/** * * \section COPYRIGHT * * Copyright 2013-2014 The libLTE Developers. See the * COPYRIGHT file at the top-level directory of this distribution. * * \section LICENSE * * This file is part of the libLTE library. * * libLTE is free software: you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation, either version 3 of * the License, or (at your option) any later version. * * libLTE 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 Lesser General Public License for more details. * * A copy of the GNU Lesser 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 "liblte/phy/sync/pss.h" #include "liblte/phy/utils/dft.h" #include "liblte/phy/utils/vector.h" #include "liblte/phy/utils/convolution.h" #include "liblte/phy/utils/debug.h" int pss_synch_init_N_id_2(cf_t *pss_signal_freq, uint32_t N_id_2, uint32_t fft_size) { dft_plan_t plan; cf_t pss_signal_pad[2048]; cf_t pss_signal_time[PSS_LEN]; int ret = LIBLTE_ERROR_INVALID_INPUTS; if (lte_N_id_2_isvalid(N_id_2) && fft_size <= 2048) { pss_generate(pss_signal_time, N_id_2); bzero(pss_signal_pad, fft_size * sizeof(cf_t)); bzero(pss_signal_freq, fft_size * sizeof(cf_t)); memcpy(&pss_signal_pad[(fft_size-PSS_LEN)/2], pss_signal_time, PSS_LEN * sizeof(cf_t)); if (dft_plan(&plan, fft_size, BACKWARD, COMPLEX)) { return LIBLTE_ERROR; } dft_plan_set_mirror(&plan, true); dft_plan_set_dc(&plan, true); dft_plan_set_norm(&plan, true); dft_run_c(&plan, pss_signal_pad, pss_signal_freq); vec_conj_cc(pss_signal_freq, pss_signal_freq, fft_size); vec_sc_prod_cfc(pss_signal_freq, 1.0/62.0, pss_signal_freq, fft_size); dft_plan_free(&plan); ret = LIBLTE_SUCCESS; } return ret; } /* Initializes the PSS synchronization object with fft_size=128 */ int pss_synch_init(pss_synch_t *q, uint32_t frame_size) { return pss_synch_init_fft(q, frame_size, 128); } /* Initializes the PSS synchronization object. * * It correlates a signal of frame_size samples with the PSS sequence in the frequency * domain. The PSS sequence is transformed using fft_size samples. */ int pss_synch_init_fft(pss_synch_t *q, uint32_t frame_size, uint32_t fft_size) { int ret = LIBLTE_ERROR_INVALID_INPUTS; if (q != NULL) { uint32_t N_id_2; uint32_t buffer_size; bzero(q, sizeof(pss_synch_t)); q->N_id_2 = 10; q->fft_size = fft_size; q->frame_size = frame_size; buffer_size = fft_size + frame_size + 1; q->tmp_input = vec_malloc(buffer_size * sizeof(cf_t)); if (!q->tmp_input) { fprintf(stderr, "Error allocating memory\n"); goto clean_and_exit; } q->conv_output = vec_malloc(buffer_size * sizeof(cf_t)); if (!q->conv_output) { fprintf(stderr, "Error allocating memory\n"); goto clean_and_exit; } for (N_id_2=0;N_id_2<3;N_id_2++) { q->pss_signal_freq[N_id_2] = vec_malloc(buffer_size * sizeof(cf_t)); if (!q->pss_signal_freq[N_id_2]) { fprintf(stderr, "Error allocating memory\n"); goto clean_and_exit; } /* The PSS is translated into the frequency domain for each N_id_2 */ if (pss_synch_init_N_id_2(q->pss_signal_freq[N_id_2], N_id_2, fft_size)) { fprintf(stderr, "Error initiating PSS detector for N_id_2=%d fft_size=%d\n", N_id_2, fft_size); goto clean_and_exit; } } #ifdef CONVOLUTION_FFT if (conv_fft_cc_init(&q->conv_fft, frame_size, fft_size)) { fprintf(stderr, "Error initiating convolution FFT\n"); goto clean_and_exit; } #endif ret = LIBLTE_SUCCESS; } clean_and_exit: if (ret == LIBLTE_ERROR) { pss_synch_free(q); } return ret; } void pss_synch_free(pss_synch_t *q) { uint32_t i; if (q) { for (i=0;i<3;i++) { if (q->pss_signal_freq[i]) { free(q->pss_signal_freq[i]); } } #ifdef CONVOLUTION_FFT conv_fft_cc_free(&q->conv_fft); #endif if (q->tmp_input) { free(q->tmp_input); } if (q->conv_output) { free(q->conv_output); } bzero(q, sizeof(pss_synch_t)); } } /** * This function calculates the Zadoff-Chu sequence. * @param signal Output array. */ int pss_generate(cf_t *signal, uint32_t N_id_2) { int i; float arg; const float root_value[] = { 25.0, 29.0, 34.0 }; int root_idx; int sign = -1; if (N_id_2 > 2) { fprintf(stderr, "Invalid N_id_2 %d\n", N_id_2); return -1; } root_idx = N_id_2; for (i = 0; i < PSS_LEN / 2; i++) { arg = (float) sign * M_PI * root_value[root_idx] * ((float) i * ((float) i + 1.0)) / 63.0; __real__ signal[i] = cosf(arg); __imag__ signal[i] = sinf(arg); } for (i = PSS_LEN / 2; i < PSS_LEN; i++) { arg = (float) sign * M_PI * root_value[root_idx] * (((float) i + 2.0) * ((float) i + 1.0)) / 63.0; __real__ signal[i] = cosf(arg); __imag__ signal[i] = sinf(arg); } return 0; } /** 36.211 10.3 section 6.11.1.2 */ void pss_put_slot(cf_t *pss_signal, cf_t *slot, uint32_t nof_prb, lte_cp_t cp) { int k; k = (CP_NSYMB(cp) - 1) * nof_prb * RE_X_RB + nof_prb * RE_X_RB / 2 - 31; memset(&slot[k - 5], 0, 5 * sizeof(cf_t)); memcpy(&slot[k], pss_signal, PSS_LEN * sizeof(cf_t)); memset(&slot[k + PSS_LEN], 0, 5 * sizeof(cf_t)); } /** Sets the current N_id_2 value. Returns -1 on error, 0 otherwise */ int pss_synch_set_N_id_2(pss_synch_t *q, uint32_t N_id_2) { if (!lte_N_id_2_isvalid((N_id_2))) { fprintf(stderr, "Invalid N_id_2 %d\n", N_id_2); return -1; } else { q->N_id_2 = N_id_2; return 0; } } /** Returns the index of the PSS correlation peak in a subframe. * The frame starts at corr_peak_pos-subframe_size/2. * The value of the correlation is stored in corr_peak_value. * * Input buffer must be subframe_size long. */ int pss_synch_find_pss(pss_synch_t *q, cf_t *input, float *corr_peak_value) { int ret = LIBLTE_ERROR_INVALID_INPUTS; if (q != NULL && input != NULL) { uint32_t corr_peak_pos; uint32_t conv_output_len; if (!lte_N_id_2_isvalid(q->N_id_2)) { fprintf(stderr, "Error finding PSS peak, Must set N_id_2 first\n"); return LIBLTE_ERROR; } bzero(&q->pss_signal_freq[q->N_id_2][q->fft_size], q->frame_size * sizeof(cf_t)); memcpy(q->tmp_input, input, q->frame_size * sizeof(cf_t)); bzero(&q->tmp_input[q->frame_size], q->fft_size * sizeof(cf_t)); /* Correlate input with PSS sequence */ #ifdef CONVOLUTION_FFT conv_output_len = conv_fft_cc_run(&q->conv_fft, q->tmp_input, q->pss_signal_freq[q->N_id_2], q->conv_output); #else conv_output_len = conv_cc(input, q->pss_signal_freq[q->N_id_2], q->conv_output, q->frame_size, q->fft_size); #endif /* Find maximum of the absolute value of the correlation */ corr_peak_pos = vec_max_abs_ci(q->conv_output, conv_output_len-1); if (corr_peak_value) { *corr_peak_value = cabsf(q->conv_output[corr_peak_pos]); } ret = (int) corr_peak_pos; } return ret; } /* Returns the CFO estimation given a PSS received sequence * * Source: An Efficient CFO Estimation Algorithm for the Downlink of 3GPP-LTE * Feng Wang and Yu Zhu */ float pss_synch_cfo_compute(pss_synch_t* q, cf_t *pss_recv) { cf_t y0, y1, yr; y0 = vec_dot_prod_ccc(q->pss_signal_freq[q->N_id_2], pss_recv, q->fft_size/2); y1 = vec_dot_prod_ccc(&q->pss_signal_freq[q->N_id_2][q->fft_size/2], &pss_recv[q->fft_size/2], q->fft_size/2); yr = conjf(y0) * y1; return atan2f(__imag__ yr, __real__ yr) / M_PI; }