5.m

维特比编解码

	randn('state', seed(2));            
	msg_enc  = bi2de(reshape(msg_enc_bi, size(msg_enc_bi,2)*k,size(msg_enc_bi,1) / k)');
	grayencod = bitxor([0:M-1],floor([0:M-1]/2)); msg_gr_enc = grayencod(msg_enc+1);
	msg_tx  = dmodce(msg_gr_enc, Fd, [Fs, pi/4], 'psk', M);
	msg_rx  = awgn(msg_tx, SNR-10*log10(1/codeRate)-10*log10(N));
	numModPlot = numEncPlot * Fs ./ k; tMod = [0:numModPlot-1] ./ Fs .* k;          
	plot(tMod, real(msg_tx(1:length(tMod))),'c-',tMod, imag(msg_tx(1:length(tMod))),'m-');
	axis([ min(tMod) max(tMod) -1.5 1.5]);  xlabel('Time'); ylabel('Amplitude'); 
    title('Encoded Symbols After QPSK Baseband Modulation' ); legend('In-phase','Quadrature',0);