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Improve CN0 estimator

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This commit is contained in:
Carles Fernandez
2019-09-16 21:03:04 +02:00
parent 8089c41735
commit 87e106ceac
14 changed files with 83 additions and 13 deletions
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47
src/algorithms/tracking/libs/lock_detectors.cc
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@@ -85,6 +85,53 @@ float cn0_svn_estimator(const gr_complex* Prompt_buffer, int length, float coh_i
}
/*
* Signal-to-Noise (SNR) (\f$\rho\f$) estimator using the Moments Method:
* \f{equation}
* \hat{\rho}=\frac{\hat{P}_s}{\hat{P}_n}=\frac{\sqrt{2*\hat{M}_2^2 - \hat{M}_4 }}{\hat{M}_2-\sqrt{2*\hat{M}_2^2 - \hat{M}_4 }},
* \f}
* 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,
* \f$ \hat{M}_2=\frac{1}{N}\sum^{N-1}_{i=0}|Pc(i)|^2 \f$, \f$\hat{M}_4 = \frac{1}{N}\sum^{N-1}_{i=0}|Pc(i)|^4 \f$, \f$|\cdot|\f$ is the absolute value,
* \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.
*
* The SNR value is converted to CN0 [dB-Hz], taking to account the coherent integration time, using the following formula:
* \f{equation}
* CN0_{dB}=10*log(\hat{\rho})-10*log(T_{int}),
* \f}
* where \f$T_{int}\f$ is the coherent integration time, in seconds.
*
*/
float cn0_mm_estimator(const gr_complex* Prompt_buffer, int length, float coh_integration_time_s)
{
float SNR_aux = 0.0;
float SNR_dB_Hz = 0.0;
float Psig = 0.0;
float m_2 = 0.0;
float m_4 = 0.0;
float aux;
auto n = static_cast<float>(length);
for (int i = 0; i < length; i++)
{
Psig += std::abs(Prompt_buffer[i].real());
aux = Prompt_buffer[i].imag() * Prompt_buffer[i].imag() + Prompt_buffer[i].real() * Prompt_buffer[i].real();
m_2 += aux;
m_4 += (aux * aux);
}
Psig /= n;
Psig = Psig * Psig;
m_2 /= n;
m_4 /= n;
aux = std::sqrt(2.0 * m_2 * m_2 - m_4);
SNR_aux = aux / (m_2 - aux);
SNR_dB_Hz = 10.0 * std::log10(SNR_aux) - 10.0 * std::log10(coh_integration_time_s);
if (std::isnan(SNR_dB_Hz))
{
SNR_dB_Hz = Psig / (m_2 - Psig);
}
return SNR_dB_Hz;
}
/*
* The estimate of the cosine of twice the carrier phase error is given by
* \f{equation}

25
src/algorithms/tracking/libs/lock_detectors.h
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@@ -51,7 +51,7 @@
#include <gnuradio/gr_complex.h>
/*! \brief CN0_SNV is a Carrier-to-Noise (CN0) estimator
/*! \brief cn0_svn_estimator is a Carrier-to-Noise (CN0) estimator
* based on the Signal-to-Noise Variance (SNV) estimator
*
* Signal-to-Noise (SNR) (\f$\rho\f$) estimator using the Signal-to-Noise Variance (SNV) estimator:
@@ -75,6 +75,29 @@
float cn0_svn_estimator(const gr_complex* Prompt_buffer, int length, float coh_integration_time_s);
/*! \brief cn0_mm_estimator is a Carrier-to-Noise (CN0) estimator
* based on the Moments Method (MM)
*
* Signal-to-Noise (SNR) (\f$\rho\f$) estimator using the Moments Method:
* \f{equation}
* \hat{\rho}=\frac{\hat{P}_s}{\hat{P}_n}=\frac{\sqrt{2*\hat{M}_2^2 - \hat{M}_4 }}{\hat{M}_2-\sqrt{2*\hat{M}_2^2 - \hat{M}_4 }},
* \f}
* 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,
* \f$ \hat{M}_2=\frac{1}{N}sum^{N-1}_{i=0}|Pc(i)|^2 \f$, \f$\hat{M}_4 = \frac{1}{N}sum^{N-1}_{i=0}|Pc(i)|^4 \f$, \f$|\cdot|\f$ is the absolute value,
* \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.
*
* The SNR value is converted to CN0 [dB-Hz], taking to account the coherent integration time, using the following formula:
* \f{equation}
* CN0_{dB}=10*log(\hat{\rho})-10*log(T_{int}),
* \f}
* where \f$T_{int}\f$ is the coherent integration time, in seconds.
* Ref: D. R. Pauluzzi, N. C. Beaulieu, "A comparison of SNR estimation
* techniques for the AWGN channel," IEEE Trans. on Comm., vol. 48,
* no. 10, pp. 1681–1691, Oct. 2000.
*/
float cn0_mm_estimator(const gr_complex* Prompt_buffer, int length, float coh_integration_time_s);
/*! \brief A carrier lock detector
*
* The Carrier Phase Lock Detector block uses the estimate of the cosine of twice the carrier phase error is given by