sdr
/
airprobe
8
0
Fork 0
Code Pull Requests Releases Wiki Activity

cleanup of fcch search related entities

This commit is contained in:
Piotr Krysik 2009-04-28 20:08:18 +02:00
parent 8591703b11
commit 1398632c44
4 changed files with 72 additions and 89 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
src/lib/gsm_constants.h
View File

@ -19,6 +19,7 @@
#define FCCH_POS TAIL_BITS
#define SYNC_POS 39
#define TRAIN_POS 58
#define SAFETY_MARGIN 6
#define FCCH_HITS_NEEDED (USEFUL_BITS - 4)
#define FCCH_MAX_MISSES 1

130
src/lib/gsm_receiver_cf.cc
View File

@ -54,14 +54,14 @@ gsm_receiver_cf::gsm_receiver_cf(gr_feval_dd *tuner, int osr)
gr_make_io_signature(MIN_OUT, MAX_OUT, 142 * sizeof(float))),
d_OSR(osr),
d_tuner(tuner),
d_prev_freq_offset(0),
d_phase_diff_buffer(BUFFER_SIZE * osr),
d_counter(0),
d_x_temp(0),
d_x2_temp(0),
d_fcch_count(0),
d_fcch_start_pos(0),
d_state(fcch_search)
d_freq_offset(0),
d_state(first_fcch_search),
d_first(false)
// d_fcch_count(0),
// d_x_temp(0),
// d_x2_temp(0)
{
gmsk_mapper(SYNC_BITS, d_sch_training_seq, N_SYNC_BITS);
}
@ -90,77 +90,56 @@ gsm_receiver_cf::general_work(int noutput_items,
switch (d_state) {
case fcch_search:
case first_fcch_search:
if (find_fcch_burst(in, ninput_items[0])) {
produced_out = 1;
set_frequency(d_freq_offset);
produced_out = 0;
d_state = next_fcch_search;
} else {
produced_out = 0;
d_state = first_fcch_search;
}
break;
case next_fcch_search:
if (find_fcch_burst(in, ninput_items[0])) {
produced_out = 0;
d_state = sch_search;
} else {
produced_out = 0;
d_state = fcch_search;
d_state = next_fcch_search;
}
break;
case sch_search:
if (find_sch_burst(in, ninput_items[0], out)) {
d_state = sch_search;
d_state = read_bcch;
} else {
for (int i = 0; i < ninput_items[0] - N_SYNC_BITS; i++) {
gr_complex result;
d_counter++;
int ninput = N_SYNC_BITS - 10;
const gr_complex * input_signal = in + i;
gr_complex * sequence = &d_sch_training_seq[5];
result = correlation(&d_sch_training_seq[5], in + i, N_SYNC_BITS-10);
if (abs(result) > 60000) {
std::cout << "Max val: " << abs(result) << " position: " << d_counter - d_fcch_start_pos << std::endl;
//
// for (int j = 1; j <= 54; j++) {
// std::cout << sequence[j-1] << " * " << conj(input_signal[(j * d_OSR)]) << std::endl;
// }
//
// gr_complex result2(0, 0);
//
// for (int j = 1; j <= 54; j++) {
// result2 += sequence[j-1] * conj(input_signal[(j * d_OSR)]);
// }
//
// std::cout << "Spr: " << abs(result2) << std::endl;
//
// std::cout << std::endl;
}
// std::cout << "(" << real(in[i]) << "," << imag(in[i]) << ")\n";
// std::cout << "(" << real(result) << "," << imag(result) << ")\n";
}
consume_each(ninput_items[0]);
d_state = sch_search;
}
break;
case read_bcch:
break;
}
// for (int i = 0; i < TS_BITS; i++) {
// out[i] = d_phase_diff_buffer[i+start_pos-USEFUL_BITS];
// }
return produced_out;
}
bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
{
circular_buffer_float phase_diff_buffer(BUFFER_SIZE * d_OSR);
float phase_diff = 0;
gr_complex conjprod;
int hit_count = 0;
int miss_count = 0;
int start_pos;
float min_phase_diff, max_phase_diff, lowest_max_min_diff;
int start_pos = -1;
float min_phase_diff;
float max_phase_diff;
float lowest_max_min_diff = 99999;
int to_consume = 0;
int sample_number = 0;
@ -183,7 +162,7 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
miss_count = 0;
start_pos = -1;
lowest_max_min_diff = 99999;
d_phase_diff_buffer.clear();
phase_diff_buffer.clear();
fcch_search_state = search;
break;
@ -196,8 +175,7 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
fcch_search_state = search_fail;
} else {
conjprod = in[sample_number] * conj(in[sample_number-1]);
phase_diff = gr_fast_atan2f(imag(conjprod), real(conjprod));
phase_diff = compute_phase_diff(in[sample_number], in[sample_number-1]);
if (phase_diff > 0) {
to_consume = sample_number;
@ -228,16 +206,16 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
//find difference between minimal and maximal element in the buffer
//for FCCH this value should be low
//this part is searching for a region where this value is lowest
min_phase_diff = *(min_element(d_phase_diff_buffer.begin(), d_phase_diff_buffer.end()));
max_phase_diff = *(max_element(d_phase_diff_buffer.begin(), d_phase_diff_buffer.end()));
min_phase_diff = *(min_element(phase_diff_buffer.begin(), phase_diff_buffer.end()));
max_phase_diff = *(max_element(phase_diff_buffer.begin(), phase_diff_buffer.end()));
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;
for (buffer_iter = (d_phase_diff_buffer.begin());
buffer_iter != (d_phase_diff_buffer.end());
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;
}
@ -251,10 +229,8 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
continue;
}
conjprod = in[sample_number] * conj(in[sample_number-1]);
phase_diff = gr_fast_atan2f(imag(conjprod), real(conjprod));
d_phase_diff_buffer.push_back(phase_diff);
phase_diff = compute_phase_diff(in[sample_number], in[sample_number-1]);
phase_diff_buffer.push_back(phase_diff);
fcch_search_state = found_something;
@ -280,7 +256,11 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
}
// DCOUT("hit_count: " << hit_count << " miss_count: " << miss_count << " d_counter: " << d_counter);
//!
for(int i = 0; i < to_consume; i++){
//std::cout << "(" << real(in[i]) << "," << imag(in[i]) << ")\n";
}
d_counter += to_consume;
consume_each(to_consume);
@ -291,24 +271,18 @@ bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
double gsm_receiver_cf::compute_freq_offset()
{
float mean, phase_offset, freq_offset;
float phase_offset, freq_offset;
DCOUT(" d_phase_diff_buffer.size(): " << d_phase_diff_buffer.size());
//mean = d_best_sum / FCCH_HITS_NEEDED;
phase_offset = d_best_sum / FCCH_HITS_NEEDED;
//phase_offset = mean - ;
freq_offset = phase_offset * 1625000.0 / (12.0 * M_PI);
DCOUT("freq_offset: " << freq_offset << " d_best_sum: " << d_best_sum);
d_fcch_count++;
d_x_temp += freq_offset;
d_x2_temp += freq_offset * freq_offset;
d_mean = d_x_temp / d_fcch_count;
d_freq_offset -= freq_offset;
set_frequency(freq_offset);
d_prev_freq_offset -= freq_offset;
DCOUT("wariancja: " << sqrt((d_x2_temp / d_fcch_count - d_mean * d_mean)) << " fcch_count:" << d_fcch_count << " d_mean: " << d_mean);
// d_x_temp += freq_offset;
// d_x2_temp += freq_offset * freq_offset;
// d_mean = d_x_temp / d_fcch_count;
// d_fcch_count++;
DCOUT("freq_offset: " << freq_offset << " d_best_sum: " << d_best_sum);
// DCOUT("wariancja: " << sqrt((d_x2_temp / d_fcch_count - d_mean * d_mean)) << " fcch_count:" << d_fcch_count << " d_mean: " << d_mean);
return freq_offset;
}

26
src/lib/gsm_receiver_cf.h
View File

@ -65,20 +65,25 @@ class gsm_receiver_cf : public gr_block
{
private:
gr_feval_dd *d_tuner;
const int d_OSR;
int d_counter;
int d_fcch_start_pos;
float d_prev_freq_offset;
circular_buffer_float d_phase_diff_buffer;
double d_x_temp, d_x2_temp, d_mean;
int d_fcch_count;
double d_best_sum;
gr_complex d_sch_training_seq[N_SYNC_BITS]; //encoded training sequence of a SCH burst
gr_feval_dd *d_tuner;
int d_counter;
//variables used to store result of the find_fcch_burst fuction
int d_fcch_start_pos;
float d_freq_offset;
double d_best_sum;
int d_fcch_count;
bool d_first;
// int d_fcch_count;
// double d_x_temp, d_x2_temp, d_mean;
enum states {
fcch_search, sch_search
first_fcch_search, next_fcch_search, sch_search, read_bcch
} d_state;
friend gsm_receiver_cf_sptr gsm_make_receiver_cf(gr_feval_dd *tuner, int osr);
@ -87,9 +92,12 @@ class gsm_receiver_cf : public gr_block
bool find_fcch_burst(const gr_complex *in, const int nitems);
double compute_freq_offset();
void set_frequency(double freq_offset);
inline float compute_phase_diff(gr_complex val1, gr_complex val2);
bool find_sch_burst(const gr_complex *in, const int nitems , float *out);
void gmsk_mapper(const int * input, gr_complex * gmsk_output, int ninput);
gr_complex correlation(const gr_complex * sequence, const gr_complex * input_signal, int ninput);
public:
~gsm_receiver_cf();

4
src/python/gsm_findfcch.py
View File

@ -18,8 +18,8 @@ class tune(gr.feval_dd):
self.top_block = top_block
self.center_freq = 0
def eval(self, freq_offet):
self.center_freq = self.center_freq - freq_offet
self.top_block.set_frequency(self.center_freq)
# self.center_freq = self.center_freq - freq_offet
self.top_block.set_frequency(freq_offet)
return self.center_freq