GNU Radio Manual and C++ API Reference 3.9.4.0
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awgn_bp.h
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1/* -*- c++ -*- */
2/*
3 * Copyright 2015 Free Software Foundation, Inc.
4 *
5 * This file is part of GNU Radio
6 *
7 * SPDX-License-Identifier: GPL-3.0-or-later
8 *
9 */
10
11/* -----------------------------------------------------------------
12 *
13 * This class defines functions for message passing mechanism for a
14 * AWGN channel. Message passing (also known as belief propagation)
15 * is used for decoding LDPC codes. Details of how LDPC codes are
16 * decoded is available in the link below
17 * - http://www.cs.utoronto.ca/~radford/ftp/LDPC-2012-02-11/decoding.html
18 *
19 * Belief propagation decoding is a suboptimal but efficient method of
20 * decoding LDPC codes.
21 *
22 */
23
24#ifndef AWGN_BP_H
25#define AWGN_BP_H
26
27#include "alist.h"
28#include "gf2mat.h"
29#include <gnuradio/fec/api.h>
30#include <cmath>
31#include <iostream>
32#include <vector>
33
35{
36public:
37 //! Default constructor
39
40 //! A constructor for given GF2Mat and sigma
41 awgn_bp(const GF2Mat X, float sgma);
42
43 //! A constructor for given alist and sigma
44 awgn_bp(alist _list, float sgma);
45
46 //! Initializes the class using given alist and sigma
47 void set_alist_sigma(alist _list, float sgma);
48
49 //! Returns the variable Q
50 std::vector<std::vector<double>> get_Q();
51
52 //! Returns the variable R
53 std::vector<std::vector<double>> get_R();
54
55 //! Returns the variable H
57
58 //! Calculates the likelihood ratios given an input vector
59 void rx_lr_calc(std::vector<float> codeword);
60
61 //! Returns the variable rx_lr
62 std::vector<double> get_rx_lr();
63
64 //! Returns the variable lr
65 std::vector<double> get_lr();
66
67 //! Initializes the sum product algorithm set-up
69
70 //! Updates the check-nodes based on messages from variable nodes
72
73 //! Updates the variable-nodes based on messages from check nodes
75
76 //! Returns the current estimate
77 std::vector<uint8_t> get_estimate();
78
79 //! Computes initial estimate based on the vector rx_word
80 void compute_init_estimate(std::vector<float> rx_word);
81
82 //! Computes the estimate based on current likelihood-ratios lr
83 void decision();
84
85 //! Returns the syndrome for the current estimate
86 std::vector<uint8_t> get_syndrome();
87
88 //! Returns the syndrome for the input codeword
89 std::vector<uint8_t> get_syndrome(const std::vector<uint8_t> codeword);
90
91 //! Checks if the current estimate is a codeword
93
94 //! Checks if the input is a codeword
95 bool is_codeword(const std::vector<uint8_t> codeword);
96
97 //! Sets the variable K
98 void set_K(int k);
99
100 //! Returns the variable K
101 int get_K();
102
103 //! Sets the variable max_iterations
105
106 //! Returns the variable max_iterations
108
109 /*!
110 * \brief Decodes the given vector rx_word by message passing.
111 *
112 * \param rx_word The received samples for decoding.
113 * \param niterations The number of message passing iterations
114 * done to decode this codeword.
115 */
116 std::vector<uint8_t> decode(std::vector<float> rx_word, int* niterations);
117
118private:
119 //! The number of check nodes in the tanner-graph
120 int M;
121
122 //! The number of variable nodes in the tanner-graph
123 int N;
124
125 //! The dimension of the code used
126 int K;
127
128 //! The maximum number of message passing iterations allowed
129 int max_iterations;
130
131 //! The parity check matrix of the LDPC code
132 GF2Mat H;
133
134 //! The standard-deviation of the AWGN channel
135 float sigma;
136
137 //! Matrix holding messages from check nodes to variable nodes
138 std::vector<std::vector<double>> R;
139
140 //! Matrix holding messages from variable nodes to check nodes
141 std::vector<std::vector<double>> Q;
142
143 //! The array of likelihood computed from the channel output
144 std::vector<double> rx_lr;
145
146 //! The array for holding likelihoods computed on BP decoding
147 std::vector<double> lr;
148
149 //! List of integer coordinates along each column with non-zero entries
150 std::vector<std::vector<int>> nlist;
151
152 //! List of integer coordinates along each row with non-zero entries
153 std::vector<std::vector<int>> mlist;
154
155 //! Weight of each column n
156 std::vector<int> num_nlist;
157
158 //! Weight of each row m
159 std::vector<int> num_mlist;
160
161 //! The array for holding estimate computed on BP decoding
162 std::vector<uint8_t> estimate;
163};
164#endif // ifndef AWGN_BP_H
Definition: gf2mat.h:18
Definition: alist.h:33
Definition: awgn_bp.h:35
std::vector< std::vector< double > > get_R()
Returns the variable R.
std::vector< double > get_lr()
Returns the variable lr.
void spa_initialize()
Initializes the sum product algorithm set-up.
std::vector< uint8_t > get_estimate()
Returns the current estimate.
void update_chks()
Updates the check-nodes based on messages from variable nodes.
bool is_codeword(const std::vector< uint8_t > codeword)
Checks if the input is a codeword.
void decision()
Computes the estimate based on current likelihood-ratios lr.
bool is_codeword()
Checks if the current estimate is a codeword.
void rx_lr_calc(std::vector< float > codeword)
Calculates the likelihood ratios given an input vector.
void set_K(int k)
Sets the variable K.
GF2Mat get_H()
Returns the variable H.
int get_K()
Returns the variable K.
std::vector< std::vector< double > > get_Q()
Returns the variable Q.
std::vector< uint8_t > get_syndrome()
Returns the syndrome for the current estimate.
void update_vars()
Updates the variable-nodes based on messages from check nodes.
void set_alist_sigma(alist _list, float sgma)
Initializes the class using given alist and sigma.
void set_max_iterations(int k)
Sets the variable max_iterations.
awgn_bp()
Default constructor.
Definition: awgn_bp.h:38
awgn_bp(const GF2Mat X, float sgma)
A constructor for given GF2Mat and sigma.
int get_max_iterations()
Returns the variable max_iterations.
std::vector< double > get_rx_lr()
Returns the variable rx_lr.
std::vector< uint8_t > get_syndrome(const std::vector< uint8_t > codeword)
Returns the syndrome for the input codeword.
std::vector< uint8_t > decode(std::vector< float > rx_word, int *niterations)
Decodes the given vector rx_word by message passing.
void compute_init_estimate(std::vector< float > rx_word)
Computes initial estimate based on the vector rx_word.
awgn_bp(alist _list, float sgma)
A constructor for given alist and sigma.
#define FEC_API
Definition: gr-fec/include/gnuradio/fec/api.h:18