/* -*- c++ -*- */
/*
- * Copyright 2007 Free Software Foundation, Inc.
+ * Copyright 2007,2008,2010 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
#include <gr_ofdm_sampler.h>
#include <gr_io_signature.h>
#include <gr_expj.h>
+#include <cstdio>
gr_ofdm_sampler_sptr
gr_make_ofdm_sampler (unsigned int fft_length,
- unsigned int symbol_length)
+ unsigned int symbol_length,
+ unsigned int timeout)
{
- return gr_ofdm_sampler_sptr (new gr_ofdm_sampler (fft_length, symbol_length));
+ return gr_ofdm_sampler_sptr (new gr_ofdm_sampler (fft_length, symbol_length, timeout));
}
gr_ofdm_sampler::gr_ofdm_sampler (unsigned int fft_length,
- unsigned int symbol_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_signature (1, 1, sizeof (gr_complex)*fft_length)),
- d_fft_length(fft_length), d_symbol_length(symbol_length)
+ 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
}
void
gr_ofdm_sampler::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 = (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
gr_ofdm_sampler::general_work (int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
- gr_complex *iptr = (gr_complex *) input_items[0];
- char *trigger = (char *) input_items[1];
+ 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.
- int found=0;
+ unsigned int index=d_fft_length; // start one fft length into the input so we can always look back this far
- int i=d_fft_length-1;
+ outsig[0] = 0; // set output to no signal by default
- while(!found && i<std::min(ninput_items[0],ninput_items[1]) )
- if(trigger[i])
- found = 1;
+ // 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
- i++;
-
- if(found) {
- assert(i-d_fft_length+1 >= 0);
- for(int j=i-d_fft_length+1;j<=i;j++)
- *optr++ = iptr[j];
- consume_each(i-d_fft_length+2);
- //printf("OFDM Sampler found: ninput_items: %d/%d noutput_items: %d consumed: %d found: %d\n",
- // ninput_items[0], ninput_items[1], noutput_items, (i-d_fft_length+2), found);
+ index++;
}
- else {
- consume_each(i-d_fft_length+1);
- //printf("OFDM Sampler not found: ninput_items: %d/%d noutput_items: %d consumed: %d found: %d\n",
- // ninput_items[0], ninput_items[1], noutput_items, (i-d_fft_length+1), found);
- }
+
+ 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 found;
+ return ret;
}
projects / debian / gnuradio / blobdiff