% Program 3-22
% qam16_fading
%
% Simulation program to realize 16QAM transmission system
% (under one path fading)
%
% Programmed by H.Harada and R.Funada
%

%******************** preparation part *************************************

sr=256000.0; % Symbol rate
ml=4;        % ml:Number of modulation levels (BPSK:ml=1, QPSK:ml=2, 16QAM:ml=4)
br=sr .* ml; % Bit rate
nd = 100;    % Number of symbols that simulates in each loop
ebn0=15;     % Eb/N0
IPOINT=8;    % Number of oversamples

%********************** Filter initialization   **************************

irfn=21;                  % Number of taps
alfs=0.5;                 % Rolloff factor
[xh] = hrollfcoef(irfn,IPOINT,sr,alfs,1);   %Transmitter filter coefficients 
[xh2] = hrollfcoef(irfn,IPOINT,sr,alfs,0);  %Receiver filter coefficients 

%******************* Fading initialization ********************
% If you use fading function "sefade", you can initialize all of parameters.
% Otherwise you can comment out the following initialization.
% The detailed explanation of all of valiables are mentioned in Program 2-8.

% Time resolution

tstp=1/sr/IPOINT; 

% Arrival time for each multipath normalized by tstp
% If you would like to simulate under one path fading model, you have only to set 
% direct wave.

itau = [0];

% Mean power for each multipath normalized by direct wave.
% If you would like to simulate under one path fading model, you have only to set 
% direct wave.
dlvl = [0];

% Number of waves to generate fading for each multipath.
% In normal case, more than six waves are needed to generate Rayleigh fading
n0=[6];

% Initial Phase of delayed wave
% In this simulation four-path Rayleigh fading are considered.
th1=[0.0];

% Number of fading counter to skip 
itnd0=nd*IPOINT*100;

% Initial value of fading counter
% In this simulation one-path Rayleigh fading are considered.
% Therefore one fading counter are needed.
  
itnd1=[1000];

% Number of directwave + Number of delayed wave
% In this simulation one-path Rayleigh fading are considered
now1=1;        

% Maximum Doppler frequency [Hz]
% You can insert your favorite value
fd=160;       

% You can decide two mode to simulate fading by changing the variable flat
% flat     : flat fading or not 
% (1->flat (only amplitude is fluctuated),0->nomal(phase and amplitude are fluctutated)
flat =1;

%************************** START CALCULATION *******************************

nloop=1000;  % Number of simulation loops

noe = 0;    % Number of error data
nod = 0;    % Number of transmitted data

for iii=1:nloop
    
%*************************** Data generation ********************************

	data1=rand(1,nd*ml)>0.5;

%*************************** 16QAM Modulation ********************************

	[ich,qch]=qammod(data1,1,nd,ml);
	[ich1,qch1]= compoversamp(ich,qch,length(ich),IPOINT); 
	[ich2,qch2]= compconv(ich1,qch1,xh); 

%**************************** Attenuation Calculation ***********************
	
    spow=sum(ich2.*ich2+qch2.*qch2)/nd;
	attn=0.5*spow*sr/br*10.^(-ebn0/10);
	attn=sqrt(attn);

%********************** Fading channel **********************

  % Generated data are fed into a fading simulator
    [ifade,qfade,ramp]=sefade(ich2,qch2,itau,dlvl,th1,n0,itnd1,now1,length(ich2),tstp,fd,flat);
  
    % Updata fading counter
    itnd1 = itnd1+ itnd0;

%********************* Add White Gaussian Noise (AWGN) **********************
	
    [ich3,qch3]= comb(ifade,qfade,attn);% add white gaussian noise
 
%*************** Compensate the fluctuation of fading by ramp*******************    
    
    ich3=ich3./ramp(1:length(ramp));
    qch3=qch3./ramp(1:length(ramp));
    
	[ich4,qch4]= compconv(ich3,qch3,xh2);

    sampl=irfn*IPOINT+1;
	ich5 = ich4(sampl:IPOINT:length(ich4));
	qch5 = qch4(sampl:IPOINT:length(ich4));
        
%**************************** 16QAM Demodulation *****************************
	
    [demodata]=qamdemod(ich5,qch5,1,nd,ml);

%******************** Bit Error Rate (BER) ****************************
	
    noe2=sum(abs(data1-demodata));
	nod2=length(data1);
	noe=noe+noe2;
	nod=nod+nod2;

	fprintf('%d\t%e\n',iii,noe2/nod2);
end % for iii=1:nloop    

%********************** Output result ***************************

ber = noe/nod;
fprintf('%d\t%d\t%d\t%e\n',ebn0,noe,nod,noe/nod);
fid = fopen('BERqamfad.dat','a');
fprintf(fid,'%d\t%e\t%f\t%f\t\n',ebn0,noe/nod,noe,nod);
fclose(fid);

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