From be6ded216211da5121f1ae30a3fbea19d182e3ca Mon Sep 17 00:00:00 2001
From: Andreas Tsouchlos <an.tsouchlos@gmail.com>
Date: Mon, 7 Nov 2022 00:32:54 +0100
Subject: [PATCH] Fixed SNR amplitude; Fixed BER calculation

---
 sw/decoders/utility.py | 10 ++++++----
 sw/main.py             |  5 +++--
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/sw/decoders/utility.py b/sw/decoders/utility.py
index 9ea4fc3..487aec5 100644
--- a/sw/decoders/utility.py
+++ b/sw/decoders/utility.py
@@ -19,15 +19,16 @@ def _get_noise_amp_from_SNR(SNR: float, signal_amp: float = 1) -> float:
     return noise_amp
 
 
-def add_awgn(c: np.array, SNR: float) -> np.array:
+def add_awgn(c: np.array, SNR: float, signal_amp: float = 1) -> np.array:
     """Add Additive White Gaussian Noise to a data vector. As this function adds random noise to the input,
     the output changes, even if it is called multiple times with the same input.
 
     :param c: Binary vector representing the data to be transmitted
     :param SNR: Signal-to-Noise-Ratio in dB
+    :param signal_amp: Amplitude of the signal. Used for the noise amplitude calculation
     :return: Data vector with added noise
     """
-    noise_amp = _get_noise_amp_from_SNR(SNR, signal_amp=1)
+    noise_amp = _get_noise_amp_from_SNR(SNR, signal_amp=signal_amp)
     y = c + np.random.normal(scale=noise_amp, size=c.size)
     return y
 
@@ -66,6 +67,7 @@ def test_decoder(decoder: typing.Any,
                     bar_format="{l_bar}{bar}| {n_fmt}/{total_fmt}"):
 
         total_bit_errors = 0
+        total_bits = 0
 
         for n in tqdm(range(N_max), desc=f"Simulating for SNR = {SNR} dB",
                       position=1,
@@ -74,15 +76,15 @@ def test_decoder(decoder: typing.Any,
 
             # TODO: Is this a valid simulation? Can we just add AWGN to the codeword, ignoring and modulation and (
             #  e.g. matched) filtering?
-            y = add_awgn(x, SNR)
+            y = add_awgn(x, SNR, signal_amp=(1 / np.sqrt(2)))
             y_hat = decoder.decode(y)
 
             total_bit_errors += count_bit_errors(c, y_hat)
+            total_bits += c.size
 
             if total_bit_errors >= target_bit_errors:
                 break
 
-        total_bits = c.size * N_max
         BERs.append(total_bit_errors / total_bits)
 
     return np.array(SNRs), np.array(BERs)
diff --git a/sw/main.py b/sw/main.py
index 0375a23..bb4d8a2 100644
--- a/sw/main.py
+++ b/sw/main.py
@@ -21,7 +21,7 @@ def main():
 
     # Test decoder
 
-    d = np.array([0, 1, 0, 1])
+    d = np.array([0, 1, 1, 1])
     c = np.dot(G.transpose(), d) % 2
 
     print(f"Simulating with c = {c}")
@@ -33,7 +33,8 @@ def main():
 
     ax = sns.lineplot(data=data, x="SNR", y="BER")
     ax.set(yscale="log")
-    #ax.set_ylim([10e-6, 10e0])
+    ax.set_yticks([10e-5, 10e-4, 10e-3, 10e-2, 10e-1, 10e0])
+    # ax.set_ylim([10e-6, 10e0])
     plt.show()