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39 lines
1.5 KiB
Plaintext
39 lines
1.5 KiB
Plaintext
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#!/bin/sh
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# Example of decoding a (7,4) Hamming code using exhaustive enumeration and
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# probability propagation, with an Additive White Gaussian Noise channel with
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# noise standard deviation of 0.5, for which Eb/N0 = 5.44 dB.
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#
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# Testing is done by transmitting zero blocks, which is sufficient because
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# both the channel and the decoding procedure are symmetrical. WARNING: But
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# things can easily become non-symmetrical with bugs, so this technique should
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# be used with caution, and only when necessary for performance reasons.
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# Decoding is done three times, once minimizing block error probability, once
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# minimizing bit error probability, and once by up to 200 iterations of
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# probability propagation.
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set -e # Stop if an error occurs
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set -v # Echo commands as they are read
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make-pchk ex-ham7a.pchk 3 7 0:0 0:3 0:4 0:5 1:1 1:3 1:4 1:6 2:2 2:4 2:5 2:6
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make-gen ex-ham7a.pchk ex-ham7a.gen dense
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transmit 7x100000 ex-ham7a.rec 1 awgn 0.5
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# DECODE BY ENUMERATION TO MINIMIZE BLOCK ERROR PROBABILITY
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decode ex-ham7a.pchk ex-ham7a.rec ex-ham7a.dec-blk awgn 0.5 \
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enum-block ex-ham7a.gen
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verify ex-ham7a.pchk ex-ham7a.dec-blk ex-ham7a.gen
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# DECODE BY ENUMERATION TO MINIMIZE BIT ERROR PROBABILITY
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decode ex-ham7a.pchk ex-ham7a.rec ex-ham7a.dec-bit awgn 0.5 \
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enum-bit ex-ham7a.gen
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verify ex-ham7a.pchk ex-ham7a.dec-bit ex-ham7a.gen
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# DECODE BY PROBABILITY PROPAGATION
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decode ex-ham7a.pchk ex-ham7a.rec ex-ham7a.dec-prp awgn 0.5 \
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prprp 200
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verify ex-ham7a.pchk ex-ham7a.dec-prp ex-ham7a.gen
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