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CDMA例子的matlab代码 
主程序： 
％file: c18_cdmasim.m 
function [BER,ErrorRun]c18_cdmasim(N,SF,EbNo,... 
    NumInterferers,MPathDelay,Kfactor_dB) 
rand('state',sum(100*clock));randn('state',sum(100*clock)); 
NIterate = 1e3; 
NumberOfIterations = ceil(N/NIterate); 
ErrorState = 0;ErrorRun = []; RunCount = 1; 
Kfactor = 10^(Kfactor_dB/10); 
EbNolinear = 10^(EbNo/10); 
MPathComponents = length(MPathDelay); 
MPathAmp(2:MPathComponents) = rand(MPathComponents-1,1); 
ScatPower = MPathAmp*MPathAmp.'; 
MPathAmp(1) = sqrt(ScatPower*Kfactor); 
[fee MaxComponent] = max(MPathAmp);MPathAmp = MPathAmp/fee; 
FilterOrder = 4; Ripple = 0.5; BW = 0.01; 
[b,a] = cheby1(FilterOrder,Ripple,BW); 
if NumInterference > (SF-1) 
    error(['NumInterferers must not exceed ',int2st(SF-1),'.']) 
end 
if length(MPathDelay) ~= length(MPathAmp) 
    error('MPathDelay and MPathAmp must have the same length.') 
end 
if min(MPathDelay) < 0 
    error('MPathDelay must not have negative components.') 
end 
fee = diff(MPathDelay); 
if min(fee) <= 0 
    error('MPathDelay must be monotonically increasing.') 
end  
clear fee 
DesiredSequence = MSequence(SF+1); 
offset = fix(length(DesireSequence)/(NumInterferers+1)); 
M = length(DesiredSequence); 
for k=1:NumInterferers 
    InterfererSequence(k,:) = [DesiredSequence(M-(k-1)*offset:M) ... 
        DesiredSequence(1:M-1-(k-1)*offset)]; 
end 
zf = zeros(FilterOrder,MPathComponents); 
for cnt=1:NumberOfIterations 
    DesiredSymbols = sign(rand(1,NIterate)-0.5); 
    InterferingSymbols = sign(rand(NumInterferers,NIterate)-0.5); 
    DesiredChips = reshape(DesiredSequence.'*DesiredSymbols,1,... 
        M*NIterate); 
    for k=1:NumInterferers 
        InterferingChips(k,:) = reshape(InterfererSequence(k,:).'*... 
            InterferingSymbols (k,:),1,M*NIterate); 
    end 
    NoiseAmplitude = sqrt(SF/(2*EbNolinear)); 
    MaxDelay = max(MPathDelay); 
    DesiredNoise = NoiseAmplitude*randn(1,M*NIterate+MaxDelay); 
    MPathLinAmp = MPathAmp; 
    MPathComponents = length(MPathDelay); 
    DesiredMPathSignal = zeros(1,M*NIterate+MaxDelay); 
if NumInterferers > 0, 
    InterferingMPathSignal = ... 
        zeros(NumInterferers,M*NIterate+MaxDelay); 
    for k=1:MPathComponents 
        index = 1+MPathDelay(k):NIterate*M+MPathDelay(k); 
        InterferingMPathSignal(:,index) = ... 
            InterferingMPathSignal(:,index) + ... 
            MPathLinAmp(k)*InterferingChips; 
    end 
end 
for k=1:MPathComponents 
    if k==1, fading = ones(1,M*NIterate); 
    else 
        fading = randn(size(DesiredSymbols))+... 
            j*randn(size(DesiredSymbols)); 
        [fading zf(:,k)] = filter(b,a,fading,zf(:,k)); 
        fading = interp(fading,SF); 
        fading = abs(fading/sqrt(mean(fading.*conj(fading)))); 
    end 
    if k == MaxComponent 
        fadesign = sign(fading); 
    end 
    faa(k,:) = MPathLinAmp(k)*fading; 
    index = 1+MPathDelay(k):NIterate*M+MPathDelay(k); 
    DesiredMPathSignal(index) = ... 
        DesiredMPathSignal(index)+... 
        (MPathLinAmp(k)*fading).*DesiredChips; 
end 
if NumInterferers > 0 
    IncomingSignal = DesiredMPathSignal+... 
        sum(InterferingMPathSignal,1)+DesiredNois; 
else 
    IncomingSignal = DesiredMPathSignal+DesiredNoise; 
end 
index = 1+MPathDelay(MaxComponent):M*NIterate+... 
    MPathDelay(MaxComponent); 
IncomingChips = reshape(fadesign.*... 
    IncomingSignal(index),M,NIterate); 
DespreadSymbols = DesiredSequence*IncomingChips; 
DetectedSymbols = sign(DespreadSymbols); 
ErrorVevtor = 0.5*abs(DetectedSymbols-DesiredSymbols); 
ErrorsIterate(cnt) = sum(ErrorVector); 
BERIterate(cnt) = ErrorsIterate(cnt)/NIterate; 
for k=1:NIterate 
    if (ErrorVector(k) == 0) & (ErrorState == 0) 
        RunCount = RunCount+1; 
    elseif (ErrorVector(k) == 0) & (ErrorState == 1) 
        ErrorRun = [ErrorRun RunCount]; 
        RunCount = 1; ErrorState = 0; 
    elseif (ErrorVector(k) == 1) & (ErrorState == 0) 
        ErrorRun = [ErrorRun RunCount]; 
        RunCount = 1; ErrorState = 1; 
    elseif (ErrorVector(k) == 1) & (ErrorState == 1) 
        RunCount = RunCount+1; 
    else 
        s1 = sprintf('ErrorVector(%d)=%d, ... 
        ErrorState=%d! Unexpected Condition!'); 
        error(s1); 
    end 
end 
end 
Errors = sum(ErrorsIterate); BER = mean(BERIterate); 
ErrorRun = [ErrorRun RunCount]; 
% End of function file.