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8/3/2019 05 DT Analysis - How to Analyze Quality Issue by DT
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HUAWEI TECHNOLOGIES CO., LTD.
www.huawei.com
Huawei Confidential
Security Level:2008-11-3
How to Analyze QualityIssue by DT
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Outline
• Downlink RxQuality Issue
What is RxQuality Issue
The problems raised by RxQuality issue
• How to detect quality issue by DT
Bad Quality due to Signal Strength – FER is Bad
Bad Quality due to Signal Strength – FER is OK
Bad Quality due to C/A Interference
Bad Quality due to Time Dispersion
• The solution to RxQuality issue
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What is RxQuality Issue
Bad RxQuality is one of the biggest problems in a Network. The
RxQuality that a network operator can offer to customers mostlydepends on the RxLevel and the interference of the network.
There are two types of RxQuality problems, uplink RxQuality
and downlink RxQuality. We can only detect downlink
RxQuality problem by DT, however, if the downlink RxQuality
is bad in one cell, there is a risk that there would be problems on
the uplink as well.
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What is RxQuality Issue
BadRxQualit
y
GoodRxQualit
y
RxQuality is divided into eight levels which are from 0 to 7, the level 0 is the
best and the level 7 is the worst.
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The problems raised by RxQuality issue
Bad RxQuality may raise many problems, such as:
Difficulty in accessing the network
Dropped calls due to bad quality
Poor handover success rate
Low MOS value
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Bad Quality due to Signal Strength – FER is
Bad As the signal strength drops
down, the quality of the call
becomes worse being effected by
interference and/ or fading.
Consequently the system becomes
weaker to handle the interference.
Drop calls and ping pong
handovers usually happen in such
environments.
RxLev (Serving Cell and
Neighbors) is not high enough
(about less than -95dbm).
Maybe there are interferences
in this region for bad FER.
Bad RxLev
Bad RxQual
Bad FER
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Bad Quality due to Signal Strength – FER is OK
This case is similar with
the previous except for FER.
Signal strength is also bad
in this, but FER is still fine.
FER is ok, it means that
there is no obvious
interference in the area.
The coverage is usually the
problem in this situation.
Bad RxLev
Bad RxQual
Fine FER
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Bad Quality due to C/A Interference
There is adjacent channel
interference in this case and
the RxQuality is not good.
Bad Quality due to Adjacent
Interference.
Adjacent BCCH between
best server and best neighbor.
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Bad Quality due to Time Dispersion
Time dispersion is caused by the reflections. The MS uses all or most of the received power, instead of only the direct signal, there is a larger probability
to decode the information. So the RxQuality will be very bad perhaps.
Site
MS
Reflecting object
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Bad Quality due to Time Dispersion
The MS is near the
cell, it is less than 1
mile far away.
The RxQuality is very bad for the bad C/R, in
which, R stands for
reflected signal and C
stands for original
signal.
The TA is too high.
It is because that TA
stands for the reflected
signal but the original
signal.
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The solution to RxQuality issue (1)
Find out the interference source or /and
adjust the azimuth or downtilt of the
antenna or /and adjust the power of the
transmitter(s).
Bad Quality due to Signal Strength – FER is Bad
There is no obvious interference in this
situation. Adjust the azimuth or
downtilt of the antenna or /and adjust
the power of the
transmitter(s).
Bad Quality due to Signal Strength – FER is OK
SolutionRxQuality Issue
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The solution to RxQuality issue (2)
Avoided adjacent frequencies in the same cell and
preferably in neighboring cells as well.Bad Quality due to C/A Interference
Move the site to be placed near the reflecting
object to prevent time dispersion. Another efficient
solution is to modify the antenna arrangement, either
in azimuth (horizontally) or by tilt (vertically).
Bad Quality due to Time Dispersion
SolutionRxQuality Issue
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