pr9_26.m

Spread Spectrum and CDMA Principles and Applications 书籍和代码

%Problem 9.26;
%finding free distance of convolutional codes;

clear all;
Go=[171;165;133]; %set matrix of generator polynomials in octal representation;
n=size(Go,1); %number of symbols in the frame, 1/R;
Gb=de2bi(oct2dec(Go),'left-msb'); %conversion octal-number representation of generation polynomial to binary vectors;
[i,j]=find(Gb); nzcl=min(j); Gb=Gb(:,nzcl:end); %removal of left zero-padding;
nu=size(Gb,2); %constraint length;
df=n*(2*nu-1); %initialization of free distance and bitstream generating minimum-weight word;
for b=1:2:2^(2*nu)-1
    bb=de2bi(b); %message polynomial;
    for k=1:n
        U(k,:)=gfadd(gfconv(bb,Gb(k,:)),zeros(1,3*nu-1)); %computing code symbols;
    end; %codeword ready;
    Wt=sum(sum(U)); if Wt<df df=Wt; end;
end;
fprintf('\n'); disp('generator polynomials'); disp(num2str(Go)); fprintf('\n');
fprintf('\n'); fprintf(['constraint length nu= ',num2str(nu)]);fprintf('\n');
fprintf('\n'); fprintf(['free distance df=',num2str(df)]); fprintf('\n');