% Assignment No.7
% ofdm_fading.m enhancement
% plot the BER-EbN0

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

para=128;   % Number of parallel channel to transmit (points)
fftlen=128; % FFT length
noc=128;    % Number of carrier
nd=6;       % Number of information OFDM symbol for one loop
ml=1;       %%%Revised Modulation level : QPSK
sr=250000;  % Symbol rate
br=sr.*ml;  % Bit rate per carrier
gilen=32;   % Length of guard interval (points)

%******************* 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/(fftlen+gilen); 

% 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*(fftlen+gilen)*10;

% 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=320;       

% 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;

%************************** main loop part **************************

ebn0=0:5:35;
for j=1:length(ebn0)

noe = 0;    % Number of error data
nod = 0;    % Number of transmitted data
eop=0;      % Number of error packet
nop=0;      % Number of transmitted packet

while noe<=1000


%************************** Data generation **************************** 

seldata=rand(1,para*nd*ml)>0.5;  %  rand : built in function

%****************** Serial to parallel conversion ***********************

paradata=reshape(seldata,para,nd*ml); %  reshape : built in function

%************************** QPSK modulation ***************************** 

ich=2.*paradata-1;%%%Revised
kmod=1/sqrt(2); %  sqrt : built in function
ich1=ich.*kmod;

%******************* IFFT ************************

x=ich1;
y=ifft(x);      %  ifft : built in function
ich2=real(y);   %  real : built in function
qch2=imag(y);   % %%Revised imag : built in function

%********* Gurad interval insertion **********

[ich3,qch3]= giins(ich2,qch2,fftlen,gilen,nd);
fftlen2=fftlen+gilen;

%********* Attenuation Calculation *********

spow=sum(ich3.^2+qch3.^2)/nd./para;  %%%Revised  sum : built in function
attn=0.5*spow*sr/br*10.^(-ebn0(j)/10);
attn=sqrt(attn);

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

% Generated data are fed into a fading simulator
[ifade,qfade]=sefade(ich3,qch3,itau,dlvl,th1,n0,itnd1,now1,length(ich3),tstp,fd,flat);
  
% Updata fading counter
itnd1 = itnd1+ itnd0;

%***************************  Receiver  *****************************
%***************** AWGN addition ********* 

[ich4,qch4]=comb(ifade,qfade,attn);

%****************** Guard interval removal *********

[ich5,qch5]= girem(ich4,qch4,fftlen2,gilen,nd);

%******************  FFT  ******************

rx=ich5+qch5.*i;
ry=fft(rx);   	% fft : built in function
ich6=real(ry);	% real : built in function

%***************** demoduration *******************

ich7=ich6./kmod;
[demodata]=ich7>0;%%%Revised   

%**************  Parallel to serial conversion  *****************

demodata1=reshape(demodata,1,para*nd*ml);

%************************** Bit Error Rate (BER) ****************************

% instantaneous number of error and data
noe2=sum(abs(demodata1-seldata));  %  sum : built in function
nod2=length(seldata);  %  length : built in function

% cumulative the number of error and data in noe and nod
noe=noe+noe2;
nod=nod+nod2;

% calculating PER
if noe2~=0  
   eop=eop+1;
else
   eop=eop;
end   
   eop;
   nop=nop+1;
      
end

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

per=eop/nop;
pack_err(j)=per;%%%Revised
ber=noe/nod;
bit_err(j)=ber;%%%Revised
end

semilogy(ebn0,bit_err,'.');%%% Revised
hold on;%%% Revised
semilogy(ebn0,pack_err,'o');%%% Revised
%******************** end of file ***************************