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Gsm Bts Trouble Shooting Issue3.0
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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved
www.huawei.com
Internal
OME200301 GSM BTS Trouble Shooting
ISSUE 3.0
HUAWEI TECHNOLOGIES CO., LTD. Page 2All rights reserved
References
M900/M1800 Base Station Subsystem
Troubleshooting Manual
M900/M1800 Base Station Controller
Technical Manual
HUAWEI TECHNOLOGIES CO., LTD. Page 3All rights reserved
Upon completion of this course, you will be
able to:
Know how to find the fault in BTS
Know the common fault types
Grasp BTS fault disposal method
Know how to prevent the fault
HUAWEI TECHNOLOGIES CO., LTD. Page 4All rights reserved
Chapter 1 General IntroductionChapter 1 General Introduction
Chapter 2 Typical CasesChapter 2 Typical Cases
Chapter 3 BTS Fault PreventionChapter 3 BTS Fault Prevention
HUAWEI TECHNOLOGIES CO., LTD. Page 5All rights reserved
Chapter 1 General IntroductionChapter 1 General Introduction
Section 1 The Way To Locate FaultSection 1 The Way To Locate Fault
Section 2 Basic Disposal MethodSection 2 Basic Disposal Method
HUAWEI TECHNOLOGIES CO., LTD. Page 6All rights reserved
The ways to locate faults
Alarm
Alarm console
Alarm box
OMC Shell
Traffic statistics
Drive test
Routine inspection
Customer complain
HUAWEI TECHNOLOGIES CO., LTD. Page 7All rights reserved
Locating fault equipment
If BSC has fault, usually it will affect some Sites or all of Sites
If BTS has fault, usually it just affect itself and the handover su
ccess rate of adjacent cells
During implementation or expansion, we can “Interchange ” BT
S and judge whether the fault is because of BSC or BTS
During maintenance, BSC faults don’t just affect one BTS
HUAWEI TECHNOLOGIES CO., LTD. Page 8All rights reserved
Common fault types
BTS fault
Antenna & Feeder
Transmission
Hardware connection fault
Hardware fault
HUAWEI TECHNOLOGIES CO., LTD. Page 9All rights reserved
Chapter 1 General IntroductionChapter 1 General Introduction
Section 1 The Way To Locate FaultSection 1 The Way To Locate Fault
Section 2 Basic Disposal MethodSection 2 Basic Disposal Method
HUAWEI TECHNOLOGIES CO., LTD. Page 10All rights reserved
Basic disposal method
Analyzing the Alarm Information
Alarm information come from the BSS alarm system, indicated usually through sound, light, LED, and screen output, etc
It includes the detailed description of the abnormality, possible causes and restoration suggestions, involves the hardware, link, trunk and CPU loading ratio, etc.. It is a gist for the fault analysis and location
Analyzing the Indicator Status
Indicators can indicate the work status of circuit, link, optical path, node and active/standby mode besides that of the corresponding boards, usually used along with the alarm information generally
Analyzing Traffic Statistics Result
It is the most useful method for locating RNO fault.
HUAWEI TECHNOLOGIES CO., LTD. Page 11All rights reserved
Basic disposal method
Analyzing Apparatus & Meter Test Result
It reflects the fault nature with the visual and quantified data
Some common Apparatus & Meter
− Signaling Analyzer, Test phone, Sitemaster, etc.
Tracing the Interface
It is applied in locating the failure causes of subscriber call connection and inter-office signaling cooperation, etc.
The trace result can help to find the cause of call failure directly and locate the problem or to get the index for the subsequent analysis
Calling Test
It is a simple and quick method to judge whether the call processing function and relative modules of the BSS are normal or not
HUAWEI TECHNOLOGIES CO., LTD. Page 12All rights reserved
Basic disposal method
Comparison/Interchange
Comparison: compare the faulted components or phenomenon with the normal ones, and find the differences so as to find the problem
− It is usually used in the situation with simple fault range
Interchange: if the fault can not be located even after the standby components are replaced, you can interchange the normal components (such as board, optical fiber, etc.) with the potential faulted components, and to compare the work status so as to specify the fault range or part
− It is usually used in the situation with complicated fault range
Switching/Resetting
It can not locate the fault cause accurately, and due to the randomness of software running, the fault may be not able to recur, thus it is difficult to know the real fault and solve the problem
This method is just an emergency method, applicable only in the emergent situation
HUAWEI TECHNOLOGIES CO., LTD. Page 13All rights reserved
Chapter 1 General IntroductionChapter 1 General Introduction
Chapter 2 Typical CasesChapter 2 Typical Cases
Chapter 3 BTS Fault PreventionChapter 3 BTS Fault Prevention
HUAWEI TECHNOLOGIES CO., LTD. Page 14All rights reserved
Chapter 2 Typical CasesChapter 2 Typical Cases
Section 1 Antenna & Feeder FaultSection 1 Antenna & Feeder Fault
Section 2 Transmission FaultSection 2 Transmission Fault
Section 3 Hardware connection faultSection 3 Hardware connection fault
Section 4 Hardware faultSection 4 Hardware fault
HUAWEI TECHNOLOGIES CO., LTD. Page 15All rights reserved
BTS feeder system structure
TX
RX
RXD
T
R
X
CDU
TTAFeeder
TTAFeeder
arrester
optional
Antenna
arrester
HUAWEI TECHNOLOGIES CO., LTD. Page 16All rights reserved
Common faults
Type Fault phenomena
On downlink signal
No downlink signal
MS fails to access the network, calls
cannot be established, call drop, TRX idle
for a long time
Downlink signal
weakened
Poor conversion quality, BTS coverage
shrink
On uplink signal
No uplink signal Calls cannot be established
BTS sensitivity
weakened
Poor conversation quality, BTS coverage
shrink
Feeder system faults
Standing wave alarm Standing wave alarm occurs at CDU
LNA alarm LNA alarm occurs at CDU
TTA alarm TTA alarm occurs at CDU
TTA feeding failsNo DC feeding voltage at CDU antenna
port after TTA configuration
HUAWEI TECHNOLOGIES CO., LTD. Page 17All rights reserved
Common faults on downlink
Description No downlink signal Downlink signal weakened
Analysis No downlink signal
− Step1: View the history alarms and real-time alarm at OMC or
local maintenance console− Step2: If there is emergent standing wave alarm at CDU, it is
the most possible cause for which TMU turns off the
transmitter power amplifier resulting in no downlink signal▪ check the standing wave ratio at jumper side of CDU
antenna port▪ If the standing wave ratio is beyond limits, locate the
faulty point segment by segment
HUAWEI TECHNOLOGIES CO., LTD. Page 18All rights reserved
Common faults on downlink
Analysis
No downlink signal
− Step3: Since there is no downlink signal, there must be a bro
ken point in the RF signal path. If this point is located at the p
art from CDU antenna port to tower top, then CDU should be
able to detect the emergent standing wave alarm. Otherwise,
it can be concluded that the broken point is located between
TRX output to CDU antenna point
▪ Check whether the cable connection between CDU TX-C
OM and TX-DUP is correct
− Step4: If the operations above fail to locate the failure, chang
e the CDU
HUAWEI TECHNOLOGIES CO., LTD. Page 19All rights reserved
Common faults on downlink
Analysis
Downlink signal weakened: The symptom of this failure is that
the coverage of BTS or carrier shrinks. Follow the steps below to
handle this problem:
− Step1: Check whether the output power of TRX is normal.
− Step2: Check whether the standing wave ratio at jumper side
of CDU antenna port is normal.
− Step3: Check insertion loss of CDU transmitting path.
− Step4: Check whether the connectors involved in the RF
signal path are tightened
HUAWEI TECHNOLOGIES CO., LTD. Page 20All rights reserved
Common faults on uplink
Description No uplink signal BTS sensitivity weakened
Analysis No uplink signal
− Step1: Try another antenna feeder (CDU excluded) which has proven
to be normal to substitute the one without uplink signal▪ If the uplink signal at the new feeder recovered while the one at
the original feeder fails, then the original antenna feeder has
problems▪ If the phenomenon remains, then CDU has problems. Check
whether the cable connection between RXD OUT and HL_IN or
between HL_OUT and HL_IN is correct
HUAWEI TECHNOLOGIES CO., LTD. Page 21All rights reserved
Common faults on uplink
Analysis No uplink signal
− Step2: If the failure cannot be located yet, change the CDU, and
make the related record ; ▪ Notes: Restore the antenna feeder connection to it original
status − When changing the antenna feeder, make sure that:
▪ The two corresponding antenna feeders should be in the same
cell/sector ▪ The antenna connection should be restored to the original
status after locating the failure. Otherwise, the coverage of the
cell may be affected. This is the basic principle to obey when
using this method to locate the problem
HUAWEI TECHNOLOGIES CO., LTD. Page 22All rights reserved
Common faults on uplink
Analysis BTS sensitivity weakened
− If TTA is configured, first check whether there is any TTA alarm▪ If so, the TTA is working abnormally ▪ Otherwise, check the CDU antenna port feeding
» If no feeding is detected, then the CDU is faulty and needs to be changed
» If DC voltage is normal, then it is considered that the TTA is normal
− After confirming that TTA is normal, check the standing wave ratio of antenna feeder
▪ If it is too large, then the connection of antenna feeder RF path is poor or something else
▪ If the standing wave is normal, check the performance of CDU receiving channel, such as gain and noise factor
HUAWEI TECHNOLOGIES CO., LTD. Page 23All rights reserved
Common faults on uplink
Analysis
BTS sensitivity weakened
− The common faults can be located by adopting the
methods above. But it is inevitable that there are some
problems which can not be located by this method since
it is not a comprehensive test. For example, if the gain
decrease and noise factor increase of TTA is not
reflected in the working current, the problem cannot be
detected
− On such occasions, make clear records of the
operations which have been done so far for further
analysis
HUAWEI TECHNOLOGIES CO., LTD. Page 24All rights reserved
Common faults on feeder system
Description
CDU alarm (SWR, TTA)
Analysis
Standing wave alarm
− Check the SWR of antenna feeder (CDU excluded). If it is lower th
an 1.5, while CDU SWR alarm has been generated, this alarm sho
uld be regarded as a mis-alarm, and the CDU needs to be changed
− If the SWR is higher than 1.5, it is necessary to adjust the connecti
on of antenna feeder until it is lower than 1.5
− The installation specification requires the SWR be lower than1.3
HUAWEI TECHNOLOGIES CO., LTD. Page 25All rights reserved
Common faults on feeder system
Analysis
TTA alarm
− CDU measures the TTA feeding current through the antenna port. If th
e current is not in the normal TTA working current range (45~170mA),
CDU generates TTA alarm
− If the feeding current is normal while there is TTA alarm, then it can b
e considered as a TTA mis-alarm. Use another CDU to substitute the f
aulty CDU. Keep the faulty CDU for further analysis.
− If the feeding current is beyond limits, TTA is faulty and needs to be c
hanged
− For the migration site, it is also necessary to confirm the type of lightni
ng arrester when using TTA
HUAWEI TECHNOLOGIES CO., LTD. Page 26All rights reserved
Chapter 2 Typical CasesChapter 2 Typical Cases
Section 1 Antenna & Feeder FaultSection 1 Antenna & Feeder Fault
Section 2 Transmission FaultSection 2 Transmission Fault
Section 3 Hardware connection faultSection 3 Hardware connection fault
Section 4 Hardware faultSection 4 Hardware fault
HUAWEI TECHNOLOGIES CO., LTD. Page 27All rights reserved
Transmission Fault
Description
Alarm console
− “BIE board PCM loss of sync.”, “LAPD_OML alarm”
Traffic Statistic console
− The handover successful rate, call drop rate of the cell is
abnormal
Consumer complaint
− Cannot take a call, bad quality, call drop
HUAWEI TECHNOLOGIES CO., LTD. Page 28All rights reserved
Transmission Fault
Possible causes
Transmission device, board or E1 is faulty
− More transmission device, more fault
Transmission code is different (use CRC4 or not)
E1 connection quality is bad
− It will cause bad quality, even transmission broken
High BER (bit error rate)
− Microwave, HDSL transmission, especially in rainy
weather
The grounding system is faulty
HUAWEI TECHNOLOGIES CO., LTD. Page 29All rights reserved
Transmission Fault 1: E1 broken
Handling process Probably the reason may be that the E1, transmission device or board is
faulty− Step1: perform self-loop test over BTS and check whether the LIU
indicator of the TMU board is OFF. If no, it can be considered that the problem lies in TMU board. Please replace TMU board
− Step2: perform self-loop test over BSC and check whether the E1 indicator of BIE board is OFF. If not, it can be considered that the problem lies in the transmission device
− Step3: check the transmission NM and check whether a transmission related alarm is given. Based on the alarm (if any), you may judge whether the problem lies in the transmission device
− Step 4: if neither of them is faulty, it can be considered that the problem lies in the cooperation between the transmission device and BSC (or BTS)
HUAWEI TECHNOLOGIES CO., LTD. Page 30All rights reserved
Transmission Fault 2: OML alarm frequently
Handling process
Generally the reason maybe that the E1 grounding is not go
od, it cause interference, or transmission device is faulty
− Check the TMU in the BTS to check E1 grounding settin
gs
− Test the resistance of the E1 connector and that of the r
ack to measure the insulation situation
− Check whether the E1 connector in the DDF (when confi
gured) is grounded
− Check whether the E1 enclosure of the transmission dev
ice is grounded
HUAWEI TECHNOLOGIES CO., LTD. Page 31All rights reserved
Transmission Fault 2: OML alarm frequently
Handling process
− Check whether the system is in the single-point-grounded state. If
not, modify the system to the single-point-grounded state, then
check whether the trouble is removed
− If the trouble is still not removed after the above measures, it may
be considered that the problem lies in the transmission device, E1 or
E1 interface board. Check the connection and perform loop test
segment by segment to locate the fault
− Check the transmission NM and check whether a transmission
related alarm is given. If yes, please handle it as the related alarm
details
HUAWEI TECHNOLOGIES CO., LTD. Page 32All rights reserved
Typical case: OML broken for E1 grounding error
Description A site’s OML was frequently interrupted and the indicator
(corresponding to the E1) at BSC flashed− The equipment room was located at the top of a 300m-high hill. The
microwave transmission equipment room was 20m away− On the site, the maintenance engineer found the following
▪ The E1 was grounded, as was checked from the DIP switch▪ The E1 connector was insulated from the cabinet enclosure.
The working grounding cable of the rack was connected with that of the equipment room
▪ The DDF, an all-metal frame, was connected to the grounding cable of the equipment room. The E1 connector contacted the metal of the DDF
▪ No lightning arrester was configured for the E1▪ The E1 indicator flashed fast
HUAWEI TECHNOLOGIES CO., LTD. Page 33All rights reserved
Typical case: OML broken for E1 grounding error
Handling process
Step1: self-loop the E1 at the top of BTS cabinet and found the indicator of the E1 cable was OFF. It means BTS is OK.
Step2: self-loop the E1 on the DDF and found the indicator of the E1 cable was OFF. It means the E1 from BTS to DDF is OK
Step3: self-loop the BSC on the DDF and found the E1 indicator is OFF. It means the E1 from BSC to DDF is OK
Step4: power the TMU off and then on, the trouble still existed
Step5: remove the E1 from the DDF, the trouble still existed
Step6: disconnect the E1 at the top of BTS cabinet, power off the rack and removed the TMU. Test the resistance between the cabinet-top E1 connector case and the grounding cable of the rack and found they were insulated from each other (normal)
HUAWEI TECHNOLOGIES CO., LTD. Page 34All rights reserved
Typical case: OML broken for E1 grounding error
Handling process
Step7: change the TMU DIP switch that corresponded to the grou
nding of the E1 cable to OFF (ungrounded), the trouble still existe
d
Step8: remove the E1 connector from the DDF and change the T
MU DIP switch that corresponded to the grounding of the E1 cabl
e to OFF (ungrounded). The trouble disappeared
Step9: for confirming the reason, replace the TMU (with the E1 ca
ble ungrounded). Let the E1 connector case contact the DDF and
found the TMU E1 indicator flash fast
Restored the TMU to the original one and removed the E1 connec
tor from DDF, the trouble disappeared
HUAWEI TECHNOLOGIES CO., LTD. Page 35All rights reserved
Chapter 2 Typical CasesChapter 2 Typical Cases
Section 1 Antenna & Feeder FaultSection 1 Antenna & Feeder Fault
Section 2 Transmission FaultSection 2 Transmission Fault
Section 3 Hardware connection faultSection 3 Hardware connection fault
Section 4 Hardware faultSection 4 Hardware fault
HUAWEI TECHNOLOGIES CO., LTD. Page 36All rights reserved
Typical case: VSWR alarm for cable broken
Description
On BTS maintenance console, one TRX board in a sector was red, alarm
console showed TRX VSWR alarm.
− The site was just established
− On the site, the maintenance engineer found the following
▪ The RF cable between TRX and CDU was well connected
▪ The RF jumper in the CDU was well connected and also the
connection was right
▪ The RF cable between CDU and lightening arrester was well
connected
HUAWEI TECHNOLOGIES CO., LTD. Page 37All rights reserved
Typical case: VSWR alarm for cable broken
Handling process Step1: check all the connection from TRX to main feeder and
lightening arrester detailed and also re-tighten all the connections , the problem was still there, meant the connection had no problem
Step1: connect the CDU in current sector to the antenna in another sector that was ok before, the TRX was still red, that meant the antenna and feeder system had no problem , recovered the connection
Step2: connected the TRX to a CDU in another sector that had nothing alarm before, the TRX was still red, that meant the problem was in the TRX side, recovered the connection
Step3: change the faulty TRX to a new one, the TRX was still red , meant the TRX had no problem, recovered the connection
Step4: change the cables between the TRX and CDU , problem disappeared . The problem was that the cable was broken during transport
HUAWEI TECHNOLOGIES CO., LTD. Page 38All rights reserved
Chapter 2 Typical CasesChapter 2 Typical Cases
Section 1 Antenna & Feeder FaultSection 1 Antenna & Feeder Fault
Section 2 Transmission FaultSection 2 Transmission Fault
Section 3 Hardware connection faultSection 3 Hardware connection fault
Section 4 Hardware faultSection 4 Hardware fault
HUAWEI TECHNOLOGIES CO., LTD. Page 39All rights reserved
Typical case: site failed for TRX fault
Description
A site had no traffic and customer complained that they could not
make a call
− It was a omni-directional site and had only one TRX
− On the site, the maintenance engineer found the following
▪ All the boards was well in place and the indicators showed
that all the boards had no alarm
▪ Antenna and feeder was well connected
▪ The whole site was well grounded
▪ The power supply had no problem
HUAWEI TECHNOLOGIES CO., LTD. Page 40All rights reserved
Typical case: site failed for TRX fault
Handling process
Step1: checked OMC alarm console , found radio link alarm in the site
Step2: checked OMC BTS maintenance console, no boards was red
Step3: queried all the boards software, all were correct
Step4: changed the TMU board to a new one, problem was still there, recovered it.
Step5: reset TRX and changed all the connections to the TRX to new one , problem was still there, recovered it
Step6: changed the TRX to a new one , problem disappeared, meant the problem was in TRX
HUAWEI TECHNOLOGIES CO., LTD. Page 41All rights reserved
Chapter 1 General IntroductionChapter 1 General Introduction
Chapter 2 Typical CasesChapter 2 Typical Cases
Chapter 3 BTS Fault PreventionChapter 3 BTS Fault Prevention
HUAWEI TECHNOLOGIES CO., LTD. Page 42All rights reserved
BTS fault preventionBTS fault prevention
nip the fault in the bud
HUAWEI TECHNOLOGIES CO., LTD. Page 43All rights reserved
Hardware: installation specifications is most important!
give more attention to E1 connector
give more attention to feeder connector
give more attention to waterproofer of antenna and feeder system
Confirming the grounding and lightning protection
BTS fault preventionBTS fault prevention
HUAWEI TECHNOLOGIES CO., LTD. Page 44All rights reserved
Checking Running status
BTS maintenance console
− First, do “multi-site fault query”, then try to remove the fault acc
ording to the alarm description and suggestion. if you cannot re
move the fault at provisionally, confirm the reason of every fault
at least
Do calling test for every timeslot
BTS fault preventionBTS fault prevention
HUAWEI TECHNOLOGIES CO., LTD. Page 45All rights reserved
Summary
In this course ,we have learned how to
Find the fault
Judge the fault
Locate the fault
Remove and prevent the fault
www.huawei.com
Thank You