05 dt analysis - how to analyze quality issue by dt

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



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



HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential


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.





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.




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




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





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




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.





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





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.




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).


SolutionRxQuality Issue




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).


SolutionRxQuality Issue



Thank youwww.huawei.com

05 dt analysis - how to analyze quality issue by dt

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