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Diffstat (limited to 'gr-digital/lib/ofdm_sampler_impl.cc')
| -rw-r--r-- | gr-digital/lib/ofdm_sampler_impl.cc | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/gr-digital/lib/ofdm_sampler_impl.cc b/gr-digital/lib/ofdm_sampler_impl.cc new file mode 100644 index 0000000000..0724b7cf26 --- /dev/null +++ b/gr-digital/lib/ofdm_sampler_impl.cc @@ -0,0 +1,144 @@ +/* -*- c++ -*- */ +/* + * Copyright 2007,2008,2010-2012 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 "ofdm_sampler_impl.h" +#include <gr_io_signature.h> +#include <gr_expj.h> +#include <cstdio> + +namespace gr { + namespace digital { + + ofdm_sampler::sptr + ofdm_sampler::make(unsigned int fft_length, + unsigned int symbol_length, + unsigned int timeout) + { + return gnuradio::get_initial_sptr + (new ofdm_sampler_impl(fft_length, symbol_length, timeout)); + } + + ofdm_sampler_impl::ofdm_sampler_impl(unsigned int fft_length, + unsigned int symbol_length, + unsigned int timeout) + : gr_block("ofdm_sampler", + gr_make_io_signature2(2, 2, sizeof(gr_complex), sizeof(char)), + gr_make_io_signature2(2, 2, sizeof(gr_complex)*fft_length, sizeof(char)*fft_length)), + d_state(STATE_NO_SIG), d_timeout_max(timeout), + d_fft_length(fft_length), d_symbol_length(symbol_length) + { + set_relative_rate(1.0/(double) fft_length); // buffer allocator hint + } + + ofdm_sampler_impl::~ofdm_sampler_impl() + { + } + + void + ofdm_sampler_impl::forecast(int noutput_items, gr_vector_int &ninput_items_required) + { + // FIXME do we need more + //int nreqd = (noutput_items-1) * d_symbol_length + d_fft_length; + int nreqd = d_symbol_length + d_fft_length; + unsigned ninputs = ninput_items_required.size(); + for(unsigned i = 0; i < ninputs; i++) + ninput_items_required[i] = nreqd; + } + + int + ofdm_sampler_impl::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 *iptr = (const gr_complex*)input_items[0]; + const char *trigger = (const char*)input_items[1]; + + gr_complex *optr = (gr_complex*)output_items[0]; + char *outsig = (char*)output_items[1]; + + //FIXME: we only process a single OFDM symbol at a time; after the preamble, we can + // process a few at a time as long as we always look out for the next preamble. + + unsigned int index = d_fft_length; // start one fft length into the input so we can always look back this far + + outsig[0] = 0; // set output to no signal by default + + // Search for a preamble trigger signal during the next symbol length + while((d_state != STATE_PREAMBLE) && (index <= (d_symbol_length+d_fft_length))) { + if(trigger[index]) { + outsig[0] = 1; // tell the next block there is a preamble coming + d_state = STATE_PREAMBLE; + } + else + index++; + } + + unsigned int i, pos, ret; + switch(d_state) { + case(STATE_PREAMBLE): + // When we found a preamble trigger, get it and set the symbol boundary here + for(i = (index - d_fft_length + 1); i <= index; i++) { + *optr++ = iptr[i]; + } + + d_timeout = d_timeout_max; // tell the system to expect at least this many symbols for a frame + d_state = STATE_FRAME; + consume_each(index - d_fft_length + 1); // consume up to one fft_length away to keep the history + ret = 1; + break; + + case(STATE_FRAME): + // use this state when we have processed a preamble and are getting the rest of the frames + //FIXME: we could also have a power squelch system here to enter STATE_NO_SIG if no power is received + + // skip over fft length history and cyclic prefix + pos = d_symbol_length; // keeps track of where we are in the input buffer + while(pos < d_symbol_length + d_fft_length) { + *optr++ = iptr[pos++]; + } + + if(d_timeout-- == 0) { + printf("TIMEOUT\n"); + d_state = STATE_NO_SIG; + } + + consume_each(d_symbol_length); // jump up by 1 fft length and the cyclic prefix length + ret = 1; + break; + + case(STATE_NO_SIG): + default: + consume_each(index-d_fft_length); // consume everything we've gone through so far leaving the fft length history + ret = 0; + break; + } + + return ret; + } + + } /* namespace digital */ +} /* namespace gr */ |