% sefade.m
%
% This function generates frequency selecting fading
%
function [iout,qout,ramp,rcos,rsin]=sefade(idata,qdata,itau,...
    dlvl,th,n0,itn,n1,nsamp,tstp,fd,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 : Sine value contaminated by fading
% itau : Delay time for each multipath fading
% dlvl : Attenuation level for each multipath fading
% th   : Initialized phase for each multipath fading
% n0   : Number of waves in order to generate each multipath fading
% itn  : Fading counter for each multipath fading
% n1   : Number of summation for direct and delayed waves
% nsamp: Total number of symbols 
% tstp : Minimum time resolution
% fd   : Maximum doppler frequency
% flat : flat fading or not

iout=zeros(1,nsamp);
qout=zeros(1,nsamp);

total_attn=sum(10.^(-1.0.*dlvl./10.0));
for k=1:n1
    atts=10.^(-0.05.*dlvl(k));
    if dlvl(k)==40.0
        atts=0.0;
    end
    theta=th(k).*pi./180.0;
    [itmp,qtmp]=delay(idata,qdata,nsamp,itau(k));
    [itmp3,qtmp3,ramp,rcos,rsin]=fade(itmp,qtmp,...
        nsamp,tstp,fd,n0(k),itn(k),flat);
    iout=iout+atts.*itmp3./sqrt(total_attn);
    qout=qout+atts.*qtmp3./sqrt(total_attn);
end