<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/xhtml;charset=UTF-8"/> <meta http-equiv="X-UA-Compatible" content="IE=9"/> <meta name="generator" content="Doxygen 1.8.3"/> <title>GNU Radio 3.6.4.1 C++ API: digital_ofdm_frame_acquisition.h Source File</title> <link href="tabs.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript" src="dynsections.js"></script> <link href="navtree.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="resize.js"></script> <script type="text/javascript" src="navtree.js"></script> <script type="text/javascript"> $(document).ready(initResizable); $(window).load(resizeHeight); </script> <link href="doxygen.css" rel="stylesheet" type="text/css" /> </head> <body> <div id="top"><!-- do not remove this div, it is closed by doxygen! --> <div id="titlearea"> <table cellspacing="0" cellpadding="0"> <tbody> <tr style="height: 56px;"> <td style="padding-left: 0.5em;"> <div id="projectname">GNU Radio 3.6.4.1 C++ API </div> </td> </tr> </tbody> </table> </div> <!-- end header part --> <!-- Generated by Doxygen 1.8.3 --> </div><!-- top --> <div id="side-nav" class="ui-resizable side-nav-resizable"> <div id="nav-tree"> <div id="nav-tree-contents"> <div id="nav-sync" class="sync"></div> </div> </div> <div id="splitbar" style="-moz-user-select:none;" class="ui-resizable-handle"> </div> </div> <script type="text/javascript"> $(document).ready(function(){initNavTree('digital__ofdm__frame__acquisition_8h_source.html','');}); </script> <div id="doc-content"> <div class="header"> <div class="headertitle"> <div class="title">digital_ofdm_frame_acquisition.h</div> </div> </div><!--header--> <div class="contents"> <a href="digital__ofdm__frame__acquisition_8h.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno"> 1</span> <span class="comment">/* -*- c++ -*- */</span></div> <div class="line"><a name="l00002"></a><span class="lineno"> 2</span> <span class="comment">/*</span></div> <div class="line"><a name="l00003"></a><span class="lineno"> 3</span> <span class="comment"> * Copyright 2006,2007,2011 Free Software Foundation, Inc.</span></div> <div class="line"><a name="l00004"></a><span class="lineno"> 4</span> <span class="comment"> * </span></div> <div class="line"><a name="l00005"></a><span class="lineno"> 5</span> <span class="comment"> * This file is part of GNU Radio</span></div> <div class="line"><a name="l00006"></a><span class="lineno"> 6</span> <span class="comment"> * </span></div> <div class="line"><a name="l00007"></a><span class="lineno"> 7</span> <span class="comment"> * GNU Radio is free software; you can redistribute it and/or modify</span></div> <div class="line"><a name="l00008"></a><span class="lineno"> 8</span> <span class="comment"> * it under the terms of the GNU General Public License as published by</span></div> <div class="line"><a name="l00009"></a><span class="lineno"> 9</span> <span class="comment"> * the Free Software Foundation; either version 3, or (at your option)</span></div> <div class="line"><a name="l00010"></a><span class="lineno"> 10</span> <span class="comment"> * any later version.</span></div> <div class="line"><a name="l00011"></a><span class="lineno"> 11</span> <span class="comment"> * </span></div> <div class="line"><a name="l00012"></a><span class="lineno"> 12</span> <span class="comment"> * GNU Radio is distributed in the hope that it will be useful,</span></div> <div class="line"><a name="l00013"></a><span class="lineno"> 13</span> <span class="comment"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</span></div> <div class="line"><a name="l00014"></a><span class="lineno"> 14</span> <span class="comment"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span></div> <div class="line"><a name="l00015"></a><span class="lineno"> 15</span> <span class="comment"> * GNU General Public License for more details.</span></div> <div class="line"><a name="l00016"></a><span class="lineno"> 16</span> <span class="comment"> * </span></div> <div class="line"><a name="l00017"></a><span class="lineno"> 17</span> <span class="comment"> * You should have received a copy of the GNU General Public License</span></div> <div class="line"><a name="l00018"></a><span class="lineno"> 18</span> <span class="comment"> * along with GNU Radio; see the file COPYING. If not, write to</span></div> <div class="line"><a name="l00019"></a><span class="lineno"> 19</span> <span class="comment"> * the Free Software Foundation, Inc., 51 Franklin Street,</span></div> <div class="line"><a name="l00020"></a><span class="lineno"> 20</span> <span class="comment"> * Boston, MA 02110-1301, USA.</span></div> <div class="line"><a name="l00021"></a><span class="lineno"> 21</span> <span class="comment"> */</span></div> <div class="line"><a name="l00022"></a><span class="lineno"> 22</span> </div> <div class="line"><a name="l00023"></a><span class="lineno"> 23</span> <span class="preprocessor">#ifndef INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H</span></div> <div class="line"><a name="l00024"></a><span class="lineno"> 24</span> <span class="preprocessor"></span><span class="preprocessor">#define INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H</span></div> <div class="line"><a name="l00025"></a><span class="lineno"> 25</span> <span class="preprocessor"></span></div> <div class="line"><a name="l00026"></a><span class="lineno"> 26</span> <span class="preprocessor">#include <<a class="code" href="digital__api_8h.html">digital_api.h</a>></span></div> <div class="line"><a name="l00027"></a><span class="lineno"> 27</span> <span class="preprocessor">#include <<a class="code" href="gr__block_8h.html">gr_block.h</a>></span></div> <div class="line"><a name="l00028"></a><span class="lineno"> 28</span> <span class="preprocessor">#include <vector></span></div> <div class="line"><a name="l00029"></a><span class="lineno"> 29</span> </div> <div class="line"><a name="l00030"></a><span class="lineno"> 30</span> <span class="keyword">class </span><a class="code" href="classdigital__ofdm__frame__acquisition.html" title="take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...">digital_ofdm_frame_acquisition</a>;</div> <div class="line"><a name="l00031"></a><span class="lineno"> 31</span> <span class="keyword">typedef</span> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">boost::shared_ptr<digital_ofdm_frame_acquisition></a> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">digital_ofdm_frame_acquisition_sptr</a>;</div> <div class="line"><a name="l00032"></a><span class="lineno"> 32</span> </div> <div class="line"><a name="l00033"></a><span class="lineno"> 33</span> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">digital_ofdm_frame_acquisition_sptr</a> </div> <div class="line"><a name="l00034"></a><span class="lineno"> 34</span> <a class="code" href="digital__api_8h.html#ae14969f36ec69051c4b2f13a0db7e9ba">DIGITAL_API</a> <a class="code" href="digital__ofdm__frame__acquisition_8h.html#a6b2e1eb93ccc511055e69c7ea460e8f1">digital_make_ofdm_frame_acquisition</a> (<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> occupied_carriers, <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> fft_length,</div> <div class="line"><a name="l00035"></a><span class="lineno"> 35</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> cplen,</div> <div class="line"><a name="l00036"></a><span class="lineno"> 36</span>  <span class="keyword">const</span> std::vector<gr_complex> &known_symbol, </div> <div class="line"><a name="l00037"></a><span class="lineno"> 37</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> max_fft_shift_len=10);</div> <div class="line"><a name="l00038"></a><span class="lineno"> 38</span> <span class="comment"></span></div> <div class="line"><a name="l00039"></a><span class="lineno"> 39</span> <span class="comment">/*!</span></div> <div class="line"><a name="l00040"></a><span class="lineno"> 40</span> <span class="comment"> * \brief take a vector of complex constellation points in from an FFT</span></div> <div class="line"><a name="l00041"></a><span class="lineno"> 41</span> <span class="comment"> * and performs a correlation and equalization.</span></div> <div class="line"><a name="l00042"></a><span class="lineno"> 42</span> <span class="comment"> * \ingroup demodulation_blk</span></div> <div class="line"><a name="l00043"></a><span class="lineno"> 43</span> <span class="comment"> * \ingroup ofdm_blk</span></div> <div class="line"><a name="l00044"></a><span class="lineno"> 44</span> <span class="comment"> *</span></div> <div class="line"><a name="l00045"></a><span class="lineno"> 45</span> <span class="comment"> * This block takes the output of an FFT of a received OFDM symbol and finds the </span></div> <div class="line"><a name="l00046"></a><span class="lineno"> 46</span> <span class="comment"> * start of a frame based on two known symbols. It also looks at the surrounding</span></div> <div class="line"><a name="l00047"></a><span class="lineno"> 47</span> <span class="comment"> * bins in the FFT output for the correlation in case there is a large frequency</span></div> <div class="line"><a name="l00048"></a><span class="lineno"> 48</span> <span class="comment"> * shift in the data. This block assumes that the fine frequency shift has already</span></div> <div class="line"><a name="l00049"></a><span class="lineno"> 49</span> <span class="comment"> * been corrected and that the samples fall in the middle of one FFT bin.</span></div> <div class="line"><a name="l00050"></a><span class="lineno"> 50</span> <span class="comment"> *</span></div> <div class="line"><a name="l00051"></a><span class="lineno"> 51</span> <span class="comment"> * It then uses one of those known</span></div> <div class="line"><a name="l00052"></a><span class="lineno"> 52</span> <span class="comment"> * symbols to estimate the channel response over all subcarriers and does a simple </span></div> <div class="line"><a name="l00053"></a><span class="lineno"> 53</span> <span class="comment"> * 1-tap equalization on all subcarriers. This corrects for the phase and amplitude</span></div> <div class="line"><a name="l00054"></a><span class="lineno"> 54</span> <span class="comment"> * distortion caused by the channel.</span></div> <div class="line"><a name="l00055"></a><span class="lineno"> 55</span> <span class="comment"> */</span></div> <div class="line"><a name="l00056"></a><span class="lineno"> 56</span> </div> <div class="line"><a name="l00057"></a><span class="lineno"><a class="code" href="classdigital__ofdm__frame__acquisition.html"> 57</a></span> <span class="keyword">class </span><a class="code" href="digital__api_8h.html#ae14969f36ec69051c4b2f13a0db7e9ba">DIGITAL_API</a> <a class="code" href="classdigital__ofdm__frame__acquisition.html" title="take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...">digital_ofdm_frame_acquisition</a> : <span class="keyword">public</span> <a class="code" href="classgr__block.html" title="The abstract base class for all 'terminal' processing blocks.A signal processing flow is constructed ...">gr_block</a></div> <div class="line"><a name="l00058"></a><span class="lineno"> 58</span> {<span class="comment"></span></div> <div class="line"><a name="l00059"></a><span class="lineno"> 59</span> <span class="comment"> /*! </span></div> <div class="line"><a name="l00060"></a><span class="lineno"> 60</span> <span class="comment"> * \brief Build an OFDM correlator and equalizer.</span></div> <div class="line"><a name="l00061"></a><span class="lineno"> 61</span> <span class="comment"> * \param occupied_carriers The number of subcarriers with data in the received symbol</span></div> <div class="line"><a name="l00062"></a><span class="lineno"> 62</span> <span class="comment"> * \param fft_length The size of the FFT vector (occupied_carriers + unused carriers)</span></div> <div class="line"><a name="l00063"></a><span class="lineno"> 63</span> <span class="comment"> * \param cplen The length of the cycle prefix</span></div> <div class="line"><a name="l00064"></a><span class="lineno"> 64</span> <span class="comment"> * \param known_symbol A vector of complex numbers representing a known symbol at the</span></div> <div class="line"><a name="l00065"></a><span class="lineno"> 65</span> <span class="comment"> * start of a frame (usually a BPSK PN sequence)</span></div> <div class="line"><a name="l00066"></a><span class="lineno"> 66</span> <span class="comment"> * \param max_fft_shift_len Set's the maximum distance you can look between bins for correlation</span></div> <div class="line"><a name="l00067"></a><span class="lineno"> 67</span> <span class="comment"> */</span></div> <div class="line"><a name="l00068"></a><span class="lineno"> 68</span>  <span class="keyword">friend</span> <a class="code" href="digital__api_8h.html#ae14969f36ec69051c4b2f13a0db7e9ba">DIGITAL_API</a> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">digital_ofdm_frame_acquisition_sptr</a></div> <div class="line"><a name="l00069"></a><span class="lineno"> 69</span>  <a class="code" href="digital__ofdm__frame__acquisition_8h.html#a6b2e1eb93ccc511055e69c7ea460e8f1">digital_make_ofdm_frame_acquisition</a> (<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> occupied_carriers, <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> fft_length,</div> <div class="line"><a name="l00070"></a><span class="lineno"> 70</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> cplen,</div> <div class="line"><a name="l00071"></a><span class="lineno"> 71</span>  <span class="keyword">const</span> std::vector<gr_complex> &known_symbol, </div> <div class="line"><a name="l00072"></a><span class="lineno"> 72</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> max_fft_shift_len);</div> <div class="line"><a name="l00073"></a><span class="lineno"> 73</span>  </div> <div class="line"><a name="l00074"></a><span class="lineno"> 74</span> <span class="keyword">protected</span>:</div> <div class="line"><a name="l00075"></a><span class="lineno"> 75</span>  <a class="code" href="classdigital__ofdm__frame__acquisition.html" title="take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...">digital_ofdm_frame_acquisition</a> (<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> occupied_carriers, <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> fft_length,</div> <div class="line"><a name="l00076"></a><span class="lineno"> 76</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> cplen,</div> <div class="line"><a name="l00077"></a><span class="lineno"> 77</span>  <span class="keyword">const</span> std::vector<gr_complex> &known_symbol, </div> <div class="line"><a name="l00078"></a><span class="lineno"> 78</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> max_fft_shift_len);</div> <div class="line"><a name="l00079"></a><span class="lineno"> 79</span>  </div> <div class="line"><a name="l00080"></a><span class="lineno"> 80</span>  <span class="keyword">private</span>:</div> <div class="line"><a name="l00081"></a><span class="lineno"> 81</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> slicer(<a class="code" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> x);</div> <div class="line"><a name="l00082"></a><span class="lineno"> 82</span>  <span class="keywordtype">void</span> correlate(<span class="keyword">const</span> <a class="code" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> *symbol, <span class="keywordtype">int</span> zeros_on_left);</div> <div class="line"><a name="l00083"></a><span class="lineno"> 83</span>  <span class="keywordtype">void</span> calculate_equalizer(<span class="keyword">const</span> <a class="code" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> *symbol, <span class="keywordtype">int</span> zeros_on_left);</div> <div class="line"><a name="l00084"></a><span class="lineno"> 84</span>  <a class="code" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> coarse_freq_comp(<span class="keywordtype">int</span> freq_delta, <span class="keywordtype">int</span> count);</div> <div class="line"><a name="l00085"></a><span class="lineno"> 85</span>  </div> <div class="line"><a name="l00086"></a><span class="lineno"> 86</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_occupied_carriers; <span class="comment">// !< \brief number of subcarriers with data</span></div> <div class="line"><a name="l00087"></a><span class="lineno"> 87</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_fft_length; <span class="comment">// !< \brief length of FFT vector</span></div> <div class="line"><a name="l00088"></a><span class="lineno"> 88</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_cplen; <span class="comment">// !< \brief length of cyclic prefix in samples</span></div> <div class="line"><a name="l00089"></a><span class="lineno"> 89</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_freq_shift_len; <span class="comment">// !< \brief number of surrounding bins to look at for correlation</span></div> <div class="line"><a name="l00090"></a><span class="lineno"> 90</span>  std::vector<gr_complex> d_known_symbol; <span class="comment">// !< \brief known symbols at start of frame</span></div> <div class="line"><a name="l00091"></a><span class="lineno"> 91</span>  std::vector<float> d_known_phase_diff; <span class="comment">// !< \brief factor used in correlation from known symbol</span></div> <div class="line"><a name="l00092"></a><span class="lineno"> 92</span>  std::vector<float> d_symbol_phase_diff; <span class="comment">// !< \brief factor used in correlation from received symbol</span></div> <div class="line"><a name="l00093"></a><span class="lineno"> 93</span>  std::vector<gr_complex> d_hestimate; <span class="comment">// !< channel estimate</span></div> <div class="line"><a name="l00094"></a><span class="lineno"> 94</span>  <span class="keywordtype">int</span> d_coarse_freq; <span class="comment">// !< \brief search distance in number of bins</span></div> <div class="line"><a name="l00095"></a><span class="lineno"> 95</span>  <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_phase_count; <span class="comment">// !< \brief accumulator for coarse freq correction</span></div> <div class="line"><a name="l00096"></a><span class="lineno"> 96</span>  <span class="keywordtype">float</span> d_snr_est; <span class="comment">// !< an estimation of the signal to noise ratio</span></div> <div class="line"><a name="l00097"></a><span class="lineno"> 97</span> </div> <div class="line"><a name="l00098"></a><span class="lineno"> 98</span>  <a class="code" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> *d_phase_lut; <span class="comment">// !< look-up table for coarse frequency compensation</span></div> <div class="line"><a name="l00099"></a><span class="lineno"> 99</span> </div> <div class="line"><a name="l00100"></a><span class="lineno"> 100</span>  <span class="keywordtype">void</span> <a class="code" href="classgr__block.html#aa1f2518b5c97126bb015adb9e2027f4a" title="Estimate input requirements given output request.">forecast</a>(<span class="keywordtype">int</span> noutput_items, <a class="code" href="gr__types_8h.html#ab02d0a829d67d39e3ac3163016d3a8be">gr_vector_int</a> &ninput_items_required);</div> <div class="line"><a name="l00101"></a><span class="lineno"> 101</span> </div> <div class="line"><a name="l00102"></a><span class="lineno"> 102</span>  <span class="keyword">public</span>:<span class="comment"></span></div> <div class="line"><a name="l00103"></a><span class="lineno"> 103</span> <span class="comment"> /*!</span></div> <div class="line"><a name="l00104"></a><span class="lineno"> 104</span> <span class="comment"> * \brief Return an estimate of the SNR of the channel</span></div> <div class="line"><a name="l00105"></a><span class="lineno"> 105</span> <span class="comment"> */</span></div> <div class="line"><a name="l00106"></a><span class="lineno"><a class="code" href="classdigital__ofdm__frame__acquisition.html#a5eaf7d26758f6cb9486fcebcbba10640"> 106</a></span>  <span class="keywordtype">float</span> <a class="code" href="classdigital__ofdm__frame__acquisition.html#a5eaf7d26758f6cb9486fcebcbba10640" title="Return an estimate of the SNR of the channel.">snr</a>() { <span class="keywordflow">return</span> d_snr_est; }</div> <div class="line"><a name="l00107"></a><span class="lineno"> 107</span> </div> <div class="line"><a name="l00108"></a><span class="lineno"> 108</span>  ~<a class="code" href="classdigital__ofdm__frame__acquisition.html" title="take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...">digital_ofdm_frame_acquisition</a>(<span class="keywordtype">void</span>);</div> <div class="line"><a name="l00109"></a><span class="lineno"> 109</span>  <span class="keywordtype">int</span> <a class="code" href="classgr__block.html#adf59080d10f322e3816b7ac8f7cb2a7c" title="compute output items from input items">general_work</a>(<span class="keywordtype">int</span> noutput_items,</div> <div class="line"><a name="l00110"></a><span class="lineno"> 110</span>  <a class="code" href="gr__types_8h.html#ab02d0a829d67d39e3ac3163016d3a8be">gr_vector_int</a> &ninput_items,</div> <div class="line"><a name="l00111"></a><span class="lineno"> 111</span>  <a class="code" href="gr__types_8h.html#a9852a3d906d823cb70eb9c29e7f2a43d">gr_vector_const_void_star</a> &input_items,</div> <div class="line"><a name="l00112"></a><span class="lineno"> 112</span>  <a class="code" href="gr__types_8h.html#acd3f499576e769966ea44554b359d949">gr_vector_void_star</a> &output_items);</div> <div class="line"><a name="l00113"></a><span class="lineno"> 113</span> };</div> <div class="line"><a name="l00114"></a><span class="lineno"> 114</span> </div> <div class="line"><a name="l00115"></a><span class="lineno"> 115</span> </div> <div class="line"><a name="l00116"></a><span class="lineno"> 116</span> <span class="preprocessor">#endif</span></div> </div><!-- fragment --></div><!-- contents --> </div><!-- doc-content --> <!-- start footer part --> <div id="nav-path" class="navpath"><!-- id is needed for treeview function! --> <ul> <li class="navelem"><a class="el" href="dir_f7216719ef3afaeb42c046b1c085d582.html">gr-digital</a></li><li class="navelem"><a class="el" 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