GNU Radio's LORA_SDR Package
signal_detector.h
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1/* -*- c++ -*- */
2/*
3 * Copyright 2020 <+YOU OR YOUR COMPANY+>.
4 *
5 * This is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3, or (at your option)
8 * any later version.
9 *
10 * This software is distributed in the hope that it will be useful,
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12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
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19 */
20
21
22#ifndef INCLUDED_LORA_SDR_SIGNAL_DETECTOR_H
23#define INCLUDED_LORA_SDR_SIGNAL_DETECTOR_H
24
25#include <lora_sdr/api.h>
26#include <gnuradio/block.h>
27
28namespace gr {
29 namespace lora_sdr {
30
31 /*!
32 *
33 * \ingroup lora_sdr
34 *
35 */
36 class LORA_SDR_API signal_detector : virtual public gr::block
37 {
38 public:
39 typedef std::shared_ptr<signal_detector> sptr;
40
41 /*!
42 * \brief This block becomes transparent after detecting a LoRa preamble at his input.
43 *
44 * It's main purpose is to prevent the rest of the receiver to run continuously as the matched filtering steps are computationally intensive.
45 * The detection of a LoRa preamble is based on the FFT of 'fft_symb' dechirped symbols. If 'fft_symb' upchirps are in the FFT, a bin should have significantly more energy than others.
46 * The decision is taken based on the ratio between the amplitude of the main bin and the median amplitude of all bins.
47 * Once a detection is triggered, the block will become transparent for the previous 'margin' symbols and the next 'transp_len' symbols.
48 * The transparency duration is reset if a new trigger occurs before the end of the previous tranparency duration.
49 *
50 * \param sf Spreading factor
51 * \param os_factor Oversampling factor
52 * \param threshold Minimal ratio between the max FFT bin and the median of the bins.(a value of 10 has proven to be effective)
53 * \param margin Number of symbols preceding the detection that will be output at the detection time. (margin in case of detection triggering late on the preamble)
54 * \param fft_symb Number of symbols used in the FFT (should be less than the number of preamble upchirps, 4 is an efficient value for the FFT complexity)
55 * \param transp_len minimal duration in symbols after a triggered detection (englobing the preamble and payload symbol is a good idea)
56 */
57 static sptr make(uint8_t sf, uint8_t os_factor, double threshold, int margin, int fft_symb, int transp_len);
58 };
59
60 } // namespace lora_sdr
61} // namespace gr
62
63#endif /* INCLUDED_LORA_SDR_SIGNAL_DETECTOR_H */
64
#define LORA_SDR_API
Definition: api.h:19
Definition: signal_detector.h:37
static sptr make(uint8_t sf, uint8_t os_factor, double threshold, int margin, int fft_symb, int transp_len)
This block becomes transparent after detecting a LoRa preamble at his input.
std::shared_ptr< signal_detector > sptr
Definition: signal_detector.h:39
Definition: add_crc.h:28