% Experiment 5, CSBOOK: Haykin% Timing (clock) recovery% Measured S-curve of the % NDA-ELD loop, Noise added, E/N=10dBclear all% time slotT=1/8000;deltaT=T/50;%Nyquest pulset=[-3*T/2+deltaT/2:deltaT:3*T/2-deltaT/2];h=sinc(2*t./T).*(cos(pi*t./T)./(1-2*t./T).^2);% Generating QPSK signalsno_of_bits=2000;b=round(rand(no_of_bits,1));bits=2*b-1;bitsi=bits(1:2:length(bits)-1);bitsq=bits(2:2:length(bits));amp=(bitsi+i*bitsq)/sqrt(2);amp=conj(amp');% signal to noise ratios  SNRdB =[30]; snr = 10^(SNRdB/10); S_curvef=0; for trial=1:100% Add AWGN with STD equal to std_value       wn = (randn(length(amp),1)+i*randn(length(amp),1))/sqrt(2)/sqrt(snr);        s_n=amp+wn';%FIR filtering  s_i=upfirdn(real(s_n),h,50,1);  s_q=upfirdn(imag(s_n),h,50,1);  s=s_i+i*s_q; x=s(1: length(s)-15);        % FIR filtering         y_i=upfirdn(real(x),h,50,1);         y_q=upfirdn(imag(x),h,50,1);         y=(y_i+y_q);	%Timing error prediction	tau=15;tauerror=-50:50;tauhat=tau-tauerror;		for k=1:990     			tp(k,:)=y(75+50*k+48+tauhat)-y(75+50*k+3+tauhat);		 	tq(k,:)=y(75+50*k+25+tauhat);     			tqconj(k,:)=conj(tq(k,:));     			e(k,:)=real(tqconj(k,:).*tp(k,:));				end	%Accumulate S_curve	for k=1:length(tauerror)  		S_curve(k)=mean(e(:,k));	end      S_curvef=S_curvef+S_curve;end S_curvef=S_curvef/trial; plot(-0.48:1/50:0.5, S_curvef(51:100))ylabel('S-curve')xlabel('Normalized timing offset, \delta/T')