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129 lines
3.0 KiB
C++
129 lines
3.0 KiB
C++
// Copyright 2020-2021 Mobilinkd LLC.
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// make CXXFLAGS="$(pkg-config --cflags gtest) $(pkg-config --libs gtest) -I. -O3" tests/TrellisTest
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#pragma once
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#include <array>
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#include <cstdlib>
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#include <cstdint>
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namespace modemm17
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{
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inline std::array<int8_t, 61> make_p1() {
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std::array<int8_t, 61> result{};
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for (size_t i = 0, j = 2; i != 61; ++i) {
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if (i == j) {
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result[i] = 0;
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j += 4;
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} else {
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result[i] = 1;
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}
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}
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return result;
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};
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/// Puncture matrix for LSF
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constexpr auto P1 = std::array<int8_t, 61>{
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1,
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1, 0, 1, 1, // M1
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1, 0, 1, 1, // M2
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1, 0, 1, 1, // M3
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1, 0, 1, 1, // M4
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1, 0, 1, 1, // M5
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1, 0, 1, 1, // M6
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1, 0, 1, 1, // M7
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1, 0, 1, 1, // M8
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1, 0, 1, 1, // M9
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1, 0, 1, 1, // M10
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1, 0, 1, 1, // M10
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1, 0, 1, 1, // M12
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1, 0, 1, 1, // M13
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1, 0, 1, 1, // M14
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1, 0, 1, 1 // M15
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};
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/// Puncture matrix for audio and BERT frames. Rate 11/12.
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constexpr auto P2 = std::array<int8_t, 12>{
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1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 0};
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/// Puncture matrix for packet frames (7/8).
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constexpr auto P3 = std::array<int8_t, 8>{
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1, 1, 1, 1, 1, 1, 1, 0};
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/**
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* Convert an integer value to an array of bits, with the
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* high-bit at index 0.
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*
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* At anything beyond -O0, the array is constructed at compile time.
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*/
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template <size_t N>
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constexpr std::array<uint8_t, N> toBitArray(int8_t value)
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{
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std::array<uint8_t, N> result{};
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for (size_t i = 0; i != N; ++i)
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{
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result[N - (i + 1)] = (value & 1);
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value >>= 1;
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}
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return result;
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}
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template <size_t N>
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struct NextStateTable
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{
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using nextStateTable_t = std::array<std::array<int8_t, N>, N>;
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nextStateTable_t nextStateTable = makeNextStateTable();
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static constexpr nextStateTable_t makeNextStateTable()
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{
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return nextStateTable_t();
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}
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};
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/**
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* Compute a cost table for a Trellis of size K, for input n of N,
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* and LLR size of LLR bits + 1. (i.e. LLR = 1 allows 2 bits to
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* represent -1, 0, +1).
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*/
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template <size_t K, size_t N, size_t LLR = 1>
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struct CostTable
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{
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static constexpr int8_t Price = 1 << LLR;
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static constexpr size_t InputValues = 1 << N;
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using cost_table_t = std::array<std::array<uint8_t, InputValues>, K>;
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};
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/**
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* Only valid for a k=1 (1:n) convolutional coder.
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*/
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template <size_t K_, size_t n_>
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struct Trellis
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{
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static constexpr size_t K = K_; // Memory depth of convolution.
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static constexpr size_t k = 1; // Number of bits per input symbol.
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static constexpr size_t n = n_; // Number of coefficients / output bits.
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static constexpr size_t NumStates = (1 << K); // Number of states in the convolutional coder.
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using polynomials_t = std::array<uint32_t, n_>;
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polynomials_t polynomials;
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Trellis(polynomials_t polys) :
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polynomials(polys)
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{}
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};
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template <size_t K, size_t n>
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constexpr Trellis<K, n> makeTrellis(std::array<uint32_t, n> polys)
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{
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return Trellis<K, n>(polys);
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}
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} // modemm17
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