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first part of sch sychronisation - getting close to sch burst

This commit is contained in:
Piotr Krysik 2009-04-28 20:09:37 +02:00
parent 1398632c44
commit 961ff106d1
1 changed files with 67 additions and 29 deletions
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96
src/lib/gsm_receiver_cf.cc
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@ -75,7 +75,7 @@ gsm_receiver_cf::~gsm_receiver_cf()
void gsm_receiver_cf::forecast(int noutput_items, gr_vector_int &ninput_items_required)
{
ninput_items_required[0] = noutput_items * TS_BITS; //TODO include oversampling ratio here
ninput_items_required[0] = noutput_items * (TS_BITS + SAFETY_MARGIN) * d_OSR;
}
int
@ -294,46 +294,73 @@ void gsm_receiver_cf::set_frequency(double freq_offset)
bool gsm_receiver_cf::find_sch_burst(const gr_complex *in, const int nitems , float *out)
{
int sample_number = 0;
// int sample_number = 0;
int to_consume = 0;
bool end = false;
bool result = false;
int sch_start = d_fcch_start_pos + FRAME_BITS * d_OSR;
int sample_nr_near_sch_start = d_fcch_start_pos + (FRAME_BITS - SAFETY_MARGIN) * d_OSR;
enum states {
init, search, sch_found, search_fail
start, reach_sch, find_sch_start, search_not_finished, sch_found
} sch_search_state;
sch_search_state = start;
while (!end) {
switch (sch_search_state) {
case init:
sch_search_state = search_fail;
break;
case search:
if ((sch_start >= d_counter) && (sch_start <= d_counter + nitems)) {
DCOUT("sch_start-d_counter: " << sch_start - d_counter);
/* for (int i = 0; i < nitems - N_SYNC_BITS; i++) {
gr_complex result = correlation(&d_sch_training_seq[5], in + i, N_SYNC_BITS-10);
//std::cout << "(" << real(in[i]) << "," << imag(in[i]) << ")\n";
std::cout << "(" << real(result) << "," << imag(result) << ")\n";
}
std::cout << std::endl;
*/
case start:
if(d_counter < sample_nr_near_sch_start){
sch_search_state = reach_sch;
} else {
sch_search_state = find_sch_start;
}
to_consume = nitems - N_SYNC_BITS;
sch_search_state = search_fail;
break;
case sch_found:
case reach_sch:
if(d_counter + nitems >= sample_nr_near_sch_start){
to_consume = sample_nr_near_sch_start - d_counter;
DCOUT("reach_sch consumes: " << to_consume << "bits");
} else {
to_consume = nitems;
}
sch_search_state = search_not_finished;
break;
case find_sch_start:
DCOUT("find_sch_start nitems" << nitems);
// if ((sch_start >= d_counter) && (sch_start <= d_counter + nitems)) {
// for (int i = 0; i < ninput_items[0] - N_SYNC_BITS; i++) {
// gr_complex result;
// d_counter++;
// result = correlation(&d_sch_training_seq[5], in + i, N_SYNC_BITS - 10);
//
// if (abs(result) > 60000) {
// DCOUT("znaleziono środek sch na pozycji: " << d_counter);
// }
//
// // std::cout << "(" << real(in[i]) << "," << imag(in[i]) << ")\n";
// // std::cout << "(" << real(result) << "," << imag(result) << ")\n";
//
// int ninput = N_SYNC_BITS - 10;
// const gr_complex * input_signal = in + i;
// gr_complex * sequence = &d_sch_training_seq[5];
// }
// }
to_consume = nitems;
sch_search_state = sch_found;
break;
case search_not_finished:
end = true;
break;
case search_fail:
case sch_found:
end = true;
break;
}
@ -341,7 +368,7 @@ bool gsm_receiver_cf::find_sch_burst(const gr_complex *in, const int nitems , fl
d_counter += to_consume;
// consume_each(to_consume);
consume_each(to_consume);
return result;
}
@ -369,10 +396,21 @@ void gsm_receiver_cf::gmsk_mapper(const int * input, gr_complex * output, int ni
gr_complex gsm_receiver_cf::correlation(const gr_complex * sequence, const gr_complex * input_signal, int ninput)
{
gr_complex result(0.0, 0.0);
int sample_number = 0;
for (int ii = 1; (ii * d_OSR) <= ninput; ii++) {
result += sequence[ii-1] * conj(input_signal[(ii * d_OSR)]);
for (int ii = 0; ii < ninput; ii++) {
sample_number = (ii * d_OSR) ;
result += sequence[ii] * conj(input_signal[sample_number]);
}
return result;
}
// gr_complex gsm_receiver_cf::calc_energy(int window_len){
//
// }
inline float gsm_receiver_cf::compute_phase_diff(gr_complex val1, gr_complex val2)
{
gr_complex conjprod = val1 * conj(val2);
return gr_fast_atan2f(imag(conjprod), real(conjprod));
}