% **************** EXAMPLE : QPSK SIGNAL WITH MULTIPATH CHANNEL*******************%
% 本程序為基帶QPSK信號通過多徑信道的產生例子
% copyright : 研學網－沉香(僅供參考)
% 2007-01-31
% channle model : COST207(TU)
 
clear all;
close all;
clc;

% ************* parameter setting ******************************* %
num = 48*100;                               % total constellation points
M  = 4;                                     % constellation order-QPSK
fb = 20e6;                     % symbol rate
fs = fb*16;                  % system sample rate
fc = 70e6;                     % carrier frequency
carrier=2*pi*fc/fs;
a =[1+1j 1-1j -1+1j -1-1j];
rolloff_t = 0.5;
delay_t = 3;
% ********  generate signal source **************
   an=zeros(1,num);
   ant=zeros(1,num);
   for i=1:num
    temp=rand;
    dsource(i)=1+floor(M*temp);
    ant(i)=a(dsource(i));
   end
   % ********* D/A ***************************%
   % pulse shape
     baseband_data = rcosflt(ant,fb,fs,'fir/normal',rolloff_t,delay_t);
% ****************** Multipath Channel ************************************%
idata = real(baseband_data);
qdata = imag(baseband_data);

% Time resolution
tstp = 1/fs;  

% delay time 
itau = floor(1e-6*[0, 0.2, 0.5, 1.6,2.3,5.0]/tstp);
% Mean power for each multipath in dB
dlvl = [-3 ,0 ,-2 ,-6,-8,-10];
% Initial value of fading counter
itn=[1000,2000, 3000, 4000,5000,6000];

% Number of  waves
n1=6;  

% Maximum Doppler frequency [Hz]
fd=200; 

% (1->flat (only amplitude is fluctuated),0->nomal(phase and amplitude are fluctutated)
flat = 0;
% for ii =1 :2
[iout,qout] = MUL_RAYLEITH(idata,qdata,itau,dlvl,itn,n1,length(idata),tstp,fd,flat);
% ---- 多次仿真的時候加上以下語句-------%
   % Updata fading counter:to skip (5us/0.05us)
%    itnd0=100;
%    itnd1 = itn+ itnd0;
% ---------------------------------------%

% ************** END *************************************%
r_sdata = (iout+1j*qout).*exp(1j*carrier*(1:length(iout)));
r_sdata = real(r_sdata);
pwelch(r_sdata,[],[],[],fs);
% end