qam.rar_QAM 信号_QAM信号_matlab qam_qaM MATLAB_qam

% Simulation of digital M-QAM modulation schemes over an AWGN channel % Prof. Robert Morelos-Zaragoza, San Jose State University, May 2003. % Needs the Communications toolbox and file "normrnd.m" clear all; Fd = 1; Fs = 1; N= 70000 ; % Number of simulated points method='qask'; % Quadrature amplitude modulation set(1) = 4; set(2) = 16; set(3) = 64; % Sizes of constellations for j=1:1:3 M = set(j); % Size of M-QAM constellation l=1:1:M; aux = sum(abs(modmap(l-1,Fd,Fs,method,M)).^2)/M; energy(j) = aux(1)+aux(2); i=1; for esno=0:2:26; sigma = sqrt(10^(-esno/10)/2)*sqrt(energy(j)); x = randint(N,1,M); % Random information symbols (integers) y = modmap(x,Fd,Fs,method,M); % Mapped signal ynoisy = y + normrnd(0,sigma,N*Fs,2); % Gaussian noise added z = demodmap(ynoisy,Fd,Fs,method,M); % Demapped noisy signal s = symerr(x,z); % Number of symbol errors after demapping ber(j,i) = (s/N)/log2(M); % Bit error rate (BER) with Gray mapping snr(i) = esno; i=i+1; end j end semilogy(snr,ber(1,:),'-b^',snr,ber(2,:),'-bo',snr,ber(3,:),'-bs'); grid on; ylabel('BER'); xlabel('E/N_0 (dB)'); legend('QPSK', '16-QAM', '64-QAM',1); title('Error performance of M-QAM. SJSU. Spring 2003.');