蜂窝小区同频干扰的Matlab仿真.docx
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蜂窝小区同频干扰的Matlab仿真.docx
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WirelessNetwork
ExperimentFour:
Co-channelInterference
ABSTRACT
Thisexperimentisdesignedtolearnthefundamentalsofthecellularwirelesscomunication.Mainlyabouttheco-interferenceandSIR.
KEYWORDS:
wirelesscommunication,cluster,pathloseexponent,SIR.
INSTRUCTION
Inthisexperiment,wearegoingtoinvestigatetheco-channelinterferenceinacellularmobilecommunicationsystem.Assumethatallcellshaveequalradii,andthatbasestationshaveequalpowerandarelocatedinthecentersofeachcell.Eachbasestationtransmitsanindependentsignalsothattheco-channelsignals'powerscanbeaddeddirectly.Inourtextbook,thesystemco-channelinterference
ischaracterizedbytheinterferenceataspecificposition,e.g.atthefringeofacelloratthecenterofacell.Becauseoftherandompositionofamobilesubscriber(MS)andotherrandomfactors,theco-channelinterferenceisalsoarandomvariable.Asknown,interferencecancelationtechniquecangreatlyimprovethesystemcapacityinthecellularmobilesystem,especiallyintheCDMAsystems.Itishelpfultoknowthedistributionoftheinterferencewhenadoptinginterferencecancelationtechniques.Therefore,ourexperimentdevotestofindthedistributionoftheco-channelinterferenceinthecellularmobilesystemwithclustersize
N.LetusassumethecellradiusR,eachMScouldappearatanypositioninthecellwithequalprobability.TheaveragereceivedpowerPratadistancedfromtransmitteris
𝑝=𝑝(𝑑)-𝑛
approximatedas𝑟
0𝑑0
,whereP0isthepowerreceivedatasmalldistanced0from
thetransmitterandnisthepathlossexponent.Theexperimentrequirementsarethefollows.
DESCRIPTIONOFTHEEXPERIMENTS
1.Writeaprogramtocalculatethesignalinterferenceratio(SIR)intheforwardlink,andrepeatsitbyrandomlychangingthepositionoftheMS.Afteranumberofsimulations,usethesimulatedresultstodrawthehistogramoftheSIR(S=I).TrytoobtainhistogramswithdifferentpathlossexponentnandclustersizeN.Concludeyourresults.
Theco-channelinterferenceintheforwardlinkcanbecharacterizedinfigure1.AMSwillbeinterferedbytheco-channelbasestation.Inoursimulation,weconsiderthe18co-channelcell,including6cellsinthefirstloopand12cellsinthesecond,nomatterwhattheclustersizeNis.
Figure1forwardlinkco-channelinterference
(1)Firstly,weshouldrandomlychoosethepositionoftheMSinthecell.Sincethecellishexagonwhichishardtohandlewecutandpasteitintoasquare.Aswecanseeinfigure2,thecenterofthecoordinationisthecenterofthecell.ThesquarewechooseisABCD.WethenrandomlychooseapairofxandyasthecoordinateofMS.IfMSlocatesintriangle1wecutandpasteittotriangle3andifitlocatesintriangle2wemoveittotriangle4.
Weassumetherangeofthebasestationis0.1asradiusofclusteris1.FortheMSwholocatedwithinthisarea,wechangeitsdistancetobe0.1asitistooclosetothebasestaion.
Figure2randomlychoosethepositionofMSinacell
Matlabcode:
RandPOS.m
%*******************************************************************
%ThisfunctionistogettherandomlylactionoftheMSwithmtimes.
%zisam*1matrixwithcoodinatevaluex,y
%*******************************************************************function[z]=RandPOS(m)
%********getrandomvalueofx,ywithinasquare*****%x=1.5*rand(m,1)-1;
y=sqrt(3)*rand(m,1)-0.5*sqrt(3);
%********useforlooptocutthesquareintoahexagon*****%fork=1:
m
ifx(k)>-1&&x(k)<-0.5&&y(k)>(1+x(k))*sqrt(3)x(k)=x(k)+1.5;
y(k)=y(k)-sqrt(3)/2;
elseifx(k)>-1&&x(k)<-0.5&&y(k)<-(1+x(k))*sqrt(3)x(k)=x(k)+1.5;
y(k)=y(k)+sqrt(3)/2;
end
%********iftheMSistoonearlytothebasestation ******%ifsqrt(x(k)^2+y(k)^2)<0.1
x(k)=0.1;
y(k)=0;
end
end
z=x+j*y;
.
(2)Secondly,weshouldcalculatethecoordinateofco-channelbasestation.AsweknowtheclustersizeNwecancalculatethe(i,j)pairbytheformula𝑁=𝑖2+𝑖*𝑗+𝑗2
Matlabcode:
ClusterN.m
%*********************************************************
%Thisfunctionistofindi&jcorrespondtoagivenN
%asN=i^2+j^2+ij
%iiandjjistheresultofi,j
%********************************************************function[ii,jj]=ClusterN(N)
%thelargestnumberofiandjissqrt(N)
fora=0:
sqrt(N)
forb=0:
sqrt(N)
ifa^2+b^2+a*b==Nii=a;
jj=b;
end; %endifend;%forjj
end;
(3)TakingN=7asexample,wecancalculatethecoordinatebyreferringtofigure3.AccordingtothevalueofIjpairandanglesinthefigurewecangetthecoordinateofthefirst loop by the formula:
𝑗×𝑝𝑖+𝑗× 𝑝𝑖 𝑗×𝑝𝑖+𝑗×𝑝𝑖
𝑙𝑜𝑐𝑎𝑡𝑖𝑜𝑛(𝑘)=3×(𝑖×𝑒 6
3×(𝑘‒1)
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