patch 20080411

8 files changed, 223 insertions, 121 deletions

diff --git a/gsm-tvoid/src/lib/Makefile.am b/gsm-tvoid/src/lib/Makefile.am
index f4072d9..e8f093f 100755
--- a/gsm-tvoid/src/lib/Makefile.am
+++ b/gsm-tvoid/src/lib/Makefile.am
@@ -47,7 +47,8 @@ _gsm_la_SOURCES = 			\
 	gsm.cc				\
 	gsm_burst.cc			\
 	gsm_burst_ff.cc			\
-	gsm_burst_cf.cc
+	gsm_burst_cf.cc			\
+	gsm_burst_sink_c.cc
 	
 
 # magic flags
@@ -74,6 +75,7 @@ grinclude_HEADERS =			\
 	system.h			\
 	gsm_burst_ff.h			\
 	gsm_burst_cf.h			\
+	gsm_burst_sink_c.h		\
 	gsm_constants.h
 
 
diff --git a/gsm-tvoid/src/lib/gsm.i b/gsm-tvoid/src/lib/gsm.i
index d990e8b..106e378 100755
--- a/gsm-tvoid/src/lib/gsm.i
+++ b/gsm-tvoid/src/lib/gsm.i
@@ -9,6 +9,7 @@
 //#include "gsm_burst.h"
 #include "gsm_burst_ff.h"
 #include "gsm_burst_cf.h"
+#include "gsm_burst_sink_c.h"
 //#include <stdexcept>
 
 %}
@@ -43,6 +44,10 @@
 
 #define CLK_CORR_TRACK		0x00000010		//adjust timing based on correlation offsets
 
+#define BURST_CB_SYNC_OFFSET	1
+#define BURST_CB_ADJ_OFFSET		2
+#define BURST_CB_TUNE			3
+
 //EQ options
 enum EQ_TYPE {
 	EQ_NONE,
@@ -73,6 +78,8 @@ public:
 	long			d_unknown_count;
 	long			d_total_count;
 	
+	long 			next_arfcn;
+
 	int				sync_state();
 	float 			last_freq_offset(void);
 	double 			mean_freq_offset(void);
@@ -81,24 +88,32 @@ public:
 	void full_reset(void);
 
 protected:
-	gsm_burst();  
+	gsm_burst(gr_feval_ll *);  
 };
 
 
 GR_SWIG_BLOCK_MAGIC(gsm,burst_ff);
-gsm_burst_ff_sptr gsm_make_burst_ff ();
+gsm_burst_ff_sptr gsm_make_burst_ff (gr_feval_ll *);
 
 class gsm_burst_ff : public gr_block, public gsm_burst {
 private:
-	gsm_burst_ff ();
+	gsm_burst_ff (gr_feval_ll *);
 };
 
 GR_SWIG_BLOCK_MAGIC(gsm,burst_cf);
-gsm_burst_cf_sptr gsm_make_burst_cf (float);
+gsm_burst_cf_sptr gsm_make_burst_cf (gr_feval_ll *,float);
 
 class gsm_burst_cf : public gr_block, public gsm_burst {
 private:
-	gsm_burst_cf (float);
+	gsm_burst_cf (gr_feval_ll *,float);
+};
+
+GR_SWIG_BLOCK_MAGIC(gsm,burst_sink_c);
+gsm_burst_sink_c_sptr gsm_make_burst_sink_c(gr_feval_ll *,float);
+
+class gsm_burst_sink_c : public gr_sync_block, public gsm_burst {
+private:
+	gsm_burst_sink_c (gr_feval_ll *,float);
 };
 
 
diff --git a/gsm-tvoid/src/lib/gsm_burst.cc b/gsm-tvoid/src/lib/gsm_burst.cc
index b862d69..c7f0acc 100755
--- a/gsm-tvoid/src/lib/gsm_burst.cc
+++ b/gsm-tvoid/src/lib/gsm_burst.cc
@@ -13,12 +13,15 @@
 #include "gsmstack.h"
 
 
-gsm_burst::gsm_burst () :
+gsm_burst::gsm_burst (gr_feval_ll *t) :
+		p_tuner(t),
 		d_clock_options(DEFAULT_CLK_OPTS),
 		d_print_options(0),
 		d_equalizer_type(EQ_FIXED_DFE)
 {
  
+//	fprintf(stderr,"gsm_burst: enter constructor (t=%8.8x)\n",(unsigned int)t);
+	  	
 //	M_PI = M_PI; //4.0 * atan(1.0); 
 
 	full_reset();
@@ -194,7 +197,17 @@ void gsm_burst::print_burst(void)
 	int print = 0;
 
 	//fprintf(stderr,"p=%8.8X ",	d_print_options);
-	
+
+	if ( PRINT_GSM_DECODE & d_print_options ) {
+
+		/*
+		 * Pass information to GSM stack. GSM stack will try to extract
+		 * information (fn, layer 2 messages, ...)
+		 */
+		diff_decode_burst();		
+		GS_process(&d_gs_ctx, d_ts, d_burst_type, d_decoded_burst);
+	}
+		
 	if ( PRINT_EVERYTHING == d_print_options )
 		print = 1;
 	else if ( (!d_ts) && (d_print_options & PRINT_TS0) )
@@ -221,18 +234,7 @@ void gsm_burst::print_burst(void)
 		
 		fprintf(stderr," ");
 	}
-	
 
-	if ( PRINT_GSM_DECODE == d_print_options ) {
-
-		/*
-		 * Pass information to GSM stack. GSM stack will try to extract
-		 * information (fn, layer 2 messages, ...)
-		 */
-		diff_decode_burst();		
-		GS_process(&d_gs_ctx, d_ts, d_burst_type, d_decoded_burst);
-	}
-	
 	if (print) {
 
 		fprintf(stderr,"%d/%d/%+d/%lu/%lu ",
@@ -275,7 +277,7 @@ void gsm_burst::print_burst(void)
 			break;		
 		}
 
-	fprintf(stderr,"\n");
+		fprintf(stderr,"\n");
 
 
 		//print the correlation pattern for visual inspection
@@ -348,14 +350,15 @@ void gsm_burst::shift_burst(int shift_bits)
 //of the mean phase  from pi/2.
 void gsm_burst::calc_freq_offset(void) 
 {
-	int start = d_burst_start + 10;
-	int end = d_burst_start + USEFUL_BITS - 10;
+	const int padding = 20;
+	int start = d_burst_start + padding;
+	int end = d_burst_start + USEFUL_BITS - padding;
 	
 	float sum = 0.0;
 	for (int j = start; j <= end; j++) {
 		sum += d_burst_buffer[j];
 	}
-	float mean = sum / ((float)USEFUL_BITS - 20.0);
+	float mean = sum / ((float)USEFUL_BITS - (2.0 * (float)padding) );
 	
 	float p_off = mean - (M_PI / 2);
 	d_freq_offset = p_off * 1625000.0 / (12.0 * M_PI);
@@ -466,7 +469,8 @@ float gsm_burst::correlate_pattern(const float *pattern,const int pat_size,const
 		corr = 0.0;
 		for (int i = 1; i < pat_size; i++) {	//Start a 1 to skip first bit due to diff encoding
 			//d_corr[j+distance] += d_burst_buffer[center+i+j] * pattern[i];
-			corr += SIGNUM(d_burst_buffer[center+i+j]) * pattern[i];  //binary corr/sliced
+			//corr += SIGNUM(d_burst_buffer[center+i+j]) * pattern[i];  //binary corr/sliced
+			corr += d_burst_buffer[center+i+j] * pattern[i];
 		}
 		corr /= pat_size - 1; //normalize, -1 for skipped first bit
 		if (corr > d_corr_max) {
@@ -609,8 +613,9 @@ int gsm_burst::get_burst(void)
 		case PARTIAL_SCH:
 			d_sync_state = WAIT_SCH;
 			break;
-		case SCH:
-			d_sync_state = SYNCHRONIZED;
+		//case SCH:
+		//let the burst type switch handle this so it knows if new or old sync
+		//	d_sync_state = SYNCHRONIZED;
 		break;
 		default:
 			break;
@@ -645,6 +650,18 @@ int gsm_burst::get_burst(void)
 		d_ts = 0;		//TODO: check this
 		break;
 	case SCH:
+#ifndef TEST_TUNE_TIMING
+		//TODO: it would be better to adjust tuning on first FCCH (for better SCH detection),
+		//		but tuning can run away with false FCCHs
+		//		Some logic to retune back to original offset on false FCCH might work
+		if (p_tuner) {
+			if (SYNCHRONIZED == d_sync_state)
+				p_tuner->calleval(BURST_CB_ADJ_OFFSET);
+			else
+				p_tuner->calleval(BURST_CB_SYNC_OFFSET);
+				
+		}
+#endif
 		d_burst_count++;
 		d_sch_count++;
 		d_last_sch = d_burst_count;
@@ -672,7 +689,6 @@ int gsm_burst::get_burst(void)
 		d_last_good = d_burst_count;
 	}
 
-
 	//Check for loss of sync
 	int bursts_since_good = d_burst_count - d_last_good;
 	if (bursts_since_good > MAX_SYNC_WAIT) {
@@ -686,6 +702,47 @@ int gsm_burst::get_burst(void)
 		//print info
 		print_burst();
 
+		/////////////////////
+		//start tune testing
+#ifdef TEST_TUNE_TIMING
+
+		static int good_count = -1; //-1: wait sch, >=0: got sch, counting
+		static int wait_count = 0;
+			
+		if (UNKNOWN == d_burst_type) {
+			if (good_count >= 0) {
+				fprintf(stdout,"good_count: %d\n",good_count);
+	
+				if (p_tuner) {
+					next_arfcn = TEST_TUNE_GOOD_ARFCN;
+					p_tuner->calleval(BURST_CB_TUNE);
+				}
+			}
+			good_count = -1;	// start again at resync
+	
+		} else {
+	
+			if (good_count >= 0 ) {
+				good_count++;
+			}
+	
+			if (SCH == d_burst_type) {	
+				if ((good_count < 0) && (++wait_count > 20)) {	// get some good syncs before trying again
+					fprintf(stdout,"restarting good_count\n");
+					good_count = wait_count = 0;
+					//tune away
+					if (p_tuner) { 
+						next_arfcn = TEST_TUNE_EMPTY_ARFCN;
+						p_tuner->calleval(BURST_CB_TUNE);
+					}
+				}
+			}
+		}
+#endif
+		//end tune testing	
+		/////////////////////
+
+
 		//Adjust the buffer write position to align on MAX_CORR_DIST
 		if ( d_clock_options & CLK_CORR_TRACK )
 			d_bbuf_pos += MAX_CORR_DIST - d_burst_start;
diff --git a/gsm-tvoid/src/lib/gsm_burst.h b/gsm-tvoid/src/lib/gsm_burst.h
index def20e0..48fafac 100755
--- a/gsm-tvoid/src/lib/gsm_burst.h
+++ b/gsm-tvoid/src/lib/gsm_burst.h
@@ -8,10 +8,15 @@
 
 #include "gsm_constants.h"
 #include <gr_math.h>
-//#include <Python.h>		//for callback testing
 #include <gr_feval.h>
 #include "gsmstack.h"
 
+//Testing Modes
+//Tune test measures hopping latency by hopping between good and empty ARFCNs
+#undef TEST_TUNE_TIMING
+#define TEST_TUNE_GOOD_ARFCN	658
+#define TEST_TUNE_EMPTY_ARFCN	655
+
 
 //Console printing options
 #define PRINT_NOTHING		0x00000000
@@ -73,13 +78,18 @@ enum EQ_TYPE {
 	EQ_VITERBI
 };
 
+#define BURST_CB_SYNC_OFFSET	1
+#define BURST_CB_ADJ_OFFSET		2
+#define BURST_CB_TUNE			3
+
+
 class gsm_burst;
 
 class gsm_burst
 {
 protected:
 	
-	gsm_burst();  
+	gsm_burst(gr_feval_ll *t);  
 
 	//Burst Buffer: Storage for burst data
 	float			d_burst_buffer[BBUF_SIZE];
@@ -116,30 +126,33 @@ protected:
 	double			d_freq_off_sum;
 	double			d_freq_off_weight;
 
+	gr_feval_ll 	*p_tuner;
+	
 	//////// Methods
 	int				get_burst(void);
 	BURST_TYPE		get_fcch_burst(void);
 	BURST_TYPE		get_sch_burst(void);
 	BURST_TYPE		get_norm_burst(void);
 	
-	void	shift_burst(int);
-	void	calc_freq_offset(void); 
-	void	equalize(void);
-	float	correlate_pattern(const float *,const int,const int,const int);
-	void	diff_decode_burst(void);
+	virtual void	shift_burst(int);
+	void			calc_freq_offset(void); 
+	virtual void	equalize(void);
+	float			correlate_pattern(const float *,const int,const int,const int);
+	void			diff_decode_burst(void);
 
-	void	sync_reset(void);
+	void			sync_reset(void);
 
-	void	print_bits(const float *data,int length);
-	void	print_hex(const unsigned char *data,int length);
-	void	soft2hardbit(char *dst, const float *data, int len);
-	void	print_burst(void);
+	void			print_bits(const float *data,int length);
+	void			print_hex(const unsigned char *data,int length);
 
-	void	diff_encode(const float *in,float *out,int length,float lastbit = 1.0);	
-	void	diff_decode(const float *in,float *out,int length,float lastbit = 1.0);	
+//	void			soft2hardbit(char *dst, const float *data, int len);	//need this?
+	void			print_burst(void);
+
+	void			diff_encode(const float *in,float *out,int length,float lastbit = 1.0);	
+	void			diff_decode(const float *in,float *out,int length,float lastbit = 1.0);	
 
 public:
-	~gsm_burst ();	
+	virtual 		~gsm_burst ();	
 
 	////// General Stats
 	//TODO: Maybe there should be a burst_stats class?
@@ -157,12 +170,17 @@ public:
 	unsigned long	d_print_options;
 	EQ_TYPE			d_equalizer_type;
 	
-	int sync_state() { return d_sync_state;}
-	float last_freq_offset() {return d_freq_offset;}
-	double mean_freq_offset(void);
 	
 	//Methods
 	void full_reset(void);
+
+	int sync_state() { return d_sync_state;}
+
+	//Frequency
+	float last_freq_offset() {return d_freq_offset;}
+	double mean_freq_offset(void);
+
+	long next_arfcn;
 };
 
 
diff --git a/gsm-tvoid/src/lib/gsm_burst_cf.cc b/gsm-tvoid/src/lib/gsm_burst_cf.cc
index a91c569..a584cd6 100755
--- a/gsm-tvoid/src/lib/gsm_burst_cf.cc
+++ b/gsm-tvoid/src/lib/gsm_burst_cf.cc
@@ -9,21 +9,23 @@
 #include <stdio.h>
 #include <gri_mmse_fir_interpolator_cc.h>
 
-gsm_burst_cf_sptr gsm_make_burst_cf (float sample_rate)
+gsm_burst_cf_sptr gsm_make_burst_cf (gr_feval_ll *t,float sample_rate)
 {
-  return gsm_burst_cf_sptr (new gsm_burst_cf (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 = 1;	// minimum number of output 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 (float sample_rate) : 
+gsm_burst_cf::gsm_burst_cf (gr_feval_ll *t, float sample_rate) : 
+	gsm_burst(t),
 	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_mu(0.5),
 	d_last_sample(0.0,0.0),
 	d_interp(new gri_mmse_fir_interpolator_cc())
 
@@ -36,7 +38,7 @@ gsm_burst_cf::gsm_burst_cf (float sample_rate) :
 	fprintf(stderr,"Sample interval      : %e\n",d_sample_interval);
 	fprintf(stderr,"Relative sample rate : %g\n",d_relative_sample_rate);
 		
-	set_history(4); 
+	set_history(4); //need history for interpolator
 	
 }
 
@@ -63,41 +65,39 @@ int gsm_burst_cf::general_work (int noutput_items,
 	
 	int ii=0;
 	int rval = 0;  //default to no output
+	int do_output = output_items.size() > 0 ? 1 : 0;
 
 	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
+	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: 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
+		
+		//from m&m
+		gr_complex sample = d_interp->interpolate (&in[ii], d_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));
 
-			gr_complex conjprod = sample * conj(d_last_sample);
-			float diff_angle = gr_fast_atan2f(imag(conjprod), real(conjprod));
+		d_last_sample = sample;
 
-			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
+		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)
@@ -106,31 +106,36 @@ int gsm_burst_cf::general_work (int noutput_items,
 						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++;
+				rval++;
+				
+				switch ( d_clock_options & QB_MASK ) {
+				case QB_QUARTER: //extra 1/4 bit each burst
+					d_mu -= d_relative_sample_rate / 4.0;
+					//d_clock_counter -= GSM_SYMBOL_PERIOD / 4.0; 
+					break;
+				case QB_FULL04:	//extra bit on timeslot 0 & 4
+					if (!(d_ts%4))
+						d_mu -= d_relative_sample_rate;
+						//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);
+			}
+		}	   
+		
+		//TODO: timing adjust
+		//d_mu = d_mu + d_omega + d_gain_mu * mm_val;
+		d_mu += d_relative_sample_rate;
+		ii += (int)floor(d_mu);
+		d_sample_count += (int)floor(d_mu);
+		d_mu -= floor(d_mu);
 	}
 	
 	//fprintf(stderr,"/ii=%d/rval=%d\n",ii,rval);
diff --git a/gsm-tvoid/src/lib/gsm_burst_cf.h b/gsm-tvoid/src/lib/gsm_burst_cf.h
index 33f61f6..40ccc83 100755
--- a/gsm-tvoid/src/lib/gsm_burst_cf.h
+++ b/gsm-tvoid/src/lib/gsm_burst_cf.h
@@ -8,7 +8,7 @@ class gsm_burst_cf;
 
 typedef boost::shared_ptr<gsm_burst_cf> gsm_burst_cf_sptr;
 
-gsm_burst_cf_sptr gsm_make_burst_cf(float);
+gsm_burst_cf_sptr gsm_make_burst_cf(gr_feval_ll *,float);
 
 class gri_mmse_fir_interpolator_cc;
 
@@ -16,15 +16,17 @@ class gsm_burst_cf : public gr_block, public gsm_burst
 {
 private:
 	
-	friend gsm_burst_cf_sptr gsm_make_burst_cf(float);
-	gsm_burst_cf(float);  
+	friend gsm_burst_cf_sptr gsm_make_burst_cf(gr_feval_ll *,float);
+	gsm_burst_cf(gr_feval_ll *,float);  
 	
 	//clocking parameters
-	float			d_relative_sample_rate;
 	double			d_sample_interval;
 	double			d_clock_counter;
 	gr_complex		d_last_sample;
 
+	float			d_relative_sample_rate;		//omega
+	float			d_mu;
+	
 	gri_mmse_fir_interpolator_cc 	*d_interp;  //sub-sample interpolator from GR
 		
 public:
diff --git a/gsm-tvoid/src/lib/gsm_burst_ff.cc b/gsm-tvoid/src/lib/gsm_burst_ff.cc
index 2980829..dd449f1 100755
--- a/gsm-tvoid/src/lib/gsm_burst_ff.cc
+++ b/gsm-tvoid/src/lib/gsm_burst_ff.cc
@@ -9,17 +9,18 @@
 #include <stdio.h>
 #include <gri_mmse_fir_interpolator_cc.h>
 
-gsm_burst_ff_sptr gsm_make_burst_ff ()
+gsm_burst_ff_sptr gsm_make_burst_ff (gr_feval_ll *t)
 {
-  return gsm_burst_ff_sptr (new gsm_burst_ff());
+  return gsm_burst_ff_sptr (new gsm_burst_ff(t));
 }
 
 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 MIN_OUT = 0;	// minimum number of output streams
 static const int MAX_OUT = 1;	// maximum number of output streams
 
-gsm_burst_ff::gsm_burst_ff () : 
+gsm_burst_ff::gsm_burst_ff (gr_feval_ll *t) : 
+	gsm_burst(t),
 	gr_block(	"burst_ff",
 				gr_make_io_signature (MIN_IN, MAX_IN, sizeof (float)),
 				gr_make_io_signature (MIN_OUT, MAX_OUT, USEFUL_BITS * sizeof (float)))
@@ -37,7 +38,7 @@ void gsm_burst_ff::forecast (int noutput_items, gr_vector_int &ninput_items_requ
 {
   unsigned ninputs = ninput_items_required.size ();
   for (unsigned i = 0; i < ninputs; i++)
-    ninput_items_required[i] = noutput_items * BBUF_SIZE + history();
+    ninput_items_required[i] = noutput_items * BBUF_SIZE;
 }
 
 
@@ -51,9 +52,10 @@ int gsm_burst_ff::general_work (int noutput_items,
 	
 	int ii=0;
 	int rval = 0;  //default to no output
-
+	int do_output = output_items.size() > 0 ? 1 : 0;
+	
 	int n_input = ninput_items[0];
-	//fprintf(stderr,"#i=%d/#o=%d",n_input,noutput_items);
+//	fprintf(stderr,"out=%8.8x/#i=%d/#o=%d",(unsigned)out,n_input,noutput_items);
 
 	while (( rval < noutput_items) && ( ii < n_input ) ) {
 
@@ -68,15 +70,16 @@ int gsm_burst_ff::general_work (int noutput_items,
 		
 			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));
+				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  ) {
@@ -98,7 +101,7 @@ int gsm_burst_ff::general_work (int noutput_items,
  		ii++;
 	}
 	
-	//fprintf(stderr,"/ii=%d/rval=%d\n",ii,rval);
+//	fprintf(stderr,"/ii=%d/rval=%d\n",ii,rval);
 
 	consume_each (ii);
 	
diff --git a/gsm-tvoid/src/lib/gsm_burst_ff.h b/gsm-tvoid/src/lib/gsm_burst_ff.h
index 30c10dc..8ca61ef 100755
--- a/gsm-tvoid/src/lib/gsm_burst_ff.h
+++ b/gsm-tvoid/src/lib/gsm_burst_ff.h
@@ -8,14 +8,14 @@ class gsm_burst_ff;
 
 typedef boost::shared_ptr<gsm_burst_ff> gsm_burst_ff_sptr;
 
-gsm_burst_ff_sptr gsm_make_burst_ff();
+gsm_burst_ff_sptr gsm_make_burst_ff(gr_feval_ll *);
 
 class gsm_burst_ff : public gr_block, public gsm_burst
 {
 private:
 	
-	friend gsm_burst_ff_sptr gsm_make_burst_ff();
-	gsm_burst_ff();  
+	friend gsm_burst_ff_sptr gsm_make_burst_ff(gr_feval_ll *);
+	gsm_burst_ff(gr_feval_ll *t);  
 	
 public:
 	~gsm_burst_ff ();