% bpsk_ber.m
%
% Simulation program to realize BPSK transmission system
%
% Programmed by H.Harada and T.Yamamura,
%
function [bpsk_ber]=berbpsk(snr_in_dB)

%******************** Preparation part **********************

sr=256000.0; % Symbol rate
ml=1;        % Number of modulation levels
br=sr.*ml;   % Bit rate (=symbol rate in this case)
nd = 100;   % Number of symbols that simulates in each loop
ebn0=snr_in_dB;          % Eb/N0
IPOINT=8;    % Number of oversamples

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

irfn=21;     % Number of filter 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


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

	data=rand(1,nd)>0.5;  % rand: built in function

%******************** BPSK Modulation ***********************  

    data1=data.*2-1;
	[data2] = oversamp( data1, nd , IPOINT) ;
	data3 = conv(data2,xh);  % conv: built in function

%****************** Attenuation Calculation *****************
	
    spow=sum(data3.*data3)/nd;
	attn=0.5*spow*sr/br*10.^(-ebn0/10);
	attn=sqrt(attn);
   
%********************** Fading channel **********************

  % Generated data are fed into a fading simulator
  % In the case of BPSK, only Ich data are fed into fading counter
  % [ifade,qfade]=sefade(data3,zeros(1,length(data3)),itau,dlvl,th1,n0,itnd1,now1,length(data3),tstp,fd,flat);
  
  % Updata fading counter
  %itnd1 = itnd1+ itnd0;

%************ Add White Gaussian Noise (AWGN) ***************
	
    inoise=randn(1,length(data3)).*attn;  % randn: built in function
	data4=data3+inoise;
	data5=conv(data4,xh2);  % conv: built in function

	sampl=irfn*IPOINT+1;
	data6 = data5(sampl:8:8*nd+sampl-1);
    
%******************** BPSK Demodulation *********************

    demodata=data6 > 0;

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

    noe2=sum(abs(data-demodata));  % sum: built in function
	nod2=length(data);  % length: built in function
	noe=noe+noe2;
	nod=nod+nod2;

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

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

bpsk_ber = noe/nod;
fprintf('%d\t%d\t%d\t%e\n',ebn0,noe,nod,noe/nod);


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