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ofdm_chanest_vcvc.h
Go to the documentation of this file.
/* -*- c++ -*- */
/*
* Copyright 2013 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifndef INCLUDED_DIGITAL_OFDM_CHANEST_VCVC_H
#define INCLUDED_DIGITAL_OFDM_CHANEST_VCVC_H
#include <gnuradio/block.h>
#include <gnuradio/digital/api.h>
namespace gr {
namespace digital {
/*! Estimate channel and coarse frequency offset for OFDM from preambles
* \ingroup ofdm_blk
* \ingroup synchronizers_blk
*
* Input: OFDM symbols (in frequency domain). The first one (or two) symbols are expected
* to be synchronisation symbols, which are used to estimate the coarse freq offset
* and the initial equalizer taps (these symbols are removed from the stream).
* The following \p n_data_symbols are passed through unmodified (the actual
* equalisation must be done elsewhere). Output: The data symbols, without the
* synchronisation symbols. The first data symbol passed through has two tags:
* 'ofdm_sync_carr_offset' (integer), the coarse frequency offset as number of
* carriers, and 'ofdm_sync_eq_taps' (complex vector). Any tags attached to the
* synchronisation symbols are attached to the first data symbol. All other tags are
* propagated as expected.
*
* Note: The vector on ofdm_sync_eq_taps is already frequency-corrected, whereas
* the rest is not.
*
* This block assumes the frequency offset is even (i.e. an integer multiple of 2).
*
* [1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing synchronization
* for OFDM", Communications, IEEE Transactions on, 1997.
* [2] K.D. Kammeyer, "Nachrichtenuebertragung," Chapter. 16.3.2.
*/
class DIGITAL_API ofdm_chanest_vcvc : virtual public block
{
public:
typedef std::shared_ptr<ofdm_chanest_vcvc> sptr;
/*!
* \param sync_symbol1 First synchronisation symbol in the frequency domain.
* Its length must be the FFT length. For Schmidl & Cox
* synchronisation, every second sub-carrier has to be zero.
* \param sync_symbol2 Second synchronisation symbol in the frequency domain.
* Must be equal to the FFT length, or zero length if
* only one synchronisation symbol is used. Using this
* symbol is how synchronisation is described in [1].
* Leaving this empty forces us to interpolate the
* equalizer taps.
* If you are using an unusual sub-carrier configuration
* (e.g. because of OFDMA), this sync symbol is used to
* identify the active sub-carriers. If you only have
* one synchronisation symbol, set the active sub-carriers
* to a non-zero value in here, and set \p force_one_sync_symbol
* parameter to true.
* \param n_data_symbols The number of data symbols following each set of
* synchronisation symbols. Must be at least 1.
* \param eq_noise_red_len If non-zero, noise reduction for the equalizer
* taps is done according to [2]. In this case, it
* is the channel influence time in number of samples.
* A good value is usually the length of the cyclic prefix.
* \param max_carr_offset Limit the number of sub-carriers the frequency
* offset can maximally be. Leave this zero to try
* all possibilities.
* \param force_one_sync_symbol See \p sync_symbol2.
*/
static sptr make(const std::vector<gr_complex>& sync_symbol1,
const std::vector<gr_complex>& sync_symbol2,
int n_data_symbols,
int eq_noise_red_len = 0,
int max_carr_offset = -1,
bool force_one_sync_symbol = false);
};
} // namespace digital
} // namespace gr
#endif /* INCLUDED_DIGITAL_OFDM_CHANEST_VCVC_H */
gr::block::block
block(void)
Definition gnuradio-runtime/include/gnuradio/block.h:806
gr::digital::ofdm_chanest_vcvc
Definition ofdm_chanest_vcvc.h:45
gr::digital::ofdm_chanest_vcvc::make
static sptr make(const std::vector< gr_complex > &sync_symbol1, const std::vector< gr_complex > &sync_symbol2, int n_data_symbols, int eq_noise_red_len=0, int max_carr_offset=-1, bool force_one_sync_symbol=false)
gr::digital::ofdm_chanest_vcvc::sptr
std::shared_ptr< ofdm_chanest_vcvc > sptr
Definition ofdm_chanest_vcvc.h:47
block.h
api.h
DIGITAL_API
#define DIGITAL_API
Definition gr-digital/include/gnuradio/digital/api.h:18
gr::digital
Definition adaptive_algorithm.h:22
gr
GNU Radio logging wrapper.
Definition basic_block.h:29