mirror of https://github.com/PentHertz/srsLTE.git
127 lines
5.4 KiB
C
127 lines
5.4 KiB
C
/*
|
|
* Copyright 2013-2020 Software Radio Systems Limited
|
|
*
|
|
* This file is part of srsLTE.
|
|
*
|
|
* 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/.
|
|
*
|
|
*/
|
|
|
|
/******************************************************************************
|
|
* File: npss.h
|
|
*
|
|
* Description: Narrowband Primary synchronization signal (NPSS) generation and detection.
|
|
*
|
|
* The srslte_npss_synch_t object provides functions for fast
|
|
* computation of the crosscorrelation between the NPSS and received
|
|
* signal and CFO estimation. Also, the function srslte_npss_synch_tperiodic()
|
|
* is designed to be called periodically every subframe, taking
|
|
* care of the correct data alignment with respect to the NPSS sequence.
|
|
*
|
|
* The object is designed to work with signals sampled at ?.? Mhz
|
|
* centered at the carrier frequency. Thus, downsampling is required
|
|
* if the signal is sampled at higher frequencies.
|
|
*
|
|
* Reference: 3GPP TS 36.211 version 13.2.0 Release 13 Sec. 10.x.x
|
|
*****************************************************************************/
|
|
|
|
#ifndef SRSLTE_NPSS_H
|
|
#define SRSLTE_NPSS_H
|
|
|
|
#include <stdbool.h>
|
|
#include <stdint.h>
|
|
|
|
#include "srslte/config.h"
|
|
#include "srslte/phy/common/phy_common.h"
|
|
#include "srslte/phy/utils/convolution.h"
|
|
|
|
#define CONVOLUTION_FFT
|
|
|
|
#define SRSLTE_NPSS_RETURN_PSR
|
|
|
|
#define SRSLTE_NPSS_LEN 11
|
|
#define SRSLTE_NPSS_NUM_OFDM_SYMS 11
|
|
#define SRSLTE_NPSS_TOT_LEN (SRSLTE_NPSS_LEN * SRSLTE_NPSS_NUM_OFDM_SYMS)
|
|
|
|
#define SRSLTE_NPSS_CORR_FILTER_LEN \
|
|
((SRSLTE_NPSS_NUM_OFDM_SYMS * SRSLTE_NBIOT_FFT_SIZE) + \
|
|
(SRSLTE_NPSS_NUM_OFDM_SYMS - 1) * SRSLTE_CP_LEN_NORM(1, SRSLTE_NBIOT_FFT_SIZE) + \
|
|
SRSLTE_CP_LEN_NORM(0, SRSLTE_NBIOT_FFT_SIZE))
|
|
|
|
// The below value corresponds to the time-domain representation of the first
|
|
// three OFDM-symbols plus cyclic prefix that are not transmitted in the sub-frame
|
|
// carrying the NPSS
|
|
#define SRSLTE_NPSS_CORR_OFFSET (SRSLTE_SF_LEN(SRSLTE_NBIOT_FFT_SIZE) - SRSLTE_NPSS_CORR_FILTER_LEN)
|
|
|
|
// CFO estimation based on the NPSS is done using the second slot of the sub-frame
|
|
#define SRSLTE_NPSS_CFO_OFFSET (SRSLTE_SF_LEN(SRSLTE_NBIOT_FFT_SIZE) / 2 - SRSLTE_NPSS_CORR_OFFSET)
|
|
#define SRSLTE_NPSS_CFO_NUM_SYMS 6 // number of symbols for CFO estimation
|
|
#define SRSLTE_NPSS_CFO_NUM_SAMPS \
|
|
((SRSLTE_NPSS_CFO_NUM_SYMS * SRSLTE_NBIOT_FFT_SIZE) + \
|
|
(SRSLTE_NPSS_CFO_NUM_SYMS - 1) * SRSLTE_CP_LEN_NORM(1, SRSLTE_NBIOT_FFT_SIZE) + \
|
|
SRSLTE_CP_LEN_NORM(0, SRSLTE_NBIOT_FFT_SIZE)) // resulting number of samples
|
|
|
|
// NPSS processing options
|
|
#define SRSLTE_NPSS_ACCUMULATE_ABS // If enabled, accumulates the correlation absolute value on consecutive calls to
|
|
// srslte_pss_synch_find_pss
|
|
|
|
#define SRSLTE_NPSS_ABS_SQUARE // If enabled, compute abs square, otherwise computes absolute value only
|
|
|
|
#define SRSLTE_NPSS_RETURN_PSR // If enabled returns peak to side-lobe ratio, otherwise returns absolute peak value
|
|
|
|
/* Low-level API */
|
|
typedef struct SRSLTE_API {
|
|
#ifdef CONVOLUTION_FFT
|
|
srslte_conv_fft_cc_t conv_fft;
|
|
#endif
|
|
|
|
uint32_t frame_size, max_frame_size;
|
|
uint32_t fft_size, max_fft_size;
|
|
|
|
cf_t* npss_signal_time;
|
|
cf_t* tmp_input;
|
|
cf_t* conv_output;
|
|
float* conv_output_abs;
|
|
float ema_alpha;
|
|
float* conv_output_avg;
|
|
float peak_value;
|
|
} srslte_npss_synch_t;
|
|
|
|
// Basic functionality
|
|
SRSLTE_API int srslte_npss_synch_init(srslte_npss_synch_t* q, uint32_t frame_size, uint32_t fft_size);
|
|
|
|
SRSLTE_API void srslte_npss_synch_reset(srslte_npss_synch_t* q);
|
|
|
|
SRSLTE_API int srslte_npss_synch_resize(srslte_npss_synch_t* q, uint32_t frame_size, uint32_t fft_size);
|
|
|
|
SRSLTE_API void srslte_npss_synch_set_ema_alpha(srslte_npss_synch_t* q, float alpha);
|
|
|
|
SRSLTE_API void srslte_npss_synch_free(srslte_npss_synch_t* q);
|
|
|
|
SRSLTE_API int srslte_npss_sync_find(srslte_npss_synch_t* q, cf_t* input, float* corr_peak_value);
|
|
|
|
// Internal functions
|
|
SRSLTE_API int srslte_npss_corr_init(cf_t* npss_signal_time, uint32_t fft_size, uint32_t frame_size);
|
|
|
|
SRSLTE_API int srslte_npss_generate(cf_t* signal);
|
|
|
|
SRSLTE_API void srslte_npss_put_subframe(srslte_npss_synch_t* q,
|
|
cf_t* npss_signal,
|
|
cf_t* sf,
|
|
const uint32_t nof_prb,
|
|
const uint32_t nbiot_prb_offset);
|
|
|
|
#endif // SRSLTE_NPSS_H
|