how to analyze crossed feeder issue by dt

7/30/2019 How to Analyze Crossed Feeder Issue by DT

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HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

Security Level:2013/5/9

How to Analyze Crossed Feeder

Issue by DT


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Outline

What is crossed feeder issue

The problems raised by crossed feeder issue

How to detect crossed feeder issue by DT


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HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 3

What is crossed feeder issue (1)

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

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

incorrectly. For Example, consider a new cel l si te that has three sectors,

A, B, and C:


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The crossed feeder problem would ari se

if the feeder for sector A is connectedto sector C and vice versa. When this

happens, the sectors typical ly continue

to provide good coverage. However, the

network parameters for the two sectors

are also reversed. For example, the

parameters stor ing the sectors' BCCH

and l ists of adj acent sectors woul d be

swapped.

For example, suppose we run a dri ve

test through the area served by the cel l

whose feeders are crossed display the

ServBCCH attribute on the Map whil e

the cel l sectors are colored by BCCH .

Th is is what we might see:


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There are server types of crossed feeder:

Crossed transmit feeders

Crossed receive feeders

Crossed transmit and receive feeders


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The problems raised by crossed feeder issue

Crossed Feeder SituationNormal Situation


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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


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Crossed transmit feeders will result in the swap of 2 or

more sectors BCCH frequency and TCHs. 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.


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CellA CellB

Tx

Tx

Tx

Tx

Div Div

DivDiv

CellA CellB



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CellA CellB


BCCH BCell ID B

Ms power control low (0-8)

with good RXlev

After HO low RxLev

Unexpected HOs

BCCH A

Cell ID A


with good Rxlev

After HO low RxLev

Unexpected HOs


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I n 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. I t

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



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Cell border Cell border

Site 3Site 2

Site 1

AA

A

BB

B

Exercise


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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


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How to detect crossed feeder issue by DTCrossed receive feeders

CellA CellB

Tx

Tx

Tx

Tx

Div Div

DivDiv

CellA CellB


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CellA CellB

BCCH ACell ID A


with good RXlev

After HO low RxLev

Unexpected HOs

BCCH B

Cell ID B


with good Rxlev

After HO low RxLev

Unexpected HOs



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

receive feeder is a possible problem.


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Site 3Site 2

Site 1

AA

A

BB

B

Exercise


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Crossed transmit and receive feeder

The symptom is similar with the fault crossed transmit and

receive feeder, and sometimes we can detect the fault by DTeasily .


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How to detect crossed feeder issue by DTCrossed feeders both two transmit &

two receive

CellA CellB

Tx

Tx

Tx

Tx

Div Div

DivDiv

CellA

CellB


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CellA CellB

BCCH B

Cell ID B

BCCH A

Cell ID A



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Crossed transmit - receive feeders


Site 3Site 2

Site 1

AA

A

BB

B

Exercise


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How to detect crossed feeder issue by DTone transmit & one receive feeders

crossed

CellA CellB

Tx

Tx

Tx

Tx

Div Div

DivDiv

CellA CellB


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CellA

RxLevA ~ RxLevB

BCCH A, BCCH A

Cell ID B, Cell ID B


with good RXlev

After HO low RxLev

Unexpected HOs



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Crossed transmit - receive feeders


Site 3Site 2

Site 1

AA

A

BB

B

Exercise


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How to detect crossed feeder issue by DTInter system antenna swap (GSM CDMA)

CDMA

GSM

In this scenario when feeders has been

swapped between antenna ports, its very

difficulty to recognize it during DT. Only

abnormal coverage area and bad

performance could be the reason for this.


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Receive

MulticouplerDual Duplex

UnitTRX RF Units

Du

plexerLNA

DuplexerLNAsplitter

splitter

TX

RX maindiv

TX

RX maindiv

Example:2 TRX/cell

Antennas

TX/RX-divant

XX

X

TX/RX ant


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Example:4 TRX/cell

Dual Duplex

Unit

AntennasTRX RF Units

TX

RX maindiv

DuplexerLNA

Duplexe

rLNA

splitter

splitter

splitter

splitter

TX

RX main

div

TX

RX maindiv

TX

RX maindiv

WBC

WBC

Receive Mul ticouplers

& Wideband Combiners

TX/RX ant

TX/RX-divant

XX

X


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how to analyze crossed feeder issue by dt

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