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