diff options
| -rw-r--r-- | docs/doxygen/other/group_defs.dox | 1 | ||||
| -rw-r--r-- | gr-digital/include/digital_impl_mpsk_snr_est.h | 194 | ||||
| -rw-r--r-- | gr-digital/include/digital_mpsk_snr_est_cc.h | 30 | ||||
| -rw-r--r-- | gr-digital/include/digital_probe_mpsk_snr_est_c.h | 27 | ||||
| -rw-r--r-- | gr-digital/swig/digital_mpsk_snr_est_cc.i | 6 | ||||
| -rw-r--r-- | gr-digital/swig/digital_probe_mpsk_snr_est_c.i | 2 |
6 files changed, 189 insertions, 71 deletions
diff --git a/docs/doxygen/other/group_defs.dox b/docs/doxygen/other/group_defs.dox index 6288d1f0a..facdc2338 100644 --- a/docs/doxygen/other/group_defs.dox +++ b/docs/doxygen/other/group_defs.dox @@ -32,6 +32,7 @@ /*! \defgroup uhd_blk UHD Interface */ /*! \defgroup audio_blk Audio Interface */ /*! \defgroup pfb_blk Polyphase Filterbank */ +/*! \defgroup snr_blk SNR estimators */ /*! * \defgroup base_blk Base classes for GR Blocks diff --git a/gr-digital/include/digital_impl_mpsk_snr_est.h b/gr-digital/include/digital_impl_mpsk_snr_est.h index e530782bc..5a85d100b 100644 --- a/gr-digital/include/digital_impl_mpsk_snr_est.h +++ b/gr-digital/include/digital_impl_mpsk_snr_est.h @@ -25,6 +25,19 @@ #include <digital_api.h> #include <gr_sync_block.h> +//! Enum for the type of SNR estimator to select +/*! \ingroup snr_blk + * \anchor ref_snr_est_types + * + * Below are some ROUGH estimates of what values of SNR each of these + * types of estimators is good for. In general, these offer a + * trade-off between accuracy and performance. + * + * \li SNR_EST_SIMPLE: Simple estimator (>= 7 dB) + * \li SNR_EST_SKEW: Skewness-base est (>= 5 dB) + * \li SNR_EST_M2M4: 2nd & 4th moment est (>= 1 dB) + * \li SNR_EST_SVR: SVR-based est (>= 0dB) +*/ enum snr_est_type_t { SNR_EST_SIMPLE = 0, // Simple estimator (>= 7 dB) SNR_EST_SKEW, // Skewness-base est (>= 5 dB) @@ -32,8 +45,9 @@ enum snr_est_type_t { SNR_EST_SVR // SVR-based est (>= 0dB) }; -/*! - * Parent class for SNR Estimators +/*! \brief A parent class for SNR estimators, specifically for M-PSK + * signals in AWGN channels. + * \ingroup snr_blk */ class DIGITAL_API digital_impl_mpsk_snr_est { @@ -41,6 +55,12 @@ class DIGITAL_API digital_impl_mpsk_snr_est double d_alpha, d_beta; public: + /*! Constructor + * + * Parameters: + * \li \p alpha: the update rate of internal running average + * calculations. + */ digital_impl_mpsk_snr_est(double alpha); virtual ~digital_impl_mpsk_snr_est(); @@ -59,6 +79,14 @@ class DIGITAL_API digital_impl_mpsk_snr_est }; +//! \brief SNR Estimator using simple mean/variance estimates. +/*! \ingroup snr_blk + * + * A very simple SNR estimator that just uses mean and variance + * estimates of an M-PSK constellation. This esimator is quick and + * cheap and accurate for high SNR (above 7 dB or so) but quickly + * starts to overestimate the SNR at low SNR. + */ class DIGITAL_API digital_impl_mpsk_snr_est_simple : public digital_impl_mpsk_snr_est { @@ -66,6 +94,12 @@ class DIGITAL_API digital_impl_mpsk_snr_est_simple : double d_y1, d_y2; public: + /*! Constructor + * + * Parameters: + * \li \p alpha: the update rate of internal running average + * calculations. + */ digital_impl_mpsk_snr_est_simple(double alpha); ~digital_impl_mpsk_snr_est_simple() {} @@ -75,6 +109,16 @@ class DIGITAL_API digital_impl_mpsk_snr_est_simple : }; +//! \brief SNR Estimator using skewness correction. +/*! \ingroup snr_blk + * + * This is an estimator that came from a discussion between Tom + * Rondeau and fred harris with no known paper reference. The idea is + * that at low SNR, the variance estimations will be affected because + * of fold-over around the decision boundaries, which results in a + * skewness to the samples. We estimate the skewness and use this as + * a correcting term. + */ class DIGITAL_API digital_impl_mpsk_snr_est_skew : public digital_impl_mpsk_snr_est { @@ -82,6 +126,12 @@ class DIGITAL_API digital_impl_mpsk_snr_est_skew : double d_y1, d_y2, d_y3; public: + /*! Constructor + * + * Parameters: + * \li \p alpha: the update rate of internal running average + * calculations. + */ digital_impl_mpsk_snr_est_skew(double alpha); ~digital_impl_mpsk_snr_est_skew() {} @@ -91,6 +141,22 @@ class DIGITAL_API digital_impl_mpsk_snr_est_skew : }; +//! \brief SNR Estimator using 2nd and 4th-order moments. +/*! \ingroup snr_blk + * + * An SNR estimator for M-PSK signals that uses 2nd (M2) and 4th (M4) + * order moments. This estimator uses knowledge of the kurtosis of + * the signal (k_a) and noise (k_w) to make its estimation. We use + * Beaulieu's approximations here to M-PSK signals and AWGN channels + * such that k_a=1 and k_w=2. These approximations significantly + * reduce the complexity of the calculations (and computations) + * required. + * + * Reference: + * D. R. Pauluzzi and N. C. Beaulieu, "A comparison of SNR + * estimation techniques for the AWGN channel," IEEE + * Trans. Communications, Vol. 48, No. 10, pp. 1681-1691, 2000. + */ class DIGITAL_API digital_impl_mpsk_snr_est_m2m4 : public digital_impl_mpsk_snr_est { @@ -98,20 +164,11 @@ class DIGITAL_API digital_impl_mpsk_snr_est_m2m4 : double d_y1, d_y2; public: - /*! \brief SNR Estimator using 2nd and 4th-order moments. - * - * An SNR estimator for M-PSK signals that uses 2nd (M2) and 4th - * (M4) order moments. This estimator uses knowledge of the - * kurtosis of the signal (k_a) and noise (k_w) to make its - * estimation. We use Beaulieu's approximations here to M-PSK - * signals and AWGN channels such that k_a=1 and k_w=2. These - * approximations significantly reduce the complexity of the - * calculations (and computations) required. + /*! Constructor * - * Reference: - * D. R. Pauluzzi and N. C. Beaulieu, "A comparison of SNR - * estimation techniques for the AWGN channel," IEEE - * Trans. Communications, Vol. 48, No. 10, pp. 1681-1691, 2000. + * Parameters: + * \li \p alpha: the update rate of internal running average + * calculations. */ digital_impl_mpsk_snr_est_m2m4(double alpha); ~digital_impl_mpsk_snr_est_m2m4() {} @@ -121,6 +178,37 @@ class DIGITAL_API digital_impl_mpsk_snr_est_m2m4 : double snr(); }; + +//! \brief SNR Estimator using 2nd and 4th-order moments. +/*! \ingroup snr_blk + * + * An SNR estimator for M-PSK signals that uses 2nd (M2) and 4th (M4) + * order moments. This estimator uses knowledge of the kurtosis of + * the signal (k_a) and noise (k_w) to make its estimation. In this + * case, you can set your own estimations for k_a and k_w, the + * kurtosis of the signal and noise, to fit this estimation better to + * your signal and channel conditions. + * + * A word of warning: this estimator has not been fully tested or + * proved with any amount of rigor. The estimation for M4 in + * particular might be ignoring effectf of when k_a and k_w are + * different. Use this estimator with caution and a copy of the + * reference on hand. + * + * The digital_mpsk_snr_est_m2m4 assumes k_a and k_w to simplify the + * computations for M-PSK and AWGN channels. Use that estimator + * unless you have a way to guess or estimate these values here. + * + * Original paper: + * R. Matzner, "An SNR estimation algorithm for complex baseband + * signal using higher order statistics," Facta Universitatis + * (Nis), no. 6, pp. 41-52, 1993. + * + * Reference used in derivation: + * D. R. Pauluzzi and N. C. Beaulieu, "A comparison of SNR + * estimation techniques for the AWGN channel," IEEE + * Trans. Communications, Vol. 48, No. 10, pp. 1681-1691, 2000. + */ class DIGITAL_API digital_impl_snr_est_m2m4 : public digital_impl_mpsk_snr_est { @@ -129,34 +217,13 @@ class DIGITAL_API digital_impl_snr_est_m2m4 : double d_ka, d_kw; public: - /*! \brief SNR Estimator using 2nd and 4th-order moments. - * - * An SNR estimator for M-PSK signals that uses 2nd (M2) and 4th - * (M4) order moments. This estimator uses knowledge of the - * kurtosis of the signal (k_a) and noise (k_w) to make its - * estimation. In this case, you can set your own estimations for - * k_a and k_w, the kurtosis of the signal and noise, to fit this - * estimation better to your signal and channel conditions. - * - * A word of warning: this estimator has not been fully tested or - * proved with any amount of rigor. The estimation for M4 in - * particular might be ignoring effectf of when k_a and k_w are - * different. Use this estimator with caution and a copy of the - * reference on hand. - * - * The digital_mpsk_snr_est_m2m4 assumes k_a and k_w to simplify - * the computations for M-PSK and AWGN channels. Use that estimator - * unless you have a way to guess or estimate these values here. + /*! Constructor * - * Original paper: - * R. Matzner, "An SNR estimation algorithm for complex baseband - * signal using higher order statistics," Facta Universitatis - * (Nis), no. 6, pp. 41-52, 1993. - * - * Reference used in derivation: - * D. R. Pauluzzi and N. C. Beaulieu, "A comparison of SNR - * estimation techniques for the AWGN channel," IEEE - * Trans. Communications, Vol. 48, No. 10, pp. 1681-1691, 2000. + * Parameters: + * \li \p alpha: the update rate of internal running average + * calculations. + * \li \p ka: estimate of the signal kurtosis (1 for PSK) + * \li \p kw: estimate of the channel noise kurtosis (2 for AWGN) */ digital_impl_snr_est_m2m4(double alpha, double ka, double kw); ~digital_impl_snr_est_m2m4() {} @@ -167,6 +234,27 @@ class DIGITAL_API digital_impl_snr_est_m2m4 : }; +//! \brief Signal-to-Variation Ratio SNR Estimator. +/*! \ingroup snr_blk + * + * This estimator actually comes from an SNR estimator for M-PSK + * signals in fading channels, but this implementation is + * specifically for AWGN channels. The math was simplified to assume + * a signal and noise kurtosis (k_a and k_w) for M-PSK signals in + * AWGN. These approximations significantly reduce the complexity of + * the calculations (and computations) required. + * + * Original paper: + * A. L. Brandao, L. B. Lopes, and D. C. McLernon, "In-service + * monitoring of multipath delay and cochannel interference for + * indoor mobile communication systems," Proc. IEEE + * Int. Conf. Communications, vol. 3, pp. 1458-1462, May 1994. + * + * Reference: + * D. R. Pauluzzi and N. C. Beaulieu, "A comparison of SNR + * estimation techniques for the AWGN channel," IEEE + * Trans. Communications, Vol. 48, No. 10, pp. 1681-1691, 2000. + */ class DIGITAL_API digital_impl_mpsk_snr_est_svr : public digital_impl_mpsk_snr_est { @@ -174,25 +262,11 @@ class DIGITAL_API digital_impl_mpsk_snr_est_svr : double d_y1, d_y2; public: - /*! \brief Signal-to-Variation Ratio SNR Estimator. - * - * This estimator actually comes from an SNR estimator for M-PSK - * signals in fading channels, but this implementation is - * specifically for AWGN channels. The math was simplified to - * assume a signal and noise kurtosis (k_a and k_w) for M-PSK - * signals in AWGN. These approximations significantly reduce the - * complexity of the calculations (and computations) required. - * - * Original paper: - * A. L. Brandao, L. B. Lopes, and D. C. McLernon, "In-service - * monitoring of multipath delay and cochannel interference for - * indoor mobile communication systems," Proc. IEEE - * Int. Conf. Communications, vol. 3, pp. 1458-1462, May 1994. + /*! Constructor * - * Reference: - * D. R. Pauluzzi and N. C. Beaulieu, "A comparison of SNR - * estimation techniques for the AWGN channel," IEEE - * Trans. Communications, Vol. 48, No. 10, pp. 1681-1691, 2000. + * Parameters: + * \li \p alpha: the update rate of internal running average + * calculations. */ digital_impl_mpsk_snr_est_svr(double alpha); ~digital_impl_mpsk_snr_est_svr() {} diff --git a/gr-digital/include/digital_mpsk_snr_est_cc.h b/gr-digital/include/digital_mpsk_snr_est_cc.h index 126b5f8c9..295c1648b 100644 --- a/gr-digital/include/digital_mpsk_snr_est_cc.h +++ b/gr-digital/include/digital_mpsk_snr_est_cc.h @@ -30,10 +30,24 @@ class digital_mpsk_snr_est_cc; typedef boost::shared_ptr<digital_mpsk_snr_est_cc> digital_mpsk_snr_est_cc_sptr; DIGITAL_API digital_mpsk_snr_est_cc_sptr -digital_make_mpsk_snr_est_cc(snr_est_type_t type, double alpha); +digital_make_mpsk_snr_est_cc(snr_est_type_t type, + double alpha=0.001); -/*! - * Provides various methods to compute SNR. +//! \brief A block for computing SNR of a signal. +/*! \ingroup snr_blk + * + * This block can be used to monitor and retrieve estimations of the + * signal SNR. It is designed to work in a flowgraph and passes all + * incoming data along to its output. + * + * The block is designed for use with M-PSK signals especially. The + * type of estimator is specified as the \p type parameter in the + * constructor. The estimators tend to trade off performance for + * accuracy, although experimentation should be done to figure out + * the right approach for a given implementation. Further, the + * current set of estimators are designed and proven theoretically + * under AWGN conditions; some amount of error should be assumed + * and/or estimated for real channel conditions. */ class DIGITAL_API digital_mpsk_snr_est_cc : public gr_sync_block { @@ -42,7 +56,15 @@ class DIGITAL_API digital_mpsk_snr_est_cc : public gr_sync_block double d_alpha; digital_impl_mpsk_snr_est *d_snr_est; - // Factory function returning shared pointer of this class + /*! Factory function returning shared pointer of this class + * + * Parameters: + * + * \li \p type: the type of estimator to use \ref ref_snr_est_types + * "snr_est_type_t" for details about the available types. + * \li \p alpha: the update rate of internal running average + * calculations. + */ friend DIGITAL_API digital_mpsk_snr_est_cc_sptr digital_make_mpsk_snr_est_cc(snr_est_type_t type, double alpha); diff --git a/gr-digital/include/digital_probe_mpsk_snr_est_c.h b/gr-digital/include/digital_probe_mpsk_snr_est_c.h index 4920a0ae3..2b03765db 100644 --- a/gr-digital/include/digital_probe_mpsk_snr_est_c.h +++ b/gr-digital/include/digital_probe_mpsk_snr_est_c.h @@ -32,8 +32,19 @@ typedef boost::shared_ptr<digital_probe_mpsk_snr_est_c> digital_probe_mpsk_snr_e DIGITAL_API digital_probe_mpsk_snr_est_c_sptr digital_make_probe_mpsk_snr_est_c(snr_est_type_t type, double alpha); -/*! - * Provides various methods to compute SNR. +//! \brief A probe for computing SNR of a signal. +/*! \ingroup snr_blk + * + * This is a probe block (a sink) that can be used to monitor and + * retrieve estimations of the signal SNR. This probe is designed for + * use with M-PSK signals especially. The type of estimator is + * specified as the \p type parameter in the constructor. The + * estimators tend to trade off performance for accuracy, although + * experimentation should be done to figure out the right approach + * for a given implementation. Further, the current set of estimators + * are designed and proven theoretically under AWGN conditions; some + * amount of error should be assumed and/or estimated for real + * channel conditions. */ class DIGITAL_API digital_probe_mpsk_snr_est_c : public gr_sync_block { @@ -42,11 +53,19 @@ class DIGITAL_API digital_probe_mpsk_snr_est_c : public gr_sync_block double d_alpha; digital_impl_mpsk_snr_est *d_snr_est; - // Factory function returning shared pointer of this class + /*! Factory function returning shared pointer of this class + * + * Parameters: + * + * \li \p type: the type of estimator to use \ref ref_snr_est_types + * "snr_est_type_t" for details about the available types. + * \li \p alpha: the update rate of internal running average + * calculations. + */ friend DIGITAL_API digital_probe_mpsk_snr_est_c_sptr digital_make_probe_mpsk_snr_est_c(snr_est_type_t type, double alpha); - // Private constructor + //! Private constructor digital_probe_mpsk_snr_est_c(snr_est_type_t type, double alpha); public: diff --git a/gr-digital/swig/digital_mpsk_snr_est_cc.i b/gr-digital/swig/digital_mpsk_snr_est_cc.i index 42114f372..947c5ab86 100644 --- a/gr-digital/swig/digital_mpsk_snr_est_cc.i +++ b/gr-digital/swig/digital_mpsk_snr_est_cc.i @@ -23,12 +23,14 @@ GR_SWIG_BLOCK_MAGIC(digital,mpsk_snr_est_cc); digital_mpsk_snr_est_cc_sptr -digital_make_mpsk_snr_est_cc(snr_est_type_t type, double alpha); +digital_make_mpsk_snr_est_cc(snr_est_type_t type, + double alpha=0.001); class digital_mpsk_snr_est_cc : public gr_sync_block { private: - void digital_mpsk_snr_est_cc(snr_est_type_t type, double alpha); + void digital_mpsk_snr_est_cc(snr_est_type_t type, + double alpha); public: double snr(); diff --git a/gr-digital/swig/digital_probe_mpsk_snr_est_c.i b/gr-digital/swig/digital_probe_mpsk_snr_est_c.i index fe3684a81..fbe04cec2 100644 --- a/gr-digital/swig/digital_probe_mpsk_snr_est_c.i +++ b/gr-digital/swig/digital_probe_mpsk_snr_est_c.i @@ -24,7 +24,7 @@ GR_SWIG_BLOCK_MAGIC(digital,probe_mpsk_snr_est_c); digital_probe_mpsk_snr_est_c_sptr digital_make_probe_mpsk_snr_est_c(snr_est_type_t type, - double alpha); + double alpha=0.001); class digital_probe_mpsk_snr_est_c : public gr_sync_block { |