01 dt analysis - how to analyze crossed feeder issue by dt - copy

HUAWEI TECHNOLOGIES CO., LTD.

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Huawei Confidential

Security Level:2008-11-3

How to Analyze Crossed Feeder Issue by DT

Outline

• What is crossed feeder issue

• The problems raised by crossed feeder issue

• How to detect crossed feeder issue by DT

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

What is crossed feeder issue (1)

The term crossed feeder is used to describe the problem that arises when

the feeders for two or more sectors in a site are inadvertently connected

incorrectly. For Example, consider a new cell site that has three sectors,

A, B, and C:



� The crossed feeder problem would arise

if the feeder for sector A is connected to

sector C and vice versa. When this

happens, the sectors typically continue

to provide good coverage. However, the

network parameters for the two sectors

are also reversed. For example, the

parameters storing the sectors' BCCH

and lists of adjacent sectors would be

swapped.

� For example, suppose we run a drive

test through the area served by the cell

whose feeders are crossed display the

ServBCCH attribute on the Map while

the cell sectors are colored by BCCH.

This is what we might see:



� There are server types of crossed feeder:

� Crossed transmit feeders

� Crossed receive feeders

� Crossed transmit and receive feeders


The problems raised by crossed feeder issue

Crossed Feeder SituationNormal Situation


The problems raised by crossed feeder

issue

� Crossed feeder will raise many problems, such as:

� A greater degree of interference

� A poor uplink signal strength

� A poor performance of handover


How to detect crossed feeder issue by DT


Crossed transmit feeders will result in the swap of 2 or

more sectors BCCH frequency and TCH’s. As the sectors are

pointing in the incorrect direction, performance will suffer as

the frequency plan has been changed and a greater degree of

interference will be present.

In DT, we will find that the handset receives the single

which shouldn't have been received in the current cell.



In the example shown above, point A is in the area of coverage of Cell D3,

but the handset at point A receives the stronger signal of Cell D2. It

indicates that TX feeders were crossed between Cell D3 and Cell D2.





It is not easy to detect this fault by DT, because the BCCH

frequencies will appear exactly as they were designed. However,

the statistics for the cell would help us to detect the fault:

� Uplink signal strength would be very poor

� Link balance would be larger than expected

� Handover success rate would be very low




The MR measurement is very useful in detecting this type of

feeder cross.

Uplink-and-Downlink Balance Measurement per TRX and

TCH Receive Level Measurement per TRX maybe are the

most useful statistics . For example, if the uplink-and-downlink

balance is always in level 10 or level 11, we can consider that

there is something wrong in the receive path of the site, crossed

receive feeder is a possible problem.



� Crossed transmit and receive feeder

The symptom is similar with the fault “crossed transmit

feeder”, and we can detect the fault by DT easily .

Thank youwww.huawei.com

01 dt analysis - how to analyze crossed feeder issue by dt - copy

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