GNU Radio Manual and C++ API Reference 3.8.5.0
The Free & Open Software Radio Ecosystem
 
Loading...
Searching...
No Matches
ofdm_carrier_allocator_cvc.h
Go to the documentation of this file.
1/* -*- c++ -*- */
2/*
3 * Copyright 2013 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
24#ifndef INCLUDED_DIGITAL_OFDM_CARRIER_ALLOCATOR_CVC_H
25#define INCLUDED_DIGITAL_OFDM_CARRIER_ALLOCATOR_CVC_H
26
29
30namespace gr {
31namespace digital {
32
33/*!
34 * \brief Create frequency domain OFDM symbols from complex values, add pilots.
35 * \ingroup ofdm_blk
36 *
37 * \details
38 * This block turns a stream of complex, scalar modulation symbols into vectors
39 * which are the input for an IFFT in an OFDM transmitter. It also supports the
40 * possibility of placing pilot symbols onto the carriers.
41 *
42 * The carriers can be allocated freely, if a carrier is not allocated, it is set
43 * to zero. This allows doing OFDMA-style carrier allocations.
44 *
45 * Input: A tagged stream of complex scalars. The first item must have a tag
46 * containing the number of complex symbols in this frame.
47 * Output: A tagged stream of complex vectors of length fft_len. This can directly
48 * be connected to an FFT block. Make sure to set this block to 'reverse'
49 * for the IFFT. If \p output_is_shifted is true, the FFT block must activate
50 * FFT shifting, otherwise, set shifting to false. If given, sync words are
51 * prepended to the output. Note that sync words are prepended verbatim,
52 * make sure they are shifted (or not).
53 *
54 * Carrier indexes are always such that index 0 is the DC carrier (note: you should
55 * not allocate this carrier). The carriers below the DC carrier are either indexed
56 * with negative numbers, or with indexes larger than \p fft_len/2. Index -1 and index
57 * \p fft_len-1 both identify the carrier below the DC carrier.
58 *
59 * There are some basic checks in place during initialization which check that the
60 * carrier allocation table is valid. However, it is possible to overwrite data symbols
61 * with pilot symbols, or provide a carrier allocation that has mismatching pilot symbol
62 * positions and -values.
63 *
64 * Tags are propagated such that a tag on an incoming complex symbol is mapped to the
65 * corresponding OFDM symbol. There is one exception: If a tag is on the first OFDM
66 * symbol, it is assumed that this tag should stay there, so it is moved to the front
67 * even if a sync word is included (any other tags will never be attached to the
68 * sync word). This allows tags to control the transmit timing to pass through in the
69 * correct position.
70 */
72{
73public:
74 typedef boost::shared_ptr<ofdm_carrier_allocator_cvc> sptr;
75
76 virtual std::string len_tag_key() = 0;
77 virtual const int fft_len() = 0;
78 virtual std::vector<std::vector<int>> occupied_carriers() = 0;
79
80 /*
81 * \param fft_len FFT length, is also the maximum width of the OFDM symbols, the
82 * output vector size and maximum value for elements in
83 * \p occupied_carriers and \p pilot_carriers.
84 * \param occupied_carriers A vector of vectors of indexes. Example: if
85 * occupied_carriers = ((1, 2, 3), (1, 2, 4)), the first
86 * three input symbols will be mapped to carriers 1, 2
87 * and 3. After that, a new OFDM symbol is started. The next
88 * three input symbols will be placed onto carriers 1, 2
89 * and 4 of the second OFDM symbol. The allocation then
90 * starts from the beginning.
91 * Order matters! The first input symbol is always mapped
92 * onto occupied_carriers[0][0].
93 * \param pilot_carriers The position of the pilot symbols. Same as occupied_carriers,
94 * but the actual symbols are taken from pilot_symbols instead
95 * of the input stream.
96 * \param pilot_symbols The pilot symbols which are placed onto the pilot carriers.
97 * pilot_symbols[0][0] is placed onto the first OFDM symbol, on
98 * carrier index pilot_carriers[0][0] etc.
99 * \param sync_words OFDM symbols that are prepended to the OFDM frame (usually for
100 * synchronisation purposes, e.g. OFDM symbols with every second
101 * sub-carrier being idle). Is a vector of complex vectors of length
102 * \p fft_len
103 * \param len_tag_key The key of the tag identifying the length of the input packet.
104 * \param output_is_shifted whether to 'fftshift' the output OFDM symbols. If used,
105 * the followup FFT should be instantaited such that it knows that the input is
106 * shifted. Default is true.
107 */
108 static sptr make(int fft_len,
109 const std::vector<std::vector<int>>& occupied_carriers,
110 const std::vector<std::vector<int>>& pilot_carriers,
111 const std::vector<std::vector<gr_complex>>& pilot_symbols,
112 const std::vector<std::vector<gr_complex>>& sync_words,
113 const std::string& len_tag_key = "packet_len",
114 const bool output_is_shifted = true);
115};
116
117} // namespace digital
118} // namespace gr
119
120#endif /* INCLUDED_DIGITAL_OFDM_CARRIER_ALLOCATOR_CVC_H */
Create frequency domain OFDM symbols from complex values, add pilots.
Definition ofdm_carrier_allocator_cvc.h:72
virtual std::vector< std::vector< int > > occupied_carriers()=0
boost::shared_ptr< ofdm_carrier_allocator_cvc > sptr
Definition ofdm_carrier_allocator_cvc.h:74
virtual std::string len_tag_key()=0
static sptr make(int fft_len, const std::vector< std::vector< int > > &occupied_carriers, const std::vector< std::vector< int > > &pilot_carriers, const std::vector< std::vector< gr_complex > > &pilot_symbols, const std::vector< std::vector< gr_complex > > &sync_words, const std::string &len_tag_key="packet_len", const bool output_is_shifted=true)
Block that operates on PDUs in form of tagged streams.
Definition tagged_stream_block.h:38
#define DIGITAL_API
Definition gr-digital/include/gnuradio/digital/api.h:30
GNU Radio logging wrapper for log4cpp library (C++ port of log4j)
Definition basic_block.h:46