16_QAM.zip_QAM 误码率_QAM误码率

% Clear all the previously used variables and close all figures clear all; close all; format long; % Frame Length 'Should be multiple of four or else padding is needed' bit_count = 4*1000; % Range of SNR over which to simulate Eb_No = -6: 1: 10; % Convert Eb/No values to channel SNR % Consult BERNARD SKLAR'S book 'Digital Communications, Principles % and Applications'. SNR = Eb_No + 10*log10(4); % Start the main calculation loop for aa = 1: 1: length(SNR) % Initiate variables T_Errors = 0; T_bits = 0; % Keep going until you get 100 errors while T_Errors < 100 % Generate some random bits uncoded_bits = round(rand(1,bit_count)); % Split the stream into 4 substreams B = reshape(uncoded_bits,4,length(uncoded_bits)/4); B1 = B(1,:); B2 = B(2,:); B3 = B(3,:); B4 = B(4,:); % 16-QAM modulator % normalizing factor a = sqrt(1/10); % bit mapping tx = a*(-2*(B3-0.5).*(3-2*B4)-j*2*(B1-0.5).*(3-2*B2)); % Noise variance N0 = 1/10^(SNR(aa)/10); % Send over Gaussian Link to the receiver rx = tx + sqrt(N0/2)*(randn(1,length(tx))+i*randn(1,length(tx))); %--------------------------------------------------------------- % 16-QAM demodulator at the Receiver a = 1/sqrt(10); B5 = imag(rx)<0; B6 = (imag(rx)<2*a) & (imag(rx)>-2*a); B7 = real(rx)<0; B8 = (real(rx)<2*a) & (real(rx)>-2*a); % Merge into single stream again temp = [B5;B6;B7;B8]; B_hat = reshape(temp,1,4*length(temp)); % Calculate Bit Errors diff = uncoded_bits - B_hat ; T_Errors = T_Errors + sum(abs(diff)); T_bits = T_bits + length(uncoded_bits); end % Calculate Bit Error Rate BER(aa) = T_Errors / T_bits; disp(sprintf('bit error probability = %f',BER(aa))); % Plot the received Symbol Constellation figure; grid on; plot(rx,'x'); xlabel('Inphase Component'); ylabel('Quadrature Component'); Title('Constellation of Transmitted Symbols'); end %------------------------------------------------------------ % Finally plot the BER Vs. SNR(dB) Curve on logarithmic scale % BER through Simulation figure(1); semilogy(SNR,BER,'or'); hold on; grid on title('BER Vs SNR Curve for QAM-16 Modulation Scheme in AWGN'); xlabel('SNR (dB)'); ylabel('BER') % Theoretical BER figure(1); theoryBer = (1/4)*3/2*erfc(sqrt(4*0.1*(10.^(Eb_No/10)))); semilogy(SNR,theoryBer); legend('Simulated','Theoretical');