mpsk_receiver_cc.h

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/* -*- c++ -*- */
/*
 * Copyright 2004,2007,2011,2012 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_MPSK_RECEIVER_CC_H
#define INCLUDED_DIGITAL_MPSK_RECEIVER_CC_H

#include <gnuradio/block.h>
#include <gnuradio/blocks/control_loop.h>
#include <gnuradio/digital/api.h>

namespace gr {
namespace digital {

/*!
 * \brief This block takes care of receiving M-PSK modulated
 * signals through phase, frequency, and symbol synchronization.
 * \ingroup synchronizers_blk
 * \ingroup deprecated_blk
 *
 * \details
 * It performs carrier frequency and phase locking as well as
 * symbol timing recovery.  It works with (D)BPSK, (D)QPSK, and
 * (D)8PSK as tested currently. It should also work for OQPSK and
 * PI/4 DQPSK.
 *
 * The phase and frequency synchronization are based on a Costas
 * loop that finds the error of the incoming signal point compared
 * to its nearest constellation point. The frequency and phase of
 * the NCO are updated according to this error. There are
 * optimized phase error detectors for BPSK and QPSK, but 8PSK is
 * done using a brute-force computation of the constellation
 * points to find the minimum.
 *
 * The symbol synchronization is done using a modified Mueller and
 * Muller circuit from the paper:
 *
 * "G. R. Danesfahani, T. G. Jeans, "Optimisation of modified Mueller
 * and Muller algorithm," Electronics Letters, Vol. 31, no. 13, 22
 * June 1995, pp. 1032 - 1033."
 *
 * This circuit interpolates the downconverted sample (using the
 * NCO developed by the Costas loop) every mu samples, then it
 * finds the sampling error based on this and the past symbols and
 * the decision made on the samples. Like the phase error
 * detector, there are optimized decision algorithms for BPSK and
 * QPKS, but 8PSK uses another brute force computation against all
 * possible symbols. The modifications to the M&M used here reduce
 * self-noise.
 *
 */
class DIGITAL_API mpsk_receiver_cc : virtual public block,
                                     virtual public blocks::control_loop
{
public:
    // gr::digital::mpsk_receiver_cc::sptr
    typedef boost::shared_ptr<mpsk_receiver_cc> sptr;

    /*!
     * \brief Make a M-PSK receiver block.
     *
     * \param M    modulation order of the M-PSK modulation
     * \param theta        any constant phase rotation from the real axis of the
     * constellation \param loop_bw        Loop bandwidth to set gains of phase/freq
     * tracking loop \param fmin       minimum normalized frequency value the loop can
     * achieve \param fmax       maximum normalized frequency value the loop can achieve
     * \param mu         initial parameter for the interpolator [0,1]
     * \param gain_mu    gain parameter of the M&M error signal to adjust mu (~0.05)
     * \param omega      initial value for the number of symbols between samples (~number
     * of samples/symbol) \param gain_omega gain parameter to adjust omega based on the
     * error (~omega^2/4) \param omega_rel  sets the maximum (omega*(1+omega_rel)) and
     * minimum (omega*(1+omega_rel)) omega (~0.005)
     *
     * The constructor also chooses which phase detector and
     * decision maker to use in the work loop based on the value of
     * M.
     */
    static sptr make(unsigned int M,
                     float theta,
                     float loop_bw,
                     float fmin,
                     float fmax,
                     float mu,
                     float gain_mu,
                     float omega,
                     float gain_omega,
                     float omega_rel);

    //! Returns the modulation order (M) currently set
    virtual float modulation_order() const = 0;

    //! Returns current value of theta
    virtual float theta() const = 0;

    //! Returns current value of mu
    virtual float mu() const = 0;

    //! Returns current value of omega
    virtual float omega() const = 0;

    //! Returns mu gain factor
    virtual float gain_mu() const = 0;

    //! Returns omega gain factor
    virtual float gain_omega() const = 0;

    //! Returns the relative omega limit
    virtual float gain_omega_rel() const = 0;

    //! Sets the modulation order (M) currently
    virtual void set_modulation_order(unsigned int M) = 0;

    //! Sets value of theta
    virtual void set_theta(float theta) = 0;

    //! Sets value of mu
    virtual void set_mu(float mu) = 0;

    //! Sets value of omega and its min and max values
    virtual void set_omega(float omega) = 0;

    //! Sets value for mu gain factor
    virtual void set_gain_mu(float gain_mu) = 0;

    //! Sets value for omega gain factor
    virtual void set_gain_omega(float gain_omega) = 0;

    //! Sets the relative omega limit and resets omega min/max values
    virtual void set_gain_omega_rel(float omega_rel) = 0;
};

} /* namespace digital */
} /* namespace gr */

#endif /* INCLUDED_DIGITAL_MPSK_RECEIVER_CC_H */