% CDMA Simulation for N Transmitter/Receiver Pairs
% data bit stream for each sender
D = [ 1 -1 1 -1 1 1 -1 -1 ;
-1 -1 1 1 1 -1 -1 1 ;
1 1 -1 -1 -1 1 1 -1 ;
1 1 1 1 -1 -1 -1 -1 ];
% unique code for each sender (determined using the Walsh Set)
C = [ -1 -1 -1 -1 ;
-1 1 -1 1 ;
-1 -1 1 1 ;
-1 1 1 -1 ];
% parameters
M = length(C); % length (number of bits) of code
Y = size(D);
N = Y(1); % number of unique senders / bit streams
I = Y(2); % number of bits per stream
T = []; % sum of all transmitted and encoded data on channel
RECON = []; % vector of reconstructed bits at receiver
% show data bits and codes
'Vector of data bits to be transmitted:', D
'Vector of codes used for transmission:', C
% encode bits and transmit
G = zeros(I,M);
for n = 1:N
Z = zeros(I,M);
for i = 1:I
for m = 1:M
Z(i,m) = [D(n,i)*C(n,m)];
end
end
G = G + Z;
end
% show channel traffic
for i = 1:I
T = [ T G(i,:) ];
end
'Resulting traffic on the channel:', T
% decode and reconstruct
for n = 1:N
TOT = zeros(1,I);
R = zeros(I,M);
for i = 1:I
for m = 1:M
R(i,m) = G(i,m) * C (n,m);
TOT(i) = TOT(i) + R (i,m);
end
end
RECON = [RECON ; TOT / M];
end
'Reconstructed data at the receiver:'
RECON
