GNU Radio Manual and C++ API Reference 3.7.14.0
The Free & Open Software Radio Ecosystem
ofdm_frame_acquisition.h
Go to the documentation of this file.
1/* -*- c++ -*- */
2/*
3 * Copyright 2006,2007,2011,2012 Free Software Foundation, Inc.
4 *
5 * This file is part of GNU Radio
6 *
7 * GNU Radio is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 3, or (at your option)
10 * any later version.
11 *
12 * GNU Radio is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with GNU Radio; see the file COPYING. If not, write to
19 * the Free Software Foundation, Inc., 51 Franklin Street,
20 * Boston, MA 02110-1301, USA.
21 */
22
23#ifndef INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H
24#define INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H
25
26#include <gnuradio/block.h>
28#include <vector>
29
30namespace gr {
31namespace digital {
32
33/*!
34 * \brief take a vector of complex constellation points in from an
35 * FFT and performs a correlation and equalization.
36 * \ingroup ofdm_blk
37 * \ingroup deprecated_blk
38 *
39 * \details
40 * This block takes the output of an FFT of a received OFDM symbol
41 * and finds the start of a frame based on two known symbols. It
42 * also looks at the surrounding bins in the FFT output for the
43 * correlation in case there is a large frequency shift in the
44 * data. This block assumes that the fine frequency shift has
45 * already been corrected and that the samples fall in the middle
46 * of one FFT bin.
47 *
48 * It then uses one of those known symbols to estimate the channel
49 * response over all subcarriers and does a simple 1-tap
50 * equalization on all subcarriers. This corrects for the phase
51 * and amplitude distortion caused by the channel.
52 */
54{
55public:
56 // gr::digital::ofdm_frame_acquisition::sptr
57 typedef boost::shared_ptr<ofdm_frame_acquisition> sptr;
58
59 /*!
60 * Make an OFDM correlator and equalizer.
61 *
62 * \param occupied_carriers The number of subcarriers with data in the received
63 * symbol \param fft_length The size of the FFT vector (occupied_carriers +
64 * unused carriers) \param cplen The length of the cycle prefix \param
65 * known_symbol A vector of complex numbers representing a known symbol at the
66 * start of a frame (usually a BPSK PN sequence)
67 * \param max_fft_shift_len Set's the maximum distance you can look between bins for
68 * correlation
69 */
70 static sptr make(unsigned int occupied_carriers,
71 unsigned int fft_length,
72 unsigned int cplen,
73 const std::vector<gr_complex>& known_symbol,
74 unsigned int max_fft_shift_len = 4);
75
76 /*!
77 * \brief Return an estimate of the SNR of the channel
78 */
79 virtual float snr() = 0;
80};
81
82} /* namespace digital */
83} /* namespace gr */
84
85#endif /* INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H */
The abstract base class for all 'terminal' processing blocks.
Definition: block.h:66
take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...
Definition: ofdm_frame_acquisition.h:54
boost::shared_ptr< ofdm_frame_acquisition > sptr
Definition: ofdm_frame_acquisition.h:57
virtual float snr()=0
Return an estimate of the SNR of the channel.
static sptr make(unsigned int occupied_carriers, unsigned int fft_length, unsigned int cplen, const std::vector< gr_complex > &known_symbol, unsigned int max_fft_shift_len=4)
#define DIGITAL_API
Definition: gr-digital/include/gnuradio/digital/api.h:30
Include this header to use the message passing features.
Definition: basic_block.h:45