int srslte_sync_get_cell_id(srslte_sync_t *q) {
if (srslte_N_id_2_isvalid(q->N_id_2) && srslte_N_id_1_isvalid(q->N_id_1)) {
return q->N_id_1*3 + q->N_id_2;
} else {
return -1;
}
}
int srslte_pss_synch_init_N_id_2(cf_t *pss_signal_freq, cf_t *pss_signal_time,
uint32_t N_id_2, uint32_t fft_size, int cfo_i) {
srslte_dft_plan_t plan;
cf_t pss_signal_pad[2048];
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (srslte_N_id_2_isvalid(N_id_2) &&
fft_size <= 2048)
{
srslte_pss_generate(pss_signal_freq, N_id_2);
bzero(pss_signal_pad, fft_size * sizeof(cf_t));
bzero(pss_signal_time, fft_size * sizeof(cf_t));
memcpy(&pss_signal_pad[(fft_size-SRSLTE_PSS_LEN)/2+cfo_i], pss_signal_freq, SRSLTE_PSS_LEN * sizeof(cf_t));
/* Convert signal into the time domain */
if (srslte_dft_plan(&plan, fft_size, SRSLTE_DFT_BACKWARD, SRSLTE_DFT_COMPLEX)) {
return SRSLTE_ERROR;
}
srslte_dft_plan_set_mirror(&plan, true);
srslte_dft_plan_set_dc(&plan, true);
srslte_dft_plan_set_norm(&plan, true);
srslte_dft_run_c(&plan, pss_signal_pad, pss_signal_time);
srslte_vec_conj_cc(pss_signal_time, pss_signal_time, fft_size);
srslte_vec_sc_prod_cfc(pss_signal_time, 1.0/SRSLTE_PSS_LEN, pss_signal_time, fft_size);
srslte_dft_plan_free(&plan);
ret = SRSLTE_SUCCESS;
}
return ret;
}
int srslte_sync_set_N_id_2(srslte_sync_t *q, uint32_t N_id_2) {
if (srslte_N_id_2_isvalid(N_id_2)) {
q->N_id_2 = N_id_2;
return SRSLTE_SUCCESS;
} else {
fprintf(stderr, "Invalid N_id_2=%d\n", N_id_2);
return SRSLTE_ERROR_INVALID_INPUTS;
}
}
/** Sets the current N_id_2 value. Returns -1 on ERROR(0 otherwise
*/
int srslte_pss_set_N_id_2(srslte_pss_t *q, uint32_t N_id_2) {
if (!srslte_N_id_2_isvalid((N_id_2))) {
ERROR("Invalid N_id_2 %d\n", N_id_2);
return -1;
} else {
q->N_id_2 = N_id_2;
return 0;
}
}
/** Sets the current N_id_2 value. Returns -1 on error, 0 otherwise
*/
int srslte_pss_synch_set_N_id_2(srslte_pss_synch_t *q, uint32_t N_id_2) {
if (!srslte_N_id_2_isvalid((N_id_2))) {
fprintf(stderr, "Invalid N_id_2 %d\n", N_id_2);
return -1;
} else {
q->N_id_2 = N_id_2;
return 0;
}
}
/** Sets the N_id_2 to search for */
int srslte_sss_synch_set_N_id_2(srslte_sss_synch_t *q, uint32_t N_id_2) {
if (!srslte_N_id_2_isvalid(N_id_2)) {
fprintf(stderr, "Invalid N_id_2 %d\n", N_id_2);
return SRSLTE_ERROR;
} else {
q->N_id_2 = N_id_2;
return SRSLTE_SUCCESS;
}
}
/* Computes frequency-domain channel estimation of the PSS symbol
* input signal is in the time-domain.
* ce is the returned frequency-domain channel estimates.
*/
int srslte_pss_chest(srslte_pss_t *q, const cf_t *input, cf_t ce[SRSLTE_PSS_LEN]) {
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL)
{
if (!srslte_N_id_2_isvalid(q->N_id_2)) {
ERROR("Error finding PSS peak, Must set N_id_2 first\n");
return SRSLTE_ERROR;
}
/* Transform to frequency-domain */
srslte_dft_run_c(&q->dftp_input, input, q->tmp_fft);
/* Compute channel estimate taking the PSS sequence as reference */
srslte_vec_prod_conj_ccc(&q->tmp_fft[(q->fft_size-SRSLTE_PSS_LEN)/2], q->pss_signal_freq[q->N_id_2], ce, SRSLTE_PSS_LEN);
ret = SRSLTE_SUCCESS;
}
return ret;
}
/** Finds the PSS sequence previously defined by a call to srslte_sync_set_N_id_2()
* around the position find_offset in the buffer input.
* Returns 1 if the correlation peak exceeds the threshold set by srslte_sync_set_threshold()
* or 0 otherwise. Returns a negative number on error (if N_id_2 has not been set)
*
* The maximum of the correlation peak is always stored in *peak_position
*/
int srslte_sync_find(srslte_sync_t *q, cf_t *input, uint32_t find_offset, uint32_t *peak_position)
{
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL &&
srslte_N_id_2_isvalid(q->N_id_2) &&
fft_size_isvalid(q->fft_size))
{
int peak_pos;
ret = SRSLTE_SUCCESS;
if (peak_position) {
*peak_position = 0;
}
/* Estimate CFO using CP */
if (q->enable_cfo_corr) {
uint32_t cp_offset = srslte_cp_synch(&q->cp_synch, input, q->nof_symbols, q->nof_symbols, SRSLTE_CP_LEN_NORM(1,q->fft_size));
cf_t cp_corr_max = srslte_cp_synch_corr_output(&q->cp_synch, cp_offset);
float cfo = -carg(cp_corr_max) / M_PI / 2;
/* compute cumulative moving average CFO */
INFO("cp_offset_pos=%d, abs=%f, cfo=%f, mean_cfo=%f, nof_symb=%d\n",
cp_offset, cabs(cp_corr_max), cfo, q->mean_cfo, q->nof_symbols);
if (q->mean_cfo) {
q->mean_cfo = SRSLTE_VEC_EMA(cfo, q->mean_cfo, q->cfo_ema_alpha);
} else {
q->mean_cfo = cfo;
}
/* Correct CFO with the averaged CFO estimation */
srslte_cfo_correct(&q->cfocorr, input, input, -q->mean_cfo / q->fft_size);
}
if (q->find_cfo_i && q->enable_cfo_corr) {
float peak_value;
float max_peak_value = -99;
peak_pos = 0;
srslte_pss_synch_t *pss_obj[3] = {&q->pss_i[0], &q->pss, &q->pss_i[1]};
for (int cfo_i=0;cfo_i<3;cfo_i++) {
srslte_pss_synch_set_N_id_2(pss_obj[cfo_i], q->N_id_2);
int p = srslte_pss_synch_find_pss(pss_obj[cfo_i], &input[find_offset], &peak_value);
if (peak_value > max_peak_value) {
max_peak_value = peak_value;
peak_pos = p;
q->peak_value = peak_value;
q->cfo_i = cfo_i-1;
}
}
if (q->cfo_i != 0) {
srslte_vec_prod_ccc(input, q->cfo_i_corr[q->cfo_i<0?0:1], input, q->frame_size);
INFO("Compensating cfo_i=%d\n", q->cfo_i);
}
} else {
srslte_pss_synch_set_N_id_2(&q->pss, q->N_id_2);
peak_pos = srslte_pss_synch_find_pss(&q->pss, &input[find_offset], &q->peak_value);
if (peak_pos < 0) {
fprintf(stderr, "Error calling finding PSS sequence\n");
return SRSLTE_ERROR;
}
}
q->mean_peak_value = SRSLTE_VEC_EMA(q->peak_value, q->mean_peak_value, MEANPEAK_EMA_ALPHA);
if (peak_position) {
*peak_position = (uint32_t) peak_pos;
}
/* If peak is over threshold, compute CFO and SSS */
if (q->peak_value >= q->threshold) {
// Try to detect SSS
if (q->sss_en) {
// Set an invalid N_id_1 indicating SSS is yet to be detected
q->N_id_1 = 1000;
if (sync_sss(q, input, find_offset + peak_pos, q->cp) < 0) {
DEBUG("No space for SSS processing. Frame starts at %d\n", peak_pos);
}
}
if (q->detect_cp) {
if (peak_pos + find_offset >= 2*(q->fft_size + SRSLTE_CP_LEN_EXT(q->fft_size))) {
srslte_sync_set_cp(q, srslte_sync_detect_cp(q, input, peak_pos + find_offset));
} else {
DEBUG("Not enough room to detect CP length. Peak position: %d\n", peak_pos);
}
}
// Return 1 (peak detected) even if we couldn't estimate CFO and SSS
ret = 1;
} else {
ret = 0;
}
DEBUG("SYNC ret=%d N_id_2=%d find_offset=%d pos=%d peak=%.2f threshold=%.2f sf_idx=%d, CFO=%.3f KHz\n",
ret, q->N_id_2, find_offset, peak_pos, q->peak_value, q->threshold, q->sf_idx, 15*(q->cfo_i+q->mean_cfo));
} else if (srslte_N_id_2_isvalid(q->N_id_2)) {
fprintf(stderr, "Must call srslte_sync_set_N_id_2() first!\n");
}
return ret;
}
/** Performs time-domain PSS correlation.
* Returns the index of the PSS correlation peak in a subframe.
* The frame starts at corr_peak_pos-subframe_size/2.
* The value of the correlation is stored in corr_peak_value.
*
* Input buffer must be subframe_size long.
*/
int srslte_pss_synch_find_pss(srslte_pss_synch_t *q, cf_t *input, float *corr_peak_value)
{
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL)
{
uint32_t corr_peak_pos;
uint32_t conv_output_len;
if (!srslte_N_id_2_isvalid(q->N_id_2)) {
fprintf(stderr, "Error finding PSS peak, Must set N_id_2 first\n");
return SRSLTE_ERROR;
}
/* Correlate input with PSS sequence */
if (q->frame_size >= q->fft_size) {
#ifdef CONVOLUTION_FFT
memcpy(q->tmp_input, input, q->frame_size * sizeof(cf_t));
conv_output_len = srslte_conv_fft_cc_run(&q->conv_fft, q->tmp_input, q->pss_signal_time[q->N_id_2], q->conv_output);
#else
conv_output_len = srslte_conv_cc(input, q->pss_signal_time[q->N_id_2], q->conv_output, q->frame_size, q->fft_size);
#endif
} else {
for (int i=0;i<q->frame_size;i++) {
q->conv_output[i] = srslte_vec_dot_prod_ccc(q->pss_signal_time[q->N_id_2], &input[i], q->fft_size);
}
conv_output_len = q->frame_size;
}
#ifdef SRSLTE_PSS_ABS_SQUARE
srslte_vec_abs_square_cf(q->conv_output, q->conv_output_abs, conv_output_len-1);
#else
srslte_vec_abs_cf(q->conv_output, q->conv_output_abs, conv_output_len-1);
#endif
srslte_vec_sc_prod_fff(q->conv_output_abs, q->ema_alpha, q->conv_output_abs, conv_output_len-1);
srslte_vec_sc_prod_fff(q->conv_output_avg, 1-q->ema_alpha, q->conv_output_avg, conv_output_len-1);
srslte_vec_sum_fff(q->conv_output_abs, q->conv_output_avg, q->conv_output_avg, conv_output_len-1);
/* Find maximum of the absolute value of the correlation */
corr_peak_pos = srslte_vec_max_fi(q->conv_output_avg, conv_output_len-1);
// save absolute value
q->peak_value = q->conv_output_avg[corr_peak_pos];
#ifdef SRSLTE_PSS_RETURN_PSR
// Find second side lobe
// Find end of peak lobe to the right
int pl_ub = corr_peak_pos+1;
while(q->conv_output_avg[pl_ub+1] <= q->conv_output_avg[pl_ub] && pl_ub < conv_output_len) {
pl_ub ++;
}
// Find end of peak lobe to the left
int pl_lb;
if (corr_peak_pos > 2) {
pl_lb = corr_peak_pos-1;
while(q->conv_output_avg[pl_lb-1] <= q->conv_output_avg[pl_lb] && pl_lb > 1) {
pl_lb --;
}
} else {
pl_lb = 0;
}
int sl_distance_right = conv_output_len-1-pl_ub;
if (sl_distance_right < 0) {
sl_distance_right = 0;
}
int sl_distance_left = pl_lb;
int sl_right = pl_ub+srslte_vec_max_fi(&q->conv_output_avg[pl_ub], sl_distance_right);
int sl_left = srslte_vec_max_fi(q->conv_output_avg, sl_distance_left);
float side_lobe_value = SRSLTE_MAX(q->conv_output_avg[sl_right], q->conv_output_avg[sl_left]);
if (corr_peak_value) {
*corr_peak_value = q->conv_output_avg[corr_peak_pos]/side_lobe_value;
DEBUG("peak_pos=%2d, pl_ub=%2d, pl_lb=%2d, sl_right: %2d, sl_left: %2d, PSR: %.2f/%.2f=%.2f\n", corr_peak_pos, pl_ub, pl_lb,
sl_right,sl_left, q->conv_output_avg[corr_peak_pos], side_lobe_value,*corr_peak_value);
}
#else
if (corr_peak_value) {
*corr_peak_value = q->conv_output_avg[corr_peak_pos];
}
#endif
if (q->frame_size >= q->fft_size) {
ret = (int) corr_peak_pos;
} else {
ret = (int) corr_peak_pos + q->fft_size;
}
}
return ret;
}
/** Performs time-domain PSS correlation.
* Returns the index of the PSS correlation peak in a subframe.
* The frame starts at corr_peak_pos-subframe_size/2.
* The value of the correlation is stored in corr_peak_value.
*
* Input buffer must be subframe_size long.
*/
int srslte_pss_find_pss(srslte_pss_t *q, const cf_t *input, float *corr_peak_value)
{
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL)
{
uint32_t corr_peak_pos;
uint32_t conv_output_len;
if (!srslte_N_id_2_isvalid(q->N_id_2)) {
ERROR("Error finding PSS peak, Must set N_id_2 first\n");
return SRSLTE_ERROR;
}
/* Correlate input with PSS sequence
*
* We do not reverse time-domain PSS signal because it's conjugate is symmetric.
* The conjugate operation on pss_signal_time has been done in srslte_pss_init_N_id_2
* This is why we can use FFT-based convolution
*/
if (q->frame_size >= q->fft_size) {
#ifdef CONVOLUTION_FFT
memcpy(q->tmp_input, input, (q->frame_size * q->decimate) * sizeof(cf_t));
if(q->decimate > 1) {
srslte_filt_decim_cc_execute(&(q->filter), q->tmp_input, q->filter.downsampled_input, q->filter.filter_output , (q->frame_size * q->decimate));
conv_output_len = srslte_conv_fft_cc_run_opt(&q->conv_fft, q->filter.filter_output,q->pss_signal_freq_full[q->N_id_2], q->conv_output);
} else {
conv_output_len = srslte_conv_fft_cc_run_opt(&q->conv_fft, q->tmp_input, q->pss_signal_freq_full[q->N_id_2], q->conv_output);
}
#else
conv_output_len = srslte_conv_cc(input, q->pss_signal_time[q->N_id_2], q->conv_output, q->frame_size, q->fft_size);
#endif
} else {
for (int i=0;i<q->frame_size;i++) {
q->conv_output[i] = srslte_vec_dot_prod_ccc(q->pss_signal_time[q->N_id_2], &input[i], q->fft_size);
}
conv_output_len = q->frame_size;
}
// Compute modulus square
srslte_vec_abs_square_cf(q->conv_output, q->conv_output_abs, conv_output_len-1);
// If enabled, average the absolute value from previous calls
if (q->ema_alpha < 1.0 && q->ema_alpha > 0.0) {
srslte_vec_sc_prod_fff(q->conv_output_abs, q->ema_alpha, q->conv_output_abs, conv_output_len-1);
srslte_vec_sc_prod_fff(q->conv_output_avg, 1-q->ema_alpha, q->conv_output_avg, conv_output_len-1);
srslte_vec_sum_fff(q->conv_output_abs, q->conv_output_avg, q->conv_output_avg, conv_output_len-1);
} else {
memcpy(q->conv_output_avg, q->conv_output_abs, sizeof(float)*(conv_output_len-1));
}
/* Find maximum of the absolute value of the correlation */
corr_peak_pos = srslte_vec_max_fi(q->conv_output_avg, conv_output_len-1);
// save absolute value
q->peak_value = q->conv_output_avg[corr_peak_pos];
#ifdef SRSLTE_PSS_RETURN_PSR
if (corr_peak_value) {
*corr_peak_value = compute_peak_sidelobe(q, corr_peak_pos, conv_output_len);
}
#else
if (corr_peak_value) {
*corr_peak_value = q->conv_output_avg[corr_peak_pos];
}
#endif
if(q->decimate >1) {
int decimation_correction = (q->filter.num_taps - 2);
corr_peak_pos = corr_peak_pos - decimation_correction;
corr_peak_pos = corr_peak_pos*q->decimate;
}
if (q->frame_size >= q->fft_size) {
ret = (int) corr_peak_pos;
} else {
ret = (int) corr_peak_pos + q->fft_size;
}
}
return ret;
}
/** Finds the PSS sequence previously defined by a call to srslte_sync_set_N_id_2()
* around the position find_offset in the buffer input.
* Returns 1 if the correlation peak exceeds the threshold set by srslte_sync_set_threshold()
* or 0 otherwise. Returns a negative number on error (if N_id_2 has not been set)
*
* The maximum of the correlation peak is always stored in *peak_position
*/
int srslte_sync_find(srslte_sync_t *q, cf_t *input, uint32_t find_offset, uint32_t *peak_position)
{
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL &&
srslte_N_id_2_isvalid(q->N_id_2) &&
fft_size_isvalid(q->fft_size))
{
int peak_pos;
ret = SRSLTE_SUCCESS;
if (peak_position) {
*peak_position = 0;
}
srslte_pss_synch_set_N_id_2(&q->pss, q->N_id_2);
peak_pos = srslte_pss_synch_find_pss(&q->pss, &input[find_offset], &q->peak_value);
if (peak_pos < 0) {
fprintf(stderr, "Error calling finding PSS sequence\n");
return SRSLTE_ERROR;
}
q->mean_peak_value = SRSLTE_VEC_EMA(q->peak_value, q->mean_peak_value, MEANPEAK_EMA_ALPHA);
if (peak_position) {
*peak_position = (uint32_t) peak_pos;
}
/* If peak is over threshold, compute CFO and SSS */
if (q->peak_value >= q->threshold) {
// Make sure we have enough space to estimate CFO
if (peak_pos + find_offset >= q->fft_size) {
float cfo = srslte_pss_synch_cfo_compute(&q->pss, &input[find_offset+peak_pos-q->fft_size]);
/* compute cumulative moving average CFO */
q->mean_cfo = SRSLTE_VEC_EMA(cfo, q->mean_cfo, CFO_EMA_ALPHA);
} else {
DEBUG("No space for CFO computation. Frame starts at \n",peak_pos);
}
/* Correct CFO with the averaged CFO estimation */
if (q->correct_cfo) {
srslte_cfo_correct(&q->cfocorr, input, input, -q->mean_cfo / q->fft_size);
}
// Try to detect SSS
if (q->sss_en) {
// Set an invalid N_id_1 indicating SSS is yet to be detected
q->N_id_1 = 1000;
if (sync_sss(q, input, find_offset + peak_pos, q->cp) < 0) {
DEBUG("No space for SSS processing. Frame starts at %d\n", peak_pos);
}
}
if (q->detect_cp) {
if (peak_pos + find_offset >= 2*(q->fft_size + SRSLTE_CP_LEN_EXT(q->fft_size))) {
q->cp = srslte_sync_detect_cp(q, input, peak_pos + find_offset);
} else {
DEBUG("Not enough room to detect CP length. Peak position: %d\n", peak_pos);
}
}
// Return 1 (peak detected) even if we couldn't estimate CFO and SSS
ret = 1;
} else {
ret = 0;
}
DEBUG("SYNC ret=%d N_id_2=%d find_offset=%d pos=%d peak=%.2f threshold=%.2f sf_idx=%d, CFO=%.3f KHz\n",
ret, q->N_id_2, find_offset, peak_pos, q->peak_value, q->threshold, q->sf_idx, 15*q->mean_cfo);
} else if (srslte_N_id_2_isvalid(q->N_id_2)) {
fprintf(stderr, "Must call srslte_sync_set_N_id_2() first!\n");
}
return ret;
}
/** Finds the PSS sequence previously defined by a call to srslte_sync_set_N_id_2()
* around the position find_offset in the buffer input.
*
* Returns 1 if the correlation peak exceeds the threshold set by srslte_sync_set_threshold()
* or 0 otherwise. Returns a negative number on error (if N_id_2 has not been set)
*
* The input signal is not modified. Any CFO correction is done in internal buffers
*
* The maximum of the correlation peak is always stored in *peak_position
*/
srslte_sync_find_ret_t srslte_sync_find(srslte_sync_t *q, const cf_t *input, uint32_t find_offset, uint32_t *peak_position)
{
srslte_sync_find_ret_t ret = SRSLTE_SYNC_ERROR;
int peak_pos = 0;
if (!q) {
return SRSLTE_ERROR_INVALID_INPUTS;
}
if (input != NULL &&
srslte_N_id_2_isvalid(q->N_id_2) &&
fft_size_isvalid(q->fft_size))
{
if (peak_position) {
*peak_position = 0;
}
const cf_t *input_ptr = input;
/* First CFO estimation stage is integer.
* Finds max PSS correlation for shifted +1/0/-1 integer versions.
* This should only used once N_id_2 is set
*/
if (q->cfo_i_enable) {
if (cfo_i_estimate(q, input_ptr, find_offset, &peak_pos, &q->cfo_i_value) < 0) {
fprintf(stderr, "Error calling finding PSS sequence at : %d \n", peak_pos);
return SRSLTE_ERROR;
}
// Correct it using precomputed signal and store in buffer (don't modify input signal)
if (q->cfo_i_value != 0) {
srslte_vec_prod_ccc((cf_t*) input_ptr, q->cfo_i_corr[q->cfo_i_value<0?0:1], q->temp, q->frame_size);
INFO("Compensating cfo_i=%d\n", q->cfo_i_value);
input_ptr = q->temp;
}
}
/* Second stage is coarse fractional CFO estimation using CP.
* In case of multi-cell, this can lead to incorrect estimations if CFO from different cells is different
*/
if (q->cfo_cp_enable) {
float cfo_cp = cfo_cp_estimate(q, input_ptr);
if (!q->cfo_cp_is_set) {
q->cfo_cp_mean = cfo_cp;
q->cfo_cp_is_set = true;
} else {
/* compute exponential moving average CFO */
q->cfo_cp_mean = SRSLTE_VEC_EMA(cfo_cp, q->cfo_cp_mean, q->cfo_ema_alpha);
}
INFO("CP-CFO: estimated=%f, mean=%f\n", cfo_cp, q->cfo_cp_mean);
/* Correct CFO with the averaged CFO estimation */
srslte_cfo_correct(&q->cfo_corr_frame, input_ptr, q->temp, -q->cfo_cp_mean / q->fft_size);
input_ptr = q->temp;
}
/* Find maximum of PSS correlation. If Integer CFO is enabled, correlation is already done
*/
if (!q->cfo_i_enable) {
srslte_pss_set_N_id_2(&q->pss, q->N_id_2);
peak_pos = srslte_pss_find_pss(&q->pss, &input_ptr[find_offset], q->threshold>0?&q->peak_value:NULL);
if (peak_pos < 0) {
fprintf(stderr, "Error calling finding PSS sequence at : %d \n", peak_pos);
return SRSLTE_ERROR;
}
}
INFO("PSS: id=%d, peak_pos=%d, peak_value=%f\n", q->N_id_2, peak_pos, q->peak_value);
// Save peak position
if (peak_position) {
*peak_position = (uint32_t) peak_pos;
}
// In case of decimation, this compensates for the constant time shift caused by the low pass filter
if(q->decimate && peak_pos < 0) {
peak_pos = 0 ;//peak_pos + q->decimate*(2);// replace 2 with q->filter_size -2;
}
/* If peak is over threshold, compute CFO and SSS */
if (q->peak_value >= q->threshold || q->threshold == 0) {
if (q->cfo_pss_enable && peak_pos >= q->fft_size) {
// Filter central bands before PSS-based CFO estimation
const cf_t *pss_ptr = &input_ptr[find_offset + peak_pos - q->fft_size];
if (q->pss_filtering_enabled) {
srslte_pss_filter(&q->pss, pss_ptr, q->pss_filt);
pss_ptr = q->pss_filt;
}
// PSS-based CFO estimation
q->cfo_pss = srslte_pss_cfo_compute(&q->pss, pss_ptr);
if (!q->cfo_pss_is_set) {
q->cfo_pss_mean = q->cfo_pss;
q->cfo_pss_is_set = true;
} else if (15000*fabsf(q->cfo_pss) < MAX_CFO_PSS_OFFSET) {
q->cfo_pss_mean = SRSLTE_VEC_EMA(q->cfo_pss, q->cfo_pss_mean, q->cfo_ema_alpha);
}
INFO("PSS-CFO: filter=%s, estimated=%f, mean=%f\n",
q->pss_filtering_enabled?"yes":"no", q->cfo_pss, q->cfo_pss_mean);
}
// If there is enough space for CP and SSS estimation
if (peak_pos + find_offset >= 2 * (q->fft_size + SRSLTE_CP_LEN_EXT(q->fft_size))) {
// If SSS search is enabled, correlate SSS sequence
if (q->sss_en) {
// Set an invalid N_id_1 indicating SSS is yet to be detected
q->N_id_1 = 1000;
int sss_idx = find_offset + peak_pos - 2 * q->fft_size -
SRSLTE_CP_LEN(q->fft_size, (SRSLTE_CP_ISNORM(q->cp) ? SRSLTE_CP_NORM_LEN : SRSLTE_CP_EXT_LEN));
const cf_t *sss_ptr = &input_ptr[sss_idx];
// Correct CFO if detected in PSS
if (q->cfo_pss_enable) {
srslte_cfo_correct(&q->cfo_corr_symbol, sss_ptr, q->sss_filt, -q->cfo_pss_mean / q->fft_size);
// Equalize channel if estimated in PSS
if (q->sss_channel_equalize && q->pss.chest_on_filter && q->pss_filtering_enabled) {
srslte_vec_prod_ccc(&q->sss_filt[q->fft_size/2-SRSLTE_PSS_LEN/2], q->pss.tmp_ce,
&q->sss_filt[q->fft_size/2-SRSLTE_PSS_LEN/2], SRSLTE_PSS_LEN);
}
sss_ptr = q->sss_filt;
}
if (sync_sss_symbol(q, sss_ptr) < 0) {
fprintf(stderr, "Error correlating SSS\n");
return -1;
}
}
// Detect CP length
if (q->detect_cp) {
srslte_sync_set_cp(q, srslte_sync_detect_cp(q, input_ptr, peak_pos + find_offset));
} else {
DEBUG("Not enough room to detect CP length. Peak position: %d\n", peak_pos);
}
ret = SRSLTE_SYNC_FOUND;
} else {
ret = SRSLTE_SYNC_FOUND_NOSPACE;
}
} else {
ret = SRSLTE_SYNC_NOFOUND;
}
DEBUG("SYNC ret=%d N_id_2=%d find_offset=%d frame_len=%d, pos=%d peak=%.2f threshold=%.2f sf_idx=%d, CFO=%.3f kHz\n",
ret, q->N_id_2, find_offset, q->frame_size, peak_pos, q->peak_value,
q->threshold, q->sf_idx, 15*(srslte_sync_get_cfo(q)));
} else if (srslte_N_id_2_isvalid(q->N_id_2)) {
fprintf(stderr, "Must call srslte_sync_set_N_id_2() first!\n");
}
return ret;
}
