Chromatic dispersion and line width phase noise

[4yp.git] / theoreticalPSK.m

diff --git a/theoreticalPSK.m b/theoreticalPSK.m
new file mode 100644 (file)
index 0000000..95fbf97
--- /dev/null
+++ b/theoreticalPSK.m
@@ -0,0 +1,20 @@
+function theoreticalPSK(EbN0_db, M, varargin)
+  %% Plot theoretical curve
+  EbN0 = 10 .^ (EbN0_db ./ 10);
+  if M == 2 || M == 4
+    %% BPSK: bit error when noise Nr > sqrt(Eb)
+    %%   Pr(Nr > sqrt(Eb))
+    %% = Pr(Z > sqrt(Eb) / sqrt(N0/2))
+    %%
+    %% QPSK = 2 BPSKs, one real and one imaginary, each with one bit
+    %% so BER is the same as BPSK (assuming Gray code)
+    ber_th = qfunc(sqrt(2 * EbN0));
+    semilogy(EbN0_db, ber_th, varargin{:});
+  else
+    %% Approximation: J.G. Proakis and M. Salehi, 2000, Contemporary
+    %%                Communication Systems using MATLAB (Equations
+    %%                7.3.18 and 7.3.19), Brooks/Cole.
+    ber_ap = 2 * qfunc(sqrt(EbN0 * log2(M) * 2) * sin(pi / M)) / log2(M);
+    semilogy(EbN0_db, ber_ap, varargin{:});
+  end
+end