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+/* -*- 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_CONSTELLATION_RECEIVER_CB_H
+#define	INCLUDED_DIGITAL_CONSTELLATION_RECEIVER_CB_H
+
+#include <gr_block.h>
+#include <digital_constellation.h>
+#include <gri_control_loop.h>
+#include <gr_complex.h>
+#include <math.h>
+#include <fstream>
+
+class digital_constellation_receiver_cb;
+typedef boost::shared_ptr<digital_constellation_receiver_cb> digital_constellation_receiver_cb_sptr;
+
+// public constructor
+digital_constellation_receiver_cb_sptr 
+digital_make_constellation_receiver_cb (digital_constellation_sptr constellation,
+					float loop_bw, float fmin, float fmax);
+
+/*!
+ * \brief This block takes care of receiving generic modulated signals
+ * through phase, frequency, and symbol synchronization.
+ * \ingroup sync_blk
+ * \ingroup demod_blk
+ * \ingroup digital
+ *
+ * This block takes care of receiving generic modulated signals
+ * through phase, frequency, and symbol synchronization. It performs
+ * carrier frequency and phase locking as well as symbol timing
+ * recovery.
+ *
+ * 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.
+ *
+ * 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_constellation_receiver_cb : public gr_block, public gri_control_loop
+{
+public:
+  int general_work (int noutput_items,
+		    gr_vector_int &ninput_items,
+		    gr_vector_const_void_star &input_items,
+		    gr_vector_void_star &output_items);
+
+protected:
+
+ /*!
+   * \brief Constructor to synchronize incoming M-PSK symbols
+   *
+   * \param constellation	constellation of points for generic modulation
+   * \param loop_bw	Loop bandwidth of the Costas Loop (~ 2pi/100)
+   * \param fmin        minimum normalized frequency value the loop can achieve
+   * \param fmax        maximum normalized frequency value the loop can achieve
+   *
+   * The constructor also chooses which phase detector and decision maker to use in the
+   * work loop based on the value of M.
+   */
+  digital_constellation_receiver_cb (digital_constellation_sptr constellation, 
+				     float loop_bw, float fmin, float fmax);
+
+  void phase_error_tracking(float phase_error);
+
+private:
+  unsigned int d_M;
+
+  digital_constellation_sptr d_constellation;
+  unsigned int d_current_const_point;
+
+  //! delay line length.
+  static const unsigned int DLLEN = 8;
+  
+  //! delay line plus some length for overflow protection
+  gr_complex d_dl[2*DLLEN] __attribute__ ((aligned(8)));
+  
+  //! index to delay line
+  unsigned int d_dl_idx;
+
+  friend digital_constellation_receiver_cb_sptr
+  digital_make_constellation_receiver_cb (digital_constellation_sptr constell,
+					  float loop_bw, float fmin, float fmax);
+};
+
+#endif