mirror of https://github.com/gnss-sdr/gnss-sdr
115 lines
4.7 KiB
C
115 lines
4.7 KiB
C
/*!
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* \file lock_detectors.h
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* \brief Interface of a library with a set of code and carrier phase lock detectors.
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*
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* SNV_CN0 is a Carrier-to-Noise (CN0) estimator
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* based on the Signal-to-Noise Variance (SNV) estimator [1].
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* Carrier lock detector using normalised estimate of the cosine
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* of twice the carrier phase error [2].
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*
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* [1] Marco Pini, Emanuela Falletti and Maurizio Fantino, "Performance
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* Evaluation of C/N0 Estimators using a Real Time GNSS Software Receiver,"
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* IEEE 10th International Symposium on Spread Spectrum Techniques and
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* Applications, pp.28-30, August 2008.
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*
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* [2] Van Dierendonck, A.J. (1996), Global Positioning System: Theory and
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* Applications,
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* Volume I, Chapter 8: GPS Receivers, AJ Systems, Los Altos, CA 94024.
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* Inc.: 329-407.
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* \authors <ul>
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* <li> Javier Arribas, 2011. jarribas(at)cttc.es
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* <li> Luis Esteve, 2012. luis(at)epsilon-formacion.com
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* </ul>
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*
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* -----------------------------------------------------------------------------
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*
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* GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
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* This file is part of GNSS-SDR.
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*
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* Copyright (C) 2010-2020 (see AUTHORS file for a list of contributors)
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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* -----------------------------------------------------------------------------
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*/
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#ifndef GNSS_SDR_LOCK_DETECTORS_H
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#define GNSS_SDR_LOCK_DETECTORS_H
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#include <gnuradio/gr_complex.h>
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/** \addtogroup Tracking
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* \{ */
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/** \addtogroup Tracking_libs
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* \{ */
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/*! \brief cn0_svn_estimator is a Carrier-to-Noise (CN0) estimator
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* based on the Signal-to-Noise Variance (SNV) estimator
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*
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* Signal-to-Noise (SNR) (\f$ \rho \f$) estimator using the Signal-to-Noise Variance (SNV) estimator:
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* \f{equation}
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* \hat{\rho}=\frac{\hat{P}_s}{\hat{P}_n}=\frac{\hat{P}_s}{\hat{P}_{tot}-\hat{P}_s},
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* \f}
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* where \f$ \hat{P}_s=\left(\frac{1}{N}\sum^{N-1}_{i=0}|Re(Pc(i))|\right)^2 \f$ is the estimation of the signal power,
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* \f$ \hat{P}_{tot}=\frac{1}{N}\sum^{N-1}_{i=0}|Pc(i)|^2 \f$ is the estimator of the total power, \f$ |\cdot| \f$ is the absolute value,
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* \f$ Re(\cdot) \f$ stands for the real part of the value, and \f$ Pc(i) \f$ is the prompt correlator output for the sample index i.
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*
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* The SNR value is converted to CN0 [dB-Hz], taking into account the coherent integration time, using the following formula:
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* \f{equation}
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* CN0_{dB}=10*log(\hat{\rho})-10*log(T_{int}),
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* \f}
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* where \f$ T_{int} \f$ is the coherent integration time, in seconds.
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*
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* Ref: Marco Pini, Emanuela Falletti and Maurizio Fantino, "Performance
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* Evaluation of C/N0 Estimators using a Real Time GNSS Software Receiver,"
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* IEEE 10th International Symposium on Spread Spectrum Techniques and
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* Applications, pp.28-30, August 2008.
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*/
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float cn0_svn_estimator(const gr_complex* Prompt_buffer, int length, float coh_integration_time_s);
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/*! \brief cn0_m2m4_estimator is a Carrier-to-Noise (CN0) estimator
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* based on the Second- and Fourth-Order Moments Method (M2M4)
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*
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* Signal-to-Noise (SNR) (\f$ \rho \f$) estimator using the Moments Method:
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* \f{equation}
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* \hat{\rho}=\frac{\sqrt{2 \hat{M}_2^2 - \hat{M}_4 }}{\hat{M}_2-\sqrt{2 \hat{M}_2^2 - \hat{M}_4 }},
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* \f}
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* where
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* \f$ \hat{M}_2=\frac{1}{N}\sum^{K-1}_{k=0}|P[k]|^2 \f$, \f$ \hat{M}_4 = \frac{1}{K}\sum^{K-1}_{k=0}|P[k]|^4 \f$, \f$ |\cdot| \f$ is the absolute value,
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* and \f$ P[k] \f$ is the prompt correlator output for the sample index k.
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*
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* The SNR value is converted to CN0 [dB-Hz] taking into account the coherent integration time, using the following formula:
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* \f{equation}
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* CN0_{dB}=10*log(\hat{\rho})-10*log(T_{int}),
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* \f}
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* where \f$ T_{int} \f$ is the coherent integration time, in seconds.
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*
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* Ref: D. R. Pauluzzi, N. C. Beaulieu, "A comparison of SNR estimation
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* techniques for the AWGN channel," IEEE Trans. on Comm., vol. 48,
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* no. 10, pp. 1681–1691, Oct. 2000.
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*/
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float cn0_m2m4_estimator(const gr_complex* Prompt_buffer, int length, float coh_integration_time_s);
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/*! \brief A carrier lock detector
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*
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* The Carrier Phase Lock Detector block uses the estimate of the cosine of twice the carrier phase error is given by
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* \f{equation}
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* C2\phi=\frac{NBD}{NBP},
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* \f}
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* where \f$ NBD=(\sum^{N-1}_{i=0}|Im(Pc(i))|)^2+(\sum^{N-1}_{i=0}|Re(Pc(i))|)^2 \f$,
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* \f$ NBP=\sum^{N-1}_{i=0}Im(Pc(i))^2-\sum^{N-1}_{i=0}Re(Pc(i))^2 \f$, and
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* \f$ Pc(i) \f$ is the prompt correlator output for the sample index i.
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* Ref: Van Dierendonck, A.J. (1996), Global Positioning System: Theory and
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* Applications,
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* Volume I, Chapter 8: GPS Receivers, AJ Systems, Los Altos, CA 94024.
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* Inc.: 329-407.
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*/
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float carrier_lock_detector(gr_complex* Prompt_buffer, int length);
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/** \} */
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/** \} */
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#endif // GNSS_SDR_LOCK_DETECTORS_H
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