new algo to eliminate +- 2400 Hz tuning ambiguity

master
Max 11 months ago
parent fbae3bcfde
commit 3492bd70b1
  1. 103
      op25/gr-op25_repeater/lib/gardner_costas_cc_impl.cc
  2. 4
      op25/gr-op25_repeater/lib/gardner_costas_cc_impl.h

@ -69,6 +69,48 @@ static inline std::complex<float> sgn(std::complex<float>c) {
d_event_type = c; \
}
static int tuning_score(gr_complex buf[], int bufp, int bufl, int sync_l, int sps) {
int n_scan_samples = sps * 6;
float atan_prev = 0;
float score = 0;
int p = bufp - (n_scan_samples + 1);
if (p < 0)
p += bufl;
int n_tests = 0;
int n_plus = 0;
// a series of N consecutive samples treated as N-1 connected line segments
// is evaluated to find the angle, in radians, at the junction of each pair
// of lines.
// when a frequency tuning error is present the algebraic sum of the angles
// will contain a significant positive or negative bias.
for (int i = 0; i < n_scan_samples; i++) {
gr_complex sample1 = buf[ (p+i) % bufl ];
gr_complex sample2 = buf[ (p+i+1) % bufl ];
gr_complex diff = sample2 - sample1;
float atan = gr::fast_atan2f(diff.real(), diff.imag());
if (i == 0) {
atan_prev = atan;
continue;
}
float atan_diff = atan - atan_prev;
if (atan_diff > M_PI)
atan_diff -= M_TWOPI;
if (atan_diff < -M_PI)
atan_diff += M_TWOPI;
atan_prev = atan;
score += atan_diff;
n_tests += 1;
if (atan_diff > 0)
n_plus += 1;
}
float f1 = (score > 0) ? n_plus : n_tests - n_plus;
float f2 = n_tests;
int pct = (int) (100*f1/f2 + 0.5);
if (score < 0)
pct *= -1;
return pct;
}
static inline bool is_future(struct timeval*t) {
struct timeval current_t;
gettimeofday(&current_t,0);
@ -95,7 +137,7 @@ void gardner_costas_cc_impl::dump_samples(int error_amt) {
if (is_future(&d_next_sample_time))
return;
gettimeofday(&d_next_sample_time,0);
d_next_sample_time.tv_sec += 5;
d_next_sample_time.tv_sec += 1;
sprintf(filename, "sample-%ld-%d.dat", unique_id(), d_sample_file_id);
d_sample_file_id ++;
d_sample_file_id = d_sample_file_id % N_FILES;
@ -114,6 +156,7 @@ void gardner_costas_cc_impl::dump_samples(int error_amt) {
uint8_t gardner_costas_cc_impl::slicer(float sym) {
uint8_t dibit = 0;
int sps = (int) (d_omega + 0.5);
static const float PI_4 = M_PI / 4.0;
static const float d_slice_levels[4] = {(float)-2.0*PI_4, (float)0.0*PI_4, (float)2.0*PI_4, (float)4.0*PI_4};
if (d_slice_levels[3] < 0) {
@ -135,44 +178,74 @@ uint8_t gardner_costas_cc_impl::slicer(float sym) {
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ P25_FRAME_SYNC_MAGIC, 0, 48)) {
// fprintf(stderr, "P25P1 Framing detect\n");
UPDATE_COUNT(' ')
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(0);
}
else if(check_frame_sync((nid_accum & P25P2_FRAME_SYNC_MASK) ^ P25P2_FRAME_SYNC_MAGIC, 0, 40)) {
// fprintf(stderr, "P25P2 Framing detect\n");
UPDATE_COUNT(' ')
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(0);
}
if (d_is_tdma) {
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0x000104015155LL, 0, 40)) {
fprintf(stderr, "TDMA: channel %d tuning error -1200\n", -1);
UPDATE_COUNT('-')
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(-1200);
}
else if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0xfefbfeaeaaLL, 0, 40)) {
fprintf(stderr, "TDMA: channel %d tuning error +1200\n", -1);
UPDATE_COUNT('+')
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(1200);
}
else if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0xa8a2a80800LL, 0, 40)) {
fprintf(stderr, "TDMA: channel %d tuning error +/- 2400\n", -1);
UPDATE_COUNT('|')
dump_samples(2400);
int score = tuning_score(d_prev_sample, d_prev_sample_p, d_n_prev_sample, 20, sps);
int error = 24;
if (score == -100) {
error = 2400;
UPDATE_COUNT('>')
fprintf(stderr, "TDMA: channel %d tuning error %d\n", -1, error);
} else if (score == 100) {
error = -2400;
UPDATE_COUNT('<')
fprintf(stderr, "TDMA: channel %d tuning error %d\n", -1, error);
} else {
fprintf(stderr, "TDMA: channel %d tuning error +/-2400, confidence %d\n", -1, score);
}
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(error);
}
} else {
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0x001050551155LL, 0, 48)) {
// fprintf(stderr, "tuning error -1200\n");
UPDATE_COUNT('-')
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(-1200);
}
else if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0xFFEFAFAAEEAALL, 0, 48)) {
// fprintf(stderr, "tuning error +1200\n");
UPDATE_COUNT('+')
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(1200);
}
else if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0xAA8A0A008800LL, 0, 48)) {
// fprintf(stderr, "tuning error +/- 2400\n");
UPDATE_COUNT('|')
dump_samples(2400);
int score = tuning_score(d_prev_sample, d_prev_sample_p, d_n_prev_sample, 24, sps);
int error = 24;
if (score == -100) {
error = 2400;
UPDATE_COUNT('>')
fprintf(stderr, "channel %d block id %ld tuning error %d\n", -1, (long)unique_id(), error);
} else if (score == 100) {
error = -2400;
UPDATE_COUNT('<')
fprintf(stderr, "channel %d block id %ld tuning error %d\n", -1, (long)unique_id(), error);
} else {
fprintf(stderr, "channel %d block id %ld tuning error +/-2400, confidence %d\n", -1, (long)unique_id(), score);
}
d_sync_valid_until = d_sample_count + 2400 * sps;
dump_samples(error);
}
}
if (d_event_type == ' ' || d_event_count < 5) {
@ -182,8 +255,10 @@ uint8_t gardner_costas_cc_impl::slicer(float sym) {
d_update_request = -1;
else if (d_event_type == '-' && d_fm < 0)
d_update_request = 1;
else if (d_event_type == '|')
d_update_request = (d_fm < 0) ? 2 : -2;
else if (d_event_type == '<')
d_update_request = -2;
else if (d_event_type == '>')
d_update_request = 2;
else d_update_request = 0;
}
return dibit;
@ -222,7 +297,8 @@ uint8_t gardner_costas_cc_impl::slicer(float sym) {
d_fm(0), d_fm_accum(0), d_fm_count(0), d_muted(false), d_is_tdma(false),
d_enable_sync_plot(false),
d_prev_sample(NULL), d_n_prev_sample(0), d_prev_sample_p(0),
d_sample_file_id(0)
d_sample_file_id(0),
d_sample_count(0), d_sync_valid_until(0)
{
set_omega(samples_per_symbol);
set_relative_rate (1.0 / d_omega);
@ -257,10 +333,14 @@ void gardner_costas_cc_impl::set_omega (float omega) {
}
float gardner_costas_cc_impl::get_freq_error (void) {
if (!recent_sync())
return 0.0;
return (d_freq);
}
int gardner_costas_cc_impl::get_error_band (void) {
if (!recent_sync())
return 0;
return (d_update_request);
}
@ -338,7 +418,7 @@ gardner_costas_cc_impl::general_work (int noutput_items,
gr_complex interp_samp, interp_samp_mid, diffdec;
float error_real, error_imag, symbol_error;
if (d_enable_sync_plot && d_prev_sample == NULL) {
if (d_prev_sample == NULL) {
d_n_prev_sample = (int) (d_omega + 0.5); // sps
d_n_prev_sample *= (d_is_tdma) ? 32 : 25; // enough for p25p1 or p25p2 sync
d_prev_sample = (gr_complex *) calloc(d_n_prev_sample, sizeof(gr_complex));
@ -371,6 +451,7 @@ gardner_costas_cc_impl::general_work (int noutput_items,
d_dl_index = d_dl_index % d_twice_sps;
i++;
d_sample_count++;
gr_complex df = symbol * conj(d_prev);
float fmd = atan2f(df.imag(), df.real());
d_fm_accum += fmd;

@ -131,9 +131,13 @@ protected:
struct timeval d_next_sample_time;
int d_sample_file_id;
unsigned int d_sample_count;
unsigned int d_sync_valid_until;
float phase_error_detector_qpsk(gr_complex sample);
void phase_error_tracking(gr_complex sample);
void dump_samples(int);
bool recent_sync(void) { return d_sample_count <= d_sync_valid_until; }
};
} // namespace op25_repeater

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