Post on 30-Jan-2016
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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.