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Cell RS based CFO estimation

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This commit is contained in:
Ismael Gomez 2017-11-29 11:30:10 +01:00
parent 15a1304395
commit 2fd2f15157
2 changed files with 47 additions and 6 deletions
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10
lib/include/srslte/phy/ch_estimation/chest_dl.h
View file

@ -82,7 +82,11 @@ typedef struct {
float rssi[SRSLTE_MAX_PORTS][SRSLTE_MAX_PORTS];
float rsrp[SRSLTE_MAX_PORTS][SRSLTE_MAX_PORTS];
float noise_estimate[SRSLTE_MAX_PORTS][SRSLTE_MAX_PORTS];
float cfo;
bool cfo_estimate_enable;
uint32_t cfo_estimate_sf_mask;
/* Use PSS for noise estimation in LS linear interpolation mode */
cf_t pss_signal[SRSLTE_PSS_LEN];
cf_t tmp_pss[SRSLTE_PSS_LEN];
@ -144,8 +148,12 @@ SRSLTE_API int srslte_chest_dl_estimate_port(srslte_chest_dl_t *q,
uint32_t port_id,
uint32_t rxant_id);
SRSLTE_API void srslte_chest_dl_cfo_estimate_enable(srslte_chest_dl_t *q, bool enable, uint32_t mask);
SRSLTE_API float srslte_chest_dl_get_noise_estimate(srslte_chest_dl_t *q);
SRSLTE_API float srslte_chest_dl_get_cfo(srslte_chest_dl_t *q);
SRSLTE_API float srslte_chest_dl_get_snr(srslte_chest_dl_t *q);
SRSLTE_API float srslte_chest_dl_get_rssi(srslte_chest_dl_t *q);

43
lib/src/phy/ch_estimation/chest_dl.c
View file

@ -410,6 +410,30 @@ float srslte_chest_dl_rssi(srslte_chest_dl_t *q, cf_t *input, uint32_t port_id)
return rssi/nsymbols;
}
// CFO estimation algorithm taken from "Carrier Frequency Synchronization in the
// Downlink of 3GPP LTE", Qi Wang, C. Mehlfuhrer, M. Rupp
float chest_estimate_cfo(srslte_chest_dl_t *q)
{
float n = (float) srslte_symbol_sz(q->cell.nof_prb);
float ns = (float) SRSLTE_CP_NSYMB(q->cell.cp);
float ng = (float) SRSLTE_CP_LEN_NORM(1, n);
uint32_t npilots = SRSLTE_REFSIGNAL_NUM_SF(q->cell.nof_prb, 0);
// Compute angles between slots
for (int i=0;i<2;i++) {
srslte_vec_prod_conj_ccc(&q->pilot_estimates[i*npilots/4],
&q->pilot_estimates[(i+2)*npilots/4],
&q->tmp_noise[i*npilots/4],
npilots/4);
}
// Average all angles
cf_t sum = srslte_vec_acc_cc(q->tmp_noise, npilots/2);
// Compute CFO
return -cargf(sum)*n/(ns*(n+ng))/2/M_PI;
}
void chest_interpolate_noise_est(srslte_chest_dl_t *q, cf_t *input, cf_t *ce, uint32_t sf_idx, uint32_t port_id, uint32_t rxant_id, srslte_sf_t ch_mode){
if (ce != NULL) {
/* Smooth estimates (if applicable) and interpolate */
@ -433,6 +457,10 @@ void chest_interpolate_noise_est(srslte_chest_dl_t *q, cf_t *input, cf_t *ce, ui
}
}
}
if (q->cfo_estimate_enable && ((1<<sf_idx) & q->cfo_estimate_sf_mask)) {
q->cfo = chest_estimate_cfo(q);
}
/* Compute RSRP for the channel estimates in this port */
q->rsrp[rxant_id][port_id] = srslte_vec_avg_power_cf(q->pilot_recv_signal, SRSLTE_REFSIGNAL_NUM_SF(q->cell.nof_prb, port_id));
@ -451,8 +479,9 @@ int srslte_chest_dl_estimate_port(srslte_chest_dl_t *q, cf_t *input, cf_t *ce, u
srslte_vec_prod_conj_ccc(q->pilot_recv_signal, q->csr_refs.pilots[port_id/2][sf_idx],
q->pilot_estimates, SRSLTE_REFSIGNAL_NUM_SF(q->cell.nof_prb, port_id));
chest_interpolate_noise_est(q, input, ce, sf_idx, port_id, rxant_id, SRSLTE_SF_NORM);
return 0;
}
int srslte_chest_dl_estimate_port_mbsfn(srslte_chest_dl_t *q, cf_t *input, cf_t *ce, uint32_t sf_idx, uint32_t port_id, uint32_t rxant_id, uint16_t mbsfn_area_id)
@ -474,10 +503,6 @@ int srslte_chest_dl_estimate_port_mbsfn(srslte_chest_dl_t *q, cf_t *input, cf_t
return 0;
}
int srslte_chest_dl_estimate_multi(srslte_chest_dl_t *q, cf_t *input[SRSLTE_MAX_PORTS], cf_t *ce[SRSLTE_MAX_PORTS][SRSLTE_MAX_PORTS], uint32_t sf_idx, uint32_t nof_rx_antennas)
{
for (uint32_t rxant_id=0;rxant_id<nof_rx_antennas;rxant_id++) {
@ -517,7 +542,15 @@ int srslte_chest_dl_estimate_multi_mbsfn(srslte_chest_dl_t *q, cf_t *input[SRSLT
return SRSLTE_SUCCESS;
}
void srslte_chest_dl_cfo_estimate_enable(srslte_chest_dl_t *q, bool enable, uint32_t mask)
{
q->cfo_estimate_enable = enable;
q->cfo_estimate_sf_mask = mask;
}
float srslte_chest_dl_get_cfo(srslte_chest_dl_t *q) {
return q->cfo;
}
float srslte_chest_dl_get_noise_estimate(srslte_chest_dl_t *q) {
float n = 0;