/** * * \section COPYRIGHT * * Copyright 2013-2015 Software Radio Systems Limited * * \section LICENSE * * This file is part of the srsLTE library. * * srsLTE is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License as * published by the Free Software Foundation, either version 3 of * the License, or (at your option) any later version. * * srsLTE is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Affero General Public License for more details. * * A copy of the GNU Affero General Public License can be found in * the LICENSE file in the top-level directory of this distribution * and at http://www.gnu.org/licenses/. * */ #include #include #include #include #include #include #include "srslte/config.h" #include "srslte/dft/dft_precoding.h" #include "srslte/ch_estimation/chest_ul.h" #include "srslte/utils/vector.h" #include "srslte/utils/convolution.h" #define NOF_REFS_SYM (q->cell.nof_prb*SRSLTE_NRE) #define NOF_REFS_SF (NOF_REFS_SYM*2) // 2 reference symbols per subframe /** 3GPP LTE Downlink channel estimator and equalizer. * Estimates the channel in the resource elements transmitting references and interpolates for the rest * of the resource grid. * * The equalizer uses the channel estimates to produce an estimation of the transmitted symbol. * * This object depends on the srslte_refsignal_t object for creating the LTE CSR signal. */ int srslte_chest_ul_init(srslte_chest_ul_t *q, srslte_cell_t cell) { int ret = SRSLTE_ERROR_INVALID_INPUTS; if (q != NULL && srslte_cell_isvalid(&cell)) { bzero(q, sizeof(srslte_chest_ul_t)); q->cell = cell; ret = srslte_refsignal_ul_init(&q->dmrs_signal, cell); if (ret != SRSLTE_SUCCESS) { fprintf(stderr, "Error initializing CSR signal (%d)\n",ret); goto clean_exit; } q->tmp_noise = srslte_vec_malloc(sizeof(cf_t) * NOF_REFS_SF); if (!q->tmp_noise) { perror("malloc"); goto clean_exit; } q->pilot_estimates = srslte_vec_malloc(sizeof(cf_t) * NOF_REFS_SF); if (!q->pilot_estimates) { perror("malloc"); goto clean_exit; } q->pilot_recv_signal = srslte_vec_malloc(sizeof(cf_t) * (NOF_REFS_SF+1)); if (!q->pilot_recv_signal) { perror("malloc"); goto clean_exit; } if (srslte_interp_linear_vector_init(&q->srslte_interp_linvec, NOF_REFS_SYM)) { fprintf(stderr, "Error initializing vector interpolator\n"); goto clean_exit; } q->smooth_filter_len = 3; srslte_chest_ul_set_smooth_filter3_coeff(q, 0.3333); q->dmrs_signal_configured = false; } ret = SRSLTE_SUCCESS; clean_exit: if (ret != SRSLTE_SUCCESS) { srslte_chest_ul_free(q); } return ret; } void srslte_chest_ul_free(srslte_chest_ul_t *q) { if (q->dmrs_signal_configured) { srslte_refsignal_dmrs_pusch_pregen_free(&q->dmrs_signal, &q->dmrs_pregen); } srslte_refsignal_ul_free(&q->dmrs_signal); if (q->tmp_noise) { free(q->tmp_noise); } srslte_interp_linear_vector_free(&q->srslte_interp_linvec); if (q->pilot_estimates) { free(q->pilot_estimates); } if (q->pilot_recv_signal) { free(q->pilot_recv_signal); } bzero(q, sizeof(srslte_chest_ul_t)); } void srslte_chest_ul_set_cfg(srslte_chest_ul_t *q, srslte_refsignal_dmrs_pusch_cfg_t *pusch_cfg, srslte_pucch_cfg_t *pucch_cfg, srslte_refsignal_srs_cfg_t *srs_cfg) { srslte_refsignal_ul_set_cfg(&q->dmrs_signal, pusch_cfg, pucch_cfg, srs_cfg); srslte_refsignal_dmrs_pusch_pregen(&q->dmrs_signal, &q->dmrs_pregen); q->dmrs_signal_configured = true; } /* Uses the difference between the averaged and non-averaged pilot estimates */ static float estimate_noise_pilots(srslte_chest_ul_t *q, cf_t *ce, uint32_t nrefs) { float power = 0; for (int i=0;i<2;i++) { power += srslte_chest_estimate_noise_pilots(&q->pilot_estimates[i*nrefs], &ce[SRSLTE_REFSIGNAL_UL_L(i, q->cell.cp)*q->cell.nof_prb*SRSLTE_NRE], q->tmp_noise, nrefs); } power/=2; if (q->smooth_filter_len == 3) { // Calibrated for filter length 3 float w=q->smooth_filter[0]; float a=7.419*w*w+0.1117*w-0.005387; return (power/(a*0.8)); } else { return power; } } #define cesymb(i) ce[SRSLTE_RE_IDX(q->cell.nof_prb,i,0)] static void interpolate_pilots(srslte_chest_ul_t *q, cf_t *ce, uint32_t nrefs) { uint32_t L1 = SRSLTE_REFSIGNAL_UL_L(0, q->cell.cp); uint32_t L2 = SRSLTE_REFSIGNAL_UL_L(1, q->cell.cp); uint32_t NL = 2*SRSLTE_CP_NSYMB(q->cell.cp); /* Interpolate in the time domain between symbols */ srslte_interp_linear_vector3(&q->srslte_interp_linvec, &cesymb(L2), &cesymb(L1), &cesymb(L1), &cesymb(L1-1), (L2-L1), L1, false, nrefs); srslte_interp_linear_vector3(&q->srslte_interp_linvec, &cesymb(L1), &cesymb(L2), NULL, &cesymb(L1+1), (L2-L1), (L2-L1)-1, true, nrefs); srslte_interp_linear_vector3(&q->srslte_interp_linvec, &cesymb(L1), &cesymb(L2), &cesymb(L2), &cesymb(L2+1), (L2-L1), (NL-L2)-1, true, nrefs); } void srslte_chest_ul_set_smooth_filter(srslte_chest_ul_t *q, float *filter, uint32_t filter_len) { if (filter_len < SRSLTE_CHEST_MAX_SMOOTH_FIL_LEN) { if (filter) { memcpy(q->smooth_filter, filter, filter_len*sizeof(float)); q->smooth_filter_len = filter_len; } else { q->smooth_filter_len = 0; } } else { fprintf(stderr, "Error setting smoothing filter: filter len exceeds maximum (%d>%d)\n", filter_len, SRSLTE_CHEST_MAX_SMOOTH_FIL_LEN); } } void srslte_chest_ul_set_smooth_filter3_coeff(srslte_chest_ul_t* q, float w) { srslte_chest_set_smooth_filter3_coeff(q->smooth_filter, w); q->smooth_filter_len = 3; } static void average_pilots(srslte_chest_ul_t *q, cf_t *input, cf_t *ce, uint32_t nrefs) { for (int i=0;i<2;i++) { srslte_chest_average_pilots(&input[i*nrefs], &ce[SRSLTE_REFSIGNAL_UL_L(i, q->cell.cp)*q->cell.nof_prb*SRSLTE_NRE], q->smooth_filter, nrefs, 1, q->smooth_filter_len); } } 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 (ce != NULL) { if (q->smooth_filter_len > 0) { average_pilots(q, q->pilot_estimates, ce, nrefs_sym); interpolate_pilots(q, ce, nrefs_sym); /* If averaging, compute noise from difference between received and averaged estimates */ q->noise_estimate = estimate_noise_pilots(q, ce, nrefs_sym); } 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], &q->pilot_estimates[i*nrefs_sym], nrefs_sym*sizeof(cf_t)); } interpolate_pilots(q, ce, nrefs_sym); q->noise_estimate = 0; } } // Estimate received pilot power q->pilot_power = srslte_vec_avg_power_cf(q->pilot_recv_signal, nrefs_sf); return 0; } float srslte_chest_ul_get_noise_estimate(srslte_chest_ul_t *q) { return q->noise_estimate; } float srslte_chest_ul_get_snr(srslte_chest_ul_t *q) { return q->pilot_power/srslte_chest_ul_get_noise_estimate(q); }