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/* -*- 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 */
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