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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gsm_burst_cf.h>
#include <gr_io_signature.h>
#include <gr_math.h>
#include <stdio.h>
#include <gri_mmse_fir_interpolator_cc.h>
gsm_burst_cf_sptr gsm_make_burst_cf (float sample_rate)
{
return gsm_burst_cf_sptr (new gsm_burst_cf (sample_rate));
}
static const int MIN_IN = 1; // minimum number of input streams
static const int MAX_IN = 1; // maximum number of input streams
static const int MIN_OUT = 1; // minimum number of output streams
static const int MAX_OUT = 1; // maximum number of output streams
gsm_burst_cf::gsm_burst_cf (float sample_rate) :
gr_block ( "burst_cf",
gr_make_io_signature (MIN_IN, MAX_IN, sizeof (gr_complex)),
gr_make_io_signature (MIN_OUT, MAX_OUT, USEFUL_BITS * sizeof (float))),
d_clock_counter(0.0),
d_last_sample(0.0,0.0),
d_interp(new gri_mmse_fir_interpolator_cc())
{
//clocking parameters
d_sample_interval = 1.0 / sample_rate;
d_relative_sample_rate = sample_rate / GSM_SYMBOL_RATE;
fprintf(stderr,"Sample interval : %e\n",d_sample_interval);
fprintf(stderr,"Relative sample rate : %g\n",d_relative_sample_rate);
set_history(4);
}
gsm_burst_cf::~gsm_burst_cf ()
{
delete d_interp;
}
void gsm_burst_cf::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] = noutput_items * (int)ceil(d_relative_sample_rate) * BBUF_SIZE + history();
}
int gsm_burst_cf::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 *in = (const gr_complex *) input_items[0];
float *out = (float *) output_items[0];
int ii=0;
int rval = 0; //default to no output
int ninput = ninput_items[0];
//fprintf(stderr,"#i=%d/#o=%d",n_input,noutput_items);
int ni = ninput - d_interp->ntaps(); // interpolator need -4/+3 samples NTAPS = 8
while (( rval < noutput_items) && ( ii < ni ) ) {
//clock symbols
//TODO: this is very basic and can be improved. Need tracking...
//TODO: use burst_start offsets as timing feedback
//TODO: save complex samples for Viterbi EQ
if ( d_clock_counter >= GSM_SYMBOL_PERIOD) {
d_clock_counter -= GSM_SYMBOL_PERIOD; //reset clock for next sample, keep the remainder
//float mu = 1.0 - d_clock_counter / GSM_SYMBOL_PERIOD;
float mu = d_clock_counter / GSM_SYMBOL_PERIOD;
gr_complex sample = d_interp->interpolate (&in[ii], mu); //FIXME: this seems noisy, make sure it is being used correctly
gr_complex conjprod = sample * conj(d_last_sample);
float diff_angle = gr_fast_atan2f(imag(conjprod), real(conjprod));
d_last_sample = sample;
assert(d_bbuf_pos <= BBUF_SIZE );
if (d_bbuf_pos >= 0) //could be negative offset from burst alignment. TODO: perhaps better just to add some padding to the buffer
d_burst_buffer[d_bbuf_pos] = diff_angle;
d_bbuf_pos++;
if ( d_bbuf_pos >= BBUF_SIZE ) {
if (get_burst()) {
//found a burst, send to output
//ensure that output data is in range
int b = d_burst_start;
if (b < 0)
b = 0;
else if (b >= 2 * MAX_CORR_DIST)
b = 2 * MAX_CORR_DIST - 1;
memcpy(out+rval*USEFUL_BITS, d_burst_buffer + b, USEFUL_BITS*sizeof(float));
rval++;
switch ( d_clock_options & QB_MASK ) {
case QB_QUARTER: //extra 1/4 bit each burst
d_clock_counter -= GSM_SYMBOL_PERIOD / 4.0;
break;
case QB_FULL04: //extra bit on timeslot 0 & 4
if (!(d_ts%4))
d_clock_counter -= GSM_SYMBOL_PERIOD;
break;
case QB_NONE: //don't adjust for quarter bits at all
default:
break;
}
d_last_burst_s_count = d_sample_count;
//fprintf(stderr,"clock: %f, pos: %d\n",d_clock_counter,d_bbuf_pos);
}
}
}
d_clock_counter += d_sample_interval;
d_sample_count++;
ii++;
}
//fprintf(stderr,"/ii=%d/rval=%d\n",ii,rval);
consume_each (ii);
return rval;
}
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