work7gmsk_turbo.m

来自「turbocoding in gmsk modulation」· M 代码 · 共 136 行

clear
clc
sr=256000.0; % Symbol rate
ml=1;        % ml:Number of modulation levels 
br=sr.*ml;   % Bit rate
nd = 10000;   % Number of symbols that simulates in each loop
ebn0=5;      % Eb/N0
SNR=[0:10];
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=10;  % Number of simulation loops


% for iiii=1:length(SNR)
 
for iiii=1:length(SNR)
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
    [data111]=convlenc(data1);
%     [data111, alpha] = turbo_encode(data1, length(data1), 1, 0, 3);
%   'seqin'   : input binary sequence, in {0,1} form; if set to the string "length" however,
%               the function just returns the codeword length as 'seqout'.
%   'len'     : length of sequence (input beeing padded or truncated).
%   'key'     : seed to use for pseudo-random interleaving during encoding.
%   'puncture': 1 to use the puncturer, giving rate 1/2; 0 otherwise, giving rate 1/3 (default).
%   'gnum'    : generator polynom, 1 (default), 2 or 3.
%*************************** GMSK Modulation ********************************  
%     data111=2*data11-1;
    data2=oversamp(data111,length(data111),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.^(-SNR(iiii)/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*2+1
         demoddata2(1,k)=ich5(1,k)*qch5(1,k-1)*cos(pi*(k))>0;
    end

    for n=2:2:nd*ml*2+1
         demoddata2(1,n)=ich5(1,n-1)*qch5(1,n)*cos(pi*(n))>0;
    end

    [demodata]=demoddata2(1,2:nd*ml*2+1);

%************************** Bit Error Rate (BER) ****************************
	[dec_op]=viterbidec(demodata);
 demodata1=2*demodata-1;
% [dec_op, alpha] = turbo_decode(demodata1, length(demodata1), 1, 1, 1, 1, 5);
%  
%function [seqout, alpha] = turbo_decode(seqin, len, key, puncture, gnum,
%dec_alg, nb_iters)
% Input:
%   'seqin'    : input codeword, in {<0, >=0} form (soft decoding);
%                should be normalized in interval [-1,1].
%   'len'      : length of original sequence.
%   'key'      : seed to use for pseudo-random interleaving during decoding.
%   'puncture' : 1 to use the puncturer, giving rate 1/2; 0 otherwise, giving rate 1/3 (default).
%   'gnum'     : generator polynom, 1 (default), 2 or 3.
%   'dec_alg'  : decoding algorithm: 1 for logmapo decoder (default), 2 for sova0 decoder.
%   'nb_iters' : maximum number of iterations (defalut: 5).
%
% Output:
%   'seqout'   : output decoded sequence, in {0,1} form;
%                note: {<0,>=0} is mapped to {0,1}
%   'alpha'    : used pseudo-random interleaving.

% ltot1 = numbits in seqin+2
    noe2=size(find(data1-dec_op),2);  % sum: built in function
	nod2=length(data1);  % length: built in function
    
end
    
% 	fprintf('%d\t%e\n',iii,noe2/nod2);  % fprintf: built in function
noe=noe+noe2;
nod=nod+nod2;
ner(iiii)=noe/nod;
end   

%********************** Output result ***************************
semilogy(SNR,ner,'bp-','LineWidth',2)
% axis([-2 13 10^-5 0.5])
xlabel('Eb/No, dB');
ylabel('Bit Error Rate');
% 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 ***************************