pr7_34.m

Spread Spectrum and CDMA Principles and Applications 书籍和代码

%Problem 7.34;
%finding minimum distance between group signals for a given synchronous signature set;

S=hadamard(12); %signature matrix, signatures are columns;
dgn=diag(S'*S); S=S*diag(1./sqrt(dgn)); %normalizing all signatures;
Ro=S'*S; %normalized signature correlation matrix;
K=size(S,2); %number of users;
dsqmin=4; %initializing dsqmin;
Eps=[2,zeros(1,K-1)]; %initialize difference vector;
t=cputime;
for k=1:3^K-3^(K-1) %in the loop all possible ternary difference vectors Eps are tried;
    ds=Eps*Ro*Eps'; %current squared disrtance;
    if ds<dsqmin dsqmin=ds; end; %update dsqmin if for current Eps it is smallest;
    %next operators in the loop perform incrementing of Eps in ternary number system {0,2,-2}:
    tr=min(find(Eps>-2)); %find minimum position where Eps>-2;
    Eps(1:tr-1)=0; %carry of ones realized;
    Eps(tr)=2-2*Eps(tr); %ternary incrementing finished;
end;
T=cputime-t;
L=4/(dsqmin+eps); Ldb=10*log10(L);
if dsqmin<1e-12 dsqmin=0; L=inf; Ldb=inf; end;
fprintf('\n');
disp('   min sqdist  loss      loss,dB    T');
disp([dsqmin,L,Ldb,T]);