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Diffstat (limited to 'gr-digital/include/digital/lms_dd_equalizer_cc.h')
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1 files changed, 101 insertions, 0 deletions
diff --git a/gr-digital/include/digital/lms_dd_equalizer_cc.h b/gr-digital/include/digital/lms_dd_equalizer_cc.h new file mode 100644 index 0000000000..8084396759 --- /dev/null +++ b/gr-digital/include/digital/lms_dd_equalizer_cc.h @@ -0,0 +1,101 @@ +/* -*- c++ -*- */ +/* + * Copyright 2011,2012 Free Software Foundation, Inc. + * + * This file is part of GNU Radio + * + * GNU Radio is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 3, or (at your option) + * any later version. + * + * GNU Radio 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with GNU Radio; see the file COPYING. If not, write to + * the Free Software Foundation, Inc., 51 Franklin Street, + * Boston, MA 02110-1301, USA. + */ + +#ifndef INCLUDED_DIGITAL_LMS_DD_EQUALIZER_CC_H +#define INCLUDED_DIGITAL_LMS_DD_EQUALIZER_CC_H + +#include <digital/api.h> +#include <gr_sync_decimator.h> +#include <digital/constellation.h> + +namespace gr { + namespace digital { + + /*! + * \brief Least-Mean-Square Decision Directed Equalizer (complex in/out) + * \ingroup eq_blk + * \ingroup digital + * + * This block implements an LMS-based decision-directed equalizer. + * It uses a set of weights, w, to correlate against the inputs, + * u, and a decisions is then made from this output. The error in + * the decision is used to update teh weight vector. + * + * y[n] = conj(w[n]) u[n] + * d[n] = decision(y[n]) + * e[n] = d[n] - y[n] + * w[n+1] = w[n] + mu u[n] conj(e[n]) + * + * Where mu is a gain value (between 0 and 1 and usualy small, + * around 0.001 - 0.01. + * + * This block uses the digital_constellation object for making the + * decision from y[n]. Create the constellation object for + * whatever constellation is to be used and pass in the object. + * In Python, you can use something like: + * + * self.constellation = digital.constellation_qpsk() + * + * To create a QPSK constellation (see the digital_constellation + * block for more details as to what constellations are available + * or how to create your own). You then pass the object to this + * block as an sptr, or using "self.constellation.base()". + * + * The theory for this algorithm can be found in Chapter 9 of: + * S. Haykin, Adaptive Filter Theory, Upper Saddle River, NJ: + * Prentice Hall, 1996. + */ + class DIGITAL_API lms_dd_equalizer_cc : + virtual public gr_sync_decimator + { + protected: + virtual gr_complex error(const gr_complex &out) = 0; + virtual void update_tap(gr_complex &tap, const gr_complex &in) = 0; + + public: + // gr::digital::lms_dd_equalizer_cc::sptr + typedef boost::shared_ptr<lms_dd_equalizer_cc> sptr; + + /*! + * Make an LMS decision-directed equalizer + * + * \param num_taps Numer of taps in the equalizer (channel size) + * \param mu Gain of the update loop + * \param sps Number of samples per symbol of the input signal + * \param cnst A constellation derived from class + * 'constellation'. Use base() method to get a shared pointer to + * this base class type. + */ + static sptr make(int num_taps, + float mu, int sps, + constellation_sptr cnst); + + virtual void set_taps(const std::vector<gr_complex> &taps) = 0; + virtual std::vector<gr_complex> taps() const = 0; + virtual float gain() const = 0; + virtual void set_gain(float mu) = 0; + }; + + } /* namespace digital */ +} /* namespace gr */ + +#endif /* INCLUDED_DIGITAL_LMS_DD_EQUALIZER_CC_H */ |