% ofdm adaptive predistorter.m
% Simulation program to realize adaptive predistortion in OFDM transmission system

%********************** 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=4;       % Modulation level : 16QAM
sr=250000;  % Symbol rate
br=sr.*ml;  % Bit rate per carrier
gilen=32;   % Length of guard interval (points)
ebn0=100;     % Eb/N0
cap=512;    % the capacity of lut
table_an=ones(1,cap); % the amplitude talbe
table_pn=zeros(1,cap);% the phase table
table_indicate=[1,zeros(1,cap-2),1];% the indicate table


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

nloop=100;  % Number of simulation loops
noe = 0;    % Number of error data
nod = 0;    % Number of transmitted data
eop=0;      % Number of error packet
nop=0;      % Number of transmitted packet

for iii=1:nloop
%************************** transmitter *******************************

%************************** 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


[ich,qch]=qammod(paradata,para,nd,ml);
%************************** QAM modulation ****************************
kmod=1/sqrt(2); %  sqrt : built in function
ich1=ich.*kmod;
qch1=qch.*kmod;

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

x=ich1+qch1.*i;
y=ifft(x);      %  ifft : built in function
ich2=real(y);   %  real : built in function
qch2=imag(y);   %  imag : built in function



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

ich3=reshape(ich2,1,para*nd);
qch3=reshape(qch2,1,para*nd);
n=para*nd;

%************** R/P transformation*************************************
[in_an,in_pn]=RP(ich3,qch3);

%************** Predistorter*******************************************
[out2_an,out2_pn,table_an,table_pn,table_indicate]=predistorter(in_an,in_pn,table_an,table_pn,table_indicate);

%**************** P/R transformation***********************************
[ich4,qch4]=PR(out2_an,out2_pn);

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

ich5=reshape(ich4,para,nd); 
qch5=reshape(qch4,para,nd);

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

[ich6,qch6]= giins(ich4,qch4,fftlen,gilen,nd);
fftlen2=fftlen+gilen;

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

spow=sum(ich6.^2+qch6.^2)/nd./para;  %  sum : built in function
attn=0.5*spow*sr/br*10.^(-ebn0/10);
attn=sqrt(attn);

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

[ich7,qch7]=comb(ich6,qch6,attn);

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

[ich8,qch8]= girem(ich7,qch7,fftlen2,gilen,nd);

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

rx=ich8+qch8.*i;
ry=fft(rx);   	% fft : built in function
ich9=real(ry);	% real : built in function
qch9=imag(ry);	% imag : built in function

end 
%**************** constellation figure********************************
figure(1)
plot(ich9,qch9,'*');
figure(2)
plot(ich2,qch2,'*');