clear;

% Maximum length of Signal vector

N=65536*8
%N=65536*8/16 % shortened version

% cut off of butterworth filter representing the channel response

fc=N/8;

% order of the butterworth filter representing the channel response

Norder=8;

% the rest of the code demonstrates how the channel will be implemented.

% formulate project for ee511 2002

Nbits=65536/4;
%Nbits=65536/(2*4); % shortened version

Nsample=N/Nbits

% filter parameter;

fmax=N/2;

% create random vector

s=rand(1,Nbits);
sb=binarize(s);
u=ones(1,Nsample);
b=kron(sb,u);

% add noise
noise=0.05*randn(1,N);
b=b+noise;

B=fft(b);

n=1:N;

% create filter

K=1; % filter gain
[f H]=lp_butterworth_oN_dft(fc,K,fmax,N,Norder);

% convolve signal with filter

R=B.*H;
r=real(ifft(R));

% plot input and output (first 16 bits)

figure(1);
if Nbits>=16
    bplot=b(1:Nsample*16);
    rplot=r(1:Nsample*16);
else
    rplot=r;
    bplot=b;
end;

a=size(bplot);
n2=1:a(2);

plot(n2,bplot,n2,rplot);
%plot(n2,rplot);

% plot spectrum of input and spectrum of output

figure(2);
B(1)=0+i*0; % suppress dc for graphical clarity
R(1)=B(1); % suppress dc for graphical clarity
plot(n,abs(B)/max(abs(B)),n,abs(R)/max(abs(R)),n,abs(H));