Chromatic dispersion and line width phase noise

[4yp.git] / CD_AWGN.m

diff --git a/CD_AWGN.m b/CD_AWGN.m
new file mode 100644 (file)
index 0000000..1ea6ad8
--- /dev/null
+++ b/CD_AWGN.m
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+numSymbs = 10000;
+M = 4;
+
+Rsym = 2.5e10; % symbol rate (sym/sec)
+
+rolloff = 0.25;
+span = 6; % filter span
+sps = 4; % samples per symbol
+
+fs = Rsym * sps; % sampling freq (Hz)
+Tsamp = 1 / fs;
+
+t = (0 : 1 / fs : numSymbs / Rsym + (1.5 * span * sps - 1) / fs)';
+
+EbN0_db = 0:0.2:14;
+EbN0 = 10 .^ (EbN0_db ./ 10);
+
+Es = 1;
+Eb = Es / log2(M);
+N0 = Eb ./ EbN0;
+
+EsN0 = EbN0 .* log2(M);
+EsN0_db = 10 .* log10(EsN0);
+
+plotlen = length(EbN0);
+
+ber = zeros(1, plotlen);
+
+data = randi([0 M - 1], numSymbs, 1);
+modData = pskmod(data, M, 0, 'gray');
+x = txFilter(modData, rolloff, span, sps);
+
+%% Simulate chromatic dispersion
+D = 20; % ps / (nm km)
+lambda = 1550; % nm
+z = 10; % km
+
+xCD = chromaticDispersion(x, D, lambda, z, Tsamp);
+xCD = normalizeEnergy(xCD, numSymbs, 1);
+
+
+for i = 1:plotlen
+  snr = EbN0_db(i) + 10 * log10(log2(M)) - 10 * log10(sps);
+  noiseEnergy = 10 ^ (-snr / 10);
+
+  y = awgn(xCD, snr, 'measured');
+
+  yCDComp = CDCompensation(y, D, lambda, z, Tsamp);
+
+  r = rxFilter(yCDComp, rolloff, span, sps);
+  %% normalize energy
+  %r = normalizeEnergy(r, numSymbs, 1 + noiseEnergy);
+
+  rSampled = r(sps*span/2+1:sps:(numSymbs + span/2) * sps);
+  demodData = pskdemod(rSampled, M, 0, 'gray');
+
+  [bitErrors, ber(i)] = biterr(data, demodData);
+end
+
+figure(1);
+clf;
+
+%% Plot simulated results
+semilogy(EbN0_db, ber, 'r', 'LineWidth', 2);
+hold on;
+
+theoreticalPSK(EbN0_db, M, 'b', 'LineWidth', 1);
+legend({'CD + AWGN + CD compensation', 'AWGN only'}, 'Location', 'southwest');
+
+title(strcat(num2str(M), '-PSK with chromatic dispersion and compensation'));
+grid on;
+xlabel('$E_b/N_0$ (dB)');
+ylabel('BER');
+
+formatFigure;