73 lines
2.4 KiB
Python
73 lines
2.4 KiB
Python
"""This file contains utility functions relating to tests and simulations of the decoders."""
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import numpy as np
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import typing
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from tqdm import tqdm
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from utility import noise
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def count_bit_errors(d: np.array, d_hat: np.array) -> int:
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"""Count the number of wrong bits in a decoded codeword.
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:param d: Originally sent data
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:param d_hat: Received data
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:return: Number of bit errors
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"""
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return np.sum(d != d_hat)
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def test_decoder(x: np.array,
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decoder: typing.Any,
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SNRs: typing.Sequence[float] = np.linspace(1, 7, 7),
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target_frame_errors: int = 100,
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N_max: int = 10000) \
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-> typing.Tuple[np.array, np.array]:
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"""Calculate the Bit Error Rate (BER) for a given decoder for a number of SNRs.
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This function assumes the all-zeros assumption holds. Progress is printed to stdout.
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:param x: Codeword to be sent (Element of [0, 1]^n)
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:param decoder: Instance of the decoder to be tested
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:param SNRs: List of SNRs for which the BER should be calculated
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:param target_frame_errors: Number of frame errors after which to stop the simulation
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:param N_max: Maximum number of iterations to perform for each SNR
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:return: Tuple of numpy arrays of the form (SNRs, BERs)
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"""
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x_bpsk = 1 - 2 * x # Map x from [0, 1]^n to [-1, 1]^n
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BERs = []
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for SNR in tqdm(SNRs, desc="Calculating Bit-Error-Rates",
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position=0,
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leave=False,
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bar_format="{l_bar}{bar}| {n_fmt}/{total_fmt}"):
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total_bit_errors = 0
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total_bits = 0
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total_frame_errors = 0
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for n in tqdm(range(N_max), desc=f"Simulating for SNR = {SNR} dB",
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position=1,
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leave=False,
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bar_format="{l_bar}{bar}| {n_fmt}/{total_fmt}"):
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# Simulate channel
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y = noise.add_awgn(x_bpsk, SNR, signal_amp=np.sqrt(2))
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# Decode received frame
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x_hat = decoder.decode(y)
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# Calculate statistics
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total_bit_errors += count_bit_errors(x, x_hat)
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total_bits += x.size
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total_frame_errors += 1 if total_bit_errors > 0 else 0
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if total_frame_errors >= target_frame_errors:
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break
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BERs.append(total_bit_errors / total_bits)
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return np.array(SNRs), np.array(BERs)
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