MATLAB: Frequency Selective Channel Coefficients in MATLAB

channelcoeffiecientsgenerate

Hello all

How can I generate the following channel coefficients in MATLAB, where these coefficients correspond to a frequency selective channel:

f_m=sum_p h_p exp(-j*2*pi*fc*tau_p) g(mTs-tau_p), m=0,1,…,L-1

where g(t) is rectangular pulse of support duration Ts, and h_p, tau_p and fc are given.

Thanks in advance

Best Answer

here is a start :

 Fs=800;
 fc=300; % Hz
 Ts=1/Fs;
 L=400;
 t=0:Ts:(L-1)*Ts;
 d=4; %  four signals per example,

tau is dependent on physical parameters, distance and coordinates, but i consider here a linear progressive phase, and the signals are sinusoidal :

 tau=(0:d-1);
 fm=0;
 for p=1:d
 fm=fm+exp(-j*2*pi*fc*tau(p))*sin(2*pi*t);
 end
 figure; plot(real(fm));

your assignment now is to replace the sin signals with the rectangular ones .

Related Solutions

MATLAB: How to create a train chirp pulse

That is an interesting problem, before trying to use pulstran function, create a linear frequency function and use square function as follows :

 fs = 1e3;                   % sample freq 1kHz
 D = 0 : 1/fs : 2;           % pulse delay times
 t = 0 : 1/fs : 20;          % signal evaluation time
 f1=1;
 f2=10;
 a=(f2-f1)/(t(end)-t(1));
 f=f1+a*t;
 x=square(2*pi*f.*t);
 figure; plot(t,x);
 axis([0 20 -2 2]);
 title('Train chirp pulse');

MATLAB: How to do this more efficiently

It isn't necessary to do the inequality test for every possible pair of kk and mm values. Since kk and mm are integers and Ts must surely be a positive number, your pair of inequalities is logically equivalent to

 kk-mm == d

where d = floor((tau(qq)-tau(pp))/Ts). Therefore you can simply add the appropriate vectors along corresponding diagonals of F. For large N, doing it this way should save quite a bit of computation time.

F=zeros(N);
for pp=1:Np
  for qq=1:Np
    d = floor((tau(qq)-tau(pp))/Ts);
    kk = max(d,0):min(N-1,N-1+d);
    mm = kk-d;
    theta=(d+1)*Ts-(tau(qq)-tau(pp));
    ix = d+1+(N+1)*mm;
    F(ix) = F(ix)+conj(H(pp))*H(qq)*theta.*exp(1i*pi*fc*theta).*sinc(fc*theta);
  end
end

Best Answer

Related Solutions

MATLAB: How to create a train chirp pulse

MATLAB: How to do this more efficiently

Related Question