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SiemensTrainin Centerfor C ommunicationNetworks

Interference Reduction

Objectives

The participant is able to

use methods for interference reduction

Contents

1 Power Control1.1 Objectives1.2 Measurement Preprocessing for Power Control1.3 Power Control Decision1.4 Power Control Execution

2 Frequency Hopping2.1 ntro!uction2.2 Frequency Hopping "ystem

3 Discontinuous #ransmission D#$4 C%annel &llocation !ue to nterference 'evel

5 Concentric Cells

6 Exercises

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1 Power Control

1.1 Objectives

The ob"ecti#e of po$er control is to adapt the transmit po$er of the %& as $ell as of the'T& to the reception conditions. (or e)ample a mobile station %& 1 located near the the'T& can use a lo$er transmit po$er than a mobile station %& 2 at the ed*e of a cell toachie#e the re+uired uplin, +ualit .

(#"

M" )

#$P*+

M" ,

#$P*+

(i*. 1

There are t$o ad#anta*es of po$er control

reduction of the a#era*e po$er consumption /especiall in the %&

reduction of the interference e)perienced b cochannel /for ad"acent channel users.

o$er control is applied separatel for the uplin, and the do$nlin, and separatel for

each lo*ical channel . t can be enabled disabled usin* the follo$in* a*s /administered$ithin the 7 ob"ect

&peci9cation :ame ;' :ame %eanin*

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1.2 Measurement Preprocessing for Power Control

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An control loop is based on measurements of the controlled s stem parameters. (or purposes for each call in pro*ress and for both lin,s /do$nlin, uplin, measurementsof

recei#ed si*nal le#el

recei#ed si*nal +ualit

are carried out o#er each &A > multiframe $hich is 104 T;%A frames /480 ms for a T > and 102 T;%A frames /4 1 ms for a &; >.

multiframe the %& sends in the ne)t &A > messa*e bloc, the do$nlin,measurements on the dedicated channel /a#era*ed o#er one &A > multiframe #ia the%easurement 7eport messa*e to the ser#in* T7X of the 'T&. This means that an&A > messa*e $ill report the a#era*ed data for the pre#ious reportin* period onl . The

T7X performs the uplin, measurements on the dedicated channel. The measurementreports /uplin, and do$nlin, referrin* to the same &A > multiframe are used as inputparameters for the %easurement 7eport a#era*in* procedures implemented $ithin the'T&.

This means that the ad"ustment of the transmit po$er of the %& and the 'T& is based onfollo$in* measurement #alues /refer to hapt. 4.2.1 %easurement reprocessin* for>ando#er

7X?

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c The 'T& ta,es care that the Efull po$erF part from the ' > carrier is correctlsubstracted from the measurement reports.

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Parameters for measurement preprocessing power control

&peci9cation :ame ;' :ame 7an*e %eanin*

A=B A?= A@7B A? AQUALPC

1-31 A#era*in* $indo$ siHe for 7XB A?#alues used for po$er controldecisions

=B A?= A@7B A?WQUALPC

1-3 ei*htin* for 7XB A?=( ?? #alues

A=?

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1.3 Power Control ecision

(or po$er control decision the a#era*e #alues of 7X?

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Power Control ecision

'/+$-.&'/$$/P

+$'E156

./+$-.&'/$$/

7

8

+$-.&'

PO*/+ED/"#EP/" 3E

'/+$'E1/$$/P ./+$'E1/$$/P

Power Decrease9goo! quality:

Power Decrease9goo! level:

Power ncrease9ba! level:

Power ncrease9ba! quality:

(i*. 5

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The follo$in* inte*rit conditions on the po$er control thresholds ha#e to be obser#ed

=7XB A?=XX= M ?=7XB A?=XX= XX G ? ;?Q

?=7X?

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(or do$nlin, po$er control the ran*e is determined b the ma)imum output po$er 'T& of the 'T& and the static reduction '&=TX 7=7 multiframes *i#en b the parameter = D:= :T

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The processes and time relations are illustrated in the 9*ure belo$

request#$P*+

(2) requested transmit power not confirmed

(1) requested transmit power confirmed

CO;F/#$P*+< +E-/#$P*+

suspension of PC !ecisionP/CO;/ ;#E+1&'

P/CO;F +M

resumePower Control

resumePower Control

9,:9):

time

(i*.

Time relations for po$er control e)ecution

case 1 re+uested transmit po$er con9rmed

case 2 re+uested transmit po$er not con9rmed

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Parameters for Power Control '(ecution

&peci9cation :ame ;' :ame

Db"ect

7an*e %eanin*

%&=TX 7=%AX %&TX %AX 'T&'

2...15 S&%0...15 ; &

2 d'

ma)imum TX 7 an %& ma use inthe ser#in* cell2 G 3! d'm 15 G 13 d'm /S&%!000 G 30 d'm 15 G 0 d'm /; &18007an*e for uplin, po$er control13 d'm ... %AX /S&% phase 15 d'm ... %AX /S&% phase 20 d'm ... %AX /; &%AX G %in /%&=TX 7=%AX po$er class of the %&

'&=TX 7=7

%a)imum inter#al for $aitin* for acon9rmation of the ne$ transmitpo$er le#el.

= D:= :T

%inimum inter#al bet$een chan*es of the 7( transmit po$er le#el /time forsuspension of a po$er controldecision after a po$er controle)ecution

(i*. 87elations to be obser#ed

To a#oid an oscillatin* po$er control due to le#el the follo$in* ine+ualit shall beful9lled

D =7

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2 )re*uenc+ %opping

2.1 Introduction

The principle of (re+uenc >oppin* used $ithin S&% is that successi#e T;%A bursts of aconnection are transmitted #ia diJerent fre+uencies - the fre+uencies belon*in* to therespecti#e cell accordin* to net$or, plannin*. This method is called &lo$ (re+uenc>oppin* /&(> since the transmission fre+uenc remains constant durin* one burst /incontrast to fast fre+uenc hoppin* $here the transmission fre+uenc chan*es $ithin oneburst .

The eJect of (re+uenc >oppin* is that lin, +ualit ma chan*e from burst to burst i.e.a burst of hi*h bit error rate ma be follo$ed b a burst of lo$ bit error rate since

short term fadin* is diJerent on diJerent fre+uencies

the interference le#el is diJerent on diJerent fre+uencies.

&ince the information for one speech frame is interlea#ed o#er 8 successi#e burst andthe successful decodin* of a speech frame depends on the a#era*e bit error rate o#erthese 8 bursts a speech frame ma be decoded e#en if there $ere some bursts $ith bad+ualit . ithout hoppin* in *eneral all 8 bursts are either *ood or bad. >ence the bene9tof (re+uenc >oppin* is a ,ind of e+ualiHation of the lin, +ualit of all connections b

fre+uenc di#ersit - a#era*in* of short term fadin*

interference di#ersit - a#era*in* of interference.

To achie#e interference di#ersit connection in diJerent co-channel cells ma not hop ina s nchronous but in an uncoordinated $a . The correspondin* hoppin* mode is called/ seudo 7andom >oppin* uncorrelated hoppin* se+uences are used in diJerent co-channel cells. >ence the probabilit of a collision /interference of t$o speci9cconnections in co-channel cells is in#erse proportional to the number of fre+uenciesused in the hoppin* se+uence. A hoppin* se+uence is characteriHed b the so-called>oppin* &e+uence :umber >&:.

n S&% there are 63 uncorrelated pseudo random hoppin* se+uences />&: G 1 ... 63 .(urthermore there is a clic >oppin* %ode characteriHed b >&: G 0.

These t$o >oppin* %odes are illustrated in (i*. !.

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2= interference averaging

> = no optimum frequency !iversity

2= optimum frequency !iversity9averaging of +ayleig% fa!ing:

> = no interference averaging

connection ,

connection )

cell , 9same frequencies as cell ):cell )

frame

Hopping "equence ;umber H"; < )

Pseudo Random Hopping:

f?

f6

f,f)

f?

f6

f,

f)

frame

e@g@ H"; < ,8 for reuse cellcollision probability < ) A no@ frequencies

f?

f6

f,

f)

frame

Ho in "e uence ;umber H"; < 7

C clic Ho in :

(i*. !

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)re*uenc+ %opping ,ain-

1. A#era*in* of &hort Term (adin*

&i*nal to noise ratio re+uired to obtain 0.2 N residual 'oppin* and Antenna ;i#ersit Sain for S&%

(or lo$ speed of the %& each doublin* of the hop step number results in an 1.5 d'impro#ement. (or hi*her speed and for hill terrain fre+uenc hoppin* does not *i#eadditional *ain since short term fadin* is alread a#era*ed b motion. The *ain of (>increases $ith increase number of fre+uencies.

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2. nterference ?e#els

n the follo$in* a simple e)ample for the eJect of interference a#era*in* is *i#en

?et us assume that if the sum of all interferences is so hi*h that is less than 5.0 /d' a call is disturbed. t is recommended to obtain a R 10 d' in most areas of a cell.e *i#e an e)ample for ratios in a cell $ith 4 fre+uencies $ith and $ithout fre+uenchoppin*.

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2.2 )re*uenc+ %opping !+stem

n this chapter $e discuss the implementation of a fre+uenc hoppin* s stem in &'& and

the diJerent al*orithms for the e#aluation of hoppin* se+uences. A hoppin* se+uence isthe time dependent se+uence of used output fre+uencies. Dne parameter used in thecreation of a fre+uenc hoppin* s stem is the so called %obile Allocation MO$ 44OC $hich is the list of all fre+uencies used in the se+uence. There are t$o possibilities toadministrate these se+uences

C+clic opping-

The c clic hoppin* is mainl used to combat the 7a lei*h fadin*. The fre+uencies areused one after another. f the %D'A??D G f1 f2 f3 f4 is created a cell the parameterfor allocatin* c clic hoppin* is >oppin* &e+uence :umber >&: G 0. The result is ahoppin* f1 f2 f3 f4 f1 f2 f3 f4 ..... The start fre+uenc for the hoppin* isadministrated $ith the parameter %obile Allocation nde) DJset M IO . ts #aluedepends on the number of *i#en fre+uencies.

Pseudo Random opping-

f another #alue for >&: is ta,en the output se+uence is pseudo random. The 7andomhoppin* is used mainl to impro#e the le#el for e)ample in cells $ith the samefre+uencies if a diJerent >&: is *i#en.

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Objects and parameters in !$! for administration of fre*uenc+ opping-

ith the &'& s stem fre+uenc hoppin* is con9*urated b creatin* fre+uenc hoppin*

s stem ob"ects / 7&C-'T&:-(>&C: and b assi*nment of radio channels tothese hoppin* s stems.

!peci"cation#ame

Object5Pac6age

$ #ame Range Meaning

>D =%D;< 'T& 'T&D >D %D;< ''>D&C:>D

(la* indicates $ether basebandor s nthesiHer hoppin* is used

'T&= &>D :S 'T& 'T&D >D T7 &C

FHSYN1...10 number to identif a fre+uenc

hoppin* s stem

>&: (>&C >&: 0...63 hoppin* se+uence number0 c clic hoppin*1...63 random hoppin*

%A (>&C %D'A??D 0...1023 ...0...1023

mobile allocationlist of fre+uencies $ithin the (>s stem /ma)imum number offre+uencies G 16 .

(>=&C&TA: (>&C ; 0 1 ...10 speci9es the fre+uenc hoppin*s stem /*i#en b (>&C: to$hich a channel shall belon*. /0no hoppin*

%A D >A: %A D 0...63 mobile allocation inde) oJsetde9nin* the startin* fre+uenc/number in the %A fre+uenc listfor a hoppin* se+uence at acertain frame number (: i.e.diJerent channels usin* the

same (> s stem shall ha#ediJerent %A Ds.

(i*. 12

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T7X 0

f0

T7X 1

f1

T7X2

f2

T7X 3

f3

>A:0' >

(>&C ; G 0%A D G 0

&; >(>&C ; G 2%A D G 0

&; >(>&C ; G 2%A D G 1

T >(>&C ; G 2

%A D G 2

>A:1 T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

>A:2 T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

>A:3 T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

>A:4 T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

>A:5 T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

>A:6 T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

>A: T >

(>&C ; G 1%A D G 0

T >(>&C ; G 1%A D G 1

T >(>&C ; G 1%A D G 2

T >(>&C ; G 1

%A D G 3

(>=&C&T&C ; G 0 -R :o >oppin*

(>=&C&T&C ; G 1 -R %D'A??D G f0 f1 f2 f3(>=&C&T&C ; G 2 -R %D'A??D G f1 f2 f3

(i*. 13

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The so called T7A frame contains not onl these 260 bit

number of bits ? number of bits ;?

frame s nchroniHation 35 35

discrimination speechdata full rate half rate

5 5

time ali*nment 6 6

bad frame indication 1

;TX mode 1 1

other info 3 1

speech 260 260

spare 5 !(i*. 15 ontents of a speech bloc, for transmission at 16 ,bit s details in S&% 08.60

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& C annel llocation due to Interference 4evel

The 'T& performs measurements of the /uplin, recei#ed le#el on all its idle traUcchannels /T >s in the same $a as for the bus channels described in hapter 4.2.1i.e. the le#el #alues in Vd'mW in each T;%A frame are a#era*ed o#er one &A > period.

The a#era*ed #alue is mapped on an 7X?

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n the case of a call setup as $ell as in the case of a hando#er a traUc channel out of thebest non-empt interference class is allocated.

A condensed form of the information on the K+ualit L of the idle traUc channels at acertain 'T& is sent from the '& to the %& usin* the 7

eriod for a#era*in* the measuredinterference le#el. A traUc channels$hich has not been idle durin* the$hole measurement and a#era*in*period it is not ta,e into account in theclassi9cation procedure.

X1 X2 ... X5 :TA@< 7interference+,re-,*.d-B*/ndarie-

0...63'oundaries of the interference classesbands.

7(=7

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Concentric Cells

oncentric ells means t$o lo*ical cells $ithin one S&% ; & cell nner area andcomplete area.The TX po$er of the T7XFs belon*in* to the inner area is stron*lreduced $hich results in a lo$er radius.

Inner 3rea

Complete 3rea

(i*. 1! ell con9*ured as concentric

This feature can be used to introduce an additional fre+uenc re-use pattern for thefre+uencies in the inner area i.e. a ne$ fre+uenc re-use pattern can be used $ith ashorter re-use distance. This $ill increase the net$or, capacit $ithout appreciableincrease of interference.

A a* is used to de9ne $hether the cell is a concentric one or not. furthrermore it has tobe speci9ed per T7X $ether this T7X should belon* to the inner area or to the completearea.Dne set of si*nallin* channels -' > I &; >- in the complete area is used forboth areas.

Objects and parameters in !$! for installation of concentric cell con"guration-

Object5Pac6age

$#ame

Range Meaning

'T& 'T&' D:

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(i*. 20

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ntracell hando#ers bet$een the t$o areas are dependin* on 9eld stren*th le#el and thelocation of the mobile. These hando#ers are e)ecuted on le#el distance conditionsde9ned b appropriate thresholds in the hando#er pac,a*e. %oreo#er durin* the call

setup procedure in a concentric cell the same #alues are also e#aluated to determine$hether the call is set up on a T > belon*in* to an inner or complete area T7X

Parameters for Concentric Cell andover be aviour

'#9CO#9C'449 I!/

Db"ect ac,a*e ;' :ame 7an*e &tep &iHe nit

>A:; ; &T T7 assi*nment is in uenced bthis threshold.

The condition $hich must be ful9lled to perform an intracell hando#er from complete- toinner area or to assi*n a T > directl in the inner area is

7X?A:; >D ; &T 0...35 1 1 m

(i*. 24

This attribute speci9es the distance limit bet$een inner and complete area of aconcentric cell $hich is ta,en into account for the intracell ando#er in addition to theattribute ho7)le#;inner respecti#el ho7)?e#;louter.

The condition $hich must be ful9lled to perform an intracell hando#er from inner- tocomplete area is

7X?

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'#9I##'R9I##'R9%O

Db"ect ac,a*e ;' :ame 7an*e &tep &iHe nit

>A:; : :>D T7

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