txcdma.m

CDMAT-ransmitter receiver-CDMA is an access technique which uses entire for communication

close all;
clear all;
%--------------------
% Generates baseband signal for the COM-8001 pattern generator
% Format is 2 (complex) * 10-bit (unsigned).
%--------------------
fs = 64;
nsamples = 64; % simulation duration, expressed as number of complex samples
n_b = 20; % Number of Data Bits
gain = .3; % prevent saturation at the D/A converter
% for long simulations, store results in output file
[fid_o1,message] = fopen('pn32spread429a.bin','w');
if(fid_o1 == -1)
message
end
% initialization
last_i = 0;
last_q = 0;
current_i = 0;
current_q = 0;
b = dec2bin(0,10);
%data that will be transmitted x(t)
%Collected data from sensors length of 19
xt_ip = 2*(rand(1,(n_b-1))>.5) - 1;
%xt_ip = rand(1,n_b)>.5;
%add 1 to begining of xt to make sequence length of 20
%this is for when receiving, you always know there is a 1
%in the beginning
xt_ipnew = [1 ; xt_ip.'];
xt_ipnew = xt_ipnew.';
xt = kron(xt_ipnew, ones(1,nsamples));
newxt = gain*xt;
%------------------------------------------------------
% MAIN LOOP
%------------------------------------------------------
% loop signal processing
%adding sequence for time sync
ts = .5*[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];
%PN code
pn = [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];
k=1;
for i = 1:length(pn)
pnf(k:k+1) = pn(i);
k=k+2;
end
pnnew = kron(ones(1,n_b), pnf);
pn_new = gain*pnnew;
%mix pn code with data sequence
new_xt = xt.*pn_new;
%design cosine filter
yf = rcosine(1,8,'fir');
%upsample and filter
yo = rcosflt(new_xt, 1, 8, 'filter', yf);
tsf = rcosflt(ts, 1, 8, 'filter',yf);
%data needed for trasmitting
%newyo = yo(25:5168-24);
newyo= yo;
%make sure to copy this matrix to receiver code
%newts = tsf(25:304-24);
newts = tsf;
%this is final signal with time sync sequence attached to front
signali = [tsf ; yo];
signalq = [tsf ; yo];
for j = 1:length(signali)
i = j;
% convert samples to 10-bit unsigned format
sigt2i = min(max((floor((signali(i)+1.)*511.5)),0.),1023);
sigt2q = min(max((floor((signalq(i)+1.)*511.5)),0.),1023);
%invert bit order because of pinout
a = dec2bin(sigt2i, 10);
b(1) = a(10);
b(2) = a(9);
b(3) = a(8);
b(4) = a(7);
b(5) = a(6);
b(6) = a(5);
b(7) = a(4);
b(8) = a(3);
b(9) = a(2);
b(10) = a(1);
outputi = bin2dec(b);
a = dec2bin(sigt2q, 10);
b(1) = a(10);
b(2) = a(9);
b(3) = a(8);
b(4) = a(7);
b(5) = a(6);
b(6) = a(5);
b(7) = a(4);
b(8) = a(3);
b(9) = a(2);
b(10) = a(1);
outputq = bin2dec(b);
% pack samples
% wait until two complex samples are collected before writing into file
if(mod(j,2) == 0)
% even sample
current_i = outputi;
current_q = outputq;
a = bitand(bitshift(last_q,-2), 255);
fprintf(fid_o1,'%c',a);
a = bitand(bitor(bitshift(last_q,6),bitshift(last_i,-4)),255);
fprintf(fid_o1,'%c',a);
a = bitand(bitor(bitshift(last_i,4),bitshift(current_q,-6)),255);
fprintf(fid_o1,'%c',a);
a = bitand(bitor(bitshift(current_q,2),bitshift(current_i,-8)),255);
fprintf(fid_o1,'%c',a);
a = bitand(current_i,255);
fprintf(fid_o1,'%c',a);
% keep track of simulation progress
if(mod(j,10000) == 0)
j/10000;
end;
else
% odd sample
% remember last sample
last_i = outputi;
last_q = outputq;
end;
end
figure(1)
%subplot(4,1,1)
plot(xt);
grid on;
xlabel('Time');
ylabel('Amplitude');
legend('Data Stream - x(t)');
figure(2)
%subplot(4,1,2)
plot(new_xt);
grid on;
xlabel('Time');
ylabel('Amplitude');
legend('Data Stream Mixed With PN Code');
figure(3)
%subplot(4,1,3)
plot(signali, 'b');
grid on;
xlabel('Time');
ylabel('Amplitude');
legend('Filtered I Values');
figure(4)
%subplot(4,1,4)
plot(signalq, 'r');
grid on;
xlabel('Time');
ylabel('Amplitude');
legend('Filtered Q Values');
% close opened files
fclose(fid_o1);