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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 <digital/api.h>
#include <gr_block.h>
namespace gr {
namespace digital {
/*!
* \brief This block takes care of receiving M-PSK modulated
* signals through phase, frequency, and symbol synchronization.
* \ingroup sync_blk
* \ingroup demod_blk
* \ingroup digital
*
* This block takes care of receiving M-PSK modulated signals
* through phase, frequency, and symbol synchronization. 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 gr_block
{
public:
// gr::digital::mpsk_receiver_cc::sptr
typedef boost::shared_ptr<mpsk_receiver_cc> sptr;
/*!
* \brief Buil 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 */
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