GNU Radio Manual and C++ API Reference
3.9.1.0
The Free & Open Software Radio Ecosystem
ofdm_sync_sc_cfb.h
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/* -*- c++ -*- */
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/*
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* Copyright 2013 Free Software Foundation, Inc.
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*
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* This file is part of GNU Radio
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*
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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*/
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#ifndef INCLUDED_DIGITAL_OFDM_SYNC_SC_CFB_H
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#define INCLUDED_DIGITAL_OFDM_SYNC_SC_CFB_H
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#include <
gnuradio/digital/api.h
>
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#include <
gnuradio/hier_block2.h
>
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namespace
gr
{
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namespace
digital {
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/*!
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* \brief Schmidl & Cox synchronisation for OFDM
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* \ingroup ofdm_blk
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* \ingroup synchronizers_blk
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*
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* \details
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* Input: complex samples.
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* Output 0: Fine frequency offset, scaled by the OFDM symbol duration.
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* This is \f$\hat{\varphi}\f$ in [1]. The normalized frequency
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* offset is then 2.0*output0/fft_len.
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* Output 1: Beginning of the first OFDM symbol after the first (doubled) OFDM
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* symbol. The beginning is marked with a 1 (it's 0 everywhere else).
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*
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* The evaluation of the coarse frequency offset is *not* done in this block.
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* Also, the initial equalizer taps are not calculated here.
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*
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* Note that we use a different normalization factor in the timing metric than
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* the authors do in their original work[1]. If the timing metric (8) is
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* \f[
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* M(d) = \frac{|P(d)|^2}{(R(d))^2},
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* \f]
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* we calculate the normalization as
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* \f[
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* R(d) = \frac{1}{2} \sum_{k=0}^{N-1} |r_{k+d}|^2,
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* \f]
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* i.e., we estimate the energy from *both* half-symbols. This avoids spurious detects
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* at the end of a burst, when the energy level suddenly drops.
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*
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* [1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing synchronization for
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* OFDM", Communications, IEEE Transactions on, 1997.
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*/
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class
DIGITAL_API
ofdm_sync_sc_cfb
:
virtual
public
hier_block2
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{
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public
:
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typedef
std::shared_ptr<ofdm_sync_sc_cfb>
sptr
;
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/*! \param fft_len FFT length
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* \param cp_len Length of the guard interval (cyclic prefix) in samples
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* \param use_even_carriers If true, the carriers in the sync preamble are occupied
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* such that the even carriers are used (0, 2, 4, ...). If you use all carriers, that
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* would include the DC carrier, so be careful. \param threshold detection threshold.
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* Default is 0.9.
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*/
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static
sptr
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make(
int
fft_len,
int
cp_len,
bool
use_even_carriers =
false
,
float
threshold = 0.9);
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virtual
void
set_threshold(
float
threshold) = 0;
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virtual
float
threshold()
const
= 0;
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};
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}
// namespace digital
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}
// namespace gr
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#endif
/* INCLUDED_DIGITAL_OFDM_SYNC_SC_CFB_H */
hier_block2.h
gr::digital::ofdm_sync_sc_cfb::sptr
std::shared_ptr< ofdm_sync_sc_cfb > sptr
Definition:
ofdm_sync_sc_cfb.h:55
DIGITAL_API
#define DIGITAL_API
Definition:
gr-digital/include/gnuradio/digital/api.h:18
api.h
gr::digital::ofdm_sync_sc_cfb
Schmidl & Cox synchronisation for OFDM.
Definition:
ofdm_sync_sc_cfb.h:52
gr
GNU Radio logging wrapper for log4cpp library (C++ port of log4j)
Definition:
basic_block.h:29
gr::hier_block2
Hierarchical container class for gr::block's and gr::hier_block2's.
Definition:
hier_block2.h:33
gr-digital
include
gnuradio
digital
ofdm_sync_sc_cfb.h
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