done

1 files changed, 140 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..8954b3f
--- /dev/null
+++ b/gsm-tvoid/src/lib/gsm_burst_cf.cc
@@ -0,0 +1,140 @@
+
+#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;
+			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;
+}