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101 lines
3.0 KiB
C
101 lines
3.0 KiB
C
/*
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* Copyright 2013-2020 Software Radio Systems Limited
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*
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* This file is part of srsLTE.
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*
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* srsLTE is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as
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* published by the Free Software Foundation, either version 3 of
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* the License, or (at your option) any later version.
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*
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* srsLTE is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* A copy of the GNU Affero General Public License can be found in
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* the LICENSE file in the top-level directory of this distribution
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* and at http://www.gnu.org/licenses/.
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*
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*/
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#include <complex.h>
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#include <math.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <strings.h>
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#include "srslte/phy/ch_estimation/chest_common.h"
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#include "srslte/phy/utils/convolution.h"
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#include "srslte/phy/utils/vector.h"
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uint32_t srslte_chest_set_triangle_filter(float* fil, int filter_len)
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{
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for (int i = 0; i < filter_len / 2; i++) {
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fil[i] = i + 1;
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fil[i + filter_len / 2 + 1] = filter_len / 2 - i;
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}
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fil[filter_len / 2] = filter_len / 2 + 1;
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float s = 0;
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for (int i = 0; i < filter_len; i++) {
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s += fil[i];
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}
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for (int i = 0; i < filter_len; i++) {
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fil[i] /= s;
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}
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return filter_len;
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}
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/* Uses the difference between the averaged and non-averaged pilot estimates */
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float srslte_chest_estimate_noise_pilots(cf_t* noisy, cf_t* noiseless, cf_t* noise_vec, uint32_t nof_pilots)
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{
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/* Substract noisy pilot estimates */
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srslte_vec_sub_ccc(noiseless, noisy, noise_vec, nof_pilots);
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/* Compute average power */
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float power = srslte_vec_avg_power_cf(noise_vec, nof_pilots);
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return power;
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}
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uint32_t srslte_chest_set_smooth_filter3_coeff(float* smooth_filter, float w)
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{
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smooth_filter[0] = w;
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smooth_filter[2] = w;
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smooth_filter[1] = 1 - 2 * w;
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return 3;
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}
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uint32_t srslte_chest_set_smooth_filter_gauss(float* filter, uint32_t order, float std_dev)
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{
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const uint32_t filterlen = order + 1;
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const int center = (filterlen - 1) / 2;
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float norm_p = 0.0f;
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if (filterlen) {
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for (int i = 0; i < filterlen; i++) {
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filter[i] = expf(-powf(i - center, 2) / (2.0f * powf(std_dev, 2)));
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norm_p += powf(filter[i], 2);
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}
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const float norm = srslte_vec_acc_ff(filter, filterlen);
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srslte_vec_sc_prod_fff(filter, 1.0f / norm, filter, filterlen);
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}
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return filterlen;
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}
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void srslte_chest_average_pilots(cf_t* input,
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cf_t* output,
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float* filter,
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uint32_t nof_ref,
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uint32_t nof_symbols,
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uint32_t filter_len)
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{
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for (int l = 0; l < nof_symbols; l++) {
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srslte_conv_same_cf(&input[l * nof_ref], filter, &output[l * nof_ref], nof_ref, filter_len);
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}
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}
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