diff options
Diffstat (limited to 'src/lib/gsm_receiver_cf.cc')
| -rw-r--r-- | src/lib/gsm_receiver_cf.cc | 39 |
1 files changed, 24 insertions, 15 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) { |