DSSS modulation

DSSS-modulation.m

clearvars;

init_seq = [0, 1, 0, 1, 0, 0, 1, 0];
bit_sample = 8; % bit sample size

% Expanding bit sequence with by bit_sample size
bit_seq = zeros(1, bit_sample .* length(init_seq));
k = 1;
for i=1:length(init_seq)
     for j=1:bit_sample
         bit_seq(k) = init_seq(i);
         k = k + 1;
     end
end

figure;
stairs(bit_seq,'linewidth',2); 
axis([0 length(bit_seq) -0.5 1.5]);
title('ORIGINAL BIT SEQUENCE b(t)');


% Generating the pseudo random bit pattern
rand_sig = round(rand(1,length(bit_seq)));

figure;
stairs(rand_sig, 'linewidth', 2);
axis([-1 length(rand_sig) -.5 1.5]);
title('PSEUDORANDOM BIT SEQUENCE rand(t)');


% XORing the pattern with the spread signal
hopped_sig = xor(bit_seq, rand_sig);
figure;
stairs(hopped_sig,'linewidth',2);
axis([0 length(hopped_sig) -.5 1.5]);
title('MULTIPLIER OUTPUT SEQUENCE: b(t) XOR rand(t)');


% Modulating the hopped signal
dsss_sig = [];
fc = 1/10;
time_axis = 0:fc:2 * pi; 

c1 = cos(time_axis);
c2 = cos(time_axis + pi);
 
for k=1:length(bit_seq)
    if hopped_sig(1, k) == 0
        dsss_sig = [dsss_sig c1];
    else
        dsss_sig = [dsss_sig c2];
    end
end
 
figure;
stairs(dsss_sig, 'linewidth', 2);
% axis([0 (length(time_axis) * 10) -1.5 1.5]);
axis([0 length(dsss_sig) -1.5 1.5]);
title('DSSS SIGNAL');