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Diffstat (limited to 'gr-fec/lib/polar_decoder_common.cc')
| -rw-r--r-- | gr-fec/lib/polar_decoder_common.cc | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/gr-fec/lib/polar_decoder_common.cc b/gr-fec/lib/polar_decoder_common.cc new file mode 100644 index 0000000000..8fc2e37fb7 --- /dev/null +++ b/gr-fec/lib/polar_decoder_common.cc @@ -0,0 +1,193 @@ +/* -*- c++ -*- */ +/* + * Copyright 2015 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include <gnuradio/io_signature.h> +#include <gnuradio/fec/polar_decoder_common.h> +#include <volk/volk.h> + +#include <cstdio> + +namespace gr { + namespace fec { + namespace code { + + polar_decoder_common::polar_decoder_common(int block_size, int num_info_bits, + std::vector<int> frozen_bit_positions, + std::vector<char> frozen_bit_values) : + polar_common(block_size, num_info_bits, frozen_bit_positions, frozen_bit_values), + d_frozen_bit_counter(0) + { + } + + polar_decoder_common::~polar_decoder_common() + { + } + + void + polar_decoder_common::initialize_decoder(unsigned char* u, float* llrs, const float* input) + { + volk_32f_s32f_multiply_32f(llrs + block_size() * block_power(), input, D_LLR_FACTOR, block_size()); + memset(u, 0, sizeof(unsigned char) * block_size() * block_power()); + d_frozen_bit_counter = 0; + } + + float + polar_decoder_common::llr_odd(const float la, const float lb) const + { + return copysignf(1.0f, la) * copysignf(1.0f, lb) * std::min(fabs(la), fabs(lb)); + } + + float + polar_decoder_common::llr_even(const float la, const float lb, const unsigned char f) const + { + switch(f){ + case 0: + return lb + la; + default: + return lb - la; + } + } + + void + polar_decoder_common::butterfly(float* llrs, unsigned char* u, const int stage, + const int u_num, const int row) + { + butterfly_volk(llrs, u, stage, u_num, row); + } + + void + polar_decoder_common::butterfly_generic(float* llrs, unsigned char* u, const int stage, + const int u_num, const int row) + { + const int next_stage = stage + 1; + const int half_stage_size = 0x01 << stage; + const int stage_size = half_stage_size << 1; + const bool is_upper_stage_half = row % stage_size < half_stage_size; + + // // this is a natural bit order impl + float* next_llrs = llrs + block_size(); // LLRs are stored in a consecutive array. + float* call_row_llr = llrs + row; + + const int section = row - (row % stage_size); + const int jump_size = ((row % half_stage_size) << 1) % stage_size; + + const int next_upper_row = section + jump_size; + const int next_lower_row = next_upper_row + 1; + + const float* upper_right_llr_ptr = next_llrs + next_upper_row; + const float* lower_right_llr_ptr = next_llrs + next_lower_row; + + if(!is_upper_stage_half){ + const int u_pos = u_num >> stage; + const unsigned char f = u[u_pos - 1]; + *call_row_llr = llr_even(*upper_right_llr_ptr, *lower_right_llr_ptr, f); + return; + } + + if(block_power() > next_stage){ + unsigned char* u_half = u + block_size(); + odd_xor_even_values(u_half, u, u_num); + butterfly(next_llrs, u_half, next_stage, u_num, next_upper_row); + + even_u_values(u_half, u, u_num); + butterfly(next_llrs, u_half, next_stage, u_num, next_lower_row); + } + + *call_row_llr = llr_odd(*upper_right_llr_ptr, *lower_right_llr_ptr); + } + + void + polar_decoder_common::butterfly_volk(float* llrs, unsigned char* u, const int stage, + const int u_num, const int row) + { + volk_32f_8u_polarbutterfly_32f(llrs, u, block_size(), block_power(), stage, u_num, row); + } + + + void + polar_decoder_common::even_u_values(unsigned char* u_even, const unsigned char* u, + const int u_num) + { + u++; + for(int i = 1; i < u_num; i += 2){ + *u_even++ = *u; + u += 2; + } + } + + void + polar_decoder_common::odd_xor_even_values(unsigned char* u_xor, const unsigned char* u, + const int u_num) + { + for(int i = 1; i < u_num; i += 2){ + *u_xor++ = *u ^ *(u + 1); + u += 2; + } + } + + const bool + polar_decoder_common::is_frozen_bit(const int u_num) const + { + return d_frozen_bit_counter < d_frozen_bit_positions.size() && u_num == d_frozen_bit_positions.at(d_frozen_bit_counter); + } + + + const unsigned char + polar_decoder_common::next_frozen_bit() + { + return d_frozen_bit_values[d_frozen_bit_counter++]; + } + + void + polar_decoder_common::extract_info_bits(unsigned char* output, const unsigned char* input) const + { + unsigned int frozenbit_num = 0; + for(int i = 0; i < block_size(); i++){ + if(frozenbit_num < d_frozen_bit_positions.size() && d_frozen_bit_positions.at(frozenbit_num) == i){ + frozenbit_num++; + } + else{ + *output++ = *input; + } + input++; + } + } + + void + polar_decoder_common::print_pretty_llr_vector(const float* llr_vec) const + { + for(int row = 0; row < block_size(); row++) { + std::cout << row << "->" << int(bit_reverse(row, block_power())) << ":\t"; + for(int stage = 0; stage < block_power() + 1; stage++) { + printf("%+4.2f, ", llr_vec[(stage * block_size()) + row]); + } + std::cout << std::endl; + } + } + + } /* namespace code */ + } /* namespace fec */ +} /* namespace gr */ |