viterbi_decoder/base.h

Go to the documentation of this file.

/*
 * Copyright (C) 2016 Bastian Bloessl <bloessl@ccs-labs.org>
 *
 * This program 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 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef INCLUDED_IEEE802_11_VITERBI_DECODER_BASE_H
#define INCLUDED_IEEE802_11_VITERBI_DECODER_BASE_H
 
#include "../utils.h"
 
namespace gr {
namespace ieee802_11 {
 
// Maximum number of traceback bytes
#define TRACEBACK_MAX 24
 
/* This Viterbi decoder was taken from the gr-dvbt module of
 * GNU Radio. It is an SSE2 version of the Viterbi Decoder
 * created by Phil Karn. The SSE2 version was made by Bogdan
 * Diaconescu. For more info see: gr-dvbt/lib/d_viterbi.h
 */
class base
{
public:
    base();
    ~base();
    virtual uint8_t* decode(ofdm_param* ofdm, frame_param* frame, uint8_t* in) = 0;
 
protected:
    // Position in circular buffer where the current decoded byte is stored
    int d_store_pos;
    // Metrics for each state
    alignas(16) unsigned char d_mmresult[64];
    // Paths for each state
    alignas(16) unsigned char d_ppresult[TRACEBACK_MAX][64];
 
    int d_ntraceback;
    int d_k;
    ofdm_param* d_ofdm;
    frame_param* d_frame;
    const unsigned char* d_depuncture_pattern;
 
    uint8_t d_depunctured[MAX_ENCODED_BITS];
    uint8_t d_decoded[MAX_ENCODED_BITS * 3 / 4];
 
    static const unsigned char PARTAB[256];
    static const unsigned char PUNCTURE_1_2[2];
    static const unsigned char PUNCTURE_2_3[4];
    static const unsigned char PUNCTURE_3_4[6];
 
    virtual void reset() = 0;
    uint8_t* depuncture(uint8_t* in);
};
 
} // namespace ieee802_11
} // namespace gr
 
#endif /* INCLUDED_IEEE802_11_VITERBI_DECODER_BASE_H */