rayleigh_channel.m

有关QPSK调制解调的仿真程序

% Program 2-6
% sefade.m
%
% This function generates frequency selecting fading
% 
% Programmed by H.Harada	 	
% 

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   : 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    : 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)   
%******************************************************

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));
    % Gives delay to input signal
    idel=itau(k);
itmp=zeros(1,nsamp);
qtmp=zeros(1,nsamp);

if idel ~= 0 
  itmp(1:idel) = zeros(1,idel);
  qtmp(1:idel) = zeros(1,idel);
end

itmp(idel+1:nsamp) = idata(1:nsamp-idel);
qtmp(idel+1:nsamp) = qdata(1:nsamp-idel);

    
    
    
    % Generate Rayleigh fading

	%[itmp3,qtmp3,ramp,rcos,rsin] = fade (itmp,qtmp,nsamp,tstp,fd,n0(k),itn(k),flat);
	
  %if fd ~= 0.0  
  fd=160;
  no=n0(k);
  counter=itn(k);
    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
    itmp3 = sqrt(xc.^2+xs.^2).*itmp(1:nsamp);    % output signal(ich)
    qtmp3 = sqrt(xc.^2+xs.^2).*qtmp(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

    
    
    
    
    
    
    
    %**********************************************************************
    %%
    iout = iout + atts .* itmp3 ./ sqrt(total_attn);
  qout = qout + atts .* qtmp3 ./ sqrt(total_attn);

end
% ************************end of file***********************************