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authorJosh Blum2011-10-17 23:40:51 -0700
committerJosh Blum2011-10-17 23:40:51 -0700
commit161910c66e88c081d267f4b2b699f7431f287279 (patch)
tree86500bb995f5afeece82042eb29eeb3716151d1d /gr-digital/lib/digital_ofdm_frame_acquisition.cc
parent41ce01bd6f602009b83422550b0b91bddd830c84 (diff)
parentf664585ddddeb040d1cd285d0b9dfb41c4979b91 (diff)
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Merge branch 'next' of http://gnuradio.org/git/gnuradio into next
Conflicts: gnuradio-core/src/lib/filter/gr_dc_blocker_cc.h gnuradio-core/src/lib/filter/gr_dc_blocker_ff.h gnuradio-core/src/lib/general/gr_ofdm_demapper_vcb.h gr-digital/include/digital_ofdm_cyclic_prefixer.h gr-digital/include/digital_ofdm_frame_acquisition.h gr-digital/include/digital_ofdm_frame_sink.h gr-digital/include/digital_ofdm_insert_preamble.h gr-digital/include/digital_ofdm_mapper_bcv.h gr-digital/include/digital_ofdm_sampler.h
Diffstat (limited to 'gr-digital/lib/digital_ofdm_frame_acquisition.cc')
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diff --git a/gr-digital/lib/digital_ofdm_frame_acquisition.cc b/gr-digital/lib/digital_ofdm_frame_acquisition.cc
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+++ b/gr-digital/lib/digital_ofdm_frame_acquisition.cc
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+/* -*- c++ -*- */
+/*
+ * Copyright 2006-2008,2010,2011 Free Software Foundation, Inc.
+ *
+ * This file is part of GNU Radio
+ *
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ *
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING. If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <digital_ofdm_frame_acquisition.h>
+#include <gr_io_signature.h>
+#include <gr_expj.h>
+#include <gr_math.h>
+#include <cstdio>
+
+#define VERBOSE 0
+#define M_TWOPI (2*M_PI)
+#define MAX_NUM_SYMBOLS 1000
+
+digital_ofdm_frame_acquisition_sptr
+digital_make_ofdm_frame_acquisition (unsigned int occupied_carriers,
+ unsigned int fft_length,
+ unsigned int cplen,
+ const std::vector<gr_complex> &known_symbol,
+ unsigned int max_fft_shift_len)
+{
+ return gnuradio::get_initial_sptr(new digital_ofdm_frame_acquisition (occupied_carriers, fft_length, cplen,
+ known_symbol, max_fft_shift_len));
+}
+
+digital_ofdm_frame_acquisition::digital_ofdm_frame_acquisition (unsigned occupied_carriers,
+ unsigned int fft_length,
+ unsigned int cplen,
+ const std::vector<gr_complex> &known_symbol,
+ unsigned int max_fft_shift_len)
+ : gr_block ("ofdm_frame_acquisition",
+ gr_make_io_signature2 (2, 2, sizeof(gr_complex)*fft_length, sizeof(char)*fft_length),
+ gr_make_io_signature2 (2, 2, sizeof(gr_complex)*occupied_carriers, sizeof(char))),
+ d_occupied_carriers(occupied_carriers),
+ d_fft_length(fft_length),
+ d_cplen(cplen),
+ d_freq_shift_len(max_fft_shift_len),
+ d_known_symbol(known_symbol),
+ d_coarse_freq(0),
+ d_phase_count(0)
+{
+ d_symbol_phase_diff.resize(d_fft_length);
+ d_known_phase_diff.resize(d_occupied_carriers);
+ d_hestimate.resize(d_occupied_carriers);
+
+ unsigned int i = 0, j = 0;
+
+ std::fill(d_known_phase_diff.begin(), d_known_phase_diff.end(), 0);
+ for(i = 0; i < d_known_symbol.size()-2; i+=2) {
+ d_known_phase_diff[i] = norm(d_known_symbol[i] - d_known_symbol[i+2]);
+ }
+
+ d_phase_lut = new gr_complex[(2*d_freq_shift_len+1) * MAX_NUM_SYMBOLS];
+ for(i = 0; i <= 2*d_freq_shift_len; i++) {
+ for(j = 0; j < MAX_NUM_SYMBOLS; j++) {
+ d_phase_lut[j + i*MAX_NUM_SYMBOLS] = gr_expj(-M_TWOPI*d_cplen/d_fft_length*(i-d_freq_shift_len)*j);
+ }
+ }
+}
+
+digital_ofdm_frame_acquisition::~digital_ofdm_frame_acquisition(void)
+{
+ delete [] d_phase_lut;
+}
+
+void
+digital_ofdm_frame_acquisition::forecast (int noutput_items, gr_vector_int &ninput_items_required)
+{
+ unsigned ninputs = ninput_items_required.size ();
+ for (unsigned i = 0; i < ninputs; i++)
+ ninput_items_required[i] = 1;
+}
+
+gr_complex
+digital_ofdm_frame_acquisition::coarse_freq_comp(int freq_delta, int symbol_count)
+{
+ // return gr_complex(cos(-M_TWOPI*freq_delta*d_cplen/d_fft_length*symbol_count),
+ // sin(-M_TWOPI*freq_delta*d_cplen/d_fft_length*symbol_count));
+
+ return gr_expj(-M_TWOPI*freq_delta*d_cplen/d_fft_length*symbol_count);
+
+ //return d_phase_lut[MAX_NUM_SYMBOLS * (d_freq_shift_len + freq_delta) + symbol_count];
+}
+
+void
+digital_ofdm_frame_acquisition::correlate(const gr_complex *symbol, int zeros_on_left)
+{
+ unsigned int i,j;
+
+ std::fill(d_symbol_phase_diff.begin(), d_symbol_phase_diff.end(), 0);
+ for(i = 0; i < d_fft_length-2; i++) {
+ d_symbol_phase_diff[i] = norm(symbol[i] - symbol[i+2]);
+ }
+
+ // sweep through all possible/allowed frequency offsets and select the best
+ int index = 0;
+ float max = 0, sum=0;
+ for(i = zeros_on_left - d_freq_shift_len; i < zeros_on_left + d_freq_shift_len; i++) {
+ sum = 0;
+ for(j = 0; j < d_occupied_carriers; j++) {
+ sum += (d_known_phase_diff[j] * d_symbol_phase_diff[i+j]);
+ }
+ if(sum > max) {
+ max = sum;
+ index = i;
+ }
+ }
+
+ // set the coarse frequency offset relative to the edge of the occupied tones
+ d_coarse_freq = index - zeros_on_left;
+}
+
+void
+digital_ofdm_frame_acquisition::calculate_equalizer(const gr_complex *symbol, int zeros_on_left)
+{
+ unsigned int i=0;
+
+ // Set first tap of equalizer
+ d_hestimate[0] = d_known_symbol[0] /
+ (coarse_freq_comp(d_coarse_freq,1)*symbol[zeros_on_left+d_coarse_freq]);
+
+ // set every even tap based on known symbol
+ // linearly interpolate between set carriers to set zero-filled carriers
+ // FIXME: is this the best way to set this?
+ for(i = 2; i < d_occupied_carriers; i+=2) {
+ d_hestimate[i] = d_known_symbol[i] /
+ (coarse_freq_comp(d_coarse_freq,1)*(symbol[i+zeros_on_left+d_coarse_freq]));
+ d_hestimate[i-1] = (d_hestimate[i] + d_hestimate[i-2]) / gr_complex(2.0, 0.0);
+ }
+
+ // with even number of carriers; last equalizer tap is wrong
+ if(!(d_occupied_carriers & 1)) {
+ d_hestimate[d_occupied_carriers-1] = d_hestimate[d_occupied_carriers-2];
+ }
+
+ if(VERBOSE) {
+ fprintf(stderr, "Equalizer setting:\n");
+ for(i = 0; i < d_occupied_carriers; i++) {
+ gr_complex sym = coarse_freq_comp(d_coarse_freq,1)*symbol[i+zeros_on_left+d_coarse_freq];
+ gr_complex output = sym * d_hestimate[i];
+ fprintf(stderr, "sym: %+.4f + j%+.4f ks: %+.4f + j%+.4f eq: %+.4f + j%+.4f ==> %+.4f + j%+.4f\n",
+ sym .real(), sym.imag(),
+ d_known_symbol[i].real(), d_known_symbol[i].imag(),
+ d_hestimate[i].real(), d_hestimate[i].imag(),
+ output.real(), output.imag());
+ }
+ fprintf(stderr, "\n");
+ }
+}
+
+int
+digital_ofdm_frame_acquisition::general_work(int noutput_items,
+ gr_vector_int &ninput_items,
+ gr_vector_const_void_star &input_items,
+ gr_vector_void_star &output_items)
+{
+ const gr_complex *symbol = (const gr_complex *)input_items[0];
+ const char *signal_in = (const char *)input_items[1];
+
+ gr_complex *out = (gr_complex *) output_items[0];
+ char *signal_out = (char *) output_items[1];
+
+ int unoccupied_carriers = d_fft_length - d_occupied_carriers;
+ int zeros_on_left = (int)ceil(unoccupied_carriers/2.0);
+
+ if(signal_in[0]) {
+ d_phase_count = 1;
+ correlate(symbol, zeros_on_left);
+ calculate_equalizer(symbol, zeros_on_left);
+ signal_out[0] = 1;
+ }
+ else {
+ signal_out[0] = 0;
+ }
+
+ for(unsigned int i = 0; i < d_occupied_carriers; i++) {
+ out[i] = d_hestimate[i]*coarse_freq_comp(d_coarse_freq,d_phase_count)
+ *symbol[i+zeros_on_left+d_coarse_freq];
+ }
+
+ d_phase_count++;
+ if(d_phase_count == MAX_NUM_SYMBOLS) {
+ d_phase_count = 1;
+ }
+
+ consume_each(1);
+ return 1;
+}