function [s]=longcod(n)e%  find the long code Sequence of 2^15 or 2^42%  s=longcode(n), n: length of code
%% Copyright: Xiaohua(Edward) Li, Assistant Professor%            Department of Electrical and Computer Engineering%            State University of New York at Binghamton%            http://ucesp.ws.binghamton.edu/~xli% June 2003%%L=15;  % choose L=15 to generate PN code with max length 2^15L=42;  % choose L=42 to generate PN code with max length 2^42
if L==15,  
   init=ones(1,L);   
   fdbk=[0 0 1 1 1 1 0 0 0 1 1 1 0 0 1];  % feedback shifting register
elseif L==42
   init=[0 ones(1,L-1)];
      fdbk=[1 1 1 0 1 1 1 0 0 1 0 0 0 0 0 ... % feedback shifting register
            1 1 1 1 0 1 1 0 0 1 1 1 0 0 0 ...
            1 0 0 0 1 0 0 0 0 0 0 1];
end
   s=zeros(1,n+L);for i=1:n+L                   % generate PN code sequence  s(i)=init(L);  f=fdbk*init.';    init(2:L)=init(1:L-1);  init(1)=mod(f,2);end s=s(L+1:n+L);s=2*s-1;                      % change code to be +/- 1