Chromatic dispersion and line width phase noise

[4yp.git] / phasenoise_AWGN.m

diff --git a/phasenoise_AWGN.m b/phasenoise_AWGN.m
new file mode 100644 (file)
index 0000000..a9c852a
--- /dev/null
+++ b/phasenoise_AWGN.m
@@ -0,0 +1,122 @@
+function phasenoise_AWGN(rolloff, M, numSymbs)
+  %% Set defaults for inputs
+  if nargin < 3
+    numSymbs = 1000;
+  end
+  if nargin < 2
+    M = 2;
+  end
+  if nargin < 1
+    rolloff = 0.25;
+  end
+
+  plotted = 0;
+
+  Rsym = 2.5e10; % symbol rate (sym/sec)
+
+  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);
+
+  linewidthTx = 0;%1e5; % Hz
+  linewidthLO = 1e6; % Hz
+  %%linewidthTx = Rsym * 1e-4; % Hz
+  %%linewidthLO = Rsym * 1e-3; % Hz
+
+  totalIterations = 1;
+
+  for iter = 1:totalIterations
+    [xPN, pTxLO] = phaseNoise(x, linewidthTx, linewidthLO, Tsamp);
+
+    for i = 1:plotlen
+      snr = EbN0_db(i) + 10 * log10(log2(M)) - 10 * log10(sps);
+      noiseEnergy = 10 ^ (-snr / 10);
+
+      y = awgn(xPN, snr, 'measured');
+
+      r = rxFilter(y, rolloff, span, sps);
+      %% normalize energy
+      %r = normalizeEnergy(r, numSymbs, 1 + noiseEnergy);
+
+      [rPhaseEq, phiests] = phaseNoiseCorr(r, M, 40 * sps);
+
+      rSampled = rPhaseEq(sps*span/2+1:sps:(numSymbs + span/2) * sps);
+      demodData = pskdemod(rSampled, M, 0, 'gray')';
+
+      %%[bitErrors, ber(i)] = biterr(data, demodData);
+      [zzz, thisBER] = biterr(data, demodData);
+      ber(i) = ber(i) + thisBER / totalIterations;
+
+
+      if plotted == 0 && EbN0_db(i) >6 && ber(i) > 1e-1
+        plotted=1
+        figure(1234);
+        plot(-phiests);
+        hold on;
+        plot(pTxLO);
+        legend('estimate', 'actual');
+        hold off;
+
+        figure(100);
+        %plot(t(1:length(x)), real(x));
+        %%plot(t, real(x(1:length(t))));
+        length(t)
+        length(x)
+        hold on
+        %%plot(t(1:length(xPhaseNoise)), real(xPhaseNoise));
+
+        plot(t, real(r), 'g')
+
+        sampledTimes = t(sps*span/2+1:sps:(numSymbs+span/2)*sps);
+
+        plot(sampledTimes, real(rSampled), 'x')
+        hold off
+
+      end
+
+    end
+  end
+
+
+  figure(1);
+  clf;
+
+  %% Plot simulated results
+  semilogy(EbN0_db, ber, 'r', 'LineWidth', 2);
+  hold on;
+
+  theoreticalPSK(EbN0_db, M, 'b', 'LineWidth', 1);
+  legend({'Simulated phase noise', 'Without phase noise'}, 'Location', 'southwest');
+
+  title(strcat(num2str(M), '-PSK with phase noise and correction'));
+  grid on;
+  xlabel('$E_b/N_0$ (dB)');
+  ylabel('BER');
+
+  formatFigure;
+end