polar_common.h

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/* -*- 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.
 */


#ifndef INCLUDED_FEC_POLAR_COMMON_H
#define INCLUDED_FEC_POLAR_COMMON_H

#include <gnuradio/fec/api.h>
#include <vector>

// Forward declaration for those objects. SWIG doesn't like them to be #include'd.
namespace gr {
namespace blocks {
namespace kernel {
class unpack_k_bits;
}
} // namespace blocks
} // namespace gr

namespace gr {
namespace fec {
namespace code {

/*!
 * \brief POLAR code common operations and attributes
 * \ingroup error_coding_blk
 *
 * \details
 * Polar codes are based on this paper by Erdal Arikan "Channel
 * Polarization: A Method for Constructing Capacity-Achieving Codes
 * for Symmetric Binary-Input Memoryless Channels", 2009 block
 * holds common information for encoders and decoders. All polar
 * encoder/decoders inherit from polar_common.
 *
 * class holds common info. It is common to all encoders and decoders.
 */
class FEC_API polar_common
{
public:
    /*!
     * \param block_size codeword size. MUST be a power of 2.
     * \param num_info_bits represents the number of information
     *        bits in a block. Also called frame_size. <= block_size
     * \param frozen_bit_positions is an integer vector which
     *        defines the position of all frozen bits in a block.
     *        Its size MUST be equal to block_size - num_info_bits.
     *        Also it must be sorted and every position must only
     *        occur once.
     * \param frozen_bit_values holds an unpacked byte for every
     *        frozen bit position.  It defines if a frozen bit is
     *        fixed to '0' or '1'. Defaults to all ZERO.
     */
    polar_common(int block_size,
                 int num_info_bits,
                 std::vector<int> frozen_bit_positions,
                 std::vector<char> frozen_bit_values);
    ~polar_common();

protected:
    const int block_size() const { return d_block_size; };
    const int block_power() const { return d_block_power; };
    const int num_info_bits() const { return d_num_info_bits; };

    // helper functions
    long bit_reverse(long value, int active_bits) const;
    void print_packed_bit_array(const unsigned char* printed_array,
                                const int num_bytes) const;
    void print_unpacked_bit_array(const unsigned char* bits,
                                  const unsigned int num_bytes) const;

    std::vector<int> d_frozen_bit_positions;
    std::vector<char> d_frozen_bit_values;
    std::vector<int> d_info_bit_positions;
    std::vector<int> d_info_bit_positions_reversed;
    void setup_info_bit_positions_reversed();
    //        std::vector<int> d_info_bit_positions_reversed;


    // VOLK methods
    void setup_volk_vectors();
    void volk_encode(unsigned char* out_buf, const unsigned char* in_buf);
    void volk_encode_block(unsigned char* out_buf, unsigned char* in_buf);
    unsigned char* d_volk_temp;
    unsigned char* d_volk_frozen_bit_mask;
    unsigned char* d_volk_frozen_bits;

private:
    int d_block_size; // depending on paper called 'N' or 'm'
    int d_block_power;
    int d_num_info_bits; // mostly abbreviated by 'K'

    void initialize_info_bit_position_vector();

    gr::blocks::kernel::unpack_k_bits*
        d_unpacker; // convenience for 'print_packed_bit_array' function.
};

} // namespace code
} // namespace fec
} // namespace gr

#endif /* INCLUDED_FEC_POLAR_COMMON_H */