diff options
Diffstat (limited to 'gsm-tvoid/src/lib/gsm_burst_cf.cc')
| -rwxr-xr-x | gsm-tvoid/src/lib/gsm_burst_cf.cc | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/gsm-tvoid/src/lib/gsm_burst_cf.cc b/gsm-tvoid/src/lib/gsm_burst_cf.cc new file mode 100755 index 0000000..73293d8 --- /dev/null +++ b/gsm-tvoid/src/lib/gsm_burst_cf.cc @@ -0,0 +1,157 @@ + +#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 <string.h> +#include <gri_mmse_fir_interpolator_cc.h> + +gsm_burst_cf_sptr gsm_make_burst_cf (gr_feval_ll *t,float sample_rate) +{ + return gsm_burst_cf_sptr (new gsm_burst_cf (t,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 = 0; // minimum number of output streams +static const int MAX_OUT = 1; // maximum number of output streams + +gsm_burst_cf::gsm_burst_cf (gr_feval_ll *t, 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)) //TODO: pad to ^2 = 256 ? + ), + gsm_burst(t), + d_clock_counter(0.0), + d_last_sample(0.0,0.0), + mm(sample_rate / GSM_SYMBOL_RATE), + d_interp(new gri_mmse_fir_interpolator_cc() + ) + +{ + + //clocking parameters + //d_sample_interval = 1.0 / sample_rate; + //d_omega = sample_rate / GSM_SYMBOL_RATE; + +// fprintf(stderr,"Sample interval : %e\n",d_sample_interval); +// fprintf(stderr,"Relative sample rate : %g\n",d_omega); + + + //set_relative_rate( mm.d_omega / 156); + set_relative_rate( 1.0 / (mm.d_omega * 156) ); + + set_history(4); //need history for interpolator + +} + +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(mm.d_omega) * TS_BITS; + //fprintf(stderr,"forecast[%d]: %d = %d\n",i,noutput_items,ninput_items_required[i]); + } +} + +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 num_outputs = output_items.size(); + int do_output = num_outputs > 0 ? 1 : 0; + + int ninput = ninput_items[0]; + //fprintf(stderr,"#i=%d/#o=%d",ninput,noutput_items); + + int ni = ninput - d_interp->ntaps() - 16; // interpolator need -4/+3 samples NTAPS = 8 , - 16 for safety margin + + while (( rval < noutput_items) && ( ii < ni ) ) { + //clock symbols + //TODO: this is very basic and can be improved. Need tracking... + //TODO: save complex samples for Viterbi EQ + + //get interpolated sample + gr_complex x_0 = d_interp->interpolate (&in[ii], mm.d_mu); + + //calulate phase difference (demod) + gr_complex conjprod = x_0 * conj(d_last_sample); + float diff_angle = gr_fast_atan2f(imag(conjprod), real(conjprod)); + + //mM&M + //mm.update(x_0); //mm_c + mm.update(diff_angle); //mm_f + + 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 + if (do_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 + mm.d_mu -= mm.d_omega / 4.0; + //d_clock_counter -= GSM_SYMBOL_PERIOD / 4.0; + break; + case QB_FULL04: //extra bit on timeslot 0 & 4 + if (!(d_ts%4)) + mm.d_mu -= mm.d_omega; + //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); + } + } + + //process mu / ii advance + ii += (int)floor(mm.d_mu); + d_sample_count += (int)floor(mm.d_mu); + mm.d_mu -= floor(mm.d_mu); + + d_last_sample = x_0; + } + + //fprintf(stderr,"/ii=%d/rval=%d\n",ii,rval); + + consume_each (ii); + + return rval; +} |