From 4cfc3dca2b252bfa65cf1633b9f966d572493547 Mon Sep 17 00:00:00 2001
From: tvoid <tvoid@lesaige.com>
Date: Tue, 8 Apr 2008 01:11:27 -0600
Subject: -fixed burst_cf sampling
---
gsm-tvoid/src/lib/gsm_burst.cc | 9 ++--
gsm-tvoid/src/lib/gsm_burst_cf.cc | 111 +++++++++++++++++++-------------------
gsm-tvoid/src/lib/gsm_burst_cf.h | 4 +-
3 files changed, 65 insertions(+), 59 deletions(-)
(limited to 'gsm-tvoid/src/lib')
diff --git a/gsm-tvoid/src/lib/gsm_burst.cc b/gsm-tvoid/src/lib/gsm_burst.cc
index cb896bc..00a5a95 100755
--- a/gsm-tvoid/src/lib/gsm_burst.cc
+++ b/gsm-tvoid/src/lib/gsm_burst.cc
@@ -358,14 +358,15 @@ 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);
@@ -701,6 +702,7 @@ int gsm_burst::get_burst(void)
/////////////////////
//start tune testing
+#ifdef TEST_TUNE_TIMING
static int good_count = -1; //-1: wait sch, >=0: got sch, counting
if (UNKNOWN == d_burst_type) {
@@ -732,6 +734,7 @@ int gsm_burst::get_burst(void)
}
}
}
+#endif
//end tune testing
/////////////////////
diff --git a/gsm-tvoid/src/lib/gsm_burst_cf.cc b/gsm-tvoid/src/lib/gsm_burst_cf.cc
index 08ff7ba..821b41f 100755
--- a/gsm-tvoid/src/lib/gsm_burst_cf.cc
+++ b/gsm-tvoid/src/lib/gsm_burst_cf.cc
@@ -25,6 +25,7 @@ gsm_burst_cf::gsm_burst_cf (gr_feval_ll *t, float sample_rate) :
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())
@@ -37,7 +38,7 @@ gsm_burst_cf::gsm_burst_cf (gr_feval_ll *t, 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
}
@@ -68,70 +69,70 @@ int gsm_burst_cf::general_work (int noutput_items,
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
- //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;
+ 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;
- 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_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_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_clock_counter += d_sample_interval;
- d_sample_count++;
- ii++;
+
+ 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 2b806e0..40ccc83 100755
--- a/gsm-tvoid/src/lib/gsm_burst_cf.h
+++ b/gsm-tvoid/src/lib/gsm_burst_cf.h
@@ -20,11 +20,13 @@ private:
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:
--
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