GNU Radio's AIS Package: corr_est_cc.h Source File

GNU Radio's AIS Package

corr_est_cc.h
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1/* -*- c++ -*- */
2/*
3 * Copyright 2015 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_CORR_EST_CC_CC_H
24#define INCLUDED_DIGITAL_CORR_EST_CC_CC_H
25
26#include <ais/api.h>
27#include <gnuradio/sync_block.h>
28
29 namespace gr {
30 namespace ais {
31
32 /*!
33 * \brief Correlate stream with a pre-defined sequence and estimate peak
34 * \ingroup synchronizers_blk
35 *
36 * \details
37 * Input:
38 * \li Stream of complex samples.
39 *
40 * Output:
41 * \li Output stream that just passes the input complex samples
42 * \li tag 'phase_est': estimate of phase offset
43 * \li tag 'time_est': estimate of symbol timing offset
44 * \li tag 'corr_est': the correlation value of the estimates
45 * \li tag 'corr_start': the start sample of the correlation and the value
46 *
47 * \li Optional 2nd output stream providing the advanced correlator output
48 *
49 * This block is designed to search for a sync word by correlation
50 * and uses the results of the correlation to get a time and phase
51 * offset estimate. These estimates are passed downstream as
52 * stream tags for use by follow-on synchronization blocks.
53 *
54 * The sync word is provided as a set of symbols along with a
55 * baseband matched filter which we use to create the filtered and
56 * upsampled symbols that we will receive over-the-air.
57 *
58 * The phase_est tag can be used by downstream blocks to adjust
59 * their phase estimatopm/correction loops, and is currently
60 * implemented by the gr::digital::costas_loop_cc block.
61 *
62 * The time_est tag can be used to adjust the sampling timing
63 * estimate of any downstream synchronization blocks and is
64 * currently implemented by the gr::digital::pfb_clock_sync_ccf
65 * block.
66 *
67 * The caller must provide a "time_est" and "phase_est" tag
68 * marking delay from the start of the correlated signal segment,
69 * in order to mark the proper point in the sync word for
70 * downstream synchronization blocks. Generally this block cannot
71 * know where the actual sync word symbols are located relative to
72 * "corr_start", given that some modulations have pulses with
73 * intentional ISI. The user should manually examine the primary
74 * output and the "corr_start" tag postition to determine the
75 * required tag delay settings for the particular modulation,
76 * sync word, and downstream blocks used.
77 *
78 * For a discussion of the properties of complex correlations,
79 * with respect to signal processing, see:
80 * Marple, Jr., S. L., "Estimating Group Delay and Phase Delay
81 * via Discrete-Time 'Analytic' Cross-Correlation, _IEEE_Transcations_
82 * _on_Signal_Processing_, Volume 47, No. 9, September 1999
83 *
84 */
85 class AIS_API corr_est_cc : virtual public sync_block
86 {
87 public:
88 typedef boost::shared_ptr<corr_est_cc> sptr;
89
90 /*!
91 * Make a block that correlates against the \p symbols vector
92 * and outputs a phase and symbol timing estimate.
93 *
94 * \param symbols Set of symbols to correlate against (e.g., a
95 * sync word).
96 * \param sps Samples per symbol
97 * \param mark_delay tag marking delay in samples after the
98 * corr_start tag
99 * \param threshold Threshold of correlator, relative to a 100%
100 * correlation (1.0). Default is 0.9.
101 */
102 static sptr make(const std::vector<gr_complex> &symbols,
103 float sps, unsigned int mark_delay, float threshold=0.9);
104
105 virtual std::vector<gr_complex> symbols() const = 0;
106 virtual void set_symbols(const std::vector<gr_complex> &symbols) = 0;
107 };
108
109 } // namespace digital
110} // namespace gr
111
112#endif /* INCLUDED_DIGITAL_CORR_EST_CC_H */
api.h
AIS_API
#define AIS_API
Definition: api.h:30
gr::ais::corr_est_cc
Correlate stream with a pre-defined sequence and estimate peak.
Definition: corr_est_cc.h:86
gr::ais::corr_est_cc::sptr
boost::shared_ptr< corr_est_cc > sptr
Definition: corr_est_cc.h:88
gr::ais::corr_est_cc::make
static sptr make(const std::vector< gr_complex > &symbols, float sps, unsigned int mark_delay, float threshold=0.9)
gr::ais::corr_est_cc::symbols
virtual std::vector< gr_complex > symbols() const =0
gr::ais::corr_est_cc::set_symbols
virtual void set_symbols(const std::vector< gr_complex > &symbols)=0
gr
Definition: corr_est_cc.h:29