GNU Radio's DAB Package
ofdm_ffe_all_in_one_impl.h
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1/* -*- c++ -*- */
2/*
3 * Copyright 2004 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#ifndef INCLUDED_DAB_OFDM_FFE_ALL_IN_ONE_IMPL_H
23#define INCLUDED_DAB_OFDM_FFE_ALL_IN_ONE_IMPL_H
24
26
27namespace gr {
28 namespace dab {
29
30/*!
31 * \brief calculates fine frequency error estimation and averages it
32 * \ingroup DAB
33 * \param symbol_length number of samples in an OFDM symbol
34 * \param fft_length number of samples in an OFDM symbol without the cyclic prefix
35 * \param num_symbols number of symbols to use for averaging (more symbols is better, but symbols towards the end of the frame tend to have larger time offsets and worse values)
36 * \param alpha how fast should we adapt to new FFS error values (1=immediately)
37 * \param sample_rate sampling rate - needed to calculate the offset estimation in Hz
38 *
39 * input: port 0: complex - actual data; port 1: byte - trigger signal indicating the start of a frame
40 * output: float fine frequency offset estimation (in radian per sample)
41 *
42 * this is an all in one version of ffe in ofdm_sync_dab.py, because the flow graph does not allow to only calculate the estimation when its needed
43 */
45{
46 private:
47
48 float calc_ffe_estimate(const gr_complex *iptr);
49
50 unsigned int d_symbol_length; // length of a symbol in samples
51 unsigned int d_fft_length; // length of a symbol without cyclic prefix in samples
52 unsigned int d_num_symbols; // number of symbols per frame to average over
53 float d_alpha; // adjustment speed factor
54 unsigned int d_sample_rate; // sample rate -- only needed to print the ffs error in Hz
55
56 unsigned int d_cur_symbol; // which symbol in the frame is currently under observation?
57 unsigned int d_cur_sample; // which sample in the symbol is currently under observation?
58 float d_ffs_error_sum; // sum of error samples in current frame
59 float d_estimated_error; // total estimated error
60 float d_estimated_error_per_sample; // total estimated error / fft_length
61
62 public:
63 ofdm_ffe_all_in_one_impl (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate);
64 /*! \return fine frequency error estimate in Hz */
65 float ffe_estimate() { return d_estimated_error_per_sample*d_sample_rate/(2*M_PI); }
66 int work (int noutput_items,
67 gr_vector_const_void_star &input_items,
68 gr_vector_void_star &output_items);
69};
70
71}
72}
73
74#endif /* INCLUDED_DAB_OFDM_FFE_ALL_IN_ONE_H */
calculates fine frequency error estimation and averages it
Definition ofdm_ffe_all_in_one_impl.h:45
float ffe_estimate()
Definition ofdm_ffe_all_in_one_impl.h:65
ofdm_ffe_all_in_one_impl(unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate)
int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
<+description of block+>
Definition ofdm_ffe_all_in_one.h:37
Definition complex_to_interleaved_float_vcf.h:28