57 lines
No EOL
1.5 KiB
Python
57 lines
No EOL
1.5 KiB
Python
# encoder_backup.py
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import numpy as np
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# System parameters
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G = 10.0 # power gain for even samples
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ENERGY_LIMIT = 2000.0 # total energy per block
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ALPHABET = (
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[chr(i) for i in range(ord('a'), ord('z')+1)] +
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[chr(i) for i in range(ord('A'), ord('Z')+1)] +
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[str(i) for i in range(10)] +
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[' ', '.']
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)
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assert len(ALPHABET) == 64, "Alphabet must be size 64"
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def hadamard(r: int) -> np.ndarray:
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if r == 0:
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return np.array([[1]], dtype=float)
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M = hadamard(r-1)
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return np.block([[M, M], [M, -M]])
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def Br(r: int) -> np.ndarray:
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M = hadamard(r)
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return np.vstack([M, -M])
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def make_codebook(r: int, num_blocks: int) -> np.ndarray:
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"""
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Build 64x64 codebook and scale blocks so energy per block ≤ ENERGY_LIMIT/num_blocks
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"""
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B_full = Br(r) #
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B = B_full[: len(ALPHABET), :] # now shape (64, 2^r)
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C = np.hstack([B, B]).astype(float) # shape (64, 2^{r+1})
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raw_norm = np.sum(C[0]**2)
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margin = 0.99
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alpha = margin * (ENERGY_LIMIT / num_blocks) / raw_norm
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return np.sqrt(alpha) * C
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def interleave(c: np.ndarray) -> np.ndarray:
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half = c.size // 2
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x = np.empty(c.size)
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x[0::2] = c[:half]
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x[1::2] = c[half:]
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return x
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def encode_message(msg: str, C: np.ndarray) -> np.ndarray:
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"""
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Encode 40-character message into interleaved code symbols
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"""
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if len(msg) != 40:
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raise ValueError("Message must be exactly 40 characters.")
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idx = [ALPHABET.index(ch) for ch in msg]
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blocks = [interleave(C[i]) for i in idx]
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return np.concatenate(blocks) |