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% Program 3-14 
% msk_fading.m 
% 
% Simulation program to realize MSK transmission system 
% (under one path fading) 
% 
% Programmed by H.Harada and T.Yamamura 
% 
 
%******************** preparation part ************************************* 
 
sr=256000.0; % Symbol rate 
ml=1;        % ml:Number of modulation levels  
br=sr.*ml;   % Bit rate 
nd = 100;    % Number of symbols that simulates in each loop 
ebn0=10;     % Eb/N0 
IPOINT=8;    % Number of oversamples 
 
%******************* 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=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; 
 
%******************** 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)>0.5;  % rand: built in function 
 
%*************************** MSK Modulation ********************************   
   
    [ich,qch]=qpskmod(data1,1,nd/2,2); 
    smooth1=cos(pi/2*[-1+1./4.*[0:IPOINT-1]]); %IPOINT point filtering 
 
    for ii=1:length(ich) 
       ich2((ii-1)*IPOINT+1:ii*IPOINT)=(-1)^(ii-1)*smooth1.*ich(ii); 
       qch2((ii-1)*IPOINT+1:ii*IPOINT)=(-1)^(ii-1)*smooth1.*qch(ii); 
    end 
 
    ich21=[ich2 zeros(1,IPOINT/2)]; 
    qch21=[zeros(1,IPOINT/2) qch2]; 
    
%**************************** Attenuation Calculation *********************** 
 
    spow=sum(ich21.*ich21+qch21.*qch21)/nd/2    ;  % sum: built in function 
	attn=0.5*spow*sr/br/2*10.^(-ebn0/10); 
	attn=sqrt(attn);                             % sqrt: built in function 
    
%********************** Fading channel ********************** 
 
  % Generated data are fed into a fading simulator 
    [ifade,qfade]=sefade(ich21,qch21,itau,dlvl,th1,n0,itnd1,now1,length(ich21),tstp,fd,flat); 
   
  % Updata fading counter 
    itnd1 = itnd1+ itnd0; 
 
%********************* Add White Gaussian Noise (AWGN) ********************** 
	 
    [ich3,qch3]= comb(ifade,qfade,attn);% add white gaussian noise 
 
    syncpoint=1; 
 
	ich5 = ich3(syncpoint+IPOINT/2:IPOINT:length(ich2)); 
	qch5 = qch3(syncpoint+IPOINT:IPOINT:length(ich2)+IPOINT/2); 
    
    ich5(2:2:length(ich5))=-1*ich5(2:2:length(ich5)); 
    qch5(2:2:length(ich5))=-1*qch5(2:2:length(ich5)); 
 
%**************************** MSK Demodulation ***************************** 
 
    [demodata]=qpskdemod(ich5,qch5,1,nd/2,2); 
 
%************************** Bit Error Rate (BER) **************************** 
 
    noe2=sum(abs(data1-demodata));  % sum: built in function 
	nod2=length(data1);  % length: built in function 
	noe=noe+noe2; 
	nod=nod+nod2; 
 
	fprintf('%d\t%e\n',iii,noe2/nod2);  % fprintf: built in function 
 
end % for iii=1:nloop     
 
%********************** Output result *************************** 
 
ber = noe/nod; 
fprintf('%d\t%d\t%d\t%e\n',ebn0,noe,nod,noe/nod);  % fprintf: built in function 
fid = fopen('BERmskfad.dat','a'); 
fprintf(fid,'%d\t%e\t%f\t%f\t\n',ebn0,noe/nod,noe,nod);  % fprintf: built in function 
fclose(fid); 
 
%******************** end of file ***************************