/* Differential SSS estimation.
* Returns m0 and m1 estimates
*
* Source: "SSS Detection Method for Initial Cell Search in 3GPP LTE FDD/TDD Dual Mode Receiver"
* Jung-In Kim, Jung-Su Han, Hee-Jin Roh and Hyung-Jin Choi
*
*/
int srslte_sss_synch_m0m1_diff_coh(srslte_sss_synch_t *q, cf_t *input, cf_t ce[2*SRSLTE_SSS_N], uint32_t *m0, float *m0_value,
uint32_t *m1, float *m1_value)
{
int ret = SRSLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL &&
m0 != NULL &&
m1 != NULL)
{
cf_t yprod[SRSLTE_SSS_N];
cf_t y[2][SRSLTE_SSS_N];
extract_pair_sss(q, input, ce, y);
srslte_vec_prod_conj_ccc(&y[0][1], y[0], yprod, SRSLTE_SSS_N - 1);
corr_all_zs(yprod, q->fc_tables[q->N_id_2].sd, q->corr_output_m0);
*m0 = srslte_vec_max_fi(q->corr_output_m0, SRSLTE_SSS_N);
if (m0_value) {
*m0_value = q->corr_output_m0[*m0];
}
srslte_vec_prod_cfc(y[1], q->fc_tables[q->N_id_2].z1[*m0], y[1], SRSLTE_SSS_N);
srslte_vec_prod_conj_ccc(&y[1][1], y[1], yprod, SRSLTE_SSS_N - 1);
corr_all_zs(yprod, q->fc_tables[q->N_id_2].sd, q->corr_output_m1);
*m1 = srslte_vec_max_fi(q->corr_output_m1, SRSLTE_SSS_N);
if (m1_value) {
*m1_value = q->corr_output_m1[*m1];
}
ret = SRSLTE_SUCCESS;
}
return ret;
}
/* Complex division is conjugate multiplication + real division */
void srslte_vec_div_ccc(cf_t *x, cf_t *y, float *y_mod, cf_t *z, float *z_real, float *z_imag, uint32_t len) {
#ifdef DIV_USE_VEC
srslte_vec_prod_conj_ccc(x,y,z,len);
srslte_vec_abs_square_cf(y,y_mod,len);
srslte_vec_div_cfc(z,y_mod,z,z_real,z_imag,len);
#else
int i;
for (i=0;i<len;i++) {
z[i] = x[i] / y[i];
}
#endif
}
int srslte_chest_ul_estimate(srslte_chest_ul_t *q, cf_t *input, cf_t *ce,
uint32_t nof_prb, uint32_t sf_idx, uint32_t cyclic_shift_for_dmrs, uint32_t n_prb[2])
{
if (!q->dmrs_signal_configured) {
fprintf(stderr, "Error must call srslte_chest_ul_set_cfg() before using the UL estimator\n");
return SRSLTE_ERROR;
}
if (!srslte_dft_precoding_valid_prb(nof_prb)) {
fprintf(stderr, "Error invalid nof_prb=%d\n", nof_prb);
return SRSLTE_ERROR_INVALID_INPUTS;
}
int nrefs_sym = nof_prb*SRSLTE_NRE;
int nrefs_sf = nrefs_sym*2;
/* Get references from the input signal */
srslte_refsignal_dmrs_pusch_get(&q->dmrs_signal, input, nof_prb, n_prb, q->pilot_recv_signal);
/* Use the known DMRS signal to compute Least-squares estimates */
srslte_vec_prod_conj_ccc(q->pilot_recv_signal, q->dmrs_pregen.r[cyclic_shift_for_dmrs][sf_idx][nof_prb],
q->pilot_estimates, nrefs_sf);
if (n_prb[0] != n_prb[1]) {
printf("ERROR: intra-subframe frequency hopping not supported in the estimator!!\n");
}
if (ce != NULL) {
if (q->smooth_filter_len > 0) {
average_pilots(q, q->pilot_estimates, ce, nrefs_sym, n_prb);
interpolate_pilots(q, ce, nrefs_sym, n_prb);
/* If averaging, compute noise from difference between received and averaged estimates */
q->noise_estimate = estimate_noise_pilots(q, ce, nrefs_sym, n_prb);
} else {
// Copy estimates to CE vector without averaging
for (int i=0;i<2;i++) {
memcpy(&ce[SRSLTE_REFSIGNAL_UL_L(i, q->cell.cp)*q->cell.nof_prb*SRSLTE_NRE+n_prb[i]*SRSLTE_NRE],
&q->pilot_estimates[i*nrefs_sym],
nrefs_sym*sizeof(cf_t));
}
interpolate_pilots(q, ce, nrefs_sym, n_prb);
q->noise_estimate = 0;
}
}
// Estimate received pilot power
q->pilot_power = srslte_vec_avg_power_cf(q->pilot_recv_signal, nrefs_sf);
return 0;
}
// Frequency-domain filtering of the central 64 sub-carriers
void srslte_pss_filter(srslte_pss_t *q, const cf_t *input, cf_t *output)
{
srslte_dft_run_c(&q->dftp_input, input, q->tmp_fft);
memcpy(&q->tmp_fft2[q->fft_size/2-SRSLTE_PSS_LEN/2],
&q->tmp_fft[q->fft_size/2-SRSLTE_PSS_LEN/2],
sizeof(cf_t)*SRSLTE_PSS_LEN);
if (q->chest_on_filter) {
srslte_vec_prod_conj_ccc(&q->tmp_fft[(q->fft_size-SRSLTE_PSS_LEN)/2], q->pss_signal_freq[q->N_id_2], q->tmp_ce, SRSLTE_PSS_LEN);
}
srslte_dft_run_c(&q->idftp_input, q->tmp_fft2, output);
}
static void extract_pair_sss(srslte_sss_synch_t *q, cf_t *input, cf_t *ce, cf_t y[2][SRSLTE_SSS_N]) {
cf_t input_fft[SRSLTE_SYMBOL_SZ_MAX];
srslte_dft_run_c(&q->dftp_input, input, input_fft);
if (ce) {
srslte_vec_prod_conj_ccc(&input_fft[q->fft_size/2-SRSLTE_SSS_N], ce, &input_fft[q->fft_size/2-SRSLTE_SSS_N], 2*SRSLTE_SSS_N);
}
for (int i = 0; i < SRSLTE_SSS_N; i++) {
y[0][i] = input_fft[q->fft_size/2-SRSLTE_SSS_N + 2 * i];
y[1][i] = input_fft[q->fft_size/2-SRSLTE_SSS_N + 2 * i + 1];
}
srslte_vec_prod_cfc(y[0], q->fc_tables[q->N_id_2].c[0], y[0], SRSLTE_SSS_N);
srslte_vec_prod_cfc(y[1], q->fc_tables[q->N_id_2].c[1], y[1], SRSLTE_SSS_N);
}
/* 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;
}
int srslte_chest_ul_estimate_pucch(srslte_chest_ul_t *q, cf_t *input, cf_t *ce,
srslte_pucch_format_t format, uint32_t n_pucch, uint32_t sf_idx,
uint8_t *pucch2_ack_bits)
{
if (!q->dmrs_signal_configured) {
fprintf(stderr, "Error must call srslte_chest_ul_set_cfg() before using the UL estimator\n");
return SRSLTE_ERROR;
}
int n_rs = srslte_refsignal_dmrs_N_rs(format, q->cell.cp);
if (!n_rs) {
fprintf(stderr, "Error computing N_rs\n");
return SRSLTE_ERROR;
}
int nrefs_sf = SRSLTE_NRE*n_rs*2;
/* Get references from the input signal */
srslte_refsignal_dmrs_pucch_get(&q->dmrs_signal, format, n_pucch, input, q->pilot_recv_signal);
/* Generate known pilots */
uint8_t pucch2_bits[2] = {0, 0};
if (format == SRSLTE_PUCCH_FORMAT_2A || format == SRSLTE_PUCCH_FORMAT_2B) {
float max = -1e9;
int i_max = 0;
int m = 0;
if (format == SRSLTE_PUCCH_FORMAT_2A) {
m = 2;
} else {
m = 4;
}
for (int i=0;i<m;i++) {
pucch2_bits[0] = i%2;
pucch2_bits[1] = i/2;
srslte_refsignal_dmrs_pucch_gen(&q->dmrs_signal, format, n_pucch, sf_idx, pucch2_bits, q->pilot_known_signal);
srslte_vec_prod_conj_ccc(q->pilot_recv_signal, q->pilot_known_signal, q->pilot_estimates_tmp[i], nrefs_sf);
float x = cabsf(srslte_vec_acc_cc(q->pilot_estimates_tmp[i], nrefs_sf));
if (x >= max) {
max = x;
i_max = i;
}
}
memcpy(q->pilot_estimates, q->pilot_estimates_tmp[i_max], nrefs_sf*sizeof(cf_t));
pucch2_ack_bits[0] = i_max%2;
pucch2_ack_bits[1] = i_max/2;
} else {
srslte_refsignal_dmrs_pucch_gen(&q->dmrs_signal, format, n_pucch, sf_idx, pucch2_bits, q->pilot_known_signal);
/* Use the known DMRS signal to compute Least-squares estimates */
srslte_vec_prod_conj_ccc(q->pilot_recv_signal, q->pilot_known_signal, q->pilot_estimates, nrefs_sf);
}
if (ce != NULL) {
/* FIXME: Currently averaging entire slot, performance good enough? */
for (int ns=0;ns<2;ns++) {
// Average all slot
for (int i=1;i<n_rs;i++) {
srslte_vec_sum_ccc(&q->pilot_estimates[ns*n_rs*SRSLTE_NRE], &q->pilot_estimates[(i+ns*n_rs)*SRSLTE_NRE],
&q->pilot_estimates[ns*n_rs*SRSLTE_NRE],
SRSLTE_NRE);
}
srslte_vec_sc_prod_ccc(&q->pilot_estimates[ns*n_rs*SRSLTE_NRE], (float) 1.0/n_rs,
&q->pilot_estimates[ns*n_rs*SRSLTE_NRE],
SRSLTE_NRE);
// Average in freq domain
srslte_chest_average_pilots(&q->pilot_estimates[ns*n_rs*SRSLTE_NRE], &q->pilot_recv_signal[ns*n_rs*SRSLTE_NRE],
q->smooth_filter, SRSLTE_NRE, 1, q->smooth_filter_len);
// Determine n_prb
uint32_t n_prb = srslte_pucch_n_prb(&q->dmrs_signal.pucch_cfg, format, n_pucch, q->cell.nof_prb, q->cell.cp, ns);
// copy estimates to slot
for (int i=0;i<SRSLTE_CP_NSYMB(q->cell.cp);i++) {
memcpy(&ce[SRSLTE_RE_IDX(q->cell.nof_prb, i+ns*SRSLTE_CP_NSYMB(q->cell.cp), n_prb*SRSLTE_NRE)],
&q->pilot_recv_signal[ns*n_rs*SRSLTE_NRE], sizeof(cf_t)*SRSLTE_NRE);
}
}
}
return 0;
}
int srslte_prach_detect_offset(srslte_prach_t *p,
uint32_t freq_offset,
cf_t *signal,
uint32_t sig_len,
uint32_t *indices,
float *t_offsets,
float *peak_to_avg,
uint32_t *n_indices)
{
int ret = SRSLTE_ERROR;
if(p != NULL &&
signal != NULL &&
sig_len > 0 &&
indices != NULL)
{
if(sig_len < p->N_ifft_prach){
fprintf(stderr, "srslte_prach_detect: Signal length is %d and should be %d\n", sig_len, p->N_ifft_prach);
return SRSLTE_ERROR_INVALID_INPUTS;
}
// FFT incoming signal
srslte_dft_run(p->fft, signal, p->signal_fft);
*n_indices = 0;
// Extract bins of interest
uint32_t N_rb_ul = srslte_nof_prb(p->N_ifft_ul);
uint32_t k_0 = freq_offset*N_RB_SC - N_rb_ul*N_RB_SC/2 + p->N_ifft_ul/2;
uint32_t K = DELTA_F/DELTA_F_RA;
uint32_t begin = PHI + (K*k_0) + (K/2);
memcpy(p->prach_bins, &p->signal_fft[begin], p->N_zc*sizeof(cf_t));
for(int i=0;i<p->N_roots;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)
{
printf("ncs=%d, nzc=%d, nwins=%d, Nroot=%d, i=%d, j=%d, start=%d, peak_value=%f, peak_offset=%d, tseq=%f\n",
p->N_cs, p->N_zc, n_wins, p->N_roots, i, j, (p->N_zc-(j*p->N_cs))%p->N_zc, p->peak_values[j],
p->peak_offsets[j], p->T_seq*1e6);
memcpy(save_corr, p->corr, p->N_zc*sizeof(float));
if (indices) {
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] = (float) p->peak_offsets[j]*p->T_seq/p->N_zc;
}
(*n_indices)++;
}
}
}
}
ret = SRSLTE_SUCCESS;
}
return ret;
}