| 1 | numSymbs = 10000; |
| 2 | M = 4; |
| 3 | |
| 4 | Rsym = 2.5e10; % symbol rate (sym/sec) |
| 5 | |
| 6 | rolloff = 0.25; |
| 7 | span = 6; % filter span |
| 8 | sps = 4; % samples per symbol |
| 9 | |
| 10 | fs = Rsym * sps; % sampling freq (Hz) |
| 11 | Tsamp = 1 / fs; |
| 12 | |
| 13 | t = (0 : 1 / fs : numSymbs / Rsym + (1.5 * span * sps - 1) / fs)'; |
| 14 | |
| 15 | EbN0_db = 0:0.2:14; |
| 16 | EbN0 = 10 .^ (EbN0_db ./ 10); |
| 17 | |
| 18 | Es = 1; |
| 19 | Eb = Es / log2(M); |
| 20 | N0 = Eb ./ EbN0; |
| 21 | |
| 22 | EsN0 = EbN0 .* log2(M); |
| 23 | EsN0_db = 10 .* log10(EsN0); |
| 24 | |
| 25 | plotlen = length(EbN0); |
| 26 | |
| 27 | ber = zeros(1, plotlen); |
| 28 | |
| 29 | data = randi([0 M - 1], numSymbs, 1); |
| 30 | modData = pskmod(data, M, 0, 'gray'); |
| 31 | x = txFilter(modData, rolloff, span, sps); |
| 32 | |
| 33 | %% Simulate chromatic dispersion |
| 34 | D = 20; % ps / (nm km) |
| 35 | lambda = 1550; % nm |
| 36 | z = 10; % km |
| 37 | |
| 38 | xCD = chromaticDispersion(x, D, lambda, z, Tsamp); |
| 39 | xCD = normalizeEnergy(xCD, numSymbs, 1); |
| 40 | |
| 41 | |
| 42 | for i = 1:plotlen |
| 43 | snr = EbN0_db(i) + 10 * log10(log2(M)) - 10 * log10(sps); |
| 44 | noiseEnergy = 10 ^ (-snr / 10); |
| 45 | |
| 46 | y = awgn(xCD, snr, 'measured'); |
| 47 | |
| 48 | yCDComp = CDCompensation(y, D, lambda, z, Tsamp); |
| 49 | |
| 50 | r = rxFilter(yCDComp, rolloff, span, sps); |
| 51 | %% normalize energy |
| 52 | %r = normalizeEnergy(r, numSymbs, 1 + noiseEnergy); |
| 53 | |
| 54 | rSampled = r(sps*span/2+1:sps:(numSymbs + span/2) * sps); |
| 55 | demodData = pskdemod(rSampled, M, 0, 'gray'); |
| 56 | |
| 57 | [bitErrors, ber(i)] = biterr(data, demodData); |
| 58 | end |
| 59 | |
| 60 | figure(1); |
| 61 | clf; |
| 62 | |
| 63 | %% Plot simulated results |
| 64 | semilogy(EbN0_db, ber, 'r', 'LineWidth', 2); |
| 65 | hold on; |
| 66 | |
| 67 | theoreticalPSK(EbN0_db, M, 'b', 'LineWidth', 1); |
| 68 | legend({'CD + AWGN + CD compensation', 'AWGN only'}, 'Location', 'southwest'); |
| 69 | |
| 70 | title(strcat(num2str(M), '-PSK with chromatic dispersion and compensation')); |
| 71 | grid on; |
| 72 | xlabel('$E_b/N_0$ (dB)'); |
| 73 | ylabel('BER'); |
| 74 | |
| 75 | formatFigure; |