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-rw-r--r--src/lib/gsm_receiver_cf.cc39
-rw-r--r--src/lib/gsm_receiver_cf.h4
2 files changed, 26 insertions, 17 deletions
diff --git a/src/lib/gsm_receiver_cf.cc b/src/lib/gsm_receiver_cf.cc
index 089a563..5453253 100644
--- a/src/lib/gsm_receiver_cf.cc
+++ b/src/lib/gsm_receiver_cf.cc
@@ -151,7 +151,19 @@ gsm_receiver_cf::general_work(int noutput_items,
switch (b_type) {
case fcch_burst: {
-
+ int ii;
+ int first_sample = (GUARD_BITS+TAIL_BITS)*d_OSR;
+ int last_sample = first_sample+USEFUL_BITS*d_OSR;
+ double phase_sum = 0;
+ for(ii = first_sample; ii < last_sample; ii++){
+ phase_sum += compute_phase_diff(in[ii], in[ii-1]) - (M_PI / 2) / d_OSR;
+ }
+ std::cout << "freq_offset: " << d_freq_offset << "\n";
+
+ double freq_offset = compute_freq_offset(phase_sum, USEFUL_BITS-TAIL_BITS);
+ d_freq_offset -= freq_offset;
+ set_frequency(d_freq_offset);
+ std::cout << "freq_offset: " << d_freq_offset << "\n";
}
break;
case sch_burst: {
@@ -200,12 +212,14 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
int start_pos = -1;
float min_phase_diff;
float max_phase_diff;
+ double best_sum;
float lowest_max_min_diff = 99999;
int to_consume = 0;
int sample_number = 0;
bool end = false;
bool result = false;
+ double freq_offset;
circular_buffer_float::iterator buffer_iter;
enum states {
@@ -269,12 +283,12 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
if (lowest_max_min_diff > max_phase_diff - min_phase_diff) {
lowest_max_min_diff = max_phase_diff - min_phase_diff;
start_pos = sample_number - FCCH_HITS_NEEDED * d_OSR - FCCH_MAX_MISSES * d_OSR;
- d_best_sum = 0;
+ best_sum = 0;
for (buffer_iter = phase_diff_buffer.begin();
buffer_iter != (phase_diff_buffer.end());
buffer_iter++) {
- d_best_sum += *buffer_iter - (M_PI / 2) / d_OSR;
+ best_sum += *buffer_iter - (M_PI / 2) / d_OSR;
}
}
}
@@ -297,7 +311,9 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
to_consume = start_pos + FCCH_HITS_NEEDED * d_OSR + 1;
d_fcch_start_pos = d_counter + start_pos;
- compute_freq_offset();
+ freq_offset = compute_freq_offset(best_sum, FCCH_HITS_NEEDED);
+ d_freq_offset -= freq_offset;
+
end = true;
result = true;
break;
@@ -315,21 +331,19 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
return result;
}
-
-double gsm_receiver_cf::compute_freq_offset()
+double gsm_receiver_cf::compute_freq_offset(double best_sum, unsigned denominator)
{
float phase_offset, freq_offset;
- phase_offset = d_best_sum / FCCH_HITS_NEEDED;
+ phase_offset = best_sum / denominator;
freq_offset = phase_offset * 1625000.0 / (12.0 * M_PI);
- d_freq_offset -= freq_offset;
// d_fcch_count++;
// d_x_temp += freq_offset;
// d_x2_temp += freq_offset * freq_offset;
// d_mean = d_x_temp / d_fcch_count;
- DCOUT("freq_offset: " << freq_offset );//" d_best_sum: " << d_best_sum
+ DCOUT("freq_offset: " << freq_offset );//" best_sum: " << best_sum
// DCOUT("wariance: " << sqrt((d_x2_temp / d_fcch_count - d_mean * d_mean)) << " fcch_count:" << d_fcch_count << " d_mean: " << d_mean);
return freq_offset;
@@ -545,12 +559,7 @@ gr_complex gsm_receiver_cf::correlate_sequence(const gr_complex * sequence, cons
// return result;
// }
-
-// gr_complex gsm_receiver_cf::calc_energy(int window_len){
-//
-// }
-
-//oblicza dodatnią część autokorelacji
+//computes autocorrelation for positive values
//TODO consider placing this funtion in a separate class for signal processing
inline void gsm_receiver_cf::autocorrelation(const gr_complex * input, gr_complex * out, int length)
{
diff --git a/src/lib/gsm_receiver_cf.h b/src/lib/gsm_receiver_cf.h
index 2bad50e..98df34d 100644
--- a/src/lib/gsm_receiver_cf.h
+++ b/src/lib/gsm_receiver_cf.h
@@ -232,7 +232,7 @@ class gsm_receiver_cf : public gr_block
//variables used to store result of the find_fcch_burst fuction
int d_fcch_start_pos;
float d_freq_offset;
- double d_best_sum;
+// double d_best_sum;
// int d_fcch_count; //!!!
// double d_x_temp, d_x2_temp, d_mean;//!!
@@ -255,7 +255,7 @@ class gsm_receiver_cf : public gr_block
gsm_receiver_cf(gr_feval_dd *tuner, int osr);
bool find_fcch_burst(const gr_complex *in, const int nitems);
- double compute_freq_offset();
+ double compute_freq_offset(double best_sum, unsigned denominator);
void set_frequency(double freq_offset);
inline float compute_phase_diff(gr_complex val1, gr_complex val2);
personal git repositories of Harald Welte. Your mileage may vary