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authorJohannes Demel <ufcsy@student.kit.edu>2015-06-18 12:14:32 +0200
committerJohannes Demel <ufcsy@student.kit.edu>2015-09-21 10:45:12 +0200
commit13592802e792a417b1db511dbb1d0445ff4955c8 (patch)
tree4ecb7d8f8527f9d501a22d871fcca5e0c4b3f838 /gr-fec/lib/polar_decoder_common.cc
parent87670ad6f14e61bf4bde6c6e5b18d19b262fe33f (diff)
polar: SC and SC List decoder implemented in C++
Diffstat (limited to 'gr-fec/lib/polar_decoder_common.cc')
-rw-r--r--gr-fec/lib/polar_decoder_common.cc209
1 files changed, 209 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
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--- /dev/null
+++ b/gr-fec/lib/polar_decoder_common.cc
@@ -0,0 +1,209 @@
+/* -*- 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>
+
+#define INT_BIT_MASK 0x80000000
+
+namespace gr {
+ namespace fec {
+
+ 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, bool is_packed) :
+ polar_common(block_size, num_info_bits, frozen_bit_positions, frozen_bit_values, is_packed),
+ D_LLR_FACTOR(2.19722458f),
+ d_frozen_bit_positions(frozen_bit_positions),
+ d_frozen_bit_values(frozen_bit_values)
+ {
+ }
+
+ polar_decoder_common::~polar_decoder_common()
+ {
+ }
+
+ void
+ polar_decoder_common::initialize_llr_vector(float* llrs, const float* input)
+ {
+ volk_32f_s32f_multiply_32f(llrs + block_size() * block_power(), input, D_LLR_FACTOR, block_size());
+ }
+
+ 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, const int stage, unsigned char* u, const int u_num)
+ {
+// if(!(block_power() > stage)){
+// return;
+// }
+ const int next_stage = stage + 1;
+ const int stage_half_block_size = block_size() >> next_stage;
+
+// // this is a natural bit order impl
+ float* next_llrs = llrs + block_size(); // LLRs are stored in an consecutive array.
+ float* call_row_llr = llrs + u_num;
+ const int upper_right = u_num >> 1; // floor divide by 2.
+ const float* upper_right_llr_ptr = next_llrs + upper_right;
+ const float* lower_right_llr_ptr = upper_right_llr_ptr + stage_half_block_size;
+
+ if(u_num % 2){
+ const unsigned char f = u[u_num - 1];
+// const unsigned char f = fetch_bit_at_pos(u, u_num - 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, next_stage, u_half, upper_right);
+
+ even_u_values(u_half, u, u_num);
+ butterfly(next_llrs + stage_half_block_size, next_stage, u_half, upper_right);
+ }
+
+ *call_row_llr = llr_odd(*upper_right_llr_ptr, *lower_right_llr_ptr);
+ }
+
+
+ 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;
+ }
+
+// short* target = (short*) u_even;
+// short* src = (short*) u;
+//
+// const int iterations = std::max(1, u_num >> 3);
+// for(int i = 0; i < iterations; i++){
+// *target = *src << 1;
+// demortonize_values((unsigned char*) target);
+// u_even++;
+// target = (short*) u_even;
+// src++;
+// }
+ }
+
+ 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;
+ }
+
+// short* target = (short*) u_xor;
+// short* src = (short*) u;
+//
+// const int iterations = std::max(1, u_num >> 3);
+// for(int i = 0; i < iterations; i++){
+// *target = *src ^ (*src << 1);
+// demortonize_values((unsigned char*) target);
+// u_xor++;
+// target = (short*) u_xor;
+// src++;
+// }
+ }
+
+ 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++;
+ }
+
+// 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++ = fetch_bit_at_pos(input, i); // *input;
+// }
+// }
+ }
+
+ void
+ polar_decoder_common::demortonize_values(unsigned char* u)
+ {
+ *u &= 0xaa; // b0d0f0h0
+ *u = (*u ^ (*u << 1)) & 0xcc; // bd00fh00
+ *u = (*u ^ (*u << 2)) & 0xf0; // bdfh0000
+
+ unsigned char* u2 = u + 1;
+ *u2 &= 0xaa; // b0d0f0h0
+ *u2 = (*u2 ^ (*u2 << 1)) & 0xcc; // bd00fh00
+ *u2 = (*u2 ^ (*u2 << 2)) & 0xf0; // bdfh0000
+ *u ^= (*u2 >> 4);
+ }
+
+ 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 fec */
+} /* namespace gr */
+
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