diff options
| -rw-r--r-- | src/lib/gsm_receiver_cf.cc | 61 | ||||
| -rw-r--r-- | src/lib/gsm_receiver_cf.h | 2 |
2 files changed, 43 insertions, 20 deletions
diff --git a/src/lib/gsm_receiver_cf.cc b/src/lib/gsm_receiver_cf.cc index 39571dc..c9ef010 100644 --- a/src/lib/gsm_receiver_cf.cc +++ b/src/lib/gsm_receiver_cf.cc @@ -28,9 +28,9 @@ #include <gr_math.h> #include <math.h> #include <Assert.h> -#include <list> #include <boost/circular_buffer.hpp> #include <algorithm> +#include <numeric> #include <gsm_receiver_cf.h> #include <viterbi_detector.h> #include <sch.h> @@ -41,13 +41,15 @@ //TODO: this shouldn't be here - remove it when gsm receiver's interface will be ready void gsm_receiver_cf::process_normal_burst(burst_counter burst_nr, const unsigned char * burst_binary) { - if (burst_nr.get_timeslot_nr() == 0) { -// printf("burst = [ "); + if (burst_nr.get_timeslot_nr() == 0) { +// std::cout << " t2:" << burst_nr.get_t2() << " fn:" << burst_nr.get_frame_nr(); +// printf(" burst = [ "); // for (int i = 0; i < BURST_SIZE ; i++) { // printf(" %d", burst_binary[i]); // } // printf("];\n"); // std::cout << " t2: " << burst_nr.get_t2() << "\n"; +// std::cout << " bcc: " << d_bcc << "\n"; GS_process(&d_gs_ctx, TIMESLOT0, 6, &burst_binary[3], burst_nr.get_frame_nr()); } } @@ -101,11 +103,19 @@ gsm_receiver_cf::gsm_receiver_cf(gr_feval_dd *tuner, int osr) gmsk_mapper(SYNC_BITS, N_SYNC_BITS, d_sch_training_seq, gr_complex(0.0, -1.0)); for (i = 0; i < TRAIN_SEQ_NUM; i++) { - gmsk_mapper(train_seq[i], N_TRAIN_BITS, d_norm_training_seq[i], gr_complex(1.0, 0.0)); + gr_complex startpoint; + if (i == 6) { //this is nasty hack + startpoint = gr_complex(-1.0, 0.0); //if I don't change it here all bits of normal bursts for BTSes with bcc=6 will have negative values + } else { + startpoint = gr_complex(1.0, 0.0); //I've checked this hack for bcc==0,1,2,3,4,6 + } //I don't know what about bcc==5 and 7 yet + //TODO:find source of this situation - this is purely mathematical problem I guess + + gmsk_mapper(train_seq[i], N_TRAIN_BITS, d_norm_training_seq[i], startpoint); } /* Initialize GSM Stack */ - GS_new(&d_gs_ctx); //TODO: remove it! it'a not right place for a decoder + GS_new(&d_gs_ctx); //TODO: remove it! it's not a right place for a decoder } /* @@ -144,9 +154,8 @@ gsm_receiver_cf::general_work(int noutput_items, } break; - case next_fcch_search: { //this state is used because it takes a bunch of buffered samples - //before previous set_frequqency cause change - float prev_freq_offset = d_freq_offset; + case next_fcch_search: { //this state is used because it takes some time (a bunch of buffered samples) + float prev_freq_offset = d_freq_offset; //before previous set_frequqency cause change if (find_fcch_burst(input, nitems_items[0])) { if (abs(prev_freq_offset - d_freq_offset) > FCCH_MAX_FREQ_OFFSET) { set_frequency(d_freq_offset); //call set_frequncy only frequency offset change is greater than some value @@ -159,6 +168,7 @@ gsm_receiver_cf::general_work(int noutput_items, } break; } + case sch_search: { vector_complex channel_imp_resp(CHAN_IMP_RESP_LENGTH*d_OSR); int t1, t2, t3; @@ -204,12 +214,21 @@ gsm_receiver_cf::general_work(int noutput_items, switch (b_type) { case fcch_burst: { //if it's FCCH burst const unsigned first_sample = ceil((GUARD_PERIOD + 2 * TAIL_BITS) * d_OSR) + 1; - const unsigned last_sample = first_sample + USEFUL_BITS * d_OSR; + const unsigned last_sample = first_sample + USEFUL_BITS * d_OSR - TAIL_BITS * d_OSR; double freq_offset = compute_freq_offset(input, first_sample, last_sample); //extract frequency offset from it - if (abs(freq_offset) > FCCH_MAX_FREQ_OFFSET) { - d_freq_offset -= freq_offset; //and adjust frequency if it have changed beyond - set_frequency(d_freq_offset); //some limit - DCOUT("Adjusting frequency, new frequency offset: " << d_freq_offset << "\n"); + + d_freq_offset_vals.push_front(freq_offset); + + if (d_freq_offset_vals.size() >= 10) { + double sum = std::accumulate(d_freq_offset_vals.begin(), d_freq_offset_vals.end(), 0); + double mean_offset = sum / d_freq_offset_vals.size(); //compute mean + d_freq_offset_vals.clear(); + if (abs(mean_offset) > FCCH_MAX_FREQ_OFFSET) { + d_freq_offset -= mean_offset; //and adjust frequency if it have changed beyond + set_frequency(d_freq_offset); //some limit + DCOUT("mean_offset: " << mean_offset); + DCOUT("Adjusting frequency, new frequency offset: " << d_freq_offset << "\n"); + } } } break; @@ -226,8 +245,10 @@ gsm_receiver_cf::general_work(int noutput_items, to_consume += offset; //adjust with offset number of samples to be consumed } else { d_failed_sch++; - if(d_failed_sch >= MAX_SCH_ERRORS){ - d_state = next_fcch_search; + if (d_failed_sch >= MAX_SCH_ERRORS) { +// d_state = next_fcch_search; //TODO: this isn't good, the receiver is going wild when it goes back to next_fcch_search from here +// d_freq_offset_vals.clear(); + DCOUT("many sch decoding errors"); } } } @@ -646,8 +667,8 @@ int gsm_receiver_cf::get_norm_chan_imp_resp(const gr_complex *input, gr_complex float energy = 0; int search_center = (int)((TRAIN_POS + GUARD_PERIOD) * d_OSR); -// int search_start_pos = search_center + 1; - int search_start_pos = search_center - d_chan_imp_length * d_OSR; + int search_start_pos = search_center + 1; +// int search_start_pos = search_center - d_chan_imp_length * d_OSR; int search_stop_pos = search_center + d_chan_imp_length * d_OSR + 2 * d_OSR; for (int ii = search_start_pos; ii < search_stop_pos; ii++) { @@ -664,7 +685,7 @@ int gsm_receiver_cf::get_norm_chan_imp_resp(const gr_complex *input, gr_complex vector_float::iterator iter_ii = iter; energy = 0; - for (int ii = 0; ii < (d_chan_imp_length-2)*d_OSR; ii++, iter_ii++) { + for (int ii = 0; ii < (d_chan_imp_length - 2)*d_OSR; ii++, iter_ii++) { // for (int ii = 0; ii < (d_chan_imp_length)*d_OSR; ii++, iter_ii++) { if (iter_ii == power_buffer.end()) { loop_end = true; @@ -680,8 +701,8 @@ int gsm_receiver_cf::get_norm_chan_imp_resp(const gr_complex *input, gr_complex window_energy_buffer.push_back(energy); } //!why doesn't this work - strongest_window_nr = max_element(window_energy_buffer.begin(), window_energy_buffer.end()) - window_energy_buffer.begin(); - //strongest_window_nr = 3; //! so I have to override it here + strongest_window_nr = max_element(window_energy_buffer.begin(), window_energy_buffer.end()) - window_energy_buffer.begin(); + strongest_window_nr = 3; //! so I have to override it here max_correlation = 0; for (int ii = 0; ii < (d_chan_imp_length)*d_OSR; ii++) { diff --git a/src/lib/gsm_receiver_cf.h b/src/lib/gsm_receiver_cf.h index c37813a..070f9cf 100644 --- a/src/lib/gsm_receiver_cf.h +++ b/src/lib/gsm_receiver_cf.h @@ -23,6 +23,7 @@ #define INCLUDED_GSM_RECEIVER_CF_H #include <vector> +#include <list> #include <gr_block.h> #include <gr_complex.h> #include <gr_feval.h> @@ -75,6 +76,7 @@ class gsm_receiver_cf : public gr_block unsigned d_fcch_start_pos; ///< position of the first sample of the fcch burst float d_freq_offset; ///< frequency offset of the received signal //@} + std::list<double> d_freq_offset_vals; /**@name Identifiers of the BTS extracted from the SCH burst */ //@{ |