packet_header_ofdm.h

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/* -*- c++ -*- */
/* Copyright 2012 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_DIGITAL_PACKET_HEADER_OFDM_H
#define INCLUDED_DIGITAL_PACKET_HEADER_OFDM_H

#include <gnuradio/digital/api.h>
#include <gnuradio/digital/packet_header_default.h>
#include <vector>

namespace gr {
namespace digital {

/*!
 * \brief Header utility for OFDM signals.
 * \ingroup ofdm_blk
 */
class DIGITAL_API packet_header_ofdm : public packet_header_default
{
public:
    typedef boost::shared_ptr<packet_header_ofdm> sptr;

    packet_header_ofdm(const std::vector<std::vector<int>>& occupied_carriers,
                       int n_syms,
                       const std::string& len_tag_key,
                       const std::string& frame_len_tag_key,
                       const std::string& num_tag_key,
                       int bits_per_header_sym,
                       int bits_per_payload_sym,
                       bool scramble_header);
    ~packet_header_ofdm();

    /*!
     * \brief Header formatter.
     *
     * Does the same as packet_header_default::header_formatter(), but
     * optionally scrambles the bits (this is more important for OFDM to avoid
     * PAPR spikes).
     */
    bool
    header_formatter(long packet_len, unsigned char* out, const std::vector<tag_t>& tags);

    /*!
     * \brief Inverse function to header_formatter().
     *
     * Does the same as packet_header_default::header_parser(), but
     * adds another tag that stores the number of OFDM symbols in the
     * packet.
     * Note that there is usually no linear connection between the number
     * of OFDM symbols and the packet length because a packet might
     * finish mid-OFDM-symbol.
     */
    bool header_parser(const unsigned char* header, std::vector<tag_t>& tags);

    /*!
     * \param occupied_carriers See carrier allocator
     * \param n_syms The number of OFDM symbols the header should be (usually 1)
     * \param len_tag_key The tag key used for the packet length (number of bytes)
     * \param frame_len_tag_key The tag key used for the frame length (number of
     *                          OFDM symbols, this is the tag key required for the
     *                          frame equalizer etc.)
     * \param num_tag_key The tag key used for packet numbering.
     * \param bits_per_header_sym Bits per complex symbol in the header, e.g. 1 if
     *                            the header is BPSK modulated, 2 if it's QPSK
     *                            modulated etc.
     * \param bits_per_payload_sym Bits per complex symbol in the payload. This is
     *                             required to figure out how many OFDM symbols
     *                             are necessary to encode the given number of
     *                             bytes.
     * \param scramble_header Set this to true to scramble the bits. This is highly
     *                        recommended, as it reduces PAPR spikes.
     */
    static sptr make(const std::vector<std::vector<int>>& occupied_carriers,
                     int n_syms,
                     const std::string& len_tag_key = "packet_len",
                     const std::string& frame_len_tag_key = "frame_len",
                     const std::string& num_tag_key = "packet_num",
                     int bits_per_header_sym = 1,
                     int bits_per_payload_sym = 1,
                     bool scramble_header = false);


protected:
    pmt::pmt_t d_frame_len_tag_key; //!< Tag key of the additional frame length tag
    const std::vector<std::vector<int>>
        d_occupied_carriers; //!< Which carriers/symbols carry data
    int d_bits_per_payload_sym;
    std::vector<unsigned char>
        d_scramble_mask; //!< Bits are xor'd with this before tx'ing
};

} // namespace digital
} // namespace gr

#endif /* INCLUDED_DIGITAL_PACKET_HEADER_OFDM_H */