8 LF_TS3001_E02_1 LTE eNodeB Troubleshooting.pdf

LTE eNodeB Troubleshooting ZTE University

Objectives 

To understand the troubleshooting process and common methods



To understand the common troubleshooting

methods for the eNodeB

Contents 

Overview 

LTE Alarm/Notification Information Structure



LTE Basic Signaling Flow



Common Troubleshooting



Typical Case Analysis

Alarm/Notification Information Structure Alarm/Notification Code Alarm/Notification Code is defined by a 32-bit field indicating the specific code value.

Alarm/Notification Detailed Information Detailed Information reflects such content as fault cause and fault phenomenon.

Alarm/Notification Type

Equipment alarm / Communication alarm / Processing alarm / Environment alarm

Alarm Level

There are four alarm levels, which are indicated in descending order of severity as Critical, Major, Minor, and Normal.

Alarm/Notification Impact

System impact refers to the impact that the alarm/notification occurs in the system or services.

Structure

Alarm/Notification Causes Solution

© ZTE Corporation. All rights reserved

Alarm/Notification Information Interface


Contents 

Overview 

LTE Alarm/Notification Information Structure



LTE Basic Signaling Flow







LTE Protocol MME UE

NAS

E-Node B

S 1AP

NAS APP RRC

RRC

S1AP

SCTP

X2AP

IP PDCP

PDCP

SCTP

RLC

RLC

MAC

MAC

GTPU

PHY

PHY

UDP

IP SGW GTPU UDP IP

Signaling Flow Data Flow © ZTE Corporation. All rights reserved

Attach Procedure: UE Powered On (1)


Attach Procedure: UE Powered On (2)


Establish NAS Signalling Connection (1)

Setup RRC Connection

Setup S1 Connection


Establish NAS Signalling Connection (2)


Detach Procedure: RRC_IDLE (1)






Detach Procedure: RRC_CONNECTED (1)


Detach Procedure: RRC_CONNECTED (2)


Detach Procedure: Power Off (1)


Detach Procedure: Power Off (2)


Contents 

Overview







Troubleshooting Process and Common Methods Troubleshooting Process：

• Understand related principles, networking information, and configurations. • Check and analyze possible causes. • Understand check measures and methods.

• Accumulate troubleshooting experience and knowledge. Common Methods： • Comparison • Exclusion • Shift • Auxiliary analysis (alarms and performance data)

• Direct inspection


Link Between RRU and BPL Fails 

Fault Symptom 

The physical or logical link between the RRU and the BPL fails, and CPRI alarms may be generated.



Fault Analysis and Locating 

Optical fiber or optical module is faulty, BPL or RRU hardware is faulty, or RRU version is incorrect.



Fault Handling Methods 

Check the optical fibers. If the optical fibers are faulty and the optical loss exceeds the upper limit, replace them.



Check the optical modules. If the optical rate is incorrect, shift the positions of the optical modules or replace them.



Check BPL hardware.



Query the RRU version over Telnet.



Check RRU hardware.


FTP Upload and Download Service Fails (1) 

Fault Symptom 

The UE is successfully connected. When it performs FTP upload and download service, the traffic is unstable, or the traffic is stable, but with large

fluctuations. 


The radio environment is abnormal.



RB and MCS configurations are incorrect.



The PDN server does not operate properly.



The EPC service board is faulty.



Transmission problems occur, for example, insufficient bandwidth.



The UE is faulty, for example, it is overheated or its components are faulty.



The firewall is not disabled, or FTP settings are incorrect.


FTP Upload and Download Service Fails (2) 


1. Check the radio environment. Ensure that the RSRP and SINR are normal.



2. Check the RB and MCS configurations. Ensure that the bandwidth, RB, and MCS configurations meet the requirements.



3. Check the PDN server. Ensure that the PCN server operates properly by the comparison method.



4. Check the EPC service board. Ensure that the EPC service board operates properly by the exclusion method.



5. Check for transmission problems (for example, insufficient bandwidth) by UDP packet injection.



6. Check the UE. Ensure that it is not overheated and its components are not faulty.



7. Check the firewall and FTP settings. Ensure that the firewall is disabled and

FTP settings are correct. © ZTE Corporation. All rights reserved

EMS or OMM Fails to Start After Server Restarts 

Fault Symptom 






After the server restarts, the EMS or OMM fails to start, and a message is displayed indicating that the database fails to be connected. The database instance does not automatically start when the server restarts, and it is required to manually start the database instance. Database monitoring may not start, and it is required to check the monitoring status.


1. Open a new CLI and execute the sqlplus system/oracle@lteomm. The system switches to the Oracle user test database connection UI.



2. Exit the connection UI.



3. Start the lteomm database instance.



4. Start the monitoring program.



5. Connect to the test database.



6. Restart the OMM service terminal. The OMM restarts successfully.


R8880 Transmit Power Is Lost 

Fault Symptom 

After the eNodeB starts, the cell status, neighboring NE status, and association are normal, and no alarm is generated. However, the R8880

transmit power is 0. 




Antennas, feeders, connectors, or RF boards are faulty.


1. Load the transmit power to the R8880 manually.



2. Telnet 192.254.1.16.



3. Enter user name and password (zte).



4. Telnet 200.254.2.0 without entering ushell.



5. Enter user name and password (zte).



6. Run the following commands: txatt 0,130, txatt 1,130


eNodeB Cannot Be Accessed Through Remote LMT (1) 

Fault Symptom 

The eNodeB is operating properly, and the local LMT is available. However, a user cannot log in to the eNodeB through LMT on the EMS.




IP address configurations of the eNodeB are incorrect, routing is abnormal, or OMCB parameters are not correctly set.




1. Set two IP addresses for the eNodeB: 20.2.100.3 for connecting to the core network and 10.11.162.193 for connecting to the EMS.


eNodeB Cannot Be Accessed Through Remote LMT (2) 2. Set two OMCB IP addresses: 10.11.162.199 for connecting to the EMS and 10.11.162.142 (IP address of the computer that holds the EMS) for

remote LMT. Ensure that the IP address type is SIGIP. 3.

Run LMT on the computer that holds the EMS and enter the IP address at the maintenance port of the eNodeB, that is, the IP

address for connecting to the EMS. © ZTE Corporation. All rights reserved

RRU Cannot Be Detected 

Fault Symptom 





The RRU cannot be detected.


The RRU version is incomplete or incorrect.



The optical link between the BBU and RRU fails.


Ensure that the RRU version is correct and the RRU is operating properly.



Check the optical port on the BPL, optical module of the RRU, and optical fiber. 

 

Connect the optical fiber of the RRU to the BPL port in another cell. If the fault persists, the optical port on the BPL is not faulty. Otherwise, replace the optical module. If the optical module of the RRU is faulty, replace it. If the optical fiber is faulty, replace it.


RRU Power Is Abnormal 

Fault Symptom 

A user connects to the RRU over Telnet and runs the tcpw command to view the RRU power, but the displayed RRU power is 0.





Digital power is available, but analog power is unavailable.

Fault Analysis and Fault Handling Methods  

The displayed RRU power is 0.

In this case,  

 

Check whether the cell is blocked. If yes, unblock the cell. Reset the RRU.

Digital power is available, but analog power is unavailable.

In this case,  

Reset the RRU. Replace the RRU.


Uplink Rate of a Cell Is Abnormal 

Fault Symptom 








The eNodeB has three cells. The uplink rate and downlink rate in cells 2 and 3 are normal. The downlink rate in cell 1 is normal, but the uplink rate in cell 1 does not meet the requirement and is unstable. Comparison among configuration data of the three cells shows that all parameters are the same, except the cell ID. Therefore, the fault is not related to data configurations. Two antennas are installed in parallel for the RRU in cell 1, with a distance of six meters. The test spot is located in an equipment room between the two antennas, where the radio environment is poor. When receiving a signal, the UE cannot quickly determine which antenna generates the signal. Therefore, the uplink rate does not meet the requirement.


Establish multiple test spots around the antennas.



Ensure that the uplink rate meets the requirement.


Dry Contact Fails to Report Alarms to EMS 

Fault Symptom 

Dry contacts configured on the EMS do not report alarms to the EMS when alarms are generated.




Dry contacts on the eNodeB are not properly connected.



The SA board on the eNodeB is faulty.




Ensure that dry contacts are properly connected.



Check the status of the SA board.

If the SA board is not in the available state, replace it.


SWR Alarms Are Generated 

Fault Symptom 

The Standing wave ratio (SWR) alarms are generated on the EMS. The SWR of the RRU is greater than 2.




No antenna is installed, antennas are loose, or antennas are not correctly installed.




1. Ensure that the two antennas of the RRU are connected to the outer ports of the RRU.



2. Alarms are generated if antennas are not correctly installed.


eNodeB Download Rate Is Insufficient 

Fault Symptom 








The download rate of the eNodeB is insufficient in a service test.

The transmission bandwidth assigned for the eNodeB is insufficient. Data configurations of the eNodeB are incorrect.




Check the transmission bandwidth of the eNodeB by packet injection. Ensure that the transmission bandwidth reaches 100 Mbit/s. The download rate is related to the downlink modulation mode and encoding mode. In superb radio environment, use the higher order modulation and set DL Maximum MCS to 28. In poor radio environment, use the lower order modulation and set DL Maximum MCS to 24 or 26.


Upgrade Fault: Link Between the BBU and RRU Fails 

Fault Symptom 

After the eNodeB is upgraded, the BBU operates properly, but the RRU cannot start.




The RRU hardware is faulty, the optical fiber is faulty, or the RRU version is incorrect.




1. Ensure that the RRU hardware and optical fiber are not faulty and the RRU operates properly before the upgrade.



2. If the fault persists, the RRU version is incorrect. The RRU cannot be directly upgraded from 050E to 060C. Instead, an intermediate version is required.



3. After the RRU is upgraded to 060C manually, it operates properly, and the link with the BBU recovers.


Upgrade Fault: Data Is Lost 

Fault Symptom 

After the eNodeB is upgraded from 050B to 050L, the MME can be pinged, but is in an unavailable state, and cell parameters are null.




Data loss occurs after the upgrade.



Fault Handling Method 

Set cell parameters. The MME becomes available.


Upgrade Fault — BootROM Version Cannot Be Queried by the MML 

Fault Symptom 

Asset information about some eNodeBs is missing. After the OMC and eNodeBs are upgraded, a user runs the MML command on the OMC to export

asset information about all eNodeBs on the network, but asset information about some eNodeBs are still missing, without BootROM version information. However, a user can obtain BootROM version information about a single

eNodeB by using the version management function. 


After eNodeBs are upgraded, the latest asset information (including BootROM version information) is not automatically synchronized to the OMC.



Fault Handling Method 

Manually synchronize asset information on the entire network or on a specific subnet by using the asset management

function of the OMC. © ZTE Corporation. All rights reserved

Contents 

Overview







Indoor Coverage: UE Cannot Find Cells (1) 

Fault Symptom 

The UE is started, and the terminal is connected. In the engineering mode window, PCI is 0, or a value obtained in the previous search is displayed, and other parameters remain the same.





“Searching Network” or “No Service” is displayed on the Samsung terminal dialing software.



The UE keeps searching for network, but the PCI and CI values remain the same.


Generally, the CSL SHOP is small, with a 10 dB attenuator and a 10 W RS transmit power. The transmit power in this environment is large. As a result, the receive power of mobile phones becomes saturated. RS reference signals cannot be properly demodulated, and therefore no network is identified.



Fault Handling Methods 1.

Lower the reference signal power in DPC. The default value is 10 dBm, but the reference signal power for the CSL SHOP must be smaller than 6 dBm. Meanwhile, set the cell transmit power to 15–20 dBm.


Indoor Coverage: UE Cannot Find Cells (2) 

Fault Handling Methods (Continued) 

Generally, the CSL SHOP uses 10 dB attenuators. Therefore, set the reference signal power to a value smaller than 6 dBm (excluding 6 dBm). In this case, the forward power and reverse power of the terminal are small, causing accessing failures. To solve this problem, modify the three UPC parameters to

increase the transmit power of the terminal.


Outdoor Coverage Accessing Failure Fault Symptom 

The RSRP value of UE searched cell is -40 to -60. Normally it should be about -

50. UE fails to dial calls. 

The RSRP value of UE searched cell is below -110. UE fails to dial calls.



The SINR of UE searched cell is 5 to15. UE fails to dial calls.

Fault Analysis and Locating  

The test spot is too close to the antenna. UE fails to access due to the high RSRP. The test spot is too far from the antenna or the radio environment is poor. The RSRP is low and SINR is small, below 10.

Fault Handling Methods  

Make sure the RSRP of UE searched cell is -60 to -90; Make sure the SINR of UE searched cell is 20 to 30.


S1 Is Disconnected Fault Symptom 

S1 is set up successfully, but the SCTP association is disconnected.



S1 status is disconnected.

Fault Analysis and Locating   

The eNB data configuration is abnormal. The transmission data is not configured or the configuration is incorrect. EPC MME failure.

Fault Handling Methods 1.

Make sure that the S1 IOT parameters are correct. • • • •

2.

Make sure that the eNB configuration and transmission is correct. • •

3.

SCTP parameters: local port No., peer end port No., MME IP address and local IP address. eNB IP address. Check whether MCC and MNC coordination is consistent with EPC configuration and planning. Check whether the TAC parameter is consistent with EPC. If not, SCTP may fail to be established. The simple method: Set PC with the eNB IP address and connect PC to SW Port 15. Ping MME address from PC. If it fails, it is the transmission problem. Otherwise, it may be the problems of eNB and EPC.

Make sure that EPC MME is operating properly.


EMS Is Disconnected Fault Symptom 

Set PC with eNB IP address and connect PC to SW Port 15. It fails to ping through the OMC IP address.



Check eNB status from the EMS side. It is disconnected.

Fault Analysis and Locating 

 

The transmission data is not configured or the configuration is incorrect; eNB is not updated. The configured eNB IP and OMC IP are not correct. The related site configuration data are not added to EMS side.

Fault Handling Methods   

Check whether the transmission configuration is completed. Check whether the EMS configuration is finished. Check whether the EMS IP configured in eNB is normal.


UE Can Attach, but Fails to Ping PDN Server Fault Symptom 

UE can attach and acquire IP address successfully.



UE fails to ping through IP address of PDN server. It fails to telnet PDN sever with FTP.

Fault Analysis and Locating   

IP data configuration is incorrect. The route from eNB to EPC xGW is not configured in the transmission equipment. PDN server is faulty. The XGW route configuration from eNB to EPC is incorrect.

Fault Handling Methods  

Make sure that the transmission configuration related route data is correct. Make sure that the PDN sServer status is normal.


UE Cannot Attach (1) Fault Symptom 

During network connection, the UE displays "connecting to network" and cannot attach.

Fault Analysis and Locating



The eNodeB is faulty.



The EPC is faulty.

Fault Handling Methods



Perform signal trace by using the single trace tool and dial again.



Analyze the traced signals.


UE Cannot Attach (2) 



Signal trace results are as follows:

The preceding signal analysis shows that no air interface information is received during the dialing process, namely, no link is established between the UE and the eNodeB. It is determined that the eNodeB process is hung up. To solve this problem, restart the CC board.


UE Cannot Attach (3) 

The following signal analysis shows that the air interface is successfully established. The eNodeB sends a UE initialization message, and the EPC sends a release message indicating UE context mismatch. This onsite analysis shows that the accessing failures are caused by errors on the core network. Report this

problem to the core network.


8 LF_TS3001_E02_1 LTE eNodeB Troubleshooting.pdf

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