8 LF_TS3001_E02_1 LTE eNodeB Troubleshooting.pdf

7/21/2019 8 LF_TS3001_E02_1 LTE eNodeB Troubleshooting.pdf

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LTE eNodeB Troubleshooting

ZTE University



Objectives

To understand the troubleshooting process and

common methods

To understand the common troubleshooting

methods for the eNodeB





© ZTE Corporation. All rights reserved

Alarm/Notification Information Structure

Structure

Alarm/Notification Code

Alarm/Notification Detailed Information

Alarm Level

Alarm/Notification Causes

Alarm/Notification Code is defined by a 32-bitfield indicating the specific code value.

Detailed Information reflects such content asfault cause and fault phenomenon.

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

Alarm/Notification Type

Alarm/Notification Impact

Solution

Equipment alarm / Communication alarm /Processing alarm / Environment alarm

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




Alarm/Notification Information Interface



Contents

Overview

LTE Alarm/Notification Information Structure

LTE Basic Signaling Flow

Common Troubleshooting

Typical Case Analysis


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LTE Protocol

Signaling Flow

Data Flow

E-Node B

PHY

UE

PHY

MAC

RLC

MAC

MME

RLC

NAS

NAS

RRC RRC

PDCP PDCP

APP

UDP

GTPU

IP

S1 AP

SCTP

SGW

IP

UDP

GTPU

IP

SCTP

S 1 AP

X2 AP



AttachProcedure:

UEPoweredOn (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

•Understand related principles, networking information, and

configurations.

•Check and analyze possible causes.

•Understand check measures and methods.

•Accumulate troubleshooting experience and knowledge.

Troubleshooting Process：

•Comparison

• Exclusion

• Shift

•Auxiliary analysis (alarms and performance data)

•Direct inspection

Common Methods：




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 positionsof 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)

Fault Handling Methods 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 thecomparison 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.




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 RemoteLMT (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 RemoteLMT (2)

2. Set two OMCB IPaddresses: 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 IPaddress at the

maintenance port of the

eNodeB, that is, the IP

address for connecting to

the EMS.




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 faultpersists, the optical port on the BPL is not faulty. Otherwise, replace the opticalmodule.

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 ratedoes 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.

Fault Analysis and Locating The transmission bandwidth assigned

for the eNodeB is insufficient.

Data configurations of the eNodeB are

incorrect.

Fault Handling Methods Check the transmission bandwidth of the

eNodeB by packet injection. Ensure thatthe transmission bandwidth reaches 100Mbit/s.

The download rate is related to thedownlink modulation mode andencoding mode. In superb radioenvironment, use the higher ordermodulation and set DL Maximum MCSto 28. In poor radio environment, usethe lower order modulation and set DLMaximum MCS to 24 or 26.




Upgrade Fault: Link Between the BBU and RRUFails

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 bedirectly 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.

Fault Analysis and

Locating

Data loss occurs after the

upgrade.

Fault Handling Method

Set cell parameters. The

MME becomes available.




Upgrade Fault — BootROM Version Cannot BeQueried by the MML

Fault Symptom

Asset information about someeNodeBs 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 notautomatically 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.



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.


1. Lower the reference signalpower in DPC. The defaultvalue is 10 dBm, but thereference signal power for theCSL SHOP must be smallerthan 6 dBm. Meanwhile, set thecell transmit power to 15–20dBm.




Indoor Coverage: UE Cannot Find Cells (2)

Fault Handling Methods (Continued)

Generally, the CSL SHOP uses 10 dB attenuators. Therefore, set the referencesignal 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

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.

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 RSRPis low and SINR is small, below 10.

Make sure the RSRP of UE searched cell is -60 to -90;

Make sure the SINR of UE searched cell is 20 to 30.



Fault Symptom




S1 Is Disconnected

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

S1 status is disconnected.

The eNB data configuration is abnormal.

The transmission data is not configured or the configuration is incorrect.

EPC MME failure.

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

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

3. Make sure that EPC MME is operating properly.



Fault Symptom




EMS Is Disconnected

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.

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.

Check whether the transmission configuration is completed.

Check whether the EMS configuration is finished.

Check whether the EMS IP configured in eNB is normal.



Fault Symptom




UE Can Attach, but Fails to Ping PDN Server

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.

IP data configuration is incorrect. The route from eNB to EPC xGW is notconfigured in the transmission equipment.

PDN server is faulty.

The XGW route configuration from eNB to EPC is incorrect.

Make sure that the transmission configuration related route data is correct.

Make sure that the PDN sServer status is normal.



Fault Symptom

UE C t Att h (1)




UE Cannot Attach (1)

During network connection, the UE displays "connecting to network" and

cannot attach.

The eNodeB is faulty.

The EPC is faulty.

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

Analyze the traced signals.

Fault Symptom







Signal trace results are as follows:

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





The following signal analysis shows that the air interface is successfully

established. The eNodeB sends a UE initialization message, and the EPC sends arelease 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.



Documents

8 LF_TS3001_E02_1 LTE eNodeB Troubleshooting.pdf