Summary
High RTWP will cause low
performance in CSSR and CCSR.
Currently the background
noise is -106dBm, if the RTWP is higher than -95dBm then the load factor will
more than 90%, CAC will be overload congestion status.
To troubleshooting a high
RTWP issue, please refer the procedure as below.
Analysis procedure
1 Check Alarm
1.1
Check
the hardware alarm.
Like RF
Module Rx Branch RTWP Difference Too High Alarm etc.
1.2
Check
whether VSWR alarm exists.
Command:
DSP VSWR
If have alarm or high VSWR (more
then 11), first escalate to BSS team, then assistant them to check whether it
is hardware problem or interference.
2 Check NodeB configuration in NodeB LMT
2.1
Check
uplink RF sensitivity
Command: DSP RFDESPARAM and DSP DESENS
Usually the value of these two
parameters should be 0, if it is not 0, fallback to 0 to check whether RTWP can
restore normal.
2.2
Check
Uplink Attenuation Value
Command: LST RXATTEN
This configuration will affect
the RX gain. If TMA is not used, then no need to configure it; and if TMA is
used then we should configure it as per TMA gain.
The default value is 0. (Without
TMA)
2.3
Check the intermodulation interference
If
primary RTWP is very high but secondary RTWP is normal, it may be caused by
this case.
Method: suggest to shut off the transmit
power then monitor the RTWP. If RTWP become normal after transmit power is
switched off and RTWP become high when transmit power is switched on, we can
suspect that it may caused by feeder joint problem, need BSS team check the feeder
connection (primary feeder).
Command to shut off the transmit
power:
SET TXSW
3 Check the interference feature
3.1
Check
the RTWP trend
Check the RTWP counter VS.MeanRTWP,
VS.MaxRTWP, VS.MinRTWP. Make a chart to show the interference trend in one day.
Trace the RTWP in NodeB LMT;
trace 24hours in one day and save the result to txt format and make chart to
show the primary and secondary RTWP trend in one day.
Through the chart, we can know
the interference feature:
What time the interference
happens, in day or night; in busy hour or always….
How about the consistency between
primary and secondary RTWP trend?
Through the trend we can analyze
whether heavy traffic causes the high RTWP; whether external or internal
interference?
3.2
Check
the site information
Check it is indoor site or
outdoor site.
For indoor site, need collect
the information as below:
l Whether
2nd carrier is implemented or not?
l Whether
the combiner is used? Combiner frequency is match or not?
For outdoor site, need collect
the information as below:
l How
many sectors experience high RTWP?
l How
about RTWP status of nearby sites?
l Is
repeater located near the site?
4 Find the interference source
4.1
Judge
external or internal interference
Disconnect the jumper (jumper at the cabinet side) from the
NodeB, and then trace the RTWP.
If
RTWP is still very high after disconnection, that means NodeB have problem.
Need BSS team check the RF module.
If RTWP
become normal after disconnection, that means NodeB have no problem. We can
conclude that the problem may exist in Feeder system or external interference.
BSS
team can help to do the VSWR test for the feeder and jumper to check the feeder
system ok or not. Or we can change jumper to verify.
4.2
Troubleshoot
the interference
Do the frequency scanning in
NodeB LMT.
From the result we can check
whether there is strong interference from some special frequency band.
If from the result we find the
interference, we need visit the site to find the interference source. We can:
l If
frequency scanning tool available (like frequency analyzer), we can use tool to
scan the interference.
The method to check the
interference by scanning tool:
Switch off the transmit power of
the interference sector. Make the test antenna of the tool toward the direction
of the antenna of the NodeB (follow the same orientation, same down tilt, also
the same attitude) and scan the interference. By this method we can check
whether external interference exists or not.
l If
frequency scanning tool unavailable, we can adjust the azimuth of the interference
to check from which direction the external interference comes from.
4.3
Common
methods
l NodeB
have two sets of RTWP, primary and secondary RTWP; if only one set of RTWP is
abnormal but the other set is OK. We can swap the primary feeder with the
secondary feeder to check whether high RTWP swap or not.
l If
two sectors are very near but only one sector experience high RTWP and the
other sector is OK. We can swap the feeder of these two sectors at the antenna
side to check whether high RTWP will swap from one sector to the other.
By these swap actions, we can
analyze the interference feature and find the interference source.
| Check List | ||||
| SN | Check Items | Check Method | Check Result | Remark |
| OMC Information Collection | ||||
| 1 | Uplink RF sensitivity | MML
command: DSP RFDESPARAM / DSP DESENS |
||
| 2 | Uplink Attenuation Value | MML
command: LST RXATTEN |
||
| 3 | Check the TMA gain(if TMA used) | MM
command: LST TMAGAIN |
||
| 4 | whether nearby sites also have the same high RTWP feature | check the RTWP counter or realtime RTWP monitor | ||
| 5 | Describe the RTWP feature (like it is always high or some times high ). What is the RTWP range | MML
command: STR RTWPRTTST (NodeB LMT) real time RTWP monitor (both primary and secondary RTWP) |
||
| 6 | analyze the interference feature | compare the traffic load with the RTWP. Check whether high traffic or interferece cause the high RTWP. | ||
| 7 | LMT uplink frequecny scannig | do the scanning in NodeB LMT (need block the sector) | ||
| 8 | Check the intermodulation | MML
command: SET TXSW switch off the downlink tansmit power and monitor whether interference disapper or not |
||
| Site visit and information collection | ||||
| 10 | Visit the site | Whether 3G system shared antenna with 2G or not? Whether TMA used or not? Whether repeater is located nearby? | ||
| 11 | whether primary and secondary RTWP are both have high | swap the primary feeder with the secondary feeder to check whether high RTWP swap or not. | ||
| 12 | differentiate internal or external interference | Disconnect the jumper from the cabinet and then monitor the RTWP. | ||
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