GNU Radio's DAB Package
dab_ofdm_ffs_sample.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_FFS_SAMPLE_H
23#define INCLUDED_DAB_OFDM_FFS_SAMPLE_H
24
25#include <gr_sync_block.h>
26
28
29typedef std::shared_ptr<dab_ofdm_ffs_sample> dab_ofdm_ffs_sample_sptr;
30
31dab_ofdm_ffs_sample_sptr dab_make_ofdm_ffs_sample (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate);
32
33/*!
34 * \brief samples FFS error estimation at the correct time and averages it
35 * \ingroup DAB
36 * \param symbol_length number of samples in an OFDM symbol
37 * \param fft_length number of samples in an OFDM symbol without the cyclic prefix
38 * \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)
39 * \param alpha how fast should we adapt to new FFS error values (1=immediately)
40 * \param sample_rate sampling rate - needed to calculate the offset estimation in Hz
41 *
42 * input: port 0: float - actual data; port 1: byte - trigger signal indicating the start of a frame
43 * output: float fine frequency offset estimation (in radian per sample)
44 */
45class dab_ofdm_ffs_sample : public gr_sync_block
46{
47 private:
48 // The friend declaration allows dab_make_ofdm_ffs_sample to
49 // access the private constructor.
50
51 friend dab_ofdm_ffs_sample_sptr dab_make_ofdm_ffs_sample (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate);
52
53 dab_ofdm_ffs_sample (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate); // private constructor
54
55 unsigned int d_symbol_length; // length of a symbol in samples
56 unsigned int d_fft_length; // length of a symbol without cyclic prefix in samples
57 unsigned int d_num_symbols; // number of symbols per frame to average over
58 float d_alpha; // adjustment speed factor
59 unsigned int d_sample_rate; // sample rate -- only needed to print the ffs error in Hz
60
61 unsigned int d_cur_symbol; // which symbol in the frame is currently under observation?
62 unsigned int d_cur_sample; // which sample in the symbol is currently under observation?
63 float d_ffs_error_sum; // sum of error samples in current frame
64 float d_estimated_error; // total estimated error
65 float d_estimated_error_per_sample; // total estimated error / fft_length
66
67 public:
68 /*! \return fine frequency error estimate in Hz */
69 float ffe_estimate() { return d_estimated_error_per_sample*d_sample_rate/(2*M_PI); }
70 int work (int noutput_items,
71 gr_vector_const_void_star &input_items,
72 gr_vector_void_star &output_items);
73};
74
75#endif /* INCLUDED_DAB_OFDM_FFS_SAMPLE_H */
samples FFS error estimation at the correct time and averages it
Definition dab_ofdm_ffs_sample.h:46
float ffe_estimate()
Definition dab_ofdm_ffs_sample.h:69
friend dab_ofdm_ffs_sample_sptr dab_make_ofdm_ffs_sample(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)
dab_ofdm_ffs_sample_sptr dab_make_ofdm_ffs_sample(unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate)