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<h1>gr_ofdm_frame_acquisition.h</h1> </div>
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<a href="gr__ofdm__frame__acquisition_8h.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* -*- c++ -*- */</span>
<a name="l00002"></a>00002 <span class="comment">/*</span>
<a name="l00003"></a>00003 <span class="comment"> * Copyright 2006, 2007 Free Software Foundation, Inc.</span>
<a name="l00004"></a>00004 <span class="comment"> * </span>
<a name="l00005"></a>00005 <span class="comment"> * This file is part of GNU Radio</span>
<a name="l00006"></a>00006 <span class="comment"> * </span>
<a name="l00007"></a>00007 <span class="comment"> * GNU Radio is free software; you can redistribute it and/or modify</span>
<a name="l00008"></a>00008 <span class="comment"> * it under the terms of the GNU General Public License as published by</span>
<a name="l00009"></a>00009 <span class="comment"> * the Free Software Foundation; either version 3, or (at your option)</span>
<a name="l00010"></a>00010 <span class="comment"> * any later version.</span>
<a name="l00011"></a>00011 <span class="comment"> * </span>
<a name="l00012"></a>00012 <span class="comment"> * GNU Radio is distributed in the hope that it will be useful,</span>
<a name="l00013"></a>00013 <span class="comment"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<a name="l00014"></a>00014 <span class="comment"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span>
<a name="l00015"></a>00015 <span class="comment"> * GNU General Public License for more details.</span>
<a name="l00016"></a>00016 <span class="comment"> * </span>
<a name="l00017"></a>00017 <span class="comment"> * You should have received a copy of the GNU General Public License</span>
<a name="l00018"></a>00018 <span class="comment"> * along with GNU Radio; see the file COPYING. If not, write to</span>
<a name="l00019"></a>00019 <span class="comment"> * the Free Software Foundation, Inc., 51 Franklin Street,</span>
<a name="l00020"></a>00020 <span class="comment"> * Boston, MA 02110-1301, USA.</span>
<a name="l00021"></a>00021 <span class="comment"> */</span>
<a name="l00022"></a>00022
<a name="l00023"></a>00023 <span class="preprocessor">#ifndef INCLUDED_GR_OFDM_FRAME_ACQUISITION_H</span>
<a name="l00024"></a>00024 <span class="preprocessor"></span><span class="preprocessor">#define INCLUDED_GR_OFDM_FRAME_ACQUISITION_H</span>
<a name="l00025"></a>00025 <span class="preprocessor"></span>
<a name="l00026"></a>00026
<a name="l00027"></a>00027 <span class="preprocessor">#include <gr_block.h></span>
<a name="l00028"></a>00028 <span class="preprocessor">#include <vector></span>
<a name="l00029"></a>00029
<a name="l00030"></a>00030 <span class="keyword">class </span><a class="code" href="classgr__ofdm__frame__acquisition.html" title="take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...">gr_ofdm_frame_acquisition</a>;
<a name="l00031"></a>00031 <span class="keyword">typedef</span> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">boost::shared_ptr<gr_ofdm_frame_acquisition></a> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">gr_ofdm_frame_acquisition_sptr</a>;
<a name="l00032"></a>00032
<a name="l00033"></a>00033 <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">gr_ofdm_frame_acquisition_sptr</a>
<a name="l00034"></a>00034 <a class="code" href="gr__ofdm__frame__acquisition_8h.html#a49a9bd0c41145f54df26ceadef2b0431">gr_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,
<a name="l00035"></a>00035 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> cplen,
<a name="l00036"></a>00036 <span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<gr_complex></a> &known_symbol,
<a name="l00037"></a>00037 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> max_fft_shift_len=10);
<a name="l00038"></a>00038 <span class="comment"></span>
<a name="l00039"></a>00039 <span class="comment">/*!</span>
<a name="l00040"></a>00040 <span class="comment"> * \brief take a vector of complex constellation points in from an FFT</span>
<a name="l00041"></a>00041 <span class="comment"> * and performs a correlation and equalization.</span>
<a name="l00042"></a>00042 <span class="comment"> * \ingroup demodulation_blk</span>
<a name="l00043"></a>00043 <span class="comment"> * \ingroup ofdm_blk</span>
<a name="l00044"></a>00044 <span class="comment"> *</span>
<a name="l00045"></a>00045 <span class="comment"> * This block takes the output of an FFT of a received OFDM symbol and finds the </span>
<a name="l00046"></a>00046 <span class="comment"> * start of a frame based on two known symbols. It also looks at the surrounding</span>
<a name="l00047"></a>00047 <span class="comment"> * bins in the FFT output for the correlation in case there is a large frequency</span>
<a name="l00048"></a>00048 <span class="comment"> * shift in the data. This block assumes that the fine frequency shift has already</span>
<a name="l00049"></a>00049 <span class="comment"> * been corrected and that the samples fall in the middle of one FFT bin.</span>
<a name="l00050"></a>00050 <span class="comment"> *</span>
<a name="l00051"></a>00051 <span class="comment"> * It then uses one of those known</span>
<a name="l00052"></a>00052 <span class="comment"> * symbols to estimate the channel response over all subcarriers and does a simple </span>
<a name="l00053"></a>00053 <span class="comment"> * 1-tap equalization on all subcarriers. This corrects for the phase and amplitude</span>
<a name="l00054"></a>00054 <span class="comment"> * distortion caused by the channel.</span>
<a name="l00055"></a>00055 <span class="comment"> */</span>
<a name="l00056"></a>00056
<a name="l00057"></a><a class="code" href="classgr__ofdm__frame__acquisition.html">00057</a> <span class="keyword">class </span><a class="code" href="classgr__ofdm__frame__acquisition.html" title="take a vector of complex constellation points in from an FFT and performs a correlation and equalizat...">gr_ofdm_frame_acquisition</a> : <span class="keyword">public</span> <a class="code" href="classgr__block.html" title="The abstract base class for all &#39;terminal&#39; processing blocks.A signal processing flow is cons...">gr_block</a>
<a name="l00058"></a>00058 {<span class="comment"></span>
<a name="l00059"></a>00059 <span class="comment"> /*! </span>
<a name="l00060"></a>00060 <span class="comment"> * \brief Build an OFDM correlator and equalizer.</span>
<a name="l00061"></a>00061 <span class="comment"> * \param occupied_carriers The number of subcarriers with data in the received symbol</span>
<a name="l00062"></a>00062 <span class="comment"> * \param fft_length The size of the FFT vector (occupied_carriers + unused carriers)</span>
<a name="l00063"></a>00063 <span class="comment"> * \param cplen The length of the cycle prefix</span>
<a name="l00064"></a>00064 <span class="comment"> * \param known_symbol A vector of complex numbers representing a known symbol at the</span>
<a name="l00065"></a>00065 <span class="comment"> * start of a frame (usually a BPSK PN sequence)</span>
<a name="l00066"></a>00066 <span class="comment"> * \param max_fft_shift_len Set's the maximum distance you can look between bins for correlation</span>
<a name="l00067"></a>00067 <span class="comment"> */</span>
<a name="l00068"></a>00068 <span class="keyword">friend</span> <a class="code" href="classboost_1_1shared__ptr.html" title="shared_ptr documentation stub">gr_ofdm_frame_acquisition_sptr</a>
<a name="l00069"></a>00069 <a class="code" href="classgr__ofdm__frame__acquisition.html#a7ef32b562ebffaa6114381c03ae05c9b" title="Build an OFDM correlator and equalizer.">gr_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,
<a name="l00070"></a>00070 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> cplen,
<a name="l00071"></a>00071 <span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<gr_complex></a> &known_symbol,
<a name="l00072"></a>00072 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> max_fft_shift_len);
<a name="l00073"></a>00073
<a name="l00074"></a>00074 <span class="keyword">protected</span>:
<a name="l00075"></a>00075 <a class="code" href="classgr__ofdm__frame__acquisition.html#a1b7330d70565b77df6304d73a247fcfc">gr_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,
<a name="l00076"></a>00076 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> cplen,
<a name="l00077"></a>00077 <span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<gr_complex></a> &known_symbol,
<a name="l00078"></a>00078 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> max_fft_shift_len);
<a name="l00079"></a>00079
<a name="l00080"></a>00080 <span class="keyword">private</span>:
<a name="l00081"></a>00081 <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> slicer(<a class="code" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> x);
<a name="l00082"></a>00082 <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);
<a name="l00083"></a>00083 <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);
<a name="l00084"></a>00084 <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);
<a name="l00085"></a>00085
<a name="l00086"></a>00086 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_occupied_carriers; <span class="comment">// !< \brief number of subcarriers with data</span>
<a name="l00087"></a>00087 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_fft_length; <span class="comment">// !< \brief length of FFT vector</span>
<a name="l00088"></a>00088 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_cplen; <span class="comment">// !< \brief length of cyclic prefix in samples</span>
<a name="l00089"></a>00089 <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>
<a name="l00090"></a>00090 <a class="code" href="classstd_1_1vector.html">std::vector<gr_complex></a> d_known_symbol; <span class="comment">// !< \brief known symbols at start of frame</span>
<a name="l00091"></a>00091 <a class="code" href="classstd_1_1vector.html">std::vector<float></a> d_known_phase_diff; <span class="comment">// !< \brief factor used in correlation from known symbol</span>
<a name="l00092"></a>00092 <a class="code" href="classstd_1_1vector.html">std::vector<float></a> d_symbol_phase_diff; <span class="comment">// !< \brief factor used in correlation from received symbol</span>
<a name="l00093"></a>00093 <a class="code" href="classstd_1_1vector.html">std::vector<gr_complex></a> d_hestimate; <span class="comment">// !< channel estimate</span>
<a name="l00094"></a>00094 <span class="keywordtype">int</span> d_coarse_freq; <span class="comment">// !< \brief search distance in number of bins</span>
<a name="l00095"></a>00095 <span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> d_phase_count; <span class="comment">// !< \brief accumulator for coarse freq correction</span>
<a name="l00096"></a>00096 <span class="keywordtype">float</span> d_snr_est; <span class="comment">// !< an estimation of the signal to noise ratio</span>
<a name="l00097"></a>00097
<a name="l00098"></a>00098 <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>
<a name="l00099"></a>00099
<a name="l00100"></a>00100 <span class="keywordtype">void</span> forecast(<span class="keywordtype">int</span> noutput_items, <a class="code" href="classstd_1_1vector.html">gr_vector_int</a> &ninput_items_required);
<a name="l00101"></a>00101
<a name="l00102"></a>00102 <span class="keyword">public</span>:<span class="comment"></span>
<a name="l00103"></a>00103 <span class="comment"> /*!</span>
<a name="l00104"></a>00104 <span class="comment"> * \brief Return an estimate of the SNR of the channel</span>
<a name="l00105"></a>00105 <span class="comment"> */</span>
<a name="l00106"></a><a class="code" href="classgr__ofdm__frame__acquisition.html#a50418e0fba566a0c8fdb24bdba52688e">00106</a> <span class="keywordtype">float</span> <a class="code" href="classgr__ofdm__frame__acquisition.html#a50418e0fba566a0c8fdb24bdba52688e" title="Return an estimate of the SNR of the channel.">snr</a>() { <span class="keywordflow">return</span> d_snr_est; }
<a name="l00107"></a>00107
<a name="l00108"></a>00108 <a class="code" href="classgr__ofdm__frame__acquisition.html#ab46c54b18587dcbcd43803a0cc8c5cef">~gr_ofdm_frame_acquisition</a>(<span class="keywordtype">void</span>);
<a name="l00109"></a>00109 <span class="keywordtype">int</span> <a class="code" href="classgr__ofdm__frame__acquisition.html#ac9e7650efc73d2febe2e90a5e1a9fd3f" title="compute output items from input items">general_work</a>(<span class="keywordtype">int</span> noutput_items,
<a name="l00110"></a>00110 <a class="code" href="classstd_1_1vector.html">gr_vector_int</a> &ninput_items,
<a name="l00111"></a>00111 <a class="code" href="classstd_1_1vector.html">gr_vector_const_void_star</a> &input_items,
<a name="l00112"></a>00112 <a class="code" href="classstd_1_1vector.html">gr_vector_void_star</a> &output_items);
<a name="l00113"></a>00113 };
<a name="l00114"></a>00114
<a name="l00115"></a>00115
<a name="l00116"></a>00116 <span class="preprocessor">#endif</span>
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