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refactoring PRACH, adding phase correction to successive cancellation

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master
yagoda 4 years ago committed by Justin Tallon
parent 4d8888aae6
commit ec7873e7cc
4 changed files with 138 additions and 82 deletions
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14
lib/include/srslte/phy/phch/prach.h
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@ -123,8 +123,9 @@ typedef struct {
typedef struct {
int idx;
float offset;
float offset;
float factor;
float phase;
} srslte_prach_cancellation_t;
typedef struct SRSLTE_API {
@ -209,4 +210,15 @@ SRSLTE_API int srslte_prach_free(srslte_prach_t* p);
SRSLTE_API int srslte_prach_print_seqs(srslte_prach_t* p);
SRSLTE_API int srslte_prach_process(srslte_prach_t* p,
cf_t* signal,
uint32_t* indices,
float* t_offsets,
float* peak_to_avg,
uint32_t* n_indices,
int cancellation_idx,
srslte_prach_cancellation_t prach_cancel,
uint32_t begin,
uint32_t sig_len);
#endif // SRSLTE_PRACH_H

2
lib/include/srslte/phy/utils/vector.h
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@ -274,6 +274,8 @@ SRSLTE_API void srslte_vec_abs_dB_cf(const cf_t* x, float default_value, float*
*/
SRSLTE_API void srslte_vec_arg_deg_cf(const cf_t* x, float default_value, float* arg, const uint32_t len);
SRSLTE_API float srslte_mean_arg_cf(const cf_t* x, uint32_t len);
SRSLTE_API void srslte_vec_interleave(const cf_t* x, const cf_t* y, cf_t* z, const int len);
SRSLTE_API void srslte_vec_interleave_add(const cf_t* x, const cf_t* y, cf_t* z, const int len);

181
lib/src/phy/phch/prach.c
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@ -566,17 +566,23 @@ int srslte_prach_detect(srslte_prach_t* p,
{
return srslte_prach_detect_offset(p, freq_offset, signal, sig_len, indices, NULL, NULL, n_indices);
}
/// this function subtracts the detected prach preamble from the signal so as to allow for lower power prach signals to
/// be detected more easily in the subsequent searches
void srslte_prach_cancellation (srslte_prach_t* p, cf_t *signal, uint32_t begin, int sig_len, srslte_prach_cancellation_t prach_cancel)
{
cf_t sub[sig_len];
memcpy(sub,&p->td_signals[p->root_seqs_idx[prach_cancel.idx]][p->N_cp], sig_len*sizeof(cf_t));
srslte_vec_sc_prod_cfc(sub, prach_cancel.factor, sub, p->N_seq);
int offset = (int) (prach_cancel.offset*sig_len*DELTA_F_RA);
srslte_vec_sc_prod_ccc(sub, cexpf(_Complex_I * prach_cancel.phase), sub, sig_len);
srslte_vec_sub_ccc(&signal[offset], sub, &signal[offset], sig_len);
srslte_dft_run(&p->fft, signal, p->signal_fft);
memcpy(p->prach_bins, &p->signal_fft[begin], p->N_zc * sizeof(cf_t));
}
// this function checks if we have already detected and stored this particular PRACH index and if so, doesnt store it
// again in the detected prachs array
bool srslte_prach_have_stored(srslte_prach_t* p,int current_idx, uint32_t* indices, uint32_t n_indices) {
for(int i = 0; i < n_indices; i++) {
if (indices[i] == current_idx) {
@ -597,6 +603,101 @@ float srslte_prach_set_offset(srslte_prach_t* p, int n_win) {
return corr * p->peak_offsets[n_win] / (DELTA_F_RA * p->N_zc);
}
// This function carries out the main processing on the incomming PRACH signal
int srslte_prach_process(srslte_prach_t* p,
cf_t* signal,
uint32_t* indices,
float* t_offsets,
float* peak_to_avg,
uint32_t* n_indices,
int cancellation_idx,
srslte_prach_cancellation_t prach_cancel,
uint32_t begin,
uint32_t sig_len)
{
float max_to_cancel = 0;
cancellation_idx = -1;
int max_idx = 0;
for (int i = 0; i < p->num_ra_preambles; i++) {
cf_t* root_spec = p->dft_seqs[p->root_seqs_idx[i]];
srslte_vec_prod_conj_ccc(p->prach_bins, root_spec, p->corr_spec, p->N_zc);
srslte_dft_run(&p->zc_ifft, p->corr_spec, p->corr_spec);
srslte_vec_abs_square_cf(p->corr_spec, p->corr, p->N_zc);
float corr_ave = srslte_vec_acc_ff(p->corr, p->N_zc) / p->N_zc;
uint32_t winsize = 0;
if (p->N_cs != 0) {
winsize = p->N_cs;
} else {
winsize = p->N_zc;
}
uint32_t n_wins = p->N_zc / winsize;
float max_peak = 0;
for (int j = 0; j < n_wins; j++) {
uint32_t start = (p->N_zc - (j * p->N_cs)) % p->N_zc;
uint32_t end = start + winsize;
if (end > p->deadzone) {
end -= p->deadzone;
}
start += p->deadzone;
p->peak_values[j] = 0;
for (int k = start; k < end; k++) {
if (p->corr[k] > p->peak_values[j]) {
p->peak_values[j] = p->corr[k];
p->peak_offsets[j] = k - start;
if (p->peak_values[j] > max_peak) {
max_peak = p->peak_values[j];
max_idx = k;
}
}
}
}
if (max_peak > p->detect_factor * corr_ave) {
for (int j = 0; j < n_wins; j++) {
if (p->peak_values[j] > p->detect_factor * corr_ave) {
if (indices) {
if (p->successive_cancellation) {
if (max_peak > max_to_cancel) {
cancellation_idx = (i * n_wins) + j;
max_to_cancel = max_peak;
prach_cancel.idx = cancellation_idx;
prach_cancel.offset = srslte_prach_set_offset(p, j);
prach_cancel.factor = sqrt((max_peak / 2) / ((sig_len / 2) * p->N_zc * p->N_zc));
prach_cancel.phase = cargf(p->corr_spec[max_idx]);
}
if (srslte_prach_have_stored(p, ((i * n_wins) + j), indices, *n_indices)) {
break;
}
}
srslte_vec_fprint_c(stdout, p->corr_spec, 10) printf("max_idx %d\n", max_idx);
printf("cargf(p->corr_spec[max_idx]) %f\n", cargf(p->corr_spec[max_idx]));
indices[*n_indices] = (i * n_wins) + j;
}
if (peak_to_avg) {
peak_to_avg[*n_indices] = p->peak_values[j] / corr_ave;
}
if (t_offsets) {
t_offsets[*n_indices] = srslte_prach_set_offset(p, j);
printf("t_offsets[*n_indices] %f\n", t_offsets[*n_indices]);
}
(*n_indices)++;
}
}
}
}
if (cancellation_idx != -1) {
srslte_prach_cancellation(p, signal, begin, sig_len, prach_cancel);
} else {
return 1;
}
return 0;
}
int srslte_prach_detect_offset(srslte_prach_t* p,
uint32_t freq_offset,
cf_t* signal,
@ -614,7 +715,7 @@ int srslte_prach_detect_offset(srslte_prach_t* p,
return SRSLTE_ERROR_INVALID_INPUTS;
}
int cancellation_idx = -2;
srslte_prach_cancellation_t prach_cancel;
srslte_prach_cancellation_t prach_cancel = {};
// FFT incoming signal
srslte_dft_run(&p->fft, signal, p->signal_fft);
@ -628,80 +729,12 @@ int srslte_prach_detect_offset(srslte_prach_t* p,
uint32_t begin = PHI + (K * k_0) + (K / 2);
memcpy(p->prach_bins, &p->signal_fft[begin], p->N_zc * sizeof(cf_t));
int loops = (p->successive_cancellation)?p->num_ra_preambles:1;
int loops = (p->successive_cancellation) ? p->num_ra_preambles : 1;
// if successive cancellation is enabled, we perform the entire search process p->num_ra_preambles times, removing
// the highest power PRACH preamble each time.
for (int l = 0; l < loops; l++) {
float max_to_cancel = 0;
cancellation_idx = -1;
for (int i = 0; i < p->num_ra_preambles; i++) {
cf_t* root_spec = p->dft_seqs[p->root_seqs_idx[i]];
srslte_vec_prod_conj_ccc(p->prach_bins, root_spec, p->corr_spec, p->N_zc);
srslte_dft_run(&p->zc_ifft, p->corr_spec, p->corr_spec);
srslte_vec_abs_square_cf(p->corr_spec, p->corr, p->N_zc);
float corr_ave = srslte_vec_acc_ff(p->corr, p->N_zc) / p->N_zc;
uint32_t winsize = 0;
if (p->N_cs != 0) {
winsize = p->N_cs;
} else {
winsize = p->N_zc;
}
uint32_t n_wins = p->N_zc / winsize;
float max_peak = 0;
for (int j = 0; j < n_wins; j++) {
uint32_t start = (p->N_zc - (j * p->N_cs)) % p->N_zc;
uint32_t end = start + winsize;
if (end > p->deadzone) {
end -= p->deadzone;
}
start += p->deadzone;
p->peak_values[j] = 0;
for (int k = start; k < end; k++) {
if (p->corr[k] > p->peak_values[j]) {
p->peak_values[j] = p->corr[k];
p->peak_offsets[j] = k - start;
if (p->peak_values[j] > max_peak) {
max_peak = p->peak_values[j];
}
}
}
}
if (max_peak > p->detect_factor * corr_ave) {
for (int j = 0; j < n_wins; j++) {
if (p->peak_values[j] > p->detect_factor * corr_ave) {
if (indices) {
if (p->successive_cancellation) {
if (max_peak > max_to_cancel) {
cancellation_idx = (i * n_wins) + j;
max_to_cancel = max_peak;
prach_cancel.idx = cancellation_idx;
prach_cancel.offset = srslte_prach_set_offset(p,j);
prach_cancel.factor = sqrt((max_peak/2)/((sig_len/2)*p->N_zc*p->N_zc));
}
if (srslte_prach_have_stored(p,((i * n_wins) + j),indices, *n_indices)) {
break;
}
}
indices[*n_indices] = (i * n_wins) + j;
}
if (peak_to_avg) {
peak_to_avg[*n_indices] = p->peak_values[j] / corr_ave;
}
if (t_offsets) {
t_offsets[*n_indices] = srslte_prach_set_offset(p,j);
}
(*n_indices)++;
}
}
}
}
if (cancellation_idx != -1) {
srslte_prach_cancellation(p, signal, begin, sig_len, prach_cancel);
} else {
if (srslte_prach_process(
p, signal, indices, t_offsets, peak_to_avg, n_indices, cancellation_idx, prach_cancel, begin, sig_len)) {
break;
}
}

23
lib/src/phy/phch/test/prach_test_multi.c
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@ -33,7 +33,7 @@
#include "srslte/phy/phch/prach.h"
#include "srslte/phy/utils/debug.h"
char* input_file_name = NULL;
#define PRACH_SRATE 1048750
#define MAX_LEN 70176
int offset = -1;
@ -45,7 +45,7 @@ uint32_t n_seqs = 64;
uint32_t num_ra_preambles = 0; // use default
bool test_successive_cancellation = false;
bool test_offset_calculation = false;
bool test_offset_calculation = true;
srslte_filesource_t fsrc;
void usage(char* prog)
@ -96,18 +96,23 @@ void stagger_prach_powers(srslte_prach_t prach, cf_t *preamble, cf_t* preamble_s
for (int seq_index = 0; seq_index < n_seqs; seq_index++) {
srslte_prach_gen(&prach, seq_index, freq_offset, preamble);
if (seq_index == 0) {
srslte_vec_sc_prod_ccc(preamble, cexpf(_Complex_I * 0.1), preamble, prach.N_cp + prach.N_seq);
srslte_vec_sc_prod_cfc(preamble, 0.1, preamble, prach.N_cp + prach.N_seq);
}
if (seq_index == 1) {
srslte_vec_sc_prod_ccc(preamble, cexpf(_Complex_I * 0.4), preamble, prach.N_cp + prach.N_seq);
srslte_vec_sc_prod_cfc(preamble, 0.4, preamble, prach.N_cp + prach.N_seq);
}
if (seq_index == 2) {
srslte_vec_sc_prod_ccc(preamble, cexpf(_Complex_I * 0.1), preamble, prach.N_cp + prach.N_seq);
srslte_vec_sc_prod_cfc(preamble, 0.07, preamble, prach.N_cp + prach.N_seq);
}
if (seq_index == 3) {
srslte_vec_sc_prod_ccc(preamble, cexpf(_Complex_I * 0.9), preamble, prach.N_cp + prach.N_seq);
srslte_vec_sc_prod_cfc(preamble,0.6, preamble, prach.N_cp + prach.N_seq);
}
if (seq_index == 4) {
srslte_vec_sc_prod_ccc(preamble, cexpf(_Complex_I * 0.3), preamble, prach.N_cp + prach.N_seq);
srslte_vec_sc_prod_cfc(preamble, 1, preamble, prach.N_cp + prach.N_seq);
}
if (seq_index == 5) {
@ -151,15 +156,16 @@ int main(int argc, char** argv)
int srate = srslte_sampling_freq_hz(nof_prb);
int divisor = srate/1048750;
int divisor = srate / PRACH_SRATE;
if (test_offset_calculation) {
n_seqs = 15;
prach_cfg.num_ra_preambles = 15;
n_seqs = 1;
prach_cfg.num_ra_preambles = 4;
prach_cfg.zero_corr_zone = 0;
printf("limiting number of preambles to 15 for offset calculation test\n");
for (int i = 0; i < 15; i++) {
offsets[i] = ((rand()%(25*divisor)));
}
memset(offsets, 0, sizeof(int) * 64);
}
if (test_successive_cancellation) {
printf("limiting number of preambles to 6 for successive cancellation test\n");
@ -206,9 +212,12 @@ int main(int argc, char** argv)
if (preamble_format == 2 || preamble_format == 3) {
prach_len /= 2;
}
struct timeval t[3];
gettimeofday(&t[1], NULL);
srslte_prach_detect_offset(&prach, 0, &preamble_sum[prach.N_cp], prach_len, indices, t_offsets , NULL, &n_indices);
gettimeofday(&t[2], NULL);
get_time_interval(t);
printf("texec=%ld us\n", t[0].tv_usec);
int err = 0;
if (n_indices != n_seqs) {
printf("n_indices %d n_seq %d\n", n_indices, n_seqs);

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