for:

Maintenance engineers

Onsite engineers
Symbol Conventions
The symbols that may be found in this document are defined in the following table.
Symbol
Description
Indicates an imminently hazardous situation which, if not
avoided, will result in death or serious injury.
Indicates a potentially hazardous situation which, if not
avoided, could result in death or serious injury.
2023-05-02
Huawei confidential. No spreading without permission.
iii
5G Troubleshooting Guide – NSA Access
Symbol
INTERNAL
Description
Indicates a potentially hazardous situation which, if not
avoided, may result in minor or moderate injury.
Indicates a potentially hazardous situation which, if not
avoided, could result in equipment damage, data loss,
performance deterioration, or unanticipated results.
NOTICE is used to address practices not related to personal
injury.
Calls attention to important information, best practices and
tips.
NOTE is used to address information not related to personal
injury, equipment damage, and environment deterioration.
2023-05-02
Huawei confidential. No spreading without permission.
iv
5G Troubleshooting Guide – NSA Access
INTERNAL
Contents
Change History ................................................................................................................................ ii
About This Document ................................................................................................................... iii
1 Basic Principles .............................................................................................................................. 1
1.1 Basic Concept ............................................................................................................................................................... 1
1.1.1 Networking Modes .................................................................................................................................................... 1
1.1.2 Network Topology ..................................................................................................................................................... 2
1.2 Interaction Between NEs .............................................................................................................................................. 3
1.2.1 Interaction Process Between NEs .............................................................................................................................. 3
1.3 NSA-related Terms ....................................................................................................................................................... 4
2 Basic Check..................................................................................................................................... 5
2.1 Checking Version Mapping........................................................................................................................................... 5
2.2 Checking Operations, Alarms, Faults, and External Events ......................................................................................... 5
2.3 Checking Parameters .................................................................................................................................................... 8
2.3.1 Key Configurations Related to NSA Access .............................................................................................................. 8
2.3.2 Automatic Check of Key Configurations Related to NSA Access ............................................................................. 9
2.3.3 Checking Basic UE Configurations ......................................................................................................................... 10
2.4 Checking SIM Card Registration ................................................................................................................................ 10
2.5 Checking RF Channels ............................................................................................................................................... 10
3 Quick Troubleshooting of NSA Access Problems ............................................................... 12
3.1 Overall Instruction Map .............................................................................................................................................. 12
3.2 Quick Troubleshooting of NSA Access Problems ...................................................................................................... 12
3.3 Common Access Logs ................................................................................................................................................ 13
4 NSA Access Problem Locating Guide ..................................................................................... 14
4.1 Procedures on the LTE Side ........................................................................................................................................ 14
4.1.1 Access Failure on the LTE Side ............................................................................................................................... 14
4.1.2 NR Measurement Is Not Delivered .......................................................................................................................... 15
4.1.3 NR Cells Cannot Be Measured ................................................................................................................................ 21
4.1.4 B1 Measurement Result Is Reported But No SgNB Addition Procedure Is Initiated .............................................. 28
4.2 Access Preparation Process ......................................................................................................................................... 31
4.2.1 The gNodeB Does Not Respond with SGNB_ADD_REQ_ACK ........................................................................... 31
4.2.2 The gNodeB Returns SGNB_ADD_REQ_REJ ....................................................................................................... 33
2023-05-02
Huawei confidential. No spreading without permission.
v
5G Troubleshooting Guide – NSA Access
INTERNAL
4.2.3 The eNodeB Does Not Return an SGNB_RECFG_CMP Message. ........................................................................ 36
4.3 NR Air Interface Access Failure ................................................................................................................................. 41
4.3.1 The UE Does Not Initiate Access After Receiving a Reconfiguration Message ...................................................... 41
4.3.2 The RAR Message over the Air Interface Times Out .............................................................................................. 43
4.3.3 Msg3 Failure ............................................................................................................................................................ 53
4.3.4 Contention Msg4 Failure ......................................................................................................................................... 58
5 Methods of Analyzing KPI-related Problems in Traffic Statistics (NSA) ....................... 64
5.1 Access KPI Definition ................................................................................................................................................ 64
5.2 Signaling Procedures and Measurement Points .......................................................................................................... 65
5.3 Method of Analyzing Access KPI-related Problems ................................................................................................... 67
5.3.1 Action 1: Determining the Problem Type ................................................................................................................ 67
5.3.2 Action 2: Time Trend Analysis ................................................................................................................................ 67
5.3.3 Action 3: Traffic Statistics Cause Analysis .............................................................................................................. 67
5.3.4 Action 4: Top N Analysis ......................................................................................................................................... 68
5.3.5 Action 5: Associated KPI Analysis .......................................................................................................................... 69
5.3.6 Action 6: Operations and External Events ............................................................................................................... 72
5.3.7 Action 7: Detailed Analysis of Top Sites or Typical Sites........................................................................................ 72
6 VIP Complaint Handling .......................................................................................................... 78
6.1 Overview .................................................................................................................................................................... 78
6.2 Complaining User Information Collection ................................................................................................................. 79
6.3 User Complaint Analysis Methods ............................................................................................................................. 79
6.4 Complaints Analysis ................................................................................................................................................... 80
2023-05-02
Huawei confidential. No spreading without permission.
vi
5G Troubleshooting Guide – NSA Access
INTERNAL
1
Basic Principles
1.1 Basic Concept
NSA introduces 5G access into existing LTE networks where E-UTRAN and EPC serve as the
anchors for mobility management and network coverage.
For details about the evolution paths of the 5G architecture, see 3GPP TR 38.801.
1.1.1 Networking Modes
The current version supports two network architectures: SCG split bearer (option 3x) and
MCG split bearer (option 3).

Option 3 (MCG split bearer)
The user-plane data received from the core network is transmitted to the PDCP layer of
the eNodeB. Then, the PDCP layer of the eNodeB distributes the data to the RLC layer
of the gNodeB through the X2 interface.
UE
eNB_PDCP
MME/S-GW
gNB
RRC CONNECTION
S1-C
S1-U
X2-C
X2-U
UE

2023-05-02
eNB_PDCP
MME/S-GW
gNB
Option 3x (SCG split bearer)
Huawei confidential. No spreading without permission.
1
5G Troubleshooting Guide – NSA Access
INTERNAL
The user-plane data is first transmitted from the core network to the PDCP layer of the
gNodeB. Then, the PDCP layer of the gNodeB distributes the data to the RLC layer of
the eNodeB through the X2 interface.
UE
eNB
MME/S-GW
gNB_PDCP
RRC CONNECTION
S1-C
X2-C
X2-U
S1-U
UE
eNB
MME/S-GW
gNB_PDCP
1.1.2 Network Topology
The following figure shows the protocol architecture of NSA networking.
Lab NSA E2E networking:
2023-05-02
Huawei confidential. No spreading without permission.
2
5G Troubleshooting Guide – NSA Access
INTERNAL
Maintenance PC
Shielding cabinet
A7 rack
Switch
O&M switch
Serial port server
Serial cable
Core network
Service switch
Feeders
CAT 6 cable
Feeders
Maintenance cable
X2 interface
1.2 Interaction Between NEs
This section describes the interaction between the UE and the eNodeB/gNodeB. It helps you
to understand how a UE accesses the NR network from the LTE network.
1.2.1 Interaction Process Between NEs
Figure 1-1 Interaction between NEs in Option 3 (MCG split bearer) and Option 3x (SCG split
bearer)
2023-05-02
Huawei confidential. No spreading without permission.
3
5G Troubleshooting Guide – NSA Access
INTERNAL
1.3 NSA-related Terms
2023-05-02
Acronym and Abbreviation
Full Name
NSA
Non-Stand Alone
NR
New Radio
LTE
Long Term Evolution
DC
Dual Connectivity
EN-DC
LTE-NR DC
eNodeB
Evolved NodeB
gNodeB
gNodeB (supporting NR and connectivity to NGC)
MeNB
Master eNodeB
SgNB
Secondary gNodeB
MN
Master Node
SN
Secondary Node
CA
Carrier Aggregation
MCG
Master Cell Group
SCG
Secondary Cell Group
PCell
Primary Cell
SCell
Secondary Cell
PSCell
Primary SCell
PCC
Primary Component Carrier
SCC
Secondary Component Carrier
PDCP
Packet Data Convergence Protocol
LNR
Long Term Evolution and New Radio
Huawei confidential. No spreading without permission.
4
5G Troubleshooting Guide – NSA Access
INTERNAL
2
Basic Check
2.1 Checking Version Mapping
Ensure that the versions of the NR base station, LTE base station, TUE, CPE, U2020, and CN
NEs are recommended ones and are compatible. For details about the version mapping, see
5G 18B/19A/19B recommended version policies.
2.2 Checking Operations, Alarms, Faults, and External
Events
The operation, alarm, and fault logs of the base station can be obtained from the U2020 and
one-click logs and can be opened using the FMA. Operation logs are used to check for
operations affecting UE access and whether the problem occurrence time is related to the
operation time. For alarms and faults, check whether there are uncleared alarms at the time
when the fault occurs. In addition, check whether there are important events based on the time
when the problem occurs, and then perform event association analysis.
The following table lists the alarms and events that need to be focused on.
Alarm ID
Alarm Name
Alarm Impact
ALM-25954
User Plane Fault
The X2-U or S1-U link fault causes access failure.
ALM-25952
User Plane Path Fault
The automatically established X2-U or S1-U link fault
causes access failure.
ALM-29841
NR Cell Unavailable
The NR cell where this alarm is reported cannot
provide services.
ALM-29840
gNodeB Out of Service
All cells where this alarm is reported cannot provide
services.
ALM-29842
NR Cell Blocked
The NR cell where this alarm is reported cannot
provide services.
ALM-29800
gNodeB X2 Interface Fault
The base station cannot continue to support the EN-DC
services with the corresponding base stations.
ALM-25888
SCTP Link Fault
The SCTP link cannot process signaling messages.
2023-05-02
Huawei confidential. No spreading without permission.
5
5G Troubleshooting Guide – NSA Access
INTERNAL
Alarm ID
Alarm Name
Alarm Impact
ALM-25889
SCTP Link Congestion
The services are disrupted because the data cannot be
transmitted due to insufficient space of the sending
buffer.
ALM-25955
SCTP Link
Unreachable
If the two configured destination IP addresses of the
SCTP link are both unreachable, the upper-layer
services will be interrupted.
ALM-25954
User Plane Fault
The user plane cannot carry services.
ALM-25886
IP Path Fault
Services carried on the IP Path cannot be normally
processed.
ALM-25952
User Plane Path Fault
User plane services cannot be processed.
ALM-29204
X2 Interface Fault
When the neighboring base station is gNodeB, the
gNodeB cannot continue to support the EN-DC
services with the corresponding base station.
ALM-29225
Maximum Number of X2
Interfaces Reached
The EN-DC service cannot be initiated with the
corresponding gNodeB.
IP
Address
Choose 5G FMA > Tools > Brdlog Unpack Tool to decompress the one-click logs of the
main control board to obtain the alarm logs and fault logs of the base stations. Then, import
the logs into the FMA for quick analysis and troubleshooting.
Figure 2-1 Operation alarms and fault logs in one-click logs
2023-05-02
Huawei confidential. No spreading without permission.
6
5G Troubleshooting Guide – NSA Access
INTERNAL
Figure 2-2 Operation logs parsed by the FMA
Figure 2-3 Fault logs parsed by the FMA
Figure 2-4 Alarm logs parsed by the FMA
2023-05-02
Huawei confidential. No spreading without permission.
7
5G Troubleshooting Guide – NSA Access
INTERNAL
2.3 Checking Parameters
Parameter check is one of the basic actions for network performance optimization. In the
current phase, many access problems are caused by configuration problems. Therefore,
checking parameters is the most convenient and efficient way to troubleshoot access
problems.
2.3.1 Key Configurations Related to NSA Access
Base
Station
Key Configuration Item
MML
eNodeB
Adding a neighboring NR
frequency
ADD NRNFREQ: LocalCellId=21, DlArfcn=636666,
UlArfcnConfigInd=NOT_CFG,
SsbOffset=0,
SsbPeriod=20MS, SubcarrierSpacing=30KHZ;
Configuring the frequency
band for a neighboring NR
frequency whose NR-ARFCN
falls within the following
ranges:
158200-160600,
285400-303400,
386000398000,
402000-404000,
422000-434000,
514000537999, 620000-653333, or
2054166-2084999
Setting the frequency band to
which the neighboring NR
frequency belongs
ADD
NRMFBIFREQ:
FrequencyBand=n78;
Adding an external NR cell
ADD NREXTERNALCELL: Mcc="262", Mnc="01",
GnodebId=255,
CellId=1,
DlArfcn=636666,
UlArfcnConfigInd=NOT_CFG,
PhyCellId=1,
Tac=1,
NrNetworkingOption=NSA;
Adding
a
neighbor
relationship with the NR cell
ADD NRNRELATIONSHIP: LocalCellId=21, Mcc="262",
Mnc="01", GnodebId=1, CellId=7;
Adding a candidate PCC
ADD PCCFREQCFG: PccDlEarfcn=1500;
Adding a candidate SCC to an
NR SCG
ADD
NRSCGFREQCONFIG:
PccDlEarfcn=1500,
ScgDlArfcn=636666,
ScgDlArfcnPriority=6,
NsaDcB1ThldRsrp=-105, NrB1TimeToTrigger=40MS;
Modifying
NSA
DC
management configuration
MOD
NSADCMGMTCONFIG:
LocalCellId=21,
NsaDcAlgoSwitch=NSA_DC_CAPABILITY_SWITCH-1;
MOD
CELLQCIPARA:
LocalCellId=21,
Qci=9,
NsaDcDefaultBearerMode=SCG_SPLIT_BEARER;
MOD
QCIPARA:
Qci=9,
NsaDcRlcPdcpParamGroupId=223;
MOD
RLCPDCPPARAGROUP:
RlcPdcpParaGroupId=223,
RlcMode=RlcMode_AM,
AmPdcpSnSize=AmPdcpSnsize_18bits;
Modifying the downlink data
split mode for NR cells
MOD GNBPDCPPARAMGROUP: PdcpParamGroupId=1,
DlDataPdcpSplitMode=SCG_ONLY;
gNodeB
2023-05-02
Huawei confidential. No spreading without permission.
DlArfcn=636666,
8
5G Troubleshooting Guide – NSA Access
Base
Station
INTERNAL
Key Configuration Item
MML
Modifying the settings of
Uplink Data Split Primary
Path and Uplink Data Split
Threshold
MOD GNBPDCPPARAMGROUP: PdcpParamGroupId=1,
UlDataSplitPrimaryPath=SCG,
UlDataSplitThreshold=INFINITY, DlPdcpSnSize=BITS18;
Setting NR cell algorithm
switches
MOD
NRCELLALGOSWITCH:
NsaDcSwitch=ON;
Modifying
the
bearer
configuration of an NR cell
with RLC Mode set to AM and
AmPdcpParamGroupId set to
the
same
value
as
PdcpParamGroupId
MOD NRCELLQCIBEARER: NrCellId=7,
AmPdcpParamGroupId=1, RlcMode=AM;
NrCellId=7,
Qci=9,
2.3.2 Automatic Check of Key Configurations Related to NSA
Access
Use the NSA Parameter Check tool (FMA > Tools > Parameter Check) to automatically
check NSA parameters.
http://3ms.huawei.com/hi/group/3402967/thread_6894907.html?mapId=8584899&for_statisti
c_from=all_group_forum&l=en (FMA download hyperlink)
1. Check NSA DC configurations, including whether the external NR cells, frequencies, and
neighbor relationships are correctly configured, and whether the NSA DC switch is turned on.
2. Check whether the X2 link configuration is correct and whether the number of X2 links has
reached the maximum.
3. Check whether PCI conflict exists in an LTE cell and its neighboring NR cells and whether
PCI conflict exists in cells served by the same NR base station.
4. Check whether the SpecUeIdentifySwitch is turned on and check PDCP parameter groups.
5. Check GNBIDLENGTH consistency.
6. Check the NR architecture option setting.
7. Check 19BC10 NRMFBIFREQ.
8. Check frame offset settings in the 2.6 GHz band.
2023-05-02
Huawei confidential. No spreading without permission.
9
5G Troubleshooting Guide – NSA Access
INTERNAL
Figure 2-5 Parameter check in the FMA tool
2.3.3 Checking Basic UE Configurations
Currently, no commercial 5G UEs are available. 5G UEs are basically Huawei TUEs and
CPEs. Check the basic configurations by referring to the TUE Product White Paper or CPE
Commissioning Guide. The reference link is as follows:
http://3ms.huawei.com/hi/group/3402967/thread_7528635.html?mapId=9300715&for_statisti
c_from=all_group_forum&l=en
2.4 Checking SIM Card Registration
Confirm with CN engineers to ensure that the SIM card is registered properly, can normally
access the LTE and 5G networks, and will not be rejected by the CN.
2.5 Checking RF Channels
When interference signals exist in a cell, the uplink and downlink services of the cell are
affected. In severe cases, UEs cannot access the network from the cell. In this case, you need
to analyze the interference. You can choose interference tracing by choosing Tracing
Monitor > NR > Cell Performance Monitoring on the U2020. For details about how to
determine the interference, see the Problem Location Guide-Channel and Interference.
2023-05-02
Huawei confidential. No spreading without permission.
10
5G Troubleshooting Guide – NSA Access
INTERNAL
Figure 2-6 U2020 interference detection tracing
2023-05-02
Huawei confidential. No spreading without permission.
11
5G Troubleshooting Guide – NSA Access
3
INTERNAL
Quick Troubleshooting of NSA Access
Problems
3.1 Overall Instruction Map
3.2 Quick Troubleshooting of NSA Access Problems
The checklists in the following attachment provide the quick troubleshooting methods:
5G Access Fault
Quick Isolation Guide_2.1_0416.xlsx
2023-05-02
Huawei confidential. No spreading without permission.
12
5G Troubleshooting Guide – NSA Access
INTERNAL
3.3 Common Access Logs
All access logs of the 5G network are mainly based on X2 signaling. The records of the
received X2 messages in the debug log are as follows:
CU_UEM_LOG_CODE(0x00AE)
"[FILE]cuuem_x2_agent.cpp [FUNCTION]CuUemX2Agent::OnMsg X2agent receive X2
msg.msg_type=17, x2_link_id=0"
Common messages over the X2 interface:
msg_type=14:
msg_type=15:
msg_type=16:
msg_type=17:
msg_type=18:
msg_type=19:
msg_type=20:
msg_type=21:
msg_type=22:
msg_type=23:
msg_type=24:
msg_type=25:
msg_type=26:
msg_type=27:
msg_type=28:
msg_type=29:
msg_type=30:
msg_type=31:
msg_type=32:
msg_type=33:
msg_type=34:
msg_type=35:
msg_type=36:
msg_type=37:
msg_type=38:
msg_type=39:
msg_type=40:
msg_type=41:
2023-05-02
X2AP_SGNB_ADD_REQ
X2AP_SGNB_ADD_ACK
X2AP_SGNB_ADD_REJ
X2AP_SGNB_RECFG_CMP
X2AP_SGNB_MOD_REQ
X2AP_SGNB_MOD_ACK
X2AP_SGNB_MOD_REJ
X2AP_SGNB_MOD_REQUIR
X2AP_SGNB_MOD_CONF
X2AP_SGNB_MOD_REFUSE
X2AP_SGNB_CHANGE_REQUIR
X2AP_SGNB_CHANGE_CONF
X2AP_SGNB_CHANGE_REFUSE
X2AP_SGNB_REL_REQ
X2AP_SGNB_REL_REQ_ACK
X2AP_SGNB_REL_REQ_REJ
X2AP_SGNB_REL_REQUIR
X2AP_SGNB_REL_CONF
X2AP_SGNB_COUNTER_CHK_REQ
X2AP_RRC_TRANSFER
X2AP_HANDOVER_REQ
X2AP_HANDOVER_REQ_ACK
X2AP_HANDOVER_PREPARATION_FAIL
X2AP_SN_STATUS_TRANSFER
X2AP_UE_CONTEXT_REL
X2AP_HANDOVER_CANCEL
X2AP_LOAD_INFORMATION
X2AP_ERR_IND
Huawei confidential. No spreading without permission.
13
5G Troubleshooting Guide – NSA Access
4
INTERNAL
NSA Access Problem Locating Guide
4.1 Procedures on the LTE Side
4.1.1 Access Failure on the LTE Side
4.1.1.1 Basic Concepts
In NSA networking, UEs need to access the LTE network first before establishing connection
to NR. When 5G signals are unavailable, the problem may not be caused by the 5G network.
Instead, UEs may fail to access the LTE network.
4.1.1.2 Identification Method
A UE fails to access the LTE network in either of the following scenarios:
1. The UE does not initiate an access procedure on the LTE network. The L3 Message tracing
results show that the UE does not send any access message.
2. The UE initiates an attach procedure on the LTE network and is rejected by the CN. The L3
Message tracing results show that the UE receives an Attach Reject message after initiating a
connection request to the LTE network.
4.1.1.3 Problem Location
1. UEs do not initiate access to the LTE network. The common problems are as follows:
2023-05-02
Huawei confidential. No spreading without permission.
14
5G Troubleshooting Guide – NSA Access
INTERNAL
The CPE does not initiate access to the LTE network because the LTE device-pipe synergy
switch is turned off. This parameter can be directly checked by using the NSA Parameter
Check tool in the parameter check phase.
The LTE cell status configuration is abnormal. (Analyze the value of the Cell Bar IE in the
SIB message.)
Problem Identification Method
Rectification Method
The SpecUeIdentifySwitch option of the
UECOOPERATIONPARA.SpecUserCooperationSwitch
parameter is deselected for an LTE cell, and the CPE does
not initiate access in the cell.
Run the following command to select the SpecUeIdentifySwitch
option:
MOD UECOOPERATIONPARA: LocalCellId=X,
SpecUserCooperationSwitch=SpecUeIdentifySwitch-1;
The cellBarred:notBarred (1) and
cellReservedForOperatorUse:reserved (0) are carried in the
SIB1. According to 3GPP TS 36.304, a UE reads the AC
information in the SIM card to determine whether to access
the network. If the AC is not 11 or 15, the UE determines
that the cell is in the barred state and does not initiate
network access.
Run the following command to modify the configuration on the
LTE side:
MOD CELLOP: LocalCellId=XX, TrackingAreaId=XX,
CellReservedForOp=CELL_NOT_RESERVED_FOR_OP;
2. The UE initiates an attach procedure on the LTE network and is rejected by the CN.
The attach problem is irrelevant to the radio access network. Contact CN engineers and
terminal engineers to locate the problem.
For details about other LTE access failures, see X Solutions for Access and Paging
Performance Optimization in the LTE Network. The link is as follows:
http://3ms.huawei.com/hi/group/9261/file_12805859.html?for_statistic_from=my_group_file
&l=en
4.1.1.4 Cases
N/A
4.1.2 NR Measurement Is Not Delivered
4.1.2.1 Basic Concept
The NR measurement message is carried in the RRC reconfiguration message over the air
interface.
An NR measurement control message contains the following IEs (key information includes
the NR frequency, bandwidth, and B1 RSRP threshold):
2023-05-02
Huawei confidential. No spreading without permission.
15
5G Troubleshooting Guide – NSA Access
INTERNAL
4.1.2.2 Identification Method
Check the Event List in the UE's Probe signaling to determine whether the eNodeB delivers a
B1 measurement control message. Alternatively, check whether a B1 measurement control
message is sent over the Uu interface by referring to section 4.1.2.1.
4.1.2.3 Problem Location
4.1.2.3.1 Signaling & Configuration Analysis
After a UE accesses the LTE network, the LTE network determines whether to deliver the
NSA B1 measurement to the UE based on the following conditions:
2023-05-02
Huawei confidential. No spreading without permission.
16
5G Troubleshooting Guide – NSA Access
INTERNAL

The UE capabilities, reported through the RRC_UE_CAP_INFO message, contain endc-r15. That is, the ueCapacityRAT-Container IE with rat-Type set to eutra carries the
irat-ParametersNR-r15 field, which contains en-DC-r15:supported.

The NSA capability of the UE is not restricted on the core network.
The core network sends an S1AP_INITIAL_CONTEXT_SETUP_REQ message
containing the nRestriction IE to restrict NSA services.

UEs do not use the QCIs specific to LTE services.
Specific QCIs vary with versions. For details, see NSA Networking based on EPC
Feature Parameter Description of the corresponding version.
2023-05-02
Huawei confidential. No spreading without permission.
17
5G Troubleshooting Guide – NSA Access
INTERNAL
Check the QCI of the established bearer in the
S1AP_INITIAL_CONTEXT_SETUP_REQ message.

The NSA DC switch and neighboring NR frequencies are correctly configured on the
LTE side.
Refer to the forward check -> parameter check. You can use the NSA Parameter Check
tool to perform an automatic check.
The following provides the results obtained by an automatic check of the NSA Parameter
Check tool. The tool compares the LTE's neighboring NR cell configuration with the
actual NR configuration to check whether the configuration is correct, whether the
frequency configuration is correct, and whether the NSA DC switch is turned on. When a
configuration exception occurs, an error message is displayed.

LTE cells support NSA. Some LTE boards do not support NSA.
The following table lists the hardware support for Option 3 and Option 3x. In actual
projects, there may be special specifications archived for tier-1 operators. If hardware
that does not meet requirements is used, contact the corresponding DPM or MO for a
desired customer to obtain the hardware requirements of the corresponding network, and
then assess the hardware requirements.
2023-05-02
Huawei confidential. No spreading without permission.
18
5G Troubleshooting Guide – NSA Access

INTERNAL
In version 19B, UE MR-DC capability supports the combination of candidate PCC and
NR SCG frequency. If the UE capabilities carry the MR-DC capability, the base station
determines whether the LTE-NR band combinations in the MR-DC capability include the
combination of the candidate PCC and NR SCG frequency.
As shown in the following figure, the MR-DC capability can be viewed from the UE
capabilities. A UE may support multiple LTE-NR band combinations. If the B1
measurement control message is not delivered, check whether the supported
BandCombinations contain the candidate PCC and NR SCG frequency configured on the
LTE side.
2023-05-02
Huawei confidential. No spreading without permission.
19
5G Troubleshooting Guide – NSA Access
INTERNAL
For details about common problems and troubleshooting methods, see the access fault tree.
CHR-based Problem Location
As shown in the following figure, if the LTE CHRs in version 19B contain the CHRs circled
in blue, NR measurement is not delivered. Select NSADC_EVENT in the Type column. The
event is printed once an hour. Based on the test time, find the event in the corresponding time.
For example, if the test time is 16:00, check the event occurred at 16:34:55 (the time segment
is 15:34:55–16:34:55).
2023-05-02
Huawei confidential. No spreading without permission.
20
5G Troubleshooting Guide – NSA Access
INTERNAL
4.1.2.4 Cases
For details, see 4.1.2.3 "Problem Location."
4.1.3 NR Cells Cannot Be Measured
4.1.3.1 Basic Concept
The air interface message carrying the NR measurement report is an RRC measurement
report.
The key IEs in the NR measurement report are as follows (the NR measurement result carries
the r15 feature field):
4.1.3.2 Identification Method
CHR-based Identification
As shown in the following figure, the LTE CHRs in version 19B contain the CHRs circled in
blue. Based on the circled CHRs, you can determine whether NR cells can be measured.
Select NSADC_EVENT in the Type column. The event is printed once an hour. Based on the
test time, find the event in the corresponding time. For example, if the test time is 16:00,
check the event occurred at 16:34:55 (the time segment is 15:34:55–16:34:55).
2023-05-02
Huawei confidential. No spreading without permission.
21
5G Troubleshooting Guide – NSA Access
INTERNAL
4.1.3.3 Problem Location
Possible Cause
After the eNodeB delivers a B1 measurement configuration, the UE sends a measurement
report if the threshold conditions are met. If the UE does not send a B1 measurement report
within 3s, the eNodeB deletes the B1 measurement configuration. If the B1 measurement
report is not sent to the eNodeB, the possible causes are as follows.
NE
Check Item
Troubleshooting Method
Recovery Measure
LTE
Incorrect
NR
frequency
configurations
Check whether the B1 threshold
is too high.
Check whether ScgDlArfcn is consistent with
the gNodeB SSB frequency.
Correct the NR frequency
configurations.
Decrease NsaDcB1ThldRsrp.
Weak coverage
RF
Check whether the test point is
within the coverage of the NR
cell.
NsaDcB1ThldRsrp
The actual signal strength does not reach the
B1 threshold.
Check engineering parameters and check
whether the NR cell covers the test point.
Check whether coverage parameters are set
properly.
Check whether the AAU cable connections
and AAU antenna space are the same as
planned.
Abnormal NR cell status
The value of the Cell Status field in the DSP
NRCELL command output is not Normal.
Abnormal AAU transmit power
Choose cell performance monitoring > AAU
channel power monitoring to monitor the
AAU transmit power. The output power of
the AAU channel is less than 50 dBm
according to the cell performance monitoring
result.
NR
2023-05-02
Optimize coverage.
Modify improper parameters and
connections.
Ensure that the cell status is
normal. For details, see NR Cell
Troubleshooting Guide.
1. Increase the transmit power of
the AAU and check whether the
problem is resolved by running the
following
command:
MOD
NRDUCELLTRP:
NrDuCellTrpId=0,
MaxTransmitPower=XX;
2. Increase the power of the PBCH
and synchronization signals and
check whether the UE can search
for the cell by running the
following
command:
MOD
Huawei confidential. No spreading without permission.
22
5G Troubleshooting Guide – NSA Access
AAU channel calibration failure
Run the DSP NRDUCELLCHNCALIB:
NrDuCellId=x; command and find that the
latest channel calibration results indicate
failures.
When the base station is close to
the TUE, the downlink power is
oversaturated. As a result, the
TUE fails to detect cells.
The distance between the UE and the base
station and the AAU power are used for
judgment. Manual determination is required.
Cell search failure due to
interference from neighboring 5G
cells
Interference from neighboring 5G cells
causes the cell search failure. Use the
frequency scanner or TUE spectrum scanning
function to check whether downlink
neighboring cell interference exists.
UE
No NR cell is found due to UE
problems.
If the problem is not caused by LTE and NR
base stations, check whether the cell search
failure is caused by UE problems.
E2E
There are too many interfrequency measurement objects.
As a result, the UE measurement
takes a long time and the timer
expires after 3s.
Check the number of inter-frequency and
inter-RAT measurement objects and the
number of measurements configured for the
UE through signaling.
INTERNAL
NRDUCELLCHNPWR:
PbchPowerOffset=2000,
SchPowerOffset=2000;
3. If the problem persists, collect
one-click
logs
of
the
AAU/BBP/MPT and send the logs
to Huawei headquarters for
analysis.
See the 5G channel fault location
guide.
Increase the attenuation on the
TUE to prevent access failures due
to oversaturated uplink and
downlink power.
Eliminate
the
downlink
interference source or modify the
center frequency.
Use other terminals to isolate the
problem.
Use blind configuration to avoid
this problem. On the LTE side, the
following parameters must be
configured and a license is
required:
NSA blind configuration switch of
neighbor relationships: MOD
NSADCMGMTCONFIG:
LocalCellId=xx,
NsaDcAlgoSwitch
=
NSA_BLIND_SCG_ADDITION_
SWITCH-1;
NR blind configuration indicator:
MOD
NRNRELATIONSHIP:
LocalCellId=xx,
Mcc="xx",
Mnc="xx",
GnodebId=xx,
CellId=xx,
BlindConfigIndicator=TRUE;
Disable inter-frequency MRs using
the inter-frequency MR blacklist
and check whether the problem is
resolved.
Abnormal AAU Transmit Power
1. Check whether L2 sends the MIB properly based on CHR logs.
Check L2CellChrBlkInfo > L2_TRPCHR_BLK_CCHP_INFO > ChrProcessRecord >
CCHPSendPBCHCnt. This event is measured every 10 minutes by cell. The following figure
shows 30000 times for 10 minutes when the NRDUCELL.SsbPeriod parameter is set to 20
ms. This indicates that the L2 sends the MIB properly. If the number of MIB sending times is
too small, contact L2 personnel for processing.
2023-05-02
Huawei confidential. No spreading without permission.
23
5G Troubleshooting Guide – NSA Access
INTERNAL
If L2 sends the MIB properly, go to the next step.
2. Check whether the MIB is sent over the L1 egress of the base station.
Obtain AAU one-click logs. The logs need to be parsed by the baseband tool. You can contact
L1 to view the logs. Check the antenna power in the DLPWRTRACE. The normal transmit
power is about 20,000 and the non-transmit power is about 7000. The following figure shows
the normal transmit power of the AAU.
The following figure shows an abnormal case:
2023-05-02
Huawei confidential. No spreading without permission.
24
5G Troubleshooting Guide – NSA Access
INTERNAL
If the egress does not transmit power, you may check the following items:

Check whether the cell is set up successfully.

Check whether related alarms are reported on the MPT alarm console.

Check whether the optical fiber is properly connected and whether the AAU experiences
wrong positioning.

Check whether L1 experiences abnormal verification (contact L1 personnel).
If the MIB is sent properly over the L1 egress, go to the next step.
3. Monitor the AAU transmit power to check whether the AAU transmits power properly.
If the AAU transmit power is abnormal, perform the following operations:

Check whether the AAU transmit power exceeds the AAU power range.

Contact AAU engineers for further check.
No NR Cells Measured Due to RF Causes
For the problem that the UE cannot measure NR cells due to RF causes, frontline engineers
need to provide engineering parameters and test locations. (For Huawei UEs, Probe logs can
be collected. For other UEs, the test locations and surrounding NR cells are marked on the
map.)
If the AAU transmit power is normal and reaches the maximum, but the UE still cannot
measure any NR cell, check whether the NR cells to be measured are proper based on the test
locations and engineering parameters, in terms of the distance, and horizontal and vertical
coverage areas of the antenna.
On the base station side, check the following parameters:

2023-05-02
Configure a proper beam scenario by using
NRDUCELLTRPBEAM.CoverageScenario based on the test result.
−
When better horizontal coverage is required, SCENARIO_1, SCENARIO_6, or
SCENARIO_12 is recommended. With the setting, cell edge UEs can obtain higher
beam gains and cell edge coverage is improved.
−
If there are any fixed interference sources at the cell edge, SCENARIO_2,
SCENARIO_3, SCENARIO_7, SCENARIO_8, or SCENARIO_13 can be used to
narrow down the horizontal coverage scope and avoid the interference.
−
When there are only isolated buildings, SCENARIO_4, SCENARIO_5,
SCENARIO_9, SCENARIO_10, SCENARIO_11, SCENARIO_14,
SCENARIO_15, or SCENARIO_16 is recommended to provide small horizontal
coverage.
Huawei confidential. No spreading without permission.
25
5G Troubleshooting Guide – NSA Access
INTERNAL

Check whether the downtilt configuration (NRDUCELLTRPBEAM.Tilt) is proper
based on the test point.

Check whether the azimuth configuration (NRDUCELLTRPBEAM.Azimuth) is proper
based on the test point.

Check whether the SSB power offset configuration
(NRDUCELLCHNPWR.MaxSsPbchPwrOffset) is proper.

If the preceding parameters are correctly set, check the physical connections of the AAU
to avoid the situation that NR cells do not cover the test points due to incorrect
connections of the AAU.
4.1.3.4 Cases
The UE Cannot Report the B1 Measurement Report Because of Too Small
Transmit Power
On December 22, 2018, the NR carrier configuration on the AAU5613 was set to 20 dBm at a
site. As a result, the UE cannot access the network. The reported power monitoring value was
N/A. The calibration was normal. The problem was resolved after the carrier power
configuration was set to 34.9 dBm on December 25, 2018.
2023-05-02
Huawei confidential. No spreading without permission.
26
5G Troubleshooting Guide – NSA Access
INTERNAL
When 20 dBm is configured, the AAU has pilot power.
When the NR carrier configuration is 20 dBm, the calibration is normal, indicating that the
AAU channel is normal. On the baseband side, power is delivered. The chip records on the
AAU indicate that the input power can be detected.
According to the log statistics on the baseband side, the power is always delivered to the
AAU.
The following figure shows the pilot power (unit: 0.01 dbfs) at the ingress of the 6219E chip
measured by the AAU5613.
2023-05-02
Huawei confidential. No spreading without permission.
27
5G Troubleshooting Guide – NSA Access
INTERNAL
According to the AAU alarms, no new AAU alarms were reported after 16:00 on December
22.
The reported value of AAU power monitoring is N/A, which is the AAU feedback power.
AAU power monitoring is used on the monitoring interface. The reported value is the AAU
feedback power.
The AAU solution for power statistics requires that the feedback power must be greater than
or equal to -47 dbfs. If the feedback power is less than -47 dbfs, the feedback power is
discarded and N/A is displayed on the monitoring interface.
The carrier configuration is 20 dBm, and the AAU pilot power is too small. When the intersite distance between outdoor sites is 100 m, the UE may not be within the main lobe beam
range. As a result, the UE cannot search for the AAU transmit signals. After you increase the
power and enable the UE to access the network, the N/A information displayed on the
monitoring interface does not indicate that the AAU does not transmit power.
4.1.4 B1 Measurement Result Is Reported But No SgNB Addition
Procedure Is Initiated
4.1.4.1 Basic Concept
After the UE reports the B1 measurement result, the LTE network initiates an SgNB addition
procedure to the cell corresponding to the PCI carried in the B1 measurement result through
the X2 interface.
4.1.4.2 Identification Method
On the Uu interface, find the Call ID corresponding to the 5G B1 measurement report.
Then, check whether the SGNB_ADD_REQ message corresponding to the Call ID exists on
the X2 interface.
2023-05-02
Huawei confidential. No spreading without permission.
28
5G Troubleshooting Guide – NSA Access
INTERNAL
4.1.4.3 Problem Location
MML Query
For LTE 19B SPC170 and later versions, the DSP SCGADDFAILUREINFO command can
be executed to check the reason why SgNB Add Req is not initiated after measurement reports
are reported. You can determine the specific cause: missing configuration of neighboring
cells, PCI conflict between neighboring cells, or X2 fault.
The following figure helps you find the specific LTE cell, NR cell, and the addition failure
cause.
Configuration Analysis
After the B1 measurement is reported, the LTE side determines that an SCG addition can be
initiated if all the following conditions are met:

Neighboring NR cells are correctly configured (can be checked using the NSA Parameter
Check tool). There is no PCI conflict.
Refer to the forward check -> parameter check. You can use the NSA Parameter Check
tool to perform an automatic check.
The following provides the results obtained by an automatic check of the NSA Parameter
Check tool. The tool compares the LTE's neighboring NR cell configuration with the
actual NR configuration to check whether the configuration is correct, whether the
frequency configuration is correct, and whether the NSA DC switch is turned on. When a
configuration exception occurs, an error message is displayed.
Manual check is required for missing neighboring cells.
Check whether the PCI in the measurement report is configured with neighbor
relationship on the LTE side.
//External NR cell: MO NREXTERNALCELL
//Neighbor relationship with an NR cell: MO NRNRELATIONSHIP
2023-05-02
Huawei confidential. No spreading without permission.
29
5G Troubleshooting Guide – NSA Access

INTERNAL
The X2 link is normal. (Use the NSA Parameter Check tool to check the X2
configuration. Check whether the X2 link is normal based on alarms.)
Run the following commands to query the status of the X2 link between the eNodeB and
the gNodeB. If the X2 link is abnormal, the eNodeB does not send the
SGNB_ADD_REQ message.
Run the DSP X2INTERFACE command on the eNodeB.
Run the DSP GNBCUX2INTERFACE command on the gNodeB.
CHR-based Problem Location
As shown in the following figure, the LTE CHRs in version 19B contain the CHRs circled in
blue. Based on the circled CHRs, you can determine whether the eNodeB has sent the
SGNB_ADD_REQ message. Select NSADC_EVENT in the Type column. The event is
printed once an hour. Based on the test time, find the event in the corresponding time. For
example, if the test time is 16:00, check the event occurred at 16:34:55 (the time segment is
15:34:55–16:34:55).
2023-05-02
Huawei confidential. No spreading without permission.
30
5G Troubleshooting Guide – NSA Access
INTERNAL
4.1.4.4 Cases
For details, see maintenance and test methods in the problem location section.
4.2 Access Preparation Process
4.2.1 The gNodeB Does Not Respond with
SGNB_ADD_REQ_ACK
4.2.1.1 Basic Concept
After receiving an SGNB_ADD_REQ message from the eNodeB, the gNodeB starts to
prepare for the access on the NR side. The following figure shows the signaling procedure.
The following figure shows the signaling tracing over the X2 interface.
After the UE reports the B1 measurement report, the eNodeB sends an SGNB_ADD_REQ
message through the X2 interface. This message carries the bearer setup message.
2023-05-02
Huawei confidential. No spreading without permission.
31
5G Troubleshooting Guide – NSA Access
INTERNAL
Upon reception of the SGNB_ADD_REQ message, the gNodeB responds with an
SGNB_ADD_REQ_ACK message. This message informs the eNodeB of the address
allocated by the gNodeB and carries the parameters required for the UE's Uu interface access.
2023-05-02
Huawei confidential. No spreading without permission.
32
5G Troubleshooting Guide – NSA Access
INTERNAL
4.2.1.2 Identification Method
If the gNodeB receives an SGNB_ADD_REQ message over the X2 interface but does not
respond with an SGNB_ADD_REQ_ACK message, the problem is caused by the 5G side.
4.2.1.3 Problem Location
Step 1 Run MML commands to check whether links are abnormal.
Check Item
MML Command
Version
X2INTERFACE
(LTE side)
LST X2INTERFACE (Whether the link is
abnormal)
19A
EPGROUP
DSP EPGROUP (Whether the link is abnormal)
19A
Step 2 Analyze why the gNodeB does not return an SGNB_ADD_REQ_ACK message based on
one-click logs.
----End
4.2.1.4 Cases
No such problem is found.
4.2.2 The gNodeB Returns SGNB_ADD_REQ_REJ
4.2.2.1 Basic Concept
After receiving an SGNB_ADD_REQ message, the NR replies with an
SGNB_ADD_REQ_REJ message to reject the access request if checking the IEs in the
SGNB_ADD_REQ message fails or the gNodeB status is abnormal.
4.2.2.2 Identification Method
The X2 signaling tracing results show that the gNodeB responds with an
SGNB_ADD_REQ_REJ message after receiving an SGNB_ADD_REQ message.
This message contains the failure cause.
2023-05-02
Huawei confidential. No spreading without permission.
33
5G Troubleshooting Guide – NSA Access
INTERNAL
4.2.2.3 Problem Location
Known Issue Check
If the gNodeB replies with an SGNB_ADD_REQ_REJ message, see the access fault tree.
CHR Analysis
In CHRs, filter the Type column by L3IChrCuSgnbAddRej to obtain all AddRej data.
In CHR events, you can view the latest 30 signaling messages, including the cause value
carried in the Add Rej message, User TMSI, CallID, CRNTI, and information about the peer
anchor site. You can summarize all the information to find the rule. TrackListInfo records
some key dbg information about the user rej, which can be used to help further analyze the rej
cause.
2023-05-02
Huawei confidential. No spreading without permission.
34
5G Troubleshooting Guide – NSA Access
INTERNAL
The 5G FMA supports statistical analysis of SgNB Add Rej. Based on this, you can perform
further analysis on DCInnerCause statistics of Add Rej, whether top UEs exist, and whether
top abnormal IP addresses exist.
4.2.2.4 Cases
4.2.2.4.1 The NR Side Returns a Setup Request Rejection in NSA Networking.
Symptom
In NSA networking, when the UE initiates an NR access, the X2 interface tracing results show
that a rejection message is returned after an SGNB_ADD_REQ message is transmitted.
2023-05-02
Huawei confidential. No spreading without permission.
35
5G Troubleshooting Guide – NSA Access
INTERNAL
Analysis

The X2 interface tracing results show that a rejection message follows an
SGNB_ADD_REQ message. This indicates that the processing on the NR side is
abnormal.

According to the analysis of logs, an error occurs when the data of the uplink cell is
queried. As a result, an exception occurs.

According to the confirmation with test personnel, the uplink and downlink decoupling
switch is turned on but the uplink cell is not configured. Therefore, this problem occurs.
In this case, the uplink and downlink decoupling switch is turned off and users can
access the network.
Conclusion
The uplink and downlink decoupling switch is turned on, but the uplink cell is not configured.
As a result, the uplink cell data cannot be found in the CU processing procedure and the
rejection procedure is performed.
4.2.3 The eNodeB Does Not Return an SGNB_RECFG_CMP
Message.
4.2.3.1 Basic Concept
The UE reconfiguration is completed when the eNodeB sends an
X2AP_SGNB_RECFG_CMP message to the gNodeB through the X2 interface.
2023-05-02
Huawei confidential. No spreading without permission.
36
5G Troubleshooting Guide – NSA Access
INTERNAL
4.2.3.2 Identification Method
The X2 signaling tracing on the NR side indicates that the gNodeB does not receive an
SGNB_RECFG_CMP message after sending an SGNB_ADD_REQ_ACK message. The
gNodeB or eNodeB initiates a release procedure.
5G does not receive the SGNB_RECFG_CMP message. After the timer expires, 5G initiates a
release procedure.
SGNB_RECFG_CMP: The LTE initiates a release procedure.
2023-05-02
Huawei confidential. No spreading without permission.
37
5G Troubleshooting Guide – NSA Access
INTERNAL
4.2.3.3 Problem Location
Known Issue Check
If LTE does not respond with an SGNB_RECFG_CMP message, check whether the SCG
addition reconfiguration message is delivered over the LTE Uu interface. If yes, check
whether the UE experiences a reestablishment or SCGFAIL occurs.
1. If the UE experiences a reestablishment, LTE does not send an SGNB_RECFG_CMP
message to 5G.
2. The reconfiguration completion message does not contain the scg-ConfigResponseNR-15
IE. As a result, LTE does not send an SGNB_RECFG_CMP message to 5G.
The following figure shows a normal reconfiguration completion message.
2023-05-02
Huawei confidential. No spreading without permission.
38
5G Troubleshooting Guide – NSA Access
INTERNAL
Troubleshoot the reestablishment and the problem that the reconfiguration completion
message does not contain the r15 IE. For details about common problems and troubleshooting
methods, see the access fault tree.
CHR Analysis
Use the statistics function of the FMA to collect statistics on the three DC fields of the
L3ChrCuAbnormalRel event, as shown in the following figure. You can check whether an
exception occurs in the ADD phase by viewing the siglist of each DC.
2023-05-02
Huawei confidential. No spreading without permission.
39
5G Troubleshooting Guide – NSA Access
INTERNAL
For example, in the case of DCInnerCause=CU_UEM_SGNBADD_PROC_ONKILL, LTE
does not respond with an SgNB_Recfg_CMP message. You can further check the cause by
using the LTE CHR or signaling.
The eNBID and tmsi information in the UEPublicInfo can help find the corresponding
eNodeB and UE.
2023-05-02
Huawei confidential. No spreading without permission.
40
5G Troubleshooting Guide – NSA Access
INTERNAL
4.2.3.4 Cases
N/A
4.3 NR Air Interface Access Failure
4.3.1 The UE Does Not Initiate Access After Receiving a
Reconfiguration Message
4.3.1.1 Basic Concept
After receiving a reconfiguration message from the SCG, the UE initiates air interface access
only after the following steps are complete:
1. The UE verifies the IEs in the reconfiguration message to check whether the UE supports
the channel resources allocated by the eNodeB. If not, the UE sends an SCG_FAIL_INFO
message carrying the cause value "scg-reconfigFailure" to the eNodeB. Alternatively, the UE
sends an RRC_CONN_REESTAB_REQ message carrying the cause value "reconfigFailure".
2. The UE searches for the 5G cell indicated in the SCG reconfiguration message and
synchronizes it with the 5G cell. If the synchronization fails, the UE sends an
SCG_FAIL_INFO message carrying the cause value "synchReconfigFailureSCG" to the
eNodeB.
4.3.1.2 Identification Method

2023-05-02
Uu message tracing
Huawei confidential. No spreading without permission.
41
5G Troubleshooting Guide – NSA Access
INTERNAL
The Uu interface tracing results show that after receiving an RRC reconfiguration
message for 5G SCG configuration, the UE immediately sends an SCG_FAIL_INFO
message carrying the cause value "scg-reconfigFailure/synchReconfigFailureSCG" to
the eNodeB.

Probe tracing
In the Probe tracing results of the UE, you can view the printing of the reconfiguration
failure from the Event List and view the possible causes of the reconfiguration failure in
the Key Event List.
4.3.1.3 Problem Location
The possible causes of the reconfiguration failure are as follows:

The 5G cell search fails because the cell that the UE accesses is not the strongest cell or
the inter-cell interference is severe.

The parameters in the SCG reconfiguration message fail to be verified on the UE side. In
this case, it is recommended that terminal engineers participate in the fault locating.
For details about common problems and troubleshooting methods, see the access fault tree.
4.3.1.4 Cases
4.3.1.4.1 Cell Search Fails Because the UE Accesses a Non-strongest Cell.
Symptom
In 19A TR6, the 5G SCG access fails after an LTE handover in a 5G mobility drive test.
2023-05-02
Huawei confidential. No spreading without permission.
42
5G Troubleshooting Guide – NSA Access
INTERNAL
Analysis
According to KeyEventList, the 5G access failure is caused by cell search failures.
Check the B1 measurement results. The cell with PCI 152 is in the third place, and the RSRP
of this cell is 13 dB lower than that of the best cell with PCI 435.
This indicates that the access failure cause is that the cell search fails because the UE accesses
a non-strongest cell. Further analysis shows that the neighbor relationships between the LTE
cell and the 5G cells with PCIs 435 and 436 are not configured. As a result, the problem
occurs.
Conclusion
The root cause of this problem is that the neighbor relationships between the LTE cell and the
5G cells with PCIs 435 and 436 are not configured. After the neighbor relationships between
the LTE cell and the 5G cells with PCIs 435 and 436 are added, the problem is solved.
4.3.2 The RAR Message over the Air Interface Times Out
4.3.2.1 Basic Concept
The first step of a random access procedure is that the UE sends a random access preamble.
The preamble is used to inform the base station of a random access request, so that the base
2023-05-02
Huawei confidential. No spreading without permission.
43
5G Troubleshooting Guide – NSA Access
INTERNAL
station can estimate the transmission delay between the base station and the UE, calibrate the
uplink timing, and send the TA adjustment information to the UE through an RAR.
After sending the preamble, the UE monitors the PDCCH in the RAR time window (RA
response window) to receive the RAR of the corresponding RA-RNTI (in this case, the
measurement gap may not be considered). If no RAR message is received from the eNodeB
within the RAR time window, the random access procedure fails.
In NSA networking, non-contention-based random access is used. The DCI of the RAR is
carried in the common search space of the PDCCH. The content of the RAR is carried on the
PDSCH and occupies one RBG.
4.3.2.2 Identification Method
The Uu interface tracing results show that, after receiving an RRC reconfiguration message
for the 5G SCG configuration, the UE returns an SCG_FAIL_INFO message with the cause
value ScgAccessFailure or scg-ChangeFailure to the eNodeB at an interval specified by T304.
In the Probe tracing result of the UE, the access failure information is displayed in the Event
List, and the RAR timeout information is displayed in the Key Event List.
4.3.2.3 Problem Location
RAR timeout scenarios are as follows:

The UE sends a Preamble but the base station does not receive it.

The base station sends an RAR message but the UE does not receive it.
Basic Configuration Check
The configuration that may affect the preamble reception function is as follows:
MOD NRDUCELLPRACH:RootSequenceIndex=0;
2023-05-02
Huawei confidential. No spreading without permission.
44
5G Troubleshooting Guide – NSA Access
INTERNAL
Root sequence index used by the preamble. The root sequence index allocated to the UE by
higher layers and the root sequence index configured for the base station must be consistent.
Otherwise, preamble parsing fails.
MOD NRDUCELL:CellRadius=9000;
Cell radius configuration. Cell radius affects the NCS parameter used for preamble sequence
generation. If this parameter is set to a small value, UEs in the middle and far points cannot
access the network.
MOD NRDUCELLRSVDPARAM:RsvdSwParam4_bit5=0;
If this parameter is set to 1, PRACH resources are allocated to the PUSCH to increase the
uplink peak rate. This switch must be configured after UEs access the network. Otherwise,
UEs cannot access the network.
CHR Analysis
Use the L2 CHRs to analyze the RAR timeout and, for the non-contention-based preamble,
find the L2USerChr at the time when the problem occurs.
The l2_user_chr_preamble_info event block is used to analyze the RAR timeout. The event
block contains the following events:
The method for analyzing whether the preamble is correctly received is as follows:

2023-05-02
Obtain the dedicated PreambleId received by L2 from L3, the reception time, and the
CRNTI of the UE, from the L3Alloc event block.
Huawei confidential. No spreading without permission.
45
5G Troubleshooting Guide – NSA Access

2023-05-02
INTERNAL
Analyze the L1Rpt event block to determine whether the base station receives the
preamble, the reception time, and PreambleId. Compare the PreambleId with the
PreambleId in the L3Alloc event block. If the event block contains the time when the
base station receives the preamble and the PreambleId is the same as the PreambleId in
the L3Alloc event block, the base station has received the preamble.
Huawei confidential. No spreading without permission.
46
5G Troubleshooting Guide – NSA Access
INTERNAL

Analyze the L2sendRar event block to determine whether the base station delivers an
RAR message. The event block records the time when the base station delivers the RAR
message, as well as the CRNTI, TA value, Msg3 Ulgrant information, and CommonDCI
content of the RAR message.

If the base station receives the preamble but the L2sendRar event block does not contain
the RAR delivery record, further analyze the following uplink and downlink scheduling
events to determine whether the RAR scheduling failure is caused by uplink scheduling
exceptions or downlink scheduling exceptions.
CellDT Analysis
The air interface access failure on the NR side can be isolated by using the No. 1 tracing of L2
TTI tracing. L2 TTI tracing uses the No. 1 tracing to locate the access problem. (No. 1 tracing
is the access process TTI tracing set, which contains a maximum of dozens of tracing
numbers in the entire access process.)
The method for isolating an access failure in TTI tracing is as follows:
The No. 212 tracing result in the No. 1 tracing task shows that L3 configures the dedicated
preamble for L2 and L1 reports the dedicated preamble.
2023-05-02
Huawei confidential. No spreading without permission.
47
5G Troubleshooting Guide – NSA Access
INTERNAL
The key information in the No. 212 tracing result is ucL3IndToSusrFlag.
ucL3IndToSusrFlag=1 indicates that the dedicated preamble is allocated by L3.
ucL3IndToSusrFlag2 and ucL3IndToSusrFlag=4 indicate that the dedicated preamble is
released by L3. ucL3IndToSusrFlag=5 indicates that the baseband reports an invalid preamble
ID.
If the time of ucL3IndToSusrFlag=2 and ucL3IndToSusrFlag=4 is 2s later than
ucL3IndToSusrFlag=1, the access fails. In this case, perform the following operations to
demarcate the failure phase:

Preamble phase failure
In the No. 1 tracing task, there is no record in the No. 210 tracing result (L2 receives the
preamble stream tracing result reported by L1). Alternatively, there are records in the No.
210 tracing result, but the reported preamble ID is different from the ID of the dedicated
preamble allocated by L3. In this case, the access fails in the preamble phase.

RAR phase failure
The No. 201 tracing result contains the process from the time L1 reports the preamble to
the time L2 assembles and delivers RAR packets.
If L2 has assembled and delivered an RAR message to L1 but the UE does not receive the
RAR message, the access fails in the RAR phase.
RAR delivery process (indicated by the ulRaStatus field):
2023-05-02

CCHP_RA_PREAMBLE_PROC indicates that the UE is obtained from the preamble
chain to be scheduled.

CCHP_RA_ADD_DLSCH_RARNTI indicates that the preamble UE is added to the
downlink scheduling chain.

CCHP_RA_ADD_ULSCH_RARNT indicates that the preamble UE is added to the
uplink scheduling chain.

CCHP_RA_DLSCH_INIT indicates that scheduling the preamble UE in the downlink
starts.
Huawei confidential. No spreading without permission.
48
5G Troubleshooting Guide – NSA Access
INTERNAL

CCHP_RA_DLSCH_SCH indicates that scheduling the preamble UE in the downlink
ends.

CCHP_RA_ULSCH_INIT_SNAP indicates that scheduling the preamble UE in the
uplink starts.

CCHP_RA_ULSCH_SCH indicates that scheduling the preamble UE in the uplink ends.

CCHP_RA_PACK_RAR indicates that RAR packets are delivered.
If RAR scheduling fails, determine whether the failure is caused by uplink or downlink
scheduling failure based on the preceding procedure. If uplink scheduling fails, check the No.
408 tracing. If downlink scheduling fails, check the No. 502 tracing. The tracing result
records the error code of the scheduling failure. Contact R&D engineers of the corresponding
module to locate the fault.
After the preceding process is completed, further analyze whether the No. 205 tracing has
corresponding content (the No. 205 tracing carries the beam information when the RAR is
delivered and the code stream of the RAR).
In the No. 205 tracing, there are two frame numbers and subframe numbers, which are the
system frame number and subframe number of the RAR packet and the frame number and
subframe number that is expected to be delivered by the RAR over the air interface. The latter
subframe number is represented by SubframeNo and SlotNo, the actual slot number is
SubframeNo x 2 + SlotNo.
4.3.2.4 Cases
4.3.2.4.1 The TUE Fails to Access the Network in RF Direct Connection Mode and
Cannot Receive the Preamble.
Symptom
In B078, the TUE fails to access the network. The L2 tracing result shows that the TUE does
not receive the preamble (no data is traced in the 210 Preamble code stream tracing). Contact
the HQ for further processing.
2023-05-02
Huawei confidential. No spreading without permission.
49
5G Troubleshooting Guide – NSA Access
INTERNAL
Analysis

The ingress can detect signals but cannot decode valid preamble data. Therefore, the
IF/RF and TUE L1 must be used together to locate the fault.

The preamble is periodically sent in the TUE L1 odd frames, and the IF/RF module is
used to collect data. Based on the data collected by the IF/RF module, it is found that the
data is transmitted to the IF/RF for a time offset. Analysis results show that an initial TA
value is configured for the TUE. The TUE data sent to the IF/RF module is beyond the
receive window. As a result, the preamble is truncated and baseband demodulation fails.
After the initial TA of the TUE is changed to 0, the problem is solved. The following
figure shows the signals received by the IF/RF module before and after the modification.
Conclusion
An initial TA value is configured for the TUE, which causes the problem that the TUE data
sent to the IF/RF module is beyond the receive window. As a result, the preamble is truncated
and baseband demodulation fails. The problem is resolved after the initial TA of the TUE is
changed to 0.
4.3.2.4.2 The TUE Fails to Access the Network in RF Direct Connection Mode and
Cannot Receive the RAR Message.
Symptom
In the CID environment, the 5G TUE fails to access the network. The TUE OMT shows that
T304 times out.
2023-05-02
Huawei confidential. No spreading without permission.
50
5G Troubleshooting Guide – NSA Access
INTERNAL
Analysis
The base station L2 tracing result shows that the preamble is successfully reported and the
RAR has been scheduled and delivered to the base station L1.
The simulation result of the base station L1's samplings shows that the RAR message has
been sent successfully and the signals are normal.
Symbol 0 is a PDCCH, symbol 6 and symbol 9 are DMRSs, and signal energy is higher.
The samplings of TUE L1 at the corresponding frame number and subframe number indicate
that there is no valid signal on the baseband ingress of the TUE.
Currently, the base station's L1 sends normal signals but the TUE's L1 does not receive the
signals. The next step is to analyze whether the channel between the base station's L1 and the
TUE's L1 is normal.
2023-05-02
Huawei confidential. No spreading without permission.
51
5G Troubleshooting Guide – NSA Access
INTERNAL
In order for the IF/RF module to collect data, the base station needs to periodically send an
RAR message. Then, the base station and TUE use the fixed offset of the frame interrupt to
check whether the intermediate channel is normal.
The stub test method is as follows:
1. Use the TUE to send preambles at a fixed subframe number. T304 does not expire.
2. After receiving the preamble, the base station returns an RAR every time, without requiring
L3 to allocate dedicated preambles. The UE is not released by the base station L3.
The IF/RF module collects data. The signal characteristics are consistent with those of RAR
signals.
The frequency domain occupies 20 MHz bandwidth (48 RBs in BWP0). The RAR uses the
PDSCH of one RBG (4 RBs) for transmission, corresponding to the 1-2 MHz bandwidth (4
RBs = 30 kHz x 12 x 4 = 1.44 MHz) in the figure.
The TUE IF/RF module collects data. The signal characteristics are the same as those of the
RAR signal.
IF/RF entry on the TUE:
The following figure shows the signals transmitted from the TUE RF output port to the TUE
baseband.
2023-05-02
Huawei confidential. No spreading without permission.
52
5G Troubleshooting Guide – NSA Access
INTERNAL
This problem occurs between the TUE IF/RF and the TUE baseband.
Conclusion
This problem occurs between the TUE IF/RF and the TUE baseband. The TUE R&D
engineers analyze the problem and find that the TUE OM is abnormal. As a result, the data
link between the TUE IF/RF and the TUE baseband is abnormal.
4.3.3 Msg3 Failure
4.3.3.1 Basic Concept
Different from the access in the LTE network or the access in SA networking, the Msg3 in
NSA networking is an MCE (carrying BSR information) but not RRC signaling. When the
uplink MAC demultiplexing receives the MCE from the UE, the UE successfully accesses the
network through the air interface.
4.3.3.2 Identification Method
The Uu interface tracing results show that, after receiving the RRC reconfiguration message
for the 5G SCG configuration, the UE returns an SCG_FAIL_INFO message with the cause
value ScgAccessFailure or scg-ChangeFailure to the eNodeB at an interval specified by T304.
In the Probe tracing result of the UE, the access failure information is displayed in the Event
List, and the RAR timeout information is displayed in the Key Event List.
2023-05-02
Huawei confidential. No spreading without permission.
53
5G Troubleshooting Guide – NSA Access
INTERNAL
4.3.3.3 Problem Location
Known Issue Check
For details about common problems and troubleshooting methods, see the access fault tree.
CHR Analysis
Use the L2 CHRs to analyze the Msg3 scheduling or demodulation failure and find the
L2UserChr at the time when the problem occurs.
Use the L2_USERCHR_ULSCH_ACCESS_INFO event block to analyze the cause for Msg
scheduling or demodulation failures.
2023-05-02
Huawei confidential. No spreading without permission.
54
5G Troubleshooting Guide – NSA Access
INTERNAL
The event block shows the results of Msg3 scheduling, reception time, and demodulation
result. As shown in the preceding figure, Msg3 scheduling is successful, but CRC errors occur
during the first transmission and five retransmissions. This indicates that the access failure is
caused by the Msg3 CRC error.
CellDT Analysis
Msg3 phase failure
The TUE OMT shows that the TUE has sent Msg3. However, the No. 324 tracing on the base
station side (DMAC demultiplexing result tracing) shows that the TBSize of the decoded
MAC PDU is 0. This indicates that Msg3 demodulation fails.
After Msg3 is successfully scheduled, L2 sends the management frame of Msg3 to L1. As
long as Msg3 fails to be demodulated, the L2 tracing result shows that Msg3 CRC is
incorrect. The cause may be either of the following: The TUE does not send Msg3, or the
TUE sends Msg3, but the baseband fails to demodulate the message.
It is recommended that the No. 1 tracing be performed on the base station side and L2 tracing
be performed on the TUE side.
Step 1 Check whether the TUE has sent Msg3. If the TUE has decoded the RAR but does not send
Msg3, continue to locate the TUE problem.
In the No. 490 tracing result, check whether the base station successfully receives Msg3.
Preamble in the bit05UsrType column indicates Msg3 scheduling. The bit02aucCrcResultTB0
column indicates the CRC value of Msg3. The value 0 indicates that the base station
demodulates Msg3 successfully. The value 1 indicates Msg3 demodulation fails.
2023-05-02
Huawei confidential. No spreading without permission.
55
5G Troubleshooting Guide – NSA Access
INTERNAL
In the No. 777 tracing, check the DMRS RSRP at the time when Msg3 is scheduled. If the
signal is good, the UE sends Msg3. If the signal is close to the background noise, the UE does
not send Msg3. Further check the DCI sent by L2 to the UE and the management frame sent
by L2 to L1.
Step 2 Check whether the DCI carried in the RAR code stream is consistent with the content of the
management frame sent by L2 to L1. The No. 404 tracing result records the Ulgrant code
stream of Msg3, and the content of the management frame can be viewed in the No. 455
tracing result. The key information to be checked is as follows: frame number, subframe
number, allocated frequency domain resources, DMRS type, DMRS Port, and codec
information (MCS, rank, and so on).
If the DCI information is the same as that of the management frame, check whether the DCI
sent by the TUE is consistent with the DCI delivered by the base station's L2.
Step 3 If the scheduling and codec information contained in the base station's L2, management
frame, and TUE L2 are consistent, the TUE L1 and the base station's L1 need to perform
simulation. Check whether the data sent by the TUE L1 contains the correct Msg3
information and whether the data collected by the entry of the base station's L1 can be used to
decode the correct data. Contact R&D personnel to locate the cause of the problem.
----End
4.3.3.4 Cases
4.3.3.4.1 UE Access Fails Because the Management Frame of Msg3 Is Verified by Layer 1.
Symptom
In B110, the TUE B092 fails to access the network. Msg3 has been sent according to the TUE
display.
2023-05-02
Huawei confidential. No spreading without permission.
56
5G Troubleshooting Guide – NSA Access
INTERNAL
Analysis
Capture the tracing results of the No. 1, No. 105, and No. 455 tracing tasks. It is found that
there is no 323 and 324 tracing in the No. 1 tracing result. That is, L2 does not receive the
CRC result of Msg3.
Further analyze the scheduling and management frames of Msg3. According to the No.404
tracing result, Msg3 has been successfully scheduled. Check whether Msg3 management
frames are framed and delivered.
The No.455 tracing result shows that the management frames of Msg3 are delivered
(including one initial transmission and four retransmissions).
2023-05-02
Huawei confidential. No spreading without permission.
57
5G Troubleshooting Guide – NSA Access
INTERNAL
The No.105 tracing result shows that the management frames are always delivered to L1.
After L1 analysis, it is found that the CRC result is not generated and sent to L2 because there
is no response to the message sent by the FPGA to the DSP at L1.
Conclusion
There is no response to the message sent by the FPGA to the DSP at L1. As a result, the CRC
result is not generated and sent to L2, and Msg3 fails to be received.
4.3.4 Contention Msg4 Failure
4.3.4.1 Basic Concept
If the UE initiates contention-based random access, the base station needs to deliver Msg4 to
the UE to complete the random access. The following figure shows a contention-based
random access procedure.
2023-05-02
Huawei confidential. No spreading without permission.
58
5G Troubleshooting Guide – NSA Access
INTERNAL
The base station does not allocate non-contention-based preambles to UEs in the following
scenarios:

The non-contention-based preambles of the base station have been used up.

The UE does not report the SSBindex in the measurement report or LTE does not send
the SSBindex to 5G.

The UE triggers resynchronization access.
4.3.4.2 Identification Method
The SCG addition reconfiguration message on the UE side or the Add Req Ack message on
the 5G side contains the CRNTI and non-contention-based preamble.
If the message contains the ra-PreambleIndex field, the base station allocates a noncontention-based preamble to the UE. If the field is not contained, the base station does not
allocate a non-contention-based preamble to the UE, and the UE initiates contention-based
random access.
2023-05-02
Huawei confidential. No spreading without permission.
59
5G Troubleshooting Guide – NSA Access
INTERNAL
The message also contains the CRNTI allocated by the base station to the UE. In the
following figure, newUE-Identity indicates the allocated CRNTI. Both the CHR and CellDT
on the base station side can use the CRNTI to align with the UE.
In the Probe tracing result of the UE, the access failure information is displayed in the Event
List, and the NR MAC receive content timeout information is displayed in the Key Event List.
4.3.4.3 Problem Location
Known Issue Check
For details about common problems and troubleshooting methods, see the access fault tree.
2023-05-02
Huawei confidential. No spreading without permission.
60
5G Troubleshooting Guide – NSA Access
INTERNAL
CHR Analysis
Use the L2 CHRs to analyze the Msg3 failure and find the L2UserChr at the time when the
problem occurs.
To analyze the Msg4 access failure, use the L2_USER_KEYCHR_ACCESS_DLSCH_INFO
to check the Msg4 scheduling.
2023-05-02
Huawei confidential. No spreading without permission.
61
5G Troubleshooting Guide – NSA Access
INTERNAL
CellDT Analysis
1. In the No. 490 tracing result, check whether the base station delivers Msg4 scheduling after
receiving Msg3. Msg4 is one false SR scheduling triggered by the base station. After
receiving it, the UE considers that the contention resolution succeeds.

Sort the DE column lastSchTti in ascending order.

Filter the time points to be analyzed, CRNTI, and UsrId.

The frame number and slot number must correspond to Air indicated by columns L and
M. You can check with those on the UE side.

The I column bit02aucCrcResultTB0 indicates the uplink CRC result. The value 0
indicates correct while the value 1 indicates incorrect.

Preamble in the O column bit05UsrType indicates Msg3. For non-contention-based
random access, Msg3 corresponds to the C-RNTI. For contention-based random access,
the C-RNTI corresponding to Msg3 is the TC-RNTI. You can map the C-RNTI and TCRNTI through the No. 716 tracing.
The following figure shows the No. 716 tracing result. You can map the CRNTI and TCRNTI in one call by checking columns T and Y.
2. If the No. 490 tracing does not contain Msg4 scheduling and the preceding known issues
are excluded, you are advised to contact R&D engineers of the corresponding module to
locate the fault.
3. If the No. 490 tracing result shows that Msg4 has been scheduled but the CRC result
always indicates incorrect, check the DCI traced in the No. 602 tracing result and compare it
with the DCI received by the UE.
2023-05-02
Huawei confidential. No spreading without permission.
62
5G Troubleshooting Guide – NSA Access

Sort the I column ttiJobCycle in ascending order.

Filter the time points to be analyzed, CRNTI, and UsrId.

The BD column is bit04DciFormat, indicating a format.

The AN column is bit08DciLength. Observe the DCI length.
INTERNAL
4. Check the uplink signal quality through the No. 777 tracing.

Sort the K column rptTti in ascending order.

Filter the time points to be analyzed, CRNTI, and UsrId.

The O column l1MeasRptTag allows you to view information about the DMRS RSRP,
DMRS SINR, SRS RSRP, SRS SINR, and SRS TA.

For the U column DmrsAvgRsrp, the measured value must be divided by 64.

For the V column DmrsFlow0Sinr, the measured value must be divided by 256.
4.3.4.4 Cases
N/A
2023-05-02
Huawei confidential. No spreading without permission.
63
5G Troubleshooting Guide – NSA Access
5
INTERNAL
Methods of Analyzing KPI-related
Problems in Traffic Statistics (NSA)
5.1 Access KPI Definition
The KPIs are defined as follows:
LTE Counter
NR Counter
Counter ID
Counter Name
L.NsaDc.SgNB.Add.A
tt
Total number of SgNB
addition attempts
Total number of
successful SgNB
additions
L.NsaDc.SgNB.Add.S
ucc
SgNB addition success rate =
L.NsaDc.SgNB.Add.Succ/L.NsaDc.SgNB.Add.Suc
c
Counter ID
Counter Name
N.NsaDc.SgNB.Add.Att
Number of SgNB addition
requests
N.NsaDc.SgNB.Add.Succ
Number of successful SgNB
additions
SgNB addition success rate
= N.NsaDc.SgNB.Add.Succ/N.NsaDc.SgNB.Add.Att
N.RA.Contention.Att
N.RA.Contention.Resolution.Succ
Number of random preamble
receptions
Number of successful
contention resolutions
N.RA.Dedicated.Att
Number of dedicated
preamble receptions
N.RA.Dedicated.Msg3
Number of Msg3 receptions
during non-contention based
random access
RA success rate = (N.RA.Contention.Resolution.Succ +
N.RA.Dedicated.Msg3)/(N.RA.Contention.Att +
N.RA.Dedicated.Att)
Non-contention RA success rate =
N.RA.Dedicated.Msg3/N.RA.Dedicated.Att
Contention RA success rate =
N.RA.Contention.Resolution.Succ/N.RA.Contention.Att
Both the LTE and NR counters measure the SgNB addition success rate. However, the values
of the two counters may be different. For example, if the SgNB Add Reject is caused by cell
unavailability, the cell counter object is not activated on the 5G side. As a result, the
N.NsaDc.SgNB.Add.Att counter on the 5G side cannot measure this.
2023-05-02
Huawei confidential. No spreading without permission.
64
5G Troubleshooting Guide – NSA Access
INTERNAL
In addition, for NSA, N.NsaDc.SgNB.Add.Succ does not mean access success. It only
indicates the completion on the signaling plane, after which the random access procedure
starts. Due to false detection of preambles, the contention resolution success rate is usually
low. For NSA, the access is generally non-contention-based. The non-contention-based RA
success rate can be more concerned.
5.2 Signaling Procedures and Measurement Points

L.NsaDc.SgNB.Add.Att/L.NsaDc.SgNB.Add.Succ

N.NsaDc.SgNB.Add.Att/N.NsaDc.SgNB.Add.Succ
As shown at point A in the following figure, the L.NsaDc.SgNB.Add.Att counter is
incremented each time the eNodeB sends an SgNB Addition Request message to the gNodeB.
As shown at point B in the following figure, the L.NsaDc.SgNB.Add.Succ counter is
incremented each time the eNodeB sends an SgNB Reconfiguration Complete message to the
gNodeB.
As shown at point A in the following figure, the N.NsaDc.SgNB.Add.Att counter is
incremented by one each time the gNodeB receives an SgNB Addition Request message from
the eNodeB. As shown at point B in the following figure, the N.NsaDc.SgNB.Add.Succ
counter is incremented by one each time the gNodeB receives an SgNB Reconfiguration
Complete message from the eNodeB. The values of these counters are accumulated in the
primary secondary cell (PSCell) specified by the gNodeB.

N.RA.Contention.Att/N.RA.Contention.Resolution.Succ
As shown at point A in the following figure, the N.RA.Contention.Att counter is incremented
by 1 each time the gNodeB receives a random preamble from a UE.
As shown at point C in the following figure, in a contention-based random access procedure,
the N.RA.Contention.Resolution.Succ counter is incremented by 1 each time the gNodeB
successfully delivers a Contention Resolution message to a UE performing contention-based
access.
2023-05-02
Huawei confidential. No spreading without permission.
65
5G Troubleshooting Guide – NSA Access

INTERNAL
N.RA.Dedicated.Att/N.RA.Dedicated.Msg3
As shown at point B in the following figure, the N.RA.Dedicated.Att counter is incremented
by 1 each time the gNodeB receives a dedicated preamble from a UE.
As shown at point D in the following figure, the N.RA.Dedicated.Msg3 counter is
incremented by 1 each time the gNodeB receives Msg3 from a UE during non-contention
based random access.
2023-05-02
Huawei confidential. No spreading without permission.
66
5G Troubleshooting Guide – NSA Access
INTERNAL
5.3 Method of Analyzing Access KPI-related Problems
5.3.1 Action 1: Determining the Problem Type
KPI problems are classified into the following four types. When frontline personnel report
problems, confirm the problem type and objective.

KPIs deteriorate suddenly or in some time segments.

KPIs change slowly and gradually deteriorate.

The current KPIs do not meet the requirements and need to be improved to certain target
values.

The KPIs in a specific area are worse than those in other areas.
For problems of type 1, mainly perform actions 4 and 6. For problems of type 3 and type 4,
skip action 6. Action 5 for type 4 problems is the analysis focus. By identifying the
differences between other KPIs in two areas, you can directly or indirectly prove the
differences in the network structure and air interface quality to quickly locate the root
problem cause or isolate the influencing factors.
5.3.2 Action 2: Time Trend Analysis
Time trend analysis is used to analyze the change trend of each counter involved in the KPI
formula and check whether the deterioration time is regular.
First check how the total number of handover attempts and the number of successful
handovers change. Based on the changes in the numerator and denominator, check whether
the problem is related to the change in the number of UEs.
Check whether the deterioration time is regular. Specifically, check whether the KPI value
decreases gradually or abruptly, or whether the KPI value restores after a decrease in a period
of time and then decreases again. In the event of abrupt decrease or repeated decrease, check
whether it always occurs in certain hours of each day, or on a certain day of each week, or at
the beginning or end of each month. When comparing KPIs at the day level, compare them
with those of other weeks at the same time, such as weekends.
Pay attention to the change of the number of cells during the analysis of traffic statistics. This
prevents incorrect judgment regarding KPI changes caused by incomplete traffic statistics
reported by frontline engineers and significant changes in the number of cells. If the number
of cells differs greatly, contact frontline engineers to check whether the feedback data is
complete and whether the number of cells and sites meet expectations. If the feedback data is
correct, the live network is gradually adding sites or closing sites, which causes KPI changes.
The check belongs to external event check.
5.3.3 Action 3: Traffic Statistics Cause Analysis
If the 5G side responds with an Add Rej message, the following counters are measured on the
5G side to determine whether the failure is caused by radio or transmission faults.
Counter
ID
Counter Name
Counter Description
Version
1911817854
N.NsaDc.SgNB.Add.Fail.Radio
Number of SgNB addition failures
caused by radio faults in LTE-NR NSA
DC scenarios
19B
SPC150
2023-05-02
Huawei confidential. No spreading without permission.
67
5G Troubleshooting Guide – NSA Access
INTERNAL
Counter
ID
Counter Name
Counter Description
Version
1911817855
N.NsaDc.SgNB.Add.Fail.Radio.No
Res
Number of SgNB addition failures
caused by the unavailability of radio
resources in LTE-NR NSA DC
scenarios
19B
SPC150
1911817856
N.NsaDc.SgNB.Add.Fail.TNL
Number of SgNB addition failures
caused by transmission faults in LTENR NSA DC scenarios
19B
SPC150
The N.NsaDc.SgNB.Add.Fail.TNL counter is incremented by 1 each time the gNodeB
receives an SgNB Addition Request message sent by the eNodeB and the gNodeB responds
with an SgNB Addition Reject message.
If the cause value indicates a radio fault, the N.NsaDc.SgNB.Add.Fail.Radio counter is
incremented by 1. If the cause value is "No Radio Resources Available", the
N.NsaDc.SgNB.Add.Fail.Radio.NoRes counter is incremented by 1. The values of these
counters are accumulated in the primary secondary cell (PSCell) specified by the gNodeB.
In later versions, the number of Add Ack responses will be added. If 5G responds with an Add
Ack message but the LTE does not respond with a CMP message, the Add AckN.NsaDc.SgNB.Add.Succ counter can be used for measurement.
5.3.4 Action 4: Top N Analysis
Then, check whether the problem occurs in top cells or on the entire network.
Top cell-level problems:
After top N cells with the lowest access success rate and the largest number of access failures
are excluded (the value of N depends on the cell scale, for example, 100), if the access success
rate of the entire network improves significantly and is basically the same as that before
deterioration (or reaches the target value), the problem is defined as a top cell-level problem.
Entire network-level problems:
If the access success rate of the entire network does not improve after the top N cells with the
lowest access success rate and the largest number of access failures are excluded, the problem
is an entire network-level problem.
When selecting top N cells, exclude the cells with a high access failure rate caused by a small
number of access attempts and a small number of access failures. The number of access
attempts must be greater than or equal to 50% of the average value based on the traffic level
on the live network. Alternatively, the number of access attempts in a single cell within an
hour must be greater than or equal to 1000.
For a top cell-level problem, if operation causes are excluded, check whether the top N cells
are distributed regularly based on the geographical location. If the problem is related to
transmission, check whether the transmission topology of the site where the top N cells are
located is regular. For example, check for the joint connection to a transmission subnode.
2023-05-02
Huawei confidential. No spreading without permission.
68
5G Troubleshooting Guide – NSA Access
INTERNAL
5.3.5 Action 5: Associated KPI Analysis
If the failure is caused by the air interface according to the isolation result of traffic statistics
counters, you need to analyze the changes of counters related to the air interface channel
quality and network load. Performing analysis of associated KPIs can directly or indirectly
prove network changes and differences. Confirm network limitation factors through
comparison of associated KPIs of different networks. Rapidly locate root causes or complete
initial isolation through coupling analysis of target KPIs and associated KPIs.
Common associated KPIs are as follows: number of UEs, uplink interference, PRB usage, cell
status, uplink and downlink bit error rates (BERs), and average CQI.

Number of UEs:
The number of UEs indicates the network load. You can analyze it together with the PRB
usage and interference level trend. Generally, when the number of UEs increases, the
KPIs of a network decrease. The causes are as follows: 1. As the number of UEs
increases, the PRB usage increases and the load between neighboring cells increases,
which is the main cause. 2. As the number of UEs increases, the number of abnormal
UEs on the network may increase. Generally, a small number of abnormal UEs can
指标ID
指标名称 of failures.
指标描述
contribute
to a large number

1911816771 N.User.RRCConn.Avg
小区内处于RRC连接态的平均用户数
1911816772 N.User.RRCConn.Max
小区内处于RRC连接态的最大用户数
1911817042 N.User.RRCConn.Max.Operator
小区运营商的最大用户数
1911817043 N.User.RRCConn.Avg.Operator
小区运营商的平均用户数
Average uplink interference
The average value is used for comparison. The maximum value, which is related to the
network load, is an instantaneous sampling result and therefore is for reference only. If
continuous strong external interference exists, the minimum value may be significantly
different. The interference granularity of the traffic statistics is large. Therefore, when the
traffic statistics indicate that interference exists, you can infer that interference probably
exists. However, if the traffic statistics cannot indicate that interference exists,
interference may or may not exist. For top N cells, you can further check whether
interference exists through U2000 interference monitoring.

Average access distance
The TA value of random access indirectly reflects the distance between the UE and the
base station. The average TA value can be used to reflect UE distribution. The larger the
average value is, the more the UEs distributed at the cell edge. In this case, the related
channel conditions and KPIs are worse theoretically.
Average TA value:
(0 x N.RA.TA.UE.Index0 + 1 x N.RA.TA.UE.Index1 + ... + 12 x
N.RA.TA.UE.Index12)/(N.RA.TA.UE.Index0 + N.RA.TA.UE.Index0 + ...+
N.RA.TA.UE.Index12)
2023-05-02
Huawei confidential. No spreading without permission.
69
5G Troubleshooting Guide – NSA Access

INTERNAL
Initial transmission/retransmission bit error
The following table lists the counters that indicate the bit errors in the uplink and
downlink. When comparing coverage in multiple areas, you can also evaluate the
coverage difference between two areas indirectly through QPSK ratios.
2023-05-02
Huawei confidential. No spreading without permission.
70
5G Troubleshooting Guide – NSA Access
INTERNAL
Downlink IBLER:
(N.DL.SCH.QPSK.ErrTB.Ibler + N.DL.SCH.16QAM.ErrTB.Ibler +
N.DL.SCH.64QAM.ErrTB.Ibler +
N.DL.SCH.256QAM.ErrTB.Ibler)/(N.DL.SCH.QPSK.TB + N.DL.SCH.16QAM.TB +
N.DL.SCH. 64QAM.TB + N.DL.SCH. 256QAM.TB) x 100%
Downlink retransmission rate:
(N.DL.SCH.QPSK.TB.Retrans + N.DL.SCH.16QAM.TB.Retrans +
N.DL.SCH.64QAM.TB.Retrans +
N.DL.SCH.256QAM.TB.Retrans)/(N.DL.SCH.QPSK.TB + N.DL.SCH.16QAM.TB +
N.DL.SCH. 64QAM.TB + N.DL.SCH. 256QAM.TB) x 100%
Downlink RBLER:
(N.DL.SCH.QPSK.ErrTB.Rbler + N.DL.SCH.16QAM.ErrTB.Rbler +
N.DL.SCH.64QAM.ErrTB.Rbler +
N.DL.SCH.256QAM.ErrTB.Rbler)/(N.DL.SCH.QPSK.TB + N.DL.SCH.16QAM.TB +
N.DL.SCH. 64QAM.TB + N.DL.SCH. 256QAM.TB) x 100%
Uplink retransmission rate:
(N.UL.SCH.HalfPiBPSK.TB.Retrans + N.UL.SCH.QPSK.TB.Retrans +
N.UL.SCH.16QAM.TB.Retrans + N.UL.SCH.64QAM.TB.Retrans +
N.UL.SCH.256QAM.TB.Retrans)/(N.UL.SCH.HalfPiBPSK.TB + N.UL.SCH.QPSK.TB
+ N.UL.SCH.16QAM.TB + N.UL.SCH. 64QAM.TB + N.UL.SCH. 256QAM.TB) x
100%
Uplink RBLER:
(N.UL.SCH.HalfPiBPSK.ErrTB.Rbler + N.UL.SCH.QPSK.ErrTB.Rbler +
N.UL.SCH.16QAM.ErrTB.Rbler + N.UL.SCH.64QAM.ErrTB.Rbler +
N.UL.SCH.256QAM.ErrTB.Rbler)/(N.UL.SCH.HalfPiBPSK.TB +
N.UL.SCH.QPSK.TB + N.UL.SCH.16QAM.TB + N.UL.SCH. 64QAM.TB +
N.UL.SCH. 256QAM.TB) x 100%

PRB usage
The PRB usage is used to evaluate the network load. High PRB usage indicates greater
interference between cells in the uplink and downlink.
Downlink PRB usage = N.PRB.DL.Used.Avg/N.PRB.DL.Avail.Avg x 100%
Uplink PRB usage = N.PRB.UL.Used.Avg/N.PRB.UL.Avail.Avg x 100%
2023-05-02

Cell status

Average CQI
Huawei confidential. No spreading without permission.
71
5G Troubleshooting Guide – NSA Access
INTERNAL
The CQI reflects the downlink channel quality and interference level and is measured by
a single codeword. Average CQI: (0 x N.ChMeas.CQI.SingleCW.0 + 1 x
N.ChMeas.CQI.SingleCW.1 + ... + 15 x
N.ChMeas.CQI.SingleCW.15)/(N.ChMeas.CQI.SingleCW.0 +
指标描述
指标名称
指标ID
N.ChMeas.CQI.SingleCW.1
+ ... + N.ChMeas.CQI.SingleCW.15)
1911816595 N.ChMeas.CQI.SingleCW.0
单码字全带宽CQI为0的上报次数
1911816596 N.ChMeas.CQI.SingleCW.1
单码字全带宽CQI为1的上报次数
1911816597 N.ChMeas.CQI.SingleCW.2
单码字全带宽CQI为2的上报次数
1911816598 N.ChMeas.CQI.SingleCW.3
单码字全带宽CQI为3的上报次数
1911816599 N.ChMeas.CQI.SingleCW.4
单码字全带宽CQI为4的上报次数
1911816600 N.ChMeas.CQI.SingleCW.5
单码字全带宽CQI为5的上报次数
1911816601 N.ChMeas.CQI.SingleCW.6
单码字全带宽CQI为6的上报次数
1911816602 N.ChMeas.CQI.SingleCW.7
单码字全带宽CQI为7的上报次数
1911816603 N.ChMeas.CQI.SingleCW.8
单码字全带宽CQI为8的上报次数
1911816604 N.ChMeas.CQI.SingleCW.9
单码字全带宽CQI为9的上报次数
1911816605 N.ChMeas.CQI.SingleCW.10
单码字全带宽CQI为10的上报次数
1911816606 N.ChMeas.CQI.SingleCW.11
单码字全带宽CQI为11的上报次数
1911816607 N.ChMeas.CQI.SingleCW.12
单码字全带宽CQI为12的上报次数
1911816608 N.ChMeas.CQI.SingleCW.13
单码字全带宽CQI为13的上报次数
1911816609 N.ChMeas.CQI.SingleCW.14
单码字全带宽CQI为14的上报次数
1911816610 N.ChMeas.CQI.SingleCW.15
单码字全带宽CQI为15的上报次数
5.3.6 Action 6: Operations and External Events
Network operations and external events include but are not limited to: Site reconstruction
(continuous new site deployment or site disconnection in some periods of time), network
adjustment (such as frequency refarming, RF optimization, and parameter modification on the
entire network), reconstruction of neighboring NEs (such as LTE NEs, core network, and
transmission), major festival activities, launch of new UEs, and version upgrade of
mainstream UEs, and changes in operators' tariff policies. These operations and events cause
changes in the network topology, UE distribution, and user behavior. As a result, the network
load and interference level change, affecting KPIs. For example, capacity expansion,
reconstruction, and frequency refarming may cause UE migration. In this case, reduce the
load of a frequency or cell to improve KPIs. Otherwise, KPIs deteriorate given that site
disconnection and damaged coverage occur due to transmission, power supply, and other
problems and the load increases due to UE splitting. In practice, the problem analysis depends
on the actual situation. This guide is for reference only.
5.3.7 Action 7: Detailed Analysis of Top Sites or Typical Sites
If the root cause cannot be located based on traffic statistics, associated counters, and external
events, and top sites exist, collect signaling tracing data of the sites for a period of time and
analyze the data together with CHRs. If the problem is not caused by top sites, select several
typical sites with more failures and collect data for detailed analysis. If different types of
problems exist during traffic statistics cause analysis, select several typical sites for detailed
data collection and analysis for each type of problem cause.
2023-05-02
Huawei confidential. No spreading without permission.
72
5G Troubleshooting Guide – NSA Access
INTERNAL
After obtaining the signaling tracing and CHR data of typical sites, use the FMA to collect
statistics on logs and check the failure scenarios. Analyze each failure scenario by referring to
chapters 1–4.

Analyzing signaling over the standard interface:
The following describes how to collect statistics on signaling failures over the standard
interface. Use the FMA to open the 4G Uu/S1/X2 signaling or 5G X2 signaling. Rightclick it and choose Diagnosis from the shortcut menu. In the displayed dialog box, select
analysis scenarios. The tool automatically processes these scenarios.
Figure 5-1 Navigation path to the automatic diagnosis function for standard interface
signaling on the FMA
The following figure shows the analysis result. The upper part of the window displays
the number and percentage of each release scenario. Click a scenario. The lower part
displays detailed information about each time and categorized statistics on each key
field.
2023-05-02
Huawei confidential. No spreading without permission.
73
5G Troubleshooting Guide – NSA Access
INTERNAL
Figure 5-2 Result display of the automatic diagnosis function for standard interface signaling
on the FMA

CHR analysis
−
For Add rej, you can directly filter L3IChrCuSgnbAddRej in the Type column.
You can summarize the cause value carried in the Add Rej message, User TMSI,
CallID, CRNTI, and information about the peer anchor site to find the rule.
TrackListInfo records some key dbg information about the user rej, which can be
used to help further analyze the rej cause.
2023-05-02
Huawei confidential. No spreading without permission.
74
5G Troubleshooting Guide – NSA Access
2023-05-02
INTERNAL
−
If LTE does not respond with an SGNB_RECFG_CMP message, you can use the
Statistic function on the FMA for CHRs and collect DC statistics by using
L3ChrCuAbnormalRel.
−
CHRs related to random access
Huawei confidential. No spreading without permission.
75
5G Troubleshooting Guide – NSA Access
INTERNAL
(1) Use the cell-level CHR event L2CellChrBlkInfo to check whether the preamble is
received, whether the RAR is sent, and the CRC result of Msg3. This event is
measured every 10 minutes, including both contention-based and non-contentionbased access.
You can check the preamble reception, RAR delivery, and Msg3 reception status
based on L2_CellCHR_BLK_CCHP_INFO and
L2_CELLCHR_BLK_ULSCH_INFO.
2023-05-02
Huawei confidential. No spreading without permission.
76
5G Troubleshooting Guide – NSA Access
INTERNAL
(2) For UE-level CHRs, check the non-contention-based preamble, RAR, and Msg3
status by referring to sections 4.3.2 to 4.3.3, and Msg4 status by referring to section
4.3.4 "Contention Msg4 Failure."
2023-05-02
Huawei confidential. No spreading without permission.
77
5G Troubleshooting Guide – NSA Access
6
INTERNAL
VIP Complaint Handling
6.1 Overview
This chapter describes basic methods of complaint handling, involving complaining user
information collection, location data collection, and basic problem analysis. It provides
guidance for quickly closing complaints.

Routine maintenance
Perform routine network performance monitoring through daily performance reports,
weekly performance reports, performance alarms, and proactive performance care.
Perform routine network health check through parameter check, interference check, and
user experience test. In this way, problems of the network, some base stations, and some
UEs can be detected in time, and hidden troubles that affect the network performance can
be eliminated, thereby reducing complaints as much as possible.

Complaint handling
Routine monitoring and check cannot exclude all problems. Therefore, customer
complaints still arise. Generally, adhere to the following principles:

−
Record the symptoms clearly. It is recommended that you record the original words
of the customer to avoid misunderstandings during the subsequent information
transmission. In addition, submit a trouble ticket in the iCare system.
−
Respond to critical customer complaints in a timely manner, and immediately initiate
customer visits to resolve and avoid problems, pacify customers, and ease customer
complaints. Then, analyze root causes of problems and provide solutions to avoid
similar problems.
−
For the complaint about a general problem, keep the environment intact. Capture
sufficient location data, analyze the root cause, provide a solution to problems of the
same type as soon as possible, and then close the complaint. Pay enough attention to
complaints about general problems to avoid the problem resolution delay. A too long
delay will escalate the complaints to critical complaints.
−
If complaints from multiple customers are received simultaneously, you need to
prioritize the complaints and analyze them one by one.
−
The essence of complaint handling is not to solve individual problems of customers,
but to summarize common problems through such individual problems and provide
solutions.
Customer return visit
−
2023-05-02
Customer return visits are mandatory for critical customer complaints. For complaints
about general problems that cannot be remotely resolved, customer return visits are
Huawei confidential. No spreading without permission.
78
5G Troubleshooting Guide – NSA Access
INTERNAL
required to collect more information for problem locating, find out the root causes,
and provide solutions.
−
For problem complaints that are remotely solved, pay telephone return visits based on
the problem importance and customer importance to confirm that the problems are
solved.
6.2 Complaining User Information Collection
By categorizing the complaints, the operator first filters out the problems about network
quality, and then provides the detailed information about the complaint user, including time,
place, problem description, mobile phone number of the complaining user, complaint type,
and estimated time for a solution. The problems can be better located and analyzed if such
information as the types of complaining UEs, the users' activity range and habits, types of the
users' business and service packages.
The IMSI and serving cell are mandatory for user complaint analysis. Engineers need to
further obtain them based on the information provided by the customer. The IMSI can be
obtained from the mobile number (MSISDN) or the customer. The serving cell information
can be obtained in either of the following ways:

Based on the geographic location information of the complaining user, engineering
parameters, and maps, find the cells closest to the user. Then, use these cells as possible
serving cells and collect data related to complaint analysis.

If the Nastar is deployed at a site, you can use the VIP analysis function to query the list
of cells where the user has accessed the network, as shown in the following figure.
6.3 User Complaint Analysis Methods

Historical data analysis
For sites where the Nastar has been deployed, preferentially use the complaint analysis
support function on the Nastar to analyze historical data.
The Nastar must be deployed at a site to support complaint handling. The complaints
must be related to accessibility, retainability, and mobility. In addition, the Nastar must
subscribe to data of eNodeBs in the complaint area. Then, you can use the complaint
analysis support function on the Nastar.
If customer complaints are generated, the Nastar analyzes the known problematic cell
and the IMSI and MSISDN about complaining user, and quickly retrieves the user's call
records related to the problematic cell. This function helps locate and resolve complaints
by analyzing causes for call setup failures, handover failures, and abnormal service
drops. The complaint analysis support function on the Nastar can display the historical
signaling procedures, uplink RSRP/SINR, and release causes of a user on the interface
and provide real-time data collection and analysis.
If the problem persists with the help of historical data, collect data in real time to obtain
related location data.
2023-05-02
Huawei confidential. No spreading without permission.
79
5G Troubleshooting Guide – NSA Access
−
INTERNAL
eNodeB/gNodeB data collection
Virtual UE trace and CellDT
−
EPC data collection (Huawei EPC)
−
EPC data collection (non-Huawei EPC)
−
If the EPC is not provided by Huawei, the customer needs to coordinate the MME of
another vendor to create and provide a trace reference number based on the IMSI. If
the trace reference number cannot be provided, real-time user monitoring cannot be
performed. The interconnection with the MMEs of Ericsson, Cisco, and Nokia
Siemens Networks for end-to-end signaling tracing has been completed
Remarks: The number of tracing or monitoring tasks and the maximum tracing duration are
limited. The specific limitation depends on the type and version of the U2020. For details, see
the U2020 online help.

Problem reproduction
You are advised to perform the following operations for problem reproduction:
−
When the problem is reproduced, the scenario must be consistent with that when the
user complains about the problem, including the time, location, UE, and service type.
−
Record related test data and trace data, including the UE logs, real-time tracing of
U2020 users, CellDT, and one-click logs after problem reproduction.
6.4 Complaints Analysis

View the exception cause, release cell, and release time.
The prerequisite for complaint analysis support is that the network side (mainly the core
network side) obtains the user identity information (such as IMSI/IMEI) through the user
authentication procedure. The authentication procedure is triggered after the RRC
connection is set up. If the RRC connection setup on the LTE side fails, the network side
cannot obtain the user identity information, and the Nastar cannot obtain the
corresponding call records for complaint analysis support. Therefore, the Nastar cannot
analyze access failures in the LTE RRC phase.

Signaling analysis
For failure signaling in virtual UE tracing or on the Nastar, refer to the introduction in
chapter 4 and analyze the root cause based on signaling before and after the current one

Geographic display
The geographic display shows the cells where UEs fail to access the network and
provides the network topology. It can be combined with the air interface quality and
signaling to help find the root cause.

CHR analysis on the base station
Based on the preceding signaling, obtain the time when the UE experiences an
exception, TMSI/C-RNTI information, and 4G/5G cell information. Then, obtain the
CHR logs of the corresponding site on the base station side for further analysis. For
detailed operations, see CHR analysis operations of accessibility problems in chapter 4.
In the following figure, you can find the time when a UE encounters an exception in
CHRs. View the TMSI and C-RNTI, and get matched to those of VIP users.
2023-05-02
Huawei confidential. No spreading without permission.
80
5G Troubleshooting Guide – NSA Access

INTERNAL
Retesting and detailed signaling tracing
If the root cause cannot be found through CHR analysis and the problem persists, collect
real-time tracing data for further analysis. The real-time tracing data related to
accessibility includes UE logs, Uu/S1/X2 signaling tracing, and CellDT tracing (No. 1).
2023-05-02
Huawei confidential. No spreading without permission.
81