From 7d1d1902c54dc8feeb5742592e28403011602708 Mon Sep 17 00:00:00 2001 From: Tom Rondeau Date: Fri, 3 Jun 2011 17:14:28 -0400 Subject: digital: adding an LMS decision-directed equalizer block. --- gr-digital/lib/digital_lms_dd_equalizer_cc.h | 88 ++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 gr-digital/lib/digital_lms_dd_equalizer_cc.h (limited to 'gr-digital/lib/digital_lms_dd_equalizer_cc.h') diff --git a/gr-digital/lib/digital_lms_dd_equalizer_cc.h b/gr-digital/lib/digital_lms_dd_equalizer_cc.h new file mode 100644 index 000000000..f33b5fc5c --- /dev/null +++ b/gr-digital/lib/digital_lms_dd_equalizer_cc.h @@ -0,0 +1,88 @@ +/* -*- c++ -*- */ +/* + * Copyright 2011 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 +#include + +class digital_lms_dd_equalizer_cc; +typedef boost::shared_ptr digital_lms_dd_equalizer_cc_sptr; + +digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (float mu, int ntaps, + digital_constellation_sptr cnst); + +/*! + * \brief Least-Mean-Square Decision Directed Equalizer (complex in/out) + * \ingroup eq_blk + * + * 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 0.01 - 0.1. + * + * 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_lms_dd_equalizer_cc : public gr_sync_block +{ +private: + friend digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (float mu, int ntaps, + digital_constellation_sptr cnst); + + float d_mu; + std::vector d_taps; + digital_constellation_sptr d_cnst; + + digital_lms_dd_equalizer_cc (float mu, int ntaps, + digital_constellation_sptr cnst); + +public: + float get_mu(); + void set_mu(float mu); + int work (int noutput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items); +}; + +#endif -- cgit From 7293ac44d02280407f2b8dfd265eafe33178086f Mon Sep 17 00:00:00 2001 From: Tom Rondeau Date: Fri, 3 Jun 2011 17:57:32 -0400 Subject: digital: fixing comments on LMS DD equalizer --- gr-digital/lib/digital_lms_dd_equalizer_cc.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'gr-digital/lib/digital_lms_dd_equalizer_cc.h') diff --git a/gr-digital/lib/digital_lms_dd_equalizer_cc.h b/gr-digital/lib/digital_lms_dd_equalizer_cc.h index f33b5fc5c..12c2ecc13 100644 --- a/gr-digital/lib/digital_lms_dd_equalizer_cc.h +++ b/gr-digital/lib/digital_lms_dd_equalizer_cc.h @@ -47,7 +47,7 @@ digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (float mu, int * 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 0.01 - 0.1. + * around 0.001 - 0.01. * * This block uses the digital_constellation object for making * the decision from y[n]. Create the constellation object for -- cgit From 86553ec410b1074bc4258b22027c5d31443d12ec Mon Sep 17 00:00:00 2001 From: Tom Rondeau Date: Mon, 6 Jun 2011 11:36:24 -0400 Subject: digital: converting LMS algorithm to use the gr_adaptive_filter structure and making naming consistent (so CMA and LMS look and behave similary with different error and upate functions). --- gr-digital/lib/digital_lms_dd_equalizer_cc.h | 50 ++++++++++++++++++++++------ 1 file changed, 39 insertions(+), 11 deletions(-) (limited to 'gr-digital/lib/digital_lms_dd_equalizer_cc.h') diff --git a/gr-digital/lib/digital_lms_dd_equalizer_cc.h b/gr-digital/lib/digital_lms_dd_equalizer_cc.h index 12c2ecc13..e3ad4bf4a 100644 --- a/gr-digital/lib/digital_lms_dd_equalizer_cc.h +++ b/gr-digital/lib/digital_lms_dd_equalizer_cc.h @@ -23,15 +23,16 @@ #ifndef INCLUDED_DIGITAL_LMS_DD_EQUALIZER_CC_H #define INCLUDED_DIGITAL_LMS_DD_EQUALIZER_CC_H -#include +#include #include class digital_lms_dd_equalizer_cc; typedef boost::shared_ptr digital_lms_dd_equalizer_cc_sptr; -digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (float mu, int ntaps, +digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (int num_taps, + float mu, int sps, digital_constellation_sptr cnst); - + /*! * \brief Least-Mean-Square Decision Directed Equalizer (complex in/out) * \ingroup eq_blk @@ -64,25 +65,52 @@ digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (float mu, int * Prentice Hall, 1996. * */ -class digital_lms_dd_equalizer_cc : public gr_sync_block +class digital_lms_dd_equalizer_cc : public gr_adaptive_fir_ccc { private: - friend digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (float mu, int ntaps, + friend digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc (int num_taps, + float mu, int sps, digital_constellation_sptr cnst); float d_mu; std::vector d_taps; digital_constellation_sptr d_cnst; - digital_lms_dd_equalizer_cc (float mu, int ntaps, + digital_lms_dd_equalizer_cc (int num_taps, + float mu, int sps, digital_constellation_sptr cnst); +protected: + + virtual gr_complex error(const gr_complex &out) + { + gr_complex decision, error; + d_cnst->map_to_points(d_cnst->decision_maker(&out), &decision); + error = decision - out; + return error; + } + + virtual void update_tap(gr_complex &tap, const gr_complex &in) + { + tap += d_mu*conj(in)*d_error; + } + public: - float get_mu(); - void set_mu(float mu); - int work (int noutput_items, - gr_vector_const_void_star &input_items, - gr_vector_void_star &output_items); + float get_gain() + { + return d_mu; + } + + void set_gain(float mu) + { + if(mu < 0.0f || mu > 1.0f) { + throw std::out_of_range("digital_lms_dd_equalizer::set_mu: Gain value must in [0, 1]"); + } + else { + d_mu = mu; + } + } + }; #endif -- cgit