INVESTIGATING BSS PERFORMANCE
DEGRADATION
Description about 7745, 7743 and 7604 alarms
NSN CARE TEAM
Description
BSS is comprised of:
• hardware equipment
• software equipment
Degradation can be affected by both factors
Hence, the agenda will be:
to look for causes instead of software factors,
in order to improve BSS performance
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Analysis
• Analyze 7745, 7743 and 7604 alarms
• Their impact on performance degradation
“These alarms’ analysis are based on our personal experiences;
Hence to improve customer’s network:
please share your personal experience with us about any of these
alarms and their solutions, if any
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BSS Performance
Factor that affects BSS Performance:
TRX Performance
Hence, things that are important to check and maintain:
• TRX;
• Cells
• BTS performance (especially with its relation to 7745, 7743
and 7604)
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Required Steps
Step 1:
RESET TRX or
Particular
Time Slot.
Step 2:
CHECK NEIGHBORS
• Every cell has some neighbors.
• Neighbors must be created and
planned properly, in order to
maintain every call’s handover to
its neighbors.
“explanation to the figure above can be found in the notes”
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Required Steps (contd.)
Step 3:
Check TRX’s TSC (Training Sequence Code)
Make sure that TSC must
have same value with its BCC
No
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7745, 7743 alarms will be raised!
Check:
TRX’s TSC using ZERO command;
BCC of its cell using ZEQO command;
Make sure they have same value.
Required Steps (contd.)
Step 4:
Switch BCCH Frequency
to another TRX
Now, we will try to identify and analyze some example situations in which
7745 & 7743 alarms can be raised:
Example 1: 7745, 7743 at one TRX only
Example 2: 7745, 7743 at two TRX
Example 3: 7745, 7743 at all TRXs under same cell
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Required Steps (contd.)
Example 1: 7745, 7743 at one TRX only
Before you do the site visit:
• make sure that you have performed parameter check (TSC)
• make sure that you have checked neighbors
• make sure that you have performed the TRX test at the TRX remotely
If you go to do the site visit:
• remember to check the SMA cable at TX connector to WCXA of the TRX
• make sure it is properly connected
• replace the TRX, BB2F and SMA cables if needed
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Required Steps (contd.)
Example 2: 7745, 7743 at two TRX
Before you do the site visit:
• make sure that you have performed parameter check (TSC)
• make sure that you have checked neighbors
• make sure that you have performed the TRX test at the TRX remotely
For example : we have 3 or 4 TRX under one cell (i.e. TRX 1, 2, 3 and/or TRx4)
If: the alarms exist at TRX 1 and 2, and BCCH frequency is at TRX 1 or 2
then: try to switch the BCCH frequency to TRX 3 or TRX 4
If: the alarms still appear at TRX 1 or 2
then: it is possible that TRX 1 and 2 have a partial cross feeder.
If you go to do the site visit:
• replace TRX, BB2F, WCXA or DVXA if needed
• check alarms on the other sector to ensure your analysis.
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Required Steps (contd.)
Example 3: 7745, 7743 at all TRXs under same cell
Before you do the site visit:
•
•
•
•
make sure that you have performed parameter check (TSC)
make sure that you have checked neighbors
make sure that you have performed the TRX test at the TRX remotely
check alarms on the other sector
Many possibilities include:
full partial cross feeder, bad feeder quality and its connection,
interference, broken DVXA, etc.
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Remote Checklist
ü Parameter check
ü Neighbours check
ü Alarms collection at least 3 or 4 days before
ü Remote TRX test
ü Use ND report to strengthen your analysis. Usually ND report 195, 196
and 208 will be useful. For example :
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Remote Checklist (contd.)
Performance Analysis:
IF: band q5 value is under 90%
THEN: we suspect that the TRX have bad quality uplink or
downlink
Solution:
replace this TRX
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Site Visit Checklist
Make sure:
you have brought all of the spare part units & tools needed
you have brought site master for VSWR check
if feeder is broken, usually 7604 will raise
if there is bad connection of SMA cables at RxMain and
RxDiv side, it will also raise 7604 alarms
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If we have 7745, 7743 alarms in our network, what is really happening?
7745, 7743 alarm is usually related to degraded transmit quality
of one sector or one TRX.
Transmit quality degradation is affected by:
neighbors interference, different TSC-BCC value, etc.
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If we have 7745, 7743 alarms in our network, what is really happening?
If: all related parameters have been checked,
Then: we can find out from hardware by checking its transmit path from
TRx unit, Tx port, SMA-cables from Tx port to WCxA, WCxA itself, and
so on, until its feeder connection and antenna.
Thus:
7604 alarm is usually related to degraded receive quality of one
sector or one TRx.
From hardware point of view:
check its receive path from TRx unit, Rx main and RxDiv port,
SMA cables from Rx port to M2xA, M2xA itself, and so on, until its
feeder connection and antenna.
Conclusion:
if we have feeder antenna cable broken, it may raise 7745,
7743 and 7604 as feeder is used as transmit and receive paths.
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Summary
Replace TRx
Replace BB2F
Replace WCxA
Replace SMA cables
Replace DVxA
Replace Feeder cable
Replace Lightning Arresster
Replace sectoral antenna
Replace feeder connector at DVxA
Change TSC value
Change BCCH frequency
Fix the partial cross feeder connection
Fix the full cross feeder connection
Replace VXTB (still in question? under investigation)
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Tips to Remember
Ø Remember to collect as much information as you can even from all
alarms, trx test, NDreport, etc
Ø Then make a deep analysis to locate the suspect fault
Ø These alarms clearing will take many days, because after we perform
some replacement, troubleshooting, etc, we have to monitor the result,
at least for one day.
Ø So, it is better if you take notes about all the activities that have been
done on a site.
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Thank You
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