www.pudn.com > MODULATION.RAR > gmsk.m, change:2001-11-30,size:3387b


% Program 3-18 
% gmsk.m 
% 
% Simulation program to realize GMSK transmission system 
% 
% Programmed by R.Sawai and H.Harada 
% 
 
%******************** Preparation part ************************************* 
 
sr=256000.0; % Symbol rate 
ml=1;        % ml:Number of modulation levels  
br=sr.*ml;   % Bit rate 
nd = 1000;   % Number of symbols that simulates in each loop 
ebn0=5;      % Eb/N0 
IPOINT=8;    % Number of oversamples 
 
%************************* Filter initialization *************************** 
 
irfn=21;                  % Number of taps 
B=0.25*sr; 
B2=0.6*sr; 
[xh] = gaussf(B,irfn,IPOINT,sr,1);   %Transmitter filter coefficients  
[xh2] =gaussf(B2,irfn,IPOINT,sr,0);  %Receiver filter coefficients  
 
%******************** START CALCULATION ************************************* 
 
nloop=100;  % 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;  % rand: built in function 
 
%*************************** GMSK Modulation ********************************   
 
    data11=2*data1-1; 
    data2=oversamp(data11,length(data11),IPOINT);     
    data3=conv(data2,xh);                           % NEW for GMSK 
 
    th=zeros(1,length(data3)+1); 
    ich2=zeros(1,length(data3)+1); 
    qch2=zeros(1,length(data3)+1); 
 
    for ii=2:length(data3)+1 
	    th(1,ii)=th(1,ii-1)+pi/2*data3(1,ii-1)./IPOINT; 
    end 
 
    ich2=cos(th); 
    qch2=sin(th); 
 
%************************** Attenuation Calculation *********************** 
 
    spow=sum(ich2.*ich2+qch2.*qch2)/nd;  % sum: built in function 
	attn=0.5*spow*sr/br*10.^(-ebn0/10); 
	attn=sqrt(attn);                     % sqrt: built in function 
    
%********************** Fading channel ********************** 
 
    %[ifade,qfade]=sefade2(data2,qdata1,itau,dlvl1,th1,n0,itnd1,now1,length(data2),fftlen2,fstp,fd,flat); 
 
%********************* Add White Gaussian Noise (AWGN) ********************** 
	 
    [ich3,qch3]= comb(ich2,qch2,attn);% add white gaussian noise 
	   
    [ich4,qch4] = compconv(ich3,qch3,xh2); 
    
    syncpoint =irfn*IPOINT-IPOINT/2+1; 
    ich5=ich4(syncpoint:IPOINT:length(ich4)); 
    qch5=qch4(syncpoint:IPOINT:length(qch4)); 
         
%**************************** GMSK Demodulation ***************************** 
 
    demoddata2(1,1)=-1; 
 
    for k=3:2:nd*ml+1 
         demoddata2(1,k)=ich5(1,k)*qch5(1,k-1)*cos(pi*(k))>0; 
    end 
 
    for n=2:2:nd*ml+1 
         demoddata2(1,n)=ich5(1,n-1)*qch5(1,n)*cos(pi*(n))>0; 
    end 
 
    [demodata]=demoddata2(1,2:nd*ml+1); 
     
%************************** 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('BERgmsk.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 ***************************