<!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"/> <title>GNU Radio 3.2.2 C++ API: gr_ofdm_frame_acquisition Class Reference</title> <link href="tabs.css" rel="stylesheet" type="text/css"/> <link href="navtree.css" rel="stylesheet" type="text/css"/> <script type="text/javascript" src="jquery.js"></script> <script type="text/javascript" src="navtree.js"></script> <script type="text/javascript" src="resize.js"></script> <script type="text/javascript"> $(document).ready(initResizable); </script> <link href="doxygen.css" rel="stylesheet" type="text/css"/> </head> <body> <!-- Generated by Doxygen 1.7.3 --> <div id="top"> <div id="titlearea"> <table cellspacing="0" cellpadding="0"> <tbody> <tr style="height: 56px;"> <td style="padding-left: 0.5em;"> <div id="projectname">GNU Radio 3.2.2 C++ API</div> </td> </tr> </tbody> </table> </div> </div> <div id="side-nav" class="ui-resizable side-nav-resizable"> <div id="nav-tree"> <div id="nav-tree-contents"> </div> </div> <div id="splitbar" style="-moz-user-select:none;" class="ui-resizable-handle"> </div> </div> <script type="text/javascript"> initNavTree('classgr__ofdm__frame__acquisition.html',''); </script> <div id="doc-content"> <div class="header"> <div class="summary"> <a href="#pub-methods">Public Member Functions</a> | <a href="#pro-methods">Protected Member Functions</a> | <a href="#friends">Friends</a> </div> <div class="headertitle"> <h1>gr_ofdm_frame_acquisition Class Reference<div class="ingroups"><a class="el" href="group__demodulation__blk.html">Signal Demodulation</a> | <a class="el" href="group__ofdm__blk.html">OFDM Blocks</a></div></h1> </div> </div> <div class="contents"> <!-- doxytag: class="gr_ofdm_frame_acquisition" --><!-- doxytag: inherits="gr_block" --> <p>take a vector of complex constellation points in from an FFT and performs a correlation and equalization.This block takes the output of an FFT of a received OFDM symbol and finds the start of a frame based on two known symbols. It also looks at the surrounding bins in the FFT output for the correlation in case there is a large frequency shift in the data. This block assumes that the fine frequency shift has already been corrected and that the samples fall in the middle of one FFT bin. <a href="#_details">More...</a></p> <p><code>#include <<a class="el" href="gr__ofdm__frame__acquisition_8h_source.html">gr_ofdm_frame_acquisition.h</a>></code></p> <div class="dynheader"> Inheritance diagram for gr_ofdm_frame_acquisition:</div> <div class="dyncontent"> <div class="center"><img src="classgr__ofdm__frame__acquisition__inherit__graph.png" border="0" usemap="#gr__ofdm__frame__acquisition_inherit__map" alt="Inheritance graph"/></div> <map name="gr__ofdm__frame__acquisition_inherit__map" id="gr__ofdm__frame__acquisition_inherit__map"> <area shape="rect" id="node2" href="classgr__block.html" title="The abstract base class for all 'terminal' processing blocks.A signal processing flow is cons..." alt="" coords="60,83,129,112"/><area shape="rect" id="node4" href="classgr__basic__block.html" title="The abstract base class for all signal processing blocks.Basic blocks are the bare abstraction of an ..." alt="" coords="40,5,149,35"/></map> <center><span class="legend">[<a target="top" href="graph_legend.html">legend</a>]</span></center></div> <p><a href="classgr__ofdm__frame__acquisition-members.html">List of all members.</a></p> <table class="memberdecls"> <tr><td colspan="2"><h2><a name="pub-methods"></a> Public Member Functions</h2></td></tr> <tr><td class="memItemLeft" align="right" valign="top">float </td><td class="memItemRight" valign="bottom"><a class="el" href="classgr__ofdm__frame__acquisition.html#a50418e0fba566a0c8fdb24bdba52688e">snr</a> ()</td></tr> <tr><td class="mdescLeft"> </td><td class="mdescRight">Return an estimate of the SNR of the channel. <a href="#a50418e0fba566a0c8fdb24bdba52688e"></a><br/></td></tr> <tr><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classgr__ofdm__frame__acquisition.html#ab46c54b18587dcbcd43803a0cc8c5cef">~gr_ofdm_frame_acquisition</a> (void)</td></tr> <tr><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="classgr__ofdm__frame__acquisition.html#ac9e7650efc73d2febe2e90a5e1a9fd3f">general_work</a> (int noutput_items, <a class="el" href="classstd_1_1vector.html">gr_vector_int</a> &ninput_items, <a class="el" href="classstd_1_1vector.html">gr_vector_const_void_star</a> &input_items, <a class="el" href="classstd_1_1vector.html">gr_vector_void_star</a> &output_items)</td></tr> <tr><td class="mdescLeft"> </td><td class="mdescRight">compute output items from input items <a href="#ac9e7650efc73d2febe2e90a5e1a9fd3f"></a><br/></td></tr> <tr><td colspan="2"><h2><a name="pro-methods"></a> Protected Member Functions</h2></td></tr> <tr><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classgr__ofdm__frame__acquisition.html#a1b7330d70565b77df6304d73a247fcfc">gr_ofdm_frame_acquisition</a> (unsigned int occupied_carriers, unsigned int fft_length, unsigned int cplen, const <a class="el" href="classstd_1_1vector.html">std::vector</a>< <a class="el" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> > &known_symbol, unsigned int max_fft_shift_len)</td></tr> <tr><td colspan="2"><h2><a name="friends"></a> Friends</h2></td></tr> <tr><td class="memItemLeft" align="right" valign="top"><a class="el" href="classboost_1_1shared__ptr.html">gr_ofdm_frame_acquisition_sptr</a> </td><td class="memItemRight" valign="bottom"><a class="el" href="classgr__ofdm__frame__acquisition.html#a7ef32b562ebffaa6114381c03ae05c9b">gr_make_ofdm_frame_acquisition</a> (unsigned int occupied_carriers, unsigned int fft_length, unsigned int cplen, const <a class="el" href="classstd_1_1vector.html">std::vector</a>< <a class="el" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> > &known_symbol, unsigned int max_fft_shift_len)</td></tr> <tr><td class="mdescLeft"> </td><td class="mdescRight">Build an OFDM correlator and equalizer. <a href="#a7ef32b562ebffaa6114381c03ae05c9b"></a><br/></td></tr> </table> <hr/><a name="_details"></a><h2>Detailed Description</h2> <div class="textblock"><p>take a vector of complex constellation points in from an FFT and performs a correlation and equalization.</p> <p>This block takes the output of an FFT of a received OFDM symbol and finds the start of a frame based on two known symbols. It also looks at the surrounding bins in the FFT output for the correlation in case there is a large frequency shift in the data. This block assumes that the fine frequency shift has already been corrected and that the samples fall in the middle of one FFT bin. </p> <p>It then uses one of those known symbols to estimate the channel response over all subcarriers and does a simple 1-tap equalization on all subcarriers. This corrects for the phase and amplitude distortion caused by the channel. </p> </div><hr/><h2>Constructor & Destructor Documentation</h2> <a class="anchor" id="a1b7330d70565b77df6304d73a247fcfc"></a><!-- doxytag: member="gr_ofdm_frame_acquisition::gr_ofdm_frame_acquisition" ref="a1b7330d70565b77df6304d73a247fcfc" args="(unsigned int occupied_carriers, unsigned int fft_length, unsigned int cplen, const std::vector< gr_complex > &known_symbol, unsigned int max_fft_shift_len)" --> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname">gr_ofdm_frame_acquisition::gr_ofdm_frame_acquisition </td> <td>(</td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>occupied_carriers</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>fft_length</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>cplen</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">const <a class="el" href="classstd_1_1vector.html">std::vector</a>< <a class="el" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> > & </td> <td class="paramname"><em>known_symbol</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>max_fft_shift_len</em> </td> </tr> <tr> <td></td> <td>)</td> <td></td><td><code> [protected]</code></td> </tr> </table> </div> <div class="memdoc"> </div> </div> <a class="anchor" id="ab46c54b18587dcbcd43803a0cc8c5cef"></a><!-- doxytag: member="gr_ofdm_frame_acquisition::~gr_ofdm_frame_acquisition" ref="ab46c54b18587dcbcd43803a0cc8c5cef" args="(void)" --> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname">gr_ofdm_frame_acquisition::~gr_ofdm_frame_acquisition </td> <td>(</td> <td class="paramtype">void </td> <td class="paramname"></td><td>)</td> <td></td> </tr> </table> </div> <div class="memdoc"> </div> </div> <hr/><h2>Member Function Documentation</h2> <a class="anchor" id="ac9e7650efc73d2febe2e90a5e1a9fd3f"></a><!-- doxytag: member="gr_ofdm_frame_acquisition::general_work" ref="ac9e7650efc73d2febe2e90a5e1a9fd3f" args="(int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)" --> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname">int gr_ofdm_frame_acquisition::general_work </td> <td>(</td> <td class="paramtype">int </td> <td class="paramname"><em>noutput_items</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype"><a class="el" href="classstd_1_1vector.html">gr_vector_int</a> & </td> <td class="paramname"><em>ninput_items</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype"><a class="el" href="classstd_1_1vector.html">gr_vector_const_void_star</a> & </td> <td class="paramname"><em>input_items</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype"><a class="el" href="classstd_1_1vector.html">gr_vector_void_star</a> & </td> <td class="paramname"><em>output_items</em> </td> </tr> <tr> <td></td> <td>)</td> <td></td><td><code> [virtual]</code></td> </tr> </table> </div> <div class="memdoc"> <p>compute output items from input items </p> <dl><dt><b>Parameters:</b></dt><dd> <table class="params"> <tr><td class="paramname">noutput_items</td><td>number of output items to write on each output stream </td></tr> <tr><td class="paramname">ninput_items</td><td>number of input items available on each input stream </td></tr> <tr><td class="paramname">input_items</td><td>vector of pointers to the input items, one entry per input stream </td></tr> <tr><td class="paramname">output_items</td><td>vector of pointers to the output items, one entry per output stream</td></tr> </table> </dd> </dl> <dl class="return"><dt><b>Returns:</b></dt><dd>number of items actually written to each output stream, or -1 on EOF. It is OK to return a value less than noutput_items. -1 <= return value <= noutput_items</dd></dl> <p>general_work must call consume or consume_each to indicate how many items were consumed on each input stream. </p> <p>Implements <a class="el" href="classgr__block.html#a137b93d87dc83bbdb6369d33f4ea8197">gr_block</a>.</p> </div> </div> <a class="anchor" id="a50418e0fba566a0c8fdb24bdba52688e"></a><!-- doxytag: member="gr_ofdm_frame_acquisition::snr" ref="a50418e0fba566a0c8fdb24bdba52688e" args="()" --> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname">float gr_ofdm_frame_acquisition::snr </td> <td>(</td> <td class="paramname"></td><td>)</td> <td><code> [inline]</code></td> </tr> </table> </div> <div class="memdoc"> <p>Return an estimate of the SNR of the channel. </p> </div> </div> <hr/><h2>Friends And Related Function Documentation</h2> <a class="anchor" id="a7ef32b562ebffaa6114381c03ae05c9b"></a><!-- doxytag: member="gr_ofdm_frame_acquisition::gr_make_ofdm_frame_acquisition" ref="a7ef32b562ebffaa6114381c03ae05c9b" args="(unsigned int occupied_carriers, unsigned int fft_length, unsigned int cplen, const std::vector< gr_complex > &known_symbol, unsigned int max_fft_shift_len)" --> <div class="memitem"> <div class="memproto"> <table class="memname"> <tr> <td class="memname"><a class="el" href="classboost_1_1shared__ptr.html">gr_ofdm_frame_acquisition_sptr</a> gr_make_ofdm_frame_acquisition </td> <td>(</td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>occupied_carriers</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>fft_length</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>cplen</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">const <a class="el" href="classstd_1_1vector.html">std::vector</a>< <a class="el" href="gr__complex_8h.html#aec4bfe41433369afae9327f1b0bc9109">gr_complex</a> > & </td> <td class="paramname"><em>known_symbol</em>, </td> </tr> <tr> <td class="paramkey"></td> <td></td> <td class="paramtype">unsigned int </td> <td class="paramname"><em>max_fft_shift_len</em> </td> </tr> <tr> <td></td> <td>)</td> <td></td><td><code> [friend]</code></td> </tr> </table> </div> <div class="memdoc"> <p>Build an OFDM correlator and equalizer. </p> <dl><dt><b>Parameters:</b></dt><dd> <table class="params"> <tr><td class="paramname">occupied_carriers</td><td>The number of subcarriers with data in the received symbol </td></tr> <tr><td class="paramname">fft_length</td><td>The size of the FFT vector (occupied_carriers + unused carriers) </td></tr> <tr><td class="paramname">cplen</td><td>The length of the cycle prefix </td></tr> <tr><td class="paramname">known_symbol</td><td>A vector of complex numbers representing a known symbol at the start of a frame (usually a BPSK PN sequence) </td></tr> <tr><td class="paramname">max_fft_shift_len</td><td>Set's the maximum distance you can look between bins for correlation </td></tr> </table> </dd> </dl> </div> </div> <hr/>The documentation for this class was generated from the following file:<ul> <li><a class="el" href="gr__ofdm__frame__acquisition_8h_source.html">gr_ofdm_frame_acquisition.h</a></li> </ul> </div> </div> <div id="nav-path" class="navpath"> <ul> <li class="navelem"><a class="el" href="classgr__ofdm__frame__acquisition.html">gr_ofdm_frame_acquisition</a> </li> <li class="footer">Generated on Thu Feb 17 2011 for GNU Radio 3.2.2 C++ API by  <a href="http://www.doxygen.org/index.html"> <img class="footer" src="doxygen.png" alt="doxygen"/></a> 1.7.3 </li> </ul> </div> </body> </html>