sfading_channel.m

一些关于调指和解调的小程序

function out=sfading_channel(input,d_counter)
%****************** 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
% 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    : Initial Fading counter for each multipath fading
% n1     : Number of summation for direct and delayed waves 
% nsamp   : Total number od symbols
% tstp   : Mininum time resolution
% fd   :  Maxmum doppler frequency
% flat     flat fading or not 
% (1->flat (only amplitude is fluctuated),0->nomal(phase and amplitude are fluctutated)   
%******************************************************
% dcounter : In oder to 
%%%%%-----------------channel parameters----------------------
%%%************ Main adjusted parameter***********************
np=24;                               %%% number of paths 
Dexp=2;                             %%% Interval time of adjacent two pathes (number of sample points) 
fd=10;                              %%% maximum Doppler frequency  
%%%***********************************************************
flat=0;                              %%% General condition

tstp=0.0125*10^(-6);                   %%% sample duration (Tsam)
br=1/tstp;                           %%% sample rate 

dt=Dexp*tstp;                        %%% delay between two paths is Dexp*tstp (us)
delay_time=[0:dt:(np-1)*dt];         %%% the unit is us
itau=floor(delay_time./tstp);        %%% number of delayed points

df=0.5;                              %%% fading step length, the unit is dB 
dlvl=[0:df:(np-1)*df];
th=zeros(1,np);                      %%% unit is degree
n0=[6,7,6,7,6,7,6,7,6,7,6,7,6,7,6,7,6,7,6,7,6,7,6,7];
%n0=6;

%itn=[1000:1000:np*1000];            %%% or [800:1000:(np-1)*1000+1000]
itn=[1000:500000:np*500000];         %%% The best interval is 5/(fd*tstp)
                                     %%% counter_test can test the optimal itn and itn0
%itn0=5000;
counter=itn+d_counter;                
n1=np;                               %%% number of paths
%%%-------------End of channel parameters--------------------


nsamp=length(input);                 %%% nsamp=50/(fd*Ts) is better
idata=real(input);                  
qdata=imag(input);

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

%ps=sum(idata.^2+qdata.^2)/length(idata)

total_attn = sum(10 .^( -1.0 .* dlvl ./ 10.0));

for k = 1 : np 

	atts = 10.^( -0.05 .* dlvl(k));         %%% amplitude factor of fading

	if dlvl(k) >= 40.0 
	       atts = 0.0;
	end

	theta = th(k) .* pi ./ 180.0;           %%% change the unit of degree into radian   
    
    %%%%%%------------delay-----------------------
    itmp=[zeros(1,itau(k)),idata(1:nsamp-itau(k))];
    qtmp=[zeros(1,itau(k)),qdata(1:nsamp-itau(k))];
         
	%%%%%%-----------------------------------------------------
    
	[itmp3,qtmp3,ramp,rcos,rsin] = fade (itmp,qtmp,nsamp,tstp,fd,n0(k),counter(k),flat);
	
    iout = iout + atts .* itmp3 ./ sqrt(total_attn);
    qout = qout + atts .* qtmp3 ./ sqrt(total_attn);
   
end
%itn=itn+itn0;
out=iout+j*qout;

%%%----------------End--------------------