GSM Network Interference & Solutions

8/18/2019 GSM Network Interference & Solutions

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GSM Network Interference &

Solutions

ZTE university


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Training goals

To know the classification of interference;

To master the analytical methods of

interference problem;

To master the flow of handling interference

problem;

To know the analytical tool of interference

problem;

To be able to handle common interferenceproblems.


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Contents

GSM Frequency Allocation

Phenomena & Classification of Interference

Flow of an!ling Interference Pro"lem

Analytical Metho!s of Interference Pro"lem

Ty#ical Cases


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GSM re!uency "llocation

Frequencyband

ULfrequency

DLfrequency

Duplexinterval

Band widthCarrier

frequencyinterval

EGSM#GSM$%%

&&%M'()$*+M'(

$,+M'()$-%M'(

+M'( /+M'( ,%%k'(

01S*&%%*2*%M'()*2&+M'(

*&%+M'()*&&%M'(

$+M'( 2+M'( ,%%k'(


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Contents





Ty#ical Cases


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3henomena of 4nterference

1all drop

5nable to

establish callsMetallic noise

6n7and7off

speech

3oor

speech!uality

3henomena


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1lassification of 4nterference

4nternal interference

4nternal interference refers to unreasonable fre!uency

planning and e!uipment hardware faults8 which could lead to

decrease in network service !uality.E9ternal interference

E9ternal interference refers to unknown signal source out of

the network8 whose e9istence could seriously disturb the

network:s signals and lead to decrease in service !uality.

5 interference

0 interference


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4nternal 4nterference


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acent cell relation may be set

unreasonable in network planning because of

planning tools or human mistakes .

4nterference will be reflected in too large0


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4nternal 4nterference < due to e!uipment fault

4nterference caused by e!uipment

fault=

?adio fault of CTS is mainly caused by

defective 5 unit parts.


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E9ternal 4nterference

0efinition= E9ternal interference refers to other interferences

caused by e9ternal factors8 but not due to e!uipment

fault or unreasonable fre!uency planning.

1ommon e9ternal interferences= due to wide7band repeater;

due to 10M" system Dtrailing signal;

due to signal >ammer;

1haracteristic= 4t:s hard to detect this kind of interference without

specific devices.


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Contents





Ty#ical Cases


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low of 'andling 4nterference 3roblem

Confirminterference

range

Check

frequency,change

frequency

points

Complete

Poor speech

quality due

to

interference

Check andchange

TRX

Checkexternal

interference

Check

VSWRantennadi!iderdupl

exer

$ne cell

Interference

e%ists

$ne

T'

Interference

e%ists

Interference

e%ists

"ny ne# sites$ %f thorough changeof frequency parameters taken

recently$

Se(eral

cells


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Contents





Ty#ical Cases


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"nalytical Methods of 4nterference 3roblem

"nalytical

&ethods of

%nterference

Pro'lem

Statistical

analysis of

net#ork

performance

indicators

"nalysis of

parameter

checking

%n!estigation

of hard#are

fault

(ri!e Test

and (ialing

Test

)xternal

interference

test


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"nalytical Methods of 4nterference 3roblem 7 Statistical analysis of network performance indicators

Statistical analysis of net#ork performance indicators

Statistics of interference 'and * When TC+s are in idle status,- noiseinterference is constantly 'eing measured .TS, and themeasurement result #ill 'e analy/ed, and interference le!el #ill 'e sent to .SC in 0 le!els1 。

Statistics of hando!er due to -(- interference * We can 2udge #hether interference exists through statistics of hando!ercaused 'y -(- interference1

Collection of -(- R3 samples during speeches * Rx3ual isan indicator to reflect speech quality, #hich is 'ased on errorrate and falls into 4 grades 56 ～ 781


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"nalytical Methods of 4nterference 3roblem 7 Statistical analysis of network performance indicators

1orresponding relation between ?9@ual and Cer


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7 "nalysis of parameter checking

Check

parameters

related to

transmitting

po#er

Check

parameters

related to

transmitting

po#er

Check antenna

engineering

parameters

Check antenna

engineering

parameters

Check frequency

planning

parameters

Check frequency

planning

parameters

Check

parameters

related to skip9

/one co!erage

Check

parameters

related to skip9

/one co!erage

3arameter

checking


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) 1hecking hardware fault

1hecking hardware fault

:&CR #arning analysisChecking latent equipment fault


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) 1hecking latent e!uipment fault

.lock the t#o

input #ays ofTRX, o'ser!e

- interference

'and; if it


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) 0rive Test and 1all @uality Test

*ri(e Test an! Call +uality Test 0rive test can effectively detect the location and

degree of interference8 which is convenient for

analy(ing the cause of interference.

4n 1@T8 we can actually feel the speech !uality

at areas being interfered8 and we can see call

!uality class on the test phone.


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) 0rive Test and 1all @uality Test 0T parameters=

1F4= co7channel carrier7to7interference ratio

%+ual , - . / 0 1 2 3

1F4dCH ,/ *$ *2 *+ */ ** &


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) 0rive Test and 1all @uality Test 0T parameters=

S@4 ： S3EE1' @5"4TI 4B0EJ is the comprehensivedescription of CE?8 E? and '"B06KE? EKEBT by TEMS.


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) Test of e9ternal interference 1onfirm e9ternal interference with S4TEM"STE? =

Test of 5 interference; 1onnect the input port of fre!uency7sweep

generator to the output port of divider to increasethe degree of sensitivity8 as shown in the figure.


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) Test of e9ternal interference 1onfirm e9ternal interference with S4TEM"STE? =

persistent strong level e9ists within the bandwidth of,%M'(8 we can conclude that serious 5 interferencee9ists.


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) Test of e9ternal interference

1onfirm e9ternal interference with ICT,+%= Make 5 interference analysis of GSM $%%M 5 fre!uency

band with fre!uency scanning meter7BetTek "naly(erDTELcompany. The model we usually use is ICT,+%.

1onnection method of ICT,+%=

6ne is to use its own test antenna ;

6ne is to obtain interference information through connection to

the output port of divider.


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1onnection method using ICT,+% to test 5 interference=

Antenna

C(

YBT 250

Feeder


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Aave graph of 5 interference tested by ICT,+%= This output is the average value of the test results of oneminute8 which shows the fre!uency and strength ofinterference. 3ersistent observation is needed to confirmif the interference continues.


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) Test of e9ternal interference Time scatter graph of 5 interference tested by ICT,+%=

TEL fre!uency scanning meter features in threedimensional recording of time8 fre!uency and signal.Thevertical bold red lines in the graph represent the timeduration8 signal level strength and fre!uency .

!ertical

axis=time

Colour

spectrum=strength

hori/ontal

axis=frequency


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Contents





Ty#ical Cases


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Typical case *= 3roblem description

Since &arch >66?, an operator has recei!ed a lot of

complaints a'out poor speech quality; sometimes calls

e!en couldn


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Typical case *= 3roblem analysis

"t the

'eginning #e

thought it #as

caused 'y

poor signal1

"fter on9site

test, #e found

it #asn


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Typical case *= 3roblem handling process—STE3*

Test - interference #ith @.T>?6 connected to C(1 C(&" #a!e

form #as strong #hen #a!e filter #asn


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Typical case *= 3roblem handling process—STE3*

%n the three dimensional graph of interference tested 'y @.T>?6, the

C(&" #a!e form #as strong and the #a!e form of BS& 'ackgroundnoise on the right #as high in a long period of time1


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Typical case *= 3roblem handling process—STE3,

se C(&" #a!e filter to eliminate C(&"interference1

"ntennaCommon

C(

ICT ,+%

eeder

C(&" #a!e

filter


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When C(&" #a!e filter #as adopted, C(&" #a!e

form #as o'!iously #eakened, 'ut it #as still strongat some certain point; the 'ackground noise in BS&

frequency 'and #as also reduced1


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.ecause of C(&" #a!e filter, the - interference in BS&

frequency 'and reduced greatly1


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Typical case *= 3roblem handling process—STE3/

With the aim to eliminate C(&" interference, adopt

%RC( DC(&" #a!e filter1

"ntennaC(&" #a!efilter

@.T >?6

%R C(


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"doption of %RC( ＋ C(&" #a!e filter can effecti!ely

filter C(&" #a!es to 'elo# 9E6Fd'm1 This kind of filteringeffect can help completely a!oid C(&" net#ork interfering

BS& - net#ork1


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"doption of %RC( ＋ C(&" #a!e filter can eliminate

C(&" #a!e form to a great extent; during the test period,C(&" interference #as almost eliminated1


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Typical case *= Summary

The interference source #as from C(&" system1

Through comparisons of tests a'o!e, #e can see after%RC(DC(&" #a!e filter #as used, call quality

o'!iously impro!ed1


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@uestions for thinking

'ow is interference resulted from wrongsetting of transmitting power7relatedparameters

Ahat is the flow of checking e9ternalinterference


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Documents

GSM Network Interference & Solutions