fade.m

用于产生频率选择性信道,其中的一个fade.m可以用来产生瑞利衰落信道.

% Program 2-5
% fade.m
%
% Generate Rayleigh fading
%
% Programmed by H. Harada
function [iout,qout,ramp,rcos,rsin]=fade(idata,qdata,...
nsamp,tstp,fd,no,counter,flat)
%********************** variables *********************
% idata : input Ich data
% qdata : input Qch data
% iout : output Ich data
% qout : output Qch data
% ramp : Amplitude contaminated by fading
% rcos : Cosine value contaminated by fading
% rsin : Cosine value contaminated by fading
% nsamp : Number of samples to be simulated
% tstp : Minimum time resolution
% fd : maximum doppler frequency
% no : number of waves in order to generate fading
% counter : fading counter
% flat : flat fading or not
% (1-flat (only amplitude is fluctuated),0-normal
% (phase and amplitude are fluctutated))
%******************************************************
if fd ~= 0.0
ac0 = sqrt(1.0 ./ (2.0.*(no + 1)));
% power normalized constant(ich)
as0 = sqrt(1.0 ./ (2.0.*no));
% power normalized constant(qch)
ic0 = counter;
% fading counter
pai = 3.14159265;
wm = 2.0.*pai.*fd;
n = 4.*no + 2;
ts = tstp;
wmts = wm.*ts;
paino = pai./no;
xc=zeros(1,nsamp);
xs=zeros(1,nsamp);
ic=[1:nsamp]+ic0;
for nn = 1: no
cwn = cos( cos(2.0.*pai.*nn./n).*ic.*wmts );
xc = xc + cos(paino.*nn).*cwn;
xs = xs + sin(paino.*nn).*cwn;
end
cwmt = sqrt(2.0).*cos(ic.*wmts);
xc = (2.0.*xc + cwmt).*ac0;
xs = 2.0.*xs.*as0;
ramp=sqrt(xc.^2+xs.^2);
rcos=xc./ramp;
rsin=xs./ramp;
if flat ==1
iout = sqrt(xc.^2+xs.^2).*idata(1:nsamp);
% output signal(ich)
qout = sqrt(xc.^2+xs.^2).*qdata(1:nsamp);
% output signal(qch)
else
iout = xc.*idata(1:nsamp) - xs.*qdata(1:nsamp);
% output signal(ich)
qout = xs.*idata(1:nsamp) + xc.*qdata(1:nsamp);
% output signal(qch)
end
else
iout=idata;
qout=qdata;
end