Added Encoder class and modified interface of utility.test_decoder()

sw/decoders/channel.py

@@ -0,0 +1,24 @@
+import numpy as np
+
+
+# TODO: Should the encoder be responsible for mapping the message from [0, 1]^n to [-1, 1]^n?
+#  (ie. should the encoder perform modulation?)
+class Encoder:
+    """Class implementing an encoder for block codes.
+    """
+    def __init__(self, G: np.array):
+        """Construct a new Encoder object.
+
+        :param G: Generator matrix
+        """
+        self._G = G
+
+    def encode(self, d: np.array) -> np.array:
+        """Map a given dataword onto the corresponding codeword.
+
+        The returned codeword is mapped from [0, 1]^n onto [-1, 1]^n.
+
+        :param d: Dataword (element of [0, 1]^n)
+        :return: Codeword (already element of [-1, 1]^n)
+        """
+        return np.dot(d, self._G) * 2 - 1

sw/decoders/utility.py

@@ -43,26 +43,28 @@ def count_bit_errors(d: np.array, d_hat: np.array) -> int:
     return np.sum(d != d_hat)
 
 
-def test_decoder(decoder: typing.Any,
+def test_decoder(encoder: typing.Any,
+                 decoder: typing.Any,
                  d: np.array,
-                 c: np.array,
                  SNRs: typing.Sequence[float] = np.linspace(1, 4, 7),
-                 target_bit_errors=100,
+                 target_bit_errors: int = 100,
-                 N_max=10000) \
+                 N_max: int = 10000) \
         -> typing.Tuple[np.array, np.array]:
     """Calculate the Bit Error Rate (BER) for a given decoder for a number of SNRs.
 
     This function prints its progress to stdout.
 
+    :param encoder: Instance of the encoder used to generate the codeword to transmit
     :param decoder: Instance of the decoder to be tested
     :param d: Dataword (element of [0, 1]^n)
-    :param c: Codeword whose transmission is to be simulated (element of [0, 1]^n)
     :param SNRs: List of SNRs for which the BER should be calculated
     :param target_bit_errors: Number of bit errors after which to stop the simulation
     :param N_max: Maximum number of iterations to perform for each SNR
     :return: Tuple of numpy arrays of the form (SNRs, BERs)
     """
-    x = c * 2 - 1  # Map the codeword from [0, 1]^n to [-1, 1]^n
+
+    x = encoder.encode(d)
+
     BERs = []
     for SNR in tqdm(SNRs, desc="Calculating Bit-Error-Rates",
                     position=0,
@@ -79,10 +81,11 @@ 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, signal_amp=np.sqrt(2))
+
             y_hat = decoder.decode(y)
 
             total_bit_errors += count_bit_errors(d, y_hat)
-            total_bits += c.size
+            total_bits += x.size
 
             if total_bit_errors >= target_bit_errors:
                 break

sw/main.py

@@ -5,6 +5,7 @@ import pandas as pd
 
 from decoders import proximal
 from decoders import naive_soft_decision
+from decoders import channel
 from decoders import utility
 
 
@@ -20,20 +21,27 @@ def main():
                   [0, 1, 1, 0, 0, 1, 1],
                   [0, 0, 0, 1, 1, 1, 1]])
 
+    encoder = channel.Encoder(G)
+
+    proximal_decoder = proximal.ProximalDecoder(H, K=100, gamma=0.01)
+    soft_decision_decoder = naive_soft_decision.SoftDecisionDecoder(G, H)
+
     # Test decoder
 
-    d = np.array([0, 0, 0, 0])
+    k, n = G.shape
-    c = np.dot(G.transpose(), d) % 2
+    d = np.zeros(k)  # All-zeros assumption
 
-    print(f"Simulating with c = {c}")
+    SNRs_sd, BERs_sd = utility.test_decoder(encoder=encoder,
+                                            decoder=soft_decision_decoder,
+                                            d=d,
+                                            SNRs=np.linspace(1, 7, 9),
+                                            target_bit_errors=500)
 
-    # decoder = proximal.ProximalDecoder(H, K=100, gamma=0.01)
+    data = pd.DataFrame({"SNR": SNRs_sd, "BER_sd": BERs_sd})
-    decoder = naive_soft_decision.SoftDecisionDecoder(G, H)
-    SNRs, BERs = utility.test_decoder(decoder, d, c, SNRs=np.linspace(1, 7, 9), target_bit_errors=500, N_max=10000)
 
-    data = pd.DataFrame({"SNR": SNRs, "BER": BERs})
+    # Plot results
 
-    ax = sns.lineplot(data=data, x="SNR", y="BER")
+    ax = sns.lineplot(data=data, x="SNR", y="BER_sd")
     ax.set(yscale="log")
     ax.set_yticks([10e-5, 10e-4, 10e-3, 10e-2, 10e-1, 10e0])
     # ax.set_ylim([10e-6, 10e0])