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author | Josh Blum | 2011-10-17 23:40:51 -0700 |
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committer | Josh Blum | 2011-10-17 23:40:51 -0700 |
commit | 161910c66e88c081d267f4b2b699f7431f287279 (patch) | |
tree | 86500bb995f5afeece82042eb29eeb3716151d1d /gr-digital/lib/digital_ofdm_frame_acquisition.cc | |
parent | 41ce01bd6f602009b83422550b0b91bddd830c84 (diff) | |
parent | f664585ddddeb040d1cd285d0b9dfb41c4979b91 (diff) | |
download | gnuradio-161910c66e88c081d267f4b2b699f7431f287279.tar.gz gnuradio-161910c66e88c081d267f4b2b699f7431f287279.tar.bz2 gnuradio-161910c66e88c081d267f4b2b699f7431f287279.zip |
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')
-rw-r--r-- | gr-digital/lib/digital_ofdm_frame_acquisition.cc | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/gr-digital/lib/digital_ofdm_frame_acquisition.cc b/gr-digital/lib/digital_ofdm_frame_acquisition.cc new file mode 100644 index 000000000..93b58aeca --- /dev/null +++ b/gr-digital/lib/digital_ofdm_frame_acquisition.cc @@ -0,0 +1,210 @@ +/* -*- 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; +} |