Introduction to No Traffic

When no traffic occurs, subscribers cannot initiate calls in a normal cell or a normal cell cannot

be occupied.

Introduction

When no traffic occurs, a cell or some TRXs serving the cell become faulty. As a result, cell

coverage may be affected. In some cases, subscribers in an area cannot make calls. Therefore,

when no traffic occurs, immediately resolve the problem to minimize the impact.

The no traffic problem in a cell has the following symptoms:

Performance counter: The value of the K3014:Traffic Volume on TCH counter is 0

during peak hours.

User experience: MSs have trouble in accessing this cell and even cannot detect the cell.

Maintenance console alarm: In the cell whose BCCH TRX is configured with TCHs or

PDTCHs, the alarm file includes ALM-28008 Radio Link Failure (tributary No. = 2).

The alarms associated with no traffic are reported at the TRX level. No traffic may occur in a

BTS, cell, board, or TRX on the board, depending on the cell configurations.

Associated Alarm

For BSC6900 versions earlier than V900R014C00, ALM-28008 Radio Link Failure with

tributary 2 serves as the no traffic alarm. For BSC6900 versions later than V900R014C00, the

diagnosis on no traffic faults is enhanced and the function for independently reporting the alarm

related to no traffic on TRXs is added. For details, see the description of ALM-28009 Carrier No

Traffic.

Whether to report the ALM-28008 Radio Link Failure or ALM-28009 Carrier No Traffic

depends on the setting of the Reporting No Traffic Alarm Independently parameter in the

MML command SET GTRXRLALM. For details, see Reporting the No Traffic Alarm

Independently and No-Traffic Self-Healing.

Symptom

Check whether there is no traffic by using the following methods:

Monitor BTS channel status. If channels in the problem cell cannot be occupied, but

channels in neighboring cells can be occupied, there is no MS to access the cell. The no

traffic problem is caused during the access phase. If the channel request has been

received but the access fails, the no traffic problem is caused during the channel

assignment.

Obtain feedback from subscribers. If subscribers provide the feedback that cell access is

difficult, MSs have no signals, or MSs cannot access the network, no traffic may occur.

Determine the fault by checking whether faults lie in some TRXs, all carriers in a cell, or

some channels on a board.

Run the MML command LST GTRXRLALM to check whether the settings of

parameters for performing self-healing operation for no traffic take effect. If the no traffic

problem persists after running the MML command SET GTRXRLALM, take the

following measures to rectify the fault: locate faults in the antenna system and hardware

devices, optimize network coverage, and eliminate interference.

==================================

Locating No Traffic

This section describes how to locate no traffic.

Principles

Channel resource usage failures caused by special traffic models or board faults may lead to no

traffic. Possible causes are antenna system problems, incorrect data configurations, hardware

problems, interference, poor Um interface quality, or software problems. You can locate and

troubleshoot the problems based on the live network conditions.

To locate the problems, first determine the search scope, such as site, cell, or TRX according to

the problem feedback information and traffic statistics. If no fault is found after the location

procedure is performed on the site, cell, or TRX, reset the software and hardware to restore

services.

In addition, no traffic may be caused by project reasons. For example, if a project is not

complete, a high-power attenuator can be added to the RF output port to prohibit network access

of MSs. Therefore, before clearing the alarms related to no traffic, have maintenance engineers

checked whether no traffic is caused by this type of reason.

The location procedure involves the following operations:

Analyzing the counters associated with a cell or TRX

Analyzing the parameters related to no traffic alarms

Handling the transmission and equipment alarms

Checking the parameter settings

Locating interference

Resetting the faulty board to check whether the board software is faulty

Locating antenna system faults

Location Procedure

Figure 1 shows the procedure for locating no traffic.

Figure 1 Procedure for locating no traffic

Table 1 No traffic location information

No. Item Description Remarks

1 Symptom Provide the start time and end time of the fault, specific

symptom, and impact range (whether the fault occurs in

a cell, a BTS, a BSC, or all BSCs under an MSC).

None

2 Operations

before and

after the fault

occurs

Provide the operations before and after the problem

occurs, such as board replacement, software upgrade,

clock source change, dynamic data configuration, BTS

reset, BSC reset, MSC swapping, and MSC data

modification.

None

3 Faulty NE

version

Obtain the BSC and BTS software versions that are

used when the problem occurs.

For details

about how to

obtain the BSC

and BTS

software

versions that

are used when

the problem

occurs, see

Appendix:

How to Collect

Fault

Information.

4 Configuration

data script

Obtain the configuration data script used when the fault

occurs.

For details

about how to

obtain the

configuration

data script, see

Appendix:

How to Collect

Fault

Information.

5 Historical

alarms

Obtain the historical alarms generated within three days

before and after the problem occurs.

For details

about how to

obtain the

historical

alarms, see

Appendix:

How to Collect

Fault

Information.

6 Original Obtain the original traffic statistics measured within For details

Table 1 No traffic location information

No. Item Description Remarks

traffic

statistics

two days before and after the problem occurs. about how to

obtain the

original traffic

statistics, see

Appendix:

How to Collect

Fault

Information.

7 Operation

logs

Obtain the operation logs generated within 10 days

before and after the problem occurs.

For details

about how to

obtain the

operation logs,

see Appendix:

How to Collect

Fault

Information.

8 Faulty

signaling

Obtain the signaling on the Abis and A interfaces and

single-user signaling of one or two faulty cells when

the problem occurs.

For details

about how to

obtain the

faulty

signaling, see

Appendix:

How to Collect

Fault

Information.

9 BTS logs Obtain all logs generated for one or two faulty BTSs. For details

about how to

obtain BTS

logs, see

Appendix:

How to Collect

Fault

Information.

10 Channel

status

Obtain the status of faulty cells and BTS channels. For details

about how to

obtain the

channel status,

see Appendix:

How to Collect

Fault

Information.

Troubleshooting No Traffic Due to No Calls

This section describes how to troubleshoot no traffic due to no calls.

Symptom

The ALM-28008 Radio Link Failure alarm with Specific Problem of No Traffic on TRX is

reported, or the value of K3014:Traffic Volume on TCH is zero.

This problem may be caused by special coverage conditions. For example, there are no travelers

at a popular tourist attraction during the off-season, no subscribers in certain districts or no

students in schools during holidays, or there is no traffic in some cells in the early morning. In

these conditions, change the settings of the correlated alarm parameters to improve alarm

detection accuracy.

Background Information

The parameters associated with this alarm are Wireless Link Alarm Flag, Statistical Period of

No-traffic, Begin Time of WLA Detection, End Time of WLA Detection, No Traffic Self-

Healing Period, No Traffic Self-Healing Mode and Reporting No Traffic Alarm

Independently. You can run the LST GTRXRLALM command to query the settings of the

preceding parameters and run the SET GTRXRLALM command to change the settings.

Location Procedure

Figure 1 shows the procedure for locating no traffic due to no calls.

Figure 1 Procedure for locating no traffic due to no calls

Troubleshooting Procedure

1. Check whether the settings of the correlated alarm parameters are correct.

Begin Time of WLA Detection, End Time of WLA Detection, and Statistical Period

of No-traffic must be set according to the traffic distribution.

o If the parameter settings are incorrect, change the parameter settings. Then, go to

Step 2.

o If they are correct, return to Procedure for locating no traffic.

2. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, return to Procedure for locating no traffic.

Typical Case

Symptom

The ALM-28008 Radio Link Failure alarm with Specific Problem of No Traffic on TRX is

frequently reported on a BTS3900 and is automatically cleared after a period of time.

Cause Analysis

The site served by the BTS3900 is a school amid summer vacation. The alarm is reported

because no phone calls were made during summer vacation.

Troubleshooting Procedure

1. Trace the RSL signaling on the Abis interface for the problem cell. No channel requests

are reported in the cell. Query the forward and reverse power of the TRX power

amplifier. The forward and reverse power as well as the downlink transmit power of the

TRX are normal.

2. Perform drive tests (DTs). Subscribers can make calls in the area covered by the cell.

This indicates that the BTS is operating properly.

3. Change the settings of the correlated alarm parameters to ensure that the ALM-28008

Radio Link Failure alarm is not reported during summer vacation.

Troubleshooting No Traffic Due to

Transmission or Equipment Faults

This section describes how to troubleshoot no traffic due to transmission or equipment faults.

Symptom

When a transmission or equipment fault occurs in a cell, the alarm system reports alarms such as

RF Unit VSWR Threshold Crossed, Trx Temperature Alarm, Transmission alarm, and TRX

Config Mismatch Alarm. In this situation, the cell may be out of service, or the TRX may be shut

down.

Background Information

Transmission or equipment faults include:

Faults in the BTS transmission management unit

BTS TRX faults

BTS antenna faults

The following alarms are associated with hardware or antenna faults:

ALM-21807 OML Fault

ALM-26235 RF Unit Maintenance Link Failure

ALM-26529 RF Unit VSWR Threshold Crossed

ALM-11272 Hardware Alarm

ALM-26503 RF Unit Optical Module Transmit/Receive Fault

The following alarms are associated with transmission faults:

ALM-21807 OML Fault

ALM-11280 E1/T1 remote alarm

ALM-25800 E1/T1 Loss of Signal

ALM-25803 E1/T1 Loss of Frame Alignment

Location Procedure

Figure 1 shows the procedure for locating no traffic due to transmission or equipment faults.

Figure 1 Procedure for locating no traffic due to transmission or equipment faults

Troubleshooting Procedure

1. Check whether any alarms associated with no traffic due to transmission or equipment

faults are reported.

o If yes, clear the alarms listed in Background Information by referring to the Alarm

Reference. Then, go to Step 2.

o If none of these alarms are reported, return to Procedure for locating no traffic.

2. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, return to Procedure for locating no traffic.

Typical Case 1

Symptom

An onsite MRFU has no traffic and reports the ALM-4812 Optic Module Abnormal Alarm and

the ALM-28008 Radio Link Failure with Specific Problem of No Traffic on TRX.

Cause Analysis

The optical module between the MRFU and the BBU is faulty, and therefore the link between

the TRX and the BBU is disconnected.

Troubleshooting Procedure

1. Analyze the RSL signaling on the Abis interface. All calls assigned to the MRFU fail to

be initiated because the MRFU does not receive any link setup indication messages after

the assignment command is delivered.

2. Check the alarms on the BSC LMT. In addition to alarms related to no traffic, alarms

related to optical module faults are also reported. Therefore, assignment failures may be

caused by optical module faults, which leads to alarms related to no traffic.

3. Replace the onsite optical module with a new one. The no traffic problem is resolved.

Typical Case 2

Symptom

After site H that supports the multi-site cell is deployed in high-speed railway scenarios, there is

no traffic at the site. After the multi-site cell is changed to a common cell, the KPIs become

normal, and the call quality is good. After the common cell is changed back to a multi-site cell,

the traffic abruptly drops to zero and the problem persists after a level-4 reset.

Cause Analysis

During the configuration of a multi-site cell, data is transmitted over the FH channel. After

receiving data from the RRU, the GTMU broadcasts the data to all the six CPRI ports. The

problem site is not configured with the CPRI 1 port and therefore encounters a self-loop. As a

result, the logical carrier receives the same data packet. The packet self-loop occurs, FIFO_R

overflows, and thereby no traffic occurs.

Troubleshooting Procedure

1. Analysis on the field information shows that all carriers on the primary and secondary

subsites have an alarm related to the FIFO_R overflow. In addition, both the primary and

secondary subsites have received the same data packets, and therefore the FIFO

overflows.

2. Run the MML command DSP BTSCPRIPORT to query the status of the CPRI optical

port on the BBU. CPRI optical ports 0, 1, and 2 (ports 0 and 2 are connected to the

primary and secondary subsites) are successfully connected. Actually, CPRI optical port

1 is not configured with the RRU.

3. Address the problem on site. The results show that CPRI optical port 1 encounters a

loopback. Cancel the loopback to resolve the problem

Troubleshooting No Traffic Due to Incorrect

Data Configurations

This section describes how to troubleshoot no traffic due to incorrect data configurations.

Symptom

The alarm system reports the ALM-28008 Radio Link Failure alarm with Specific Problem of

No Traffic on TRX.

Background Information

The ALM-28008 Radio Link Failure is reported if certain parameters are set incorrectly or

certain functions are enabled.

If mobile country code (MCC), mobile network code (MNC), location area code (LAC),

cell identity (CI), and network parameters are not set correctly, no traffic may occur in

the cell. For example, if no MS has accessed the cell but an incoming handover exists,

query the data configuration to check whether the cell is not allowed to access; that is,

run the SET GCELLIDLEBASIC to check the values of Cell Bar Access and Cell Bar

Qualify.

Enabling energy saving functions may result in no traffic. For example, when the

intelligent shutdown of TRX power amplifier function or dynamic cell shutdown function

is started, the BTS checks the traffic volume of a cell or TRX. Upon determining that the

traffic volume of a cell or TRX is low, the BTS powers off the cell or TRX to reduce

power consumption. After the cell or TRX is powered off, there is no traffic in the cell or

on the TRX.

The power level configured for the TRX is low or the power levels configured for the

BCCH TRX and non-BCCH TRXs in the same cell are different.

Location Procedure

Figure 1 shows the procedure for locating no traffic due to incorrect data configurations.

Figure 1 Procedure for locating no traffic due to incorrect data configuration

Troubleshooting Procedure

1. Check whether the parameters listed in Background Information are set correctly.

o If no, change the parameter settings. Then, go to Step 2.

o If yes, return to Procedure for locating no traffic.

NOTE:

If the parameter settings are incorrect, check the items listed in Background Information.

Alternatively, have network operation and maintenance (O&M) engineers checked

changes in the parameter settings before and after the problem occurs. Then, check the

changed parameter settings.

2. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, return to Procedure for locating no traffic.

Typical Case

Symptom

The traffic volumes of three cells under a BSC at site A suddenly decrease to zero and no

channel requests are reported in these cells. However, the traffic volumes of the cells are restored

to normal after several hours.

Cause Analysis

The dynamic cell shutdown function is enabled.

Troubleshooting Procedure

1. View the traffic statistics. Several hours before no traffic occurs, the number of channel

requests reported in the cell gradually decreases. When the no traffic problem occurs, the

number of channel requests decreases to zero.

2. Analyze the operation logs when the problem occurs and when it is resolved. Before the

problem occurs, the dynamic cell shutdown function is enabled. As a result, the BSC

constantly checks the cell load. If the cell load is less than Same Coverage Cell Load

Threshold (with the default value of 50%) within Same Coverage Cell Load Stat.

Time, the cell is shut down and has no traffic. After the dynamic cell shutdown function

is disabled, the problem is resolved.

Troubleshooting No Traffic Due to Poor Um

Interface Quality

This section describes how to troubleshoot no traffic due to poor Um interface quality.

Symptom

If the Um interface quality is poor, an MS may fail to receive an IMM ASS CMD or ASS CMD

message from the BSC, or the BTS cannot decode an EST IND message from an MS. As a

result, the target cell fails to be occupied.

Background Information

Interference may deteriorate the signal quality of the target cell. As a result, MSs fail to

occupy channels in the cell even if the downlink receive level of the target cell is

favorable.

Unbalanced load or poor coverage on the uplink and downlink may deteriorate the Um

interface quality, and therefore MSs fail to receive messages from the BTS.

For dual-Rx cells, check the main and diversity balancing (S4556 and S4557). For BTSs

earlier than BTS3012, the main and diversity difference must not exceed 6 dBm. For

3900 series base stations, the main and diversity difference must not exceed 10 dBm.

Unbalanced main and diversity results in various access problems. For more information,

see Faults on Main and Diversity RX Channels.

Location Procedure

Figure 1 shows the procedure for locating no traffic due to poor Um interface quality.

Figure 1 Procedure for locating no traffic due to poor Um interface quality

Troubleshooting Procedure

1. View the traffic statistics associated with interference bands to check whether there is

interference in the cell.

o If yes, remove the interference source or replace the interfered frequency. Then,

go to Step 2.

o If no, go to Step 3.

2. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, go to Step 3.

3. View the traffic statistics associated with the uplink and downlink signal quality to check

whether the Um interface quality was poor before no traffic occurred.

o If yes, perform network optimization to improve the Um interface quality. Then,

go to Step 4.

o If no, go to Step 5.

4. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, go to Step 5.

5. Perform operations provided in Resetting. Then, go to Step 6.

6. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, return to Procedure for locating no traffic.

Typical Case

Symptom

There is no traffic on an onsite TRX and the alarm system reports the ALM-28008 Radio Link

Failure alarm with Specific Problem of No Traffic on TRX. The system occasionally clears the

alarm, but the traffic volume is low.

Cause Analysis

There is severe uplink interference on the frequency used by the problem TRX.

Troubleshooting Procedure

1. Analyze the traffic statistics when the problem occurred. Although few assignment

commands were delivered to the problem TRX, no TCHs were assigned to the MSs.

2. Analyze the RSL signaling on the Abis interface. Channel requests are reported in the

cell and there is traffic in the cell. However, MSs fail to access the assigned TCHs on the

problem TRX, and do not send any link setup indication messages.

3. Check that no operations are performed on the cell before and after the problem occurs.

4. Analyze the traffic statistics associated with the TRX interference bands. Most uplink

interference bands of the TRX are interference band 5 and the TRX is configured in non-

frequency hopping (non-FH) mode.

5. Change the frequency used by the TRX. The problem is resolved. This indicates that the

problem is caused by single-frequency interference.

Troubleshooting No Traffic Due to Antenna

System Faults

This section describes how to troubleshoot no traffic due to antenna system faults.

Symptom

If the no traffic problem persists after the possible causes of no calls, transmission or equipment

faults, incorrect data configuration, or poor Um interface quality are excluded, the problem may

be caused by antenna system faults.

Antenna system faults refer to incorrect antenna connections and faulty cables to the antenna. If

the antenna system is faulty, the TRXs with no traffic may be bound to the same transmit path.

Background Information

If the antenna system is faulty, the BTS cannot transmit downlink signals properly. As a

result, no coverage or poor coverage problem may occur, or uplink signals cannot be sent

to or decoded by the BTS.

If the antenna connections are incorrect, the coverage area of the BCCH TRX in the cell

may be different from the coverage areas of non-BCCH TRXs. As a result, MSs fail to

access the assigned TCHs on non-BCCH TRXs after they initially access the TCHs on

the BCCH TRX. This results in no traffic on non-BCCH TRXs.

Location Procedure

Figure 1 shows the procedure for locating no traffic due to antenna system faults.

Figure 1 Procedure for locating no traffic due to antenna system faults

Troubleshooting Procedure

Use TEMS or Probe MSs to perform drive tests (DTs). If TEMS or Probe MSs are not available,

use common MSs.

1. Check whether the dialing tests can be performed on the TRX power output port.

Use a TEMS MS to lock the BCCH frequency of the faulty cell and perform dialing tests

on the TRX power output port.

o If the dialing tests cannot be performed and the frequency cannot be scanned on

the TRX power output port, replace the board with a new one. Then, go to Step 2.

o If the dialing tests can be performed, go to Step 3.

2. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, go to Step 3.

3. Check whether the antenna connections are consistent with configurations.

o If no, correct the antenna connections. Then, go to Step 4.

o If yes, go to Step 5.

4. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, go to Step 5.

5. Check whether the antenna tilt is correct and whether the tilt direction is consistent with

the coverage area.

o If no, adjust the antenna tilt. Then, go to Step 6.

o If yes, go to Step 7.

6. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, go to Step 7.

7. Check whether the distributed indoor antenna system is powered off or faulty.

o If yes, contact the manufacturer of the distributed indoor antenna system to rectify

the fault. Then, go to Step 8.

o If no, go to Step 9.

8. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, go to Step 9.

9. Check whether the antenna system is faulty.

Use one cable to connect the TRX of cell A to the antenna of cell B and use one cable to

connect the TRX of cell B to the antenna of cell A. If the problem is resolved, the

problem is caused by antenna system faults.

o If yes, reconnect the cables to the antenna system or replace the components in

the antenna system. Then, go to Step 10.

o If no, Contact Huawei Customer Service Center.

10. Check whether the no traffic problem is resolved.

o If yes, no further action is required.

o If no, Contact Huawei Customer Service Center.

Typical Case

Symptom

The onsite traffic volume suddenly decreases to zero and the ALM-28008 Radio Link Failure

alarm with Specific Problem of No Traffic on TRX is reported on the system and is not cleared

for several days.

Cause Analysis

The distributed indoor antenna system is powered off, and therefore no downlink signals are

available. As a result, MSs fail to access the network.

Troubleshooting Procedure

1. View the traffic statistics when the problem occurs in the cell. No channel requests are

reported in the cell, but the interference band messages are reported. The downlink

transmit power may be abnormal.

2. Reset the board hardware and software. The problem persists.

3. Perform the dialing tests onsite. No cell signals can be searched for in the coverage area.

4. Locate faults in the distributed indoor antenna system. The antenna connections are

correct and calls can be initiated on the TRX power output port.

5. Locate faults in the distributed indoor antenna system again. Extra power is supplied to

the distributed indoor antenna system. This indicates that no traffic occurs because the

distributed indoor antenna system is powered off.

Reporting the No Traffic Alarm

Independently

This section describes how to set the mode for reporting the no traffic alarm.

Function Description

The ALM-28008 Radio Link Failure alarm has seven tributaries, of which tributary 2 indicates

that no traffic is available on TRX.

Due to this reason, ALM-28008 Radio Link Failure is ignorable when it is reported. This

function is used for users to independently report the no traffic alarm and enabled by running the

MML command SET GTRXRLALM with Reporting No Traffic Alarm Independently set to

ON(On). After that, the TRX reports ALM-28009 Carrier No Traffic if no calls are processed on

the TRX within the specified period.

NOTE:

1. 3900 series base stations in V100R014C00 and later support reporting ALM-28009 Carrier No Traffic.

2. 3900 series base stations in versions later than BTS3000 V100R009 support reporting ALM-28008 Radio Link Failure . 3900 series base stations, 3012 series base stations, and other base stations in versions earlier than BTS3000 V300R008 still report ALM-4122 Radio Link Prompt Alarm for indicating no traffic on a TRX or BCCH TRX.

Procedure

GBTS

1. Run the MML command SET GTRXRLALM to enable the function for reporting the no traffic alarm independently. In this step, set the following parameters as follows:

o Set Wireless Link Alarm Flag to YES(Yes). o Set Reporting No Traffic Alarm Independently to ON(On).

2. Run the MML command LST GTRXRLALM to query the parameter settings of the function for reporting the no traffic alarm independently.

eGBTS

For an eGBTS, there is no command for enabling the BTS to report the no traffic alarm. By

default, the BTS reports the no traffic alarm.

Operation Results

GBTS

If Reporting No Traffic Alarm Independently is set to ON(On) and if there is no traffic on any TRX, the BTS reports the ALM-28009 Carrier No Traffic alarm.

If Reporting No Traffic Alarm Independently is set to OFF(Off) and if there is no traffic on any TRX, the BTS reports the ALM-28008 Radio Link Failure alarm with the specific cause of No Traffic on TRX.

eGBTS

If the no traffic alarm is reported, ALM-28009 Carrier No Traffic is reported on the BSC LMT.