7 files changed, 412 insertions, 0 deletions
diff --git a/gr-digital/grc/digital_msk_timing_recovery_cc.xml b/gr-digital/grc/digital_msk_timing_recovery_cc.xml
new file mode 100644
index 0000000000..cda780d685
--- /dev/null
+++ b/gr-digital/grc/digital_msk_timing_recovery_cc.xml
@@ -0,0 +1,49 @@
+<?xml version="1.0"?>
+<block>
+  <name>MSK Timing Recovery</name>
+  <key>digital_msk_timing_recovery_cc</key>
+  <import>from gnuradio import digital</import>
+  <make>digital.msk_timing_recovery_cc($sps, $gain, $limit, $osps)</make>
+  <callback>set_gain($gain)</callback>
+  <callback>set_sps($sps)</callback>
+  <callback>set_limit($limit)</callback>
+  <param>
+    <name>Gain</name>
+    <key>gain</key>
+    <type>float</type>
+  </param>
+  <param>
+    <name>Samples per symbol</name>
+    <key>sps</key>
+    <type>float</type>
+  </param>
+  <param>
+    <name>Error limit</name>
+    <key>limit</key>
+    <type>float</type>
+  </param>
+  <param>
+    <name>Output samples per symbol</name>
+    <key>osps</key>
+    <type>int</type>
+  </param>
+  <sink>
+    <name>in</name>
+    <type>complex</type>
+  </sink>
+  <source>
+    <name>out</name>
+    <type>complex</type>
+  </source>
+  <source>
+    <name>err</name>
+    <type>float</type>
+    <optional>1</optional>
+  </source>
+  <source>
+    <name>omega</name>
+    <type>float</type>
+    <optional>1</optional>
+  </source>
+
+</block>
diff --git a/gr-digital/include/gnuradio/digital/CMakeLists.txt b/gr-digital/include/gnuradio/digital/CMakeLists.txt
index 2993497e93..e85e5bcc33 100644
--- a/gr-digital/include/gnuradio/digital/CMakeLists.txt
+++ b/gr-digital/include/gnuradio/digital/CMakeLists.txt
@@ -74,6 +74,7 @@ install(FILES
     mpsk_receiver_cc.h
     mpsk_snr_est.h
     mpsk_snr_est_cc.h
+    msk_timing_recovery_cc.h
     ofdm_carrier_allocator_cvc.h
     ofdm_chanest_vcvc.h
     ofdm_cyclic_prefixer.h
diff --git a/gr-digital/include/gnuradio/digital/msk_timing_recovery_cc.h b/gr-digital/include/gnuradio/digital/msk_timing_recovery_cc.h
new file mode 100644
index 0000000000..770bd91da1
--- /dev/null
+++ b/gr-digital/include/gnuradio/digital/msk_timing_recovery_cc.h
@@ -0,0 +1,76 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2014 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_MSK_TIMING_RECOVERY_CC_H
+#define INCLUDED_DIGITAL_MSK_TIMING_RECOVERY_CC_H
+
+#include <gnuradio/digital/api.h>
+#include <gnuradio/block.h>
+
+namespace gr {
+  namespace digital {
+
+    /*!
+     * \brief MSK/GMSK timing recovery
+     * \ingroup synchronizers_blk
+     *
+     * This block performs timing synchronization on CPM modulations using a
+     * fourth-order nonlinearity feedback method which is non-data-aided. The
+     * block does not require prior phase synchronization but is relatively
+     * sensitive to frequency offset (keep offset to 0.1x symbol rate).
+     *
+     * For details on the algorithm, see:
+     * A.N. D'Andrea, U. Mengali, R. Reggiannini: A digital approach to clock
+     * recovery in generalized minimum shift keying. IEEE Transactions on
+     * Vehicular Technology, Vol. 39, Issue 3.
+     */
+    class DIGITAL_API msk_timing_recovery_cc : virtual public gr::block
+    {
+     public:
+      typedef boost::shared_ptr<msk_timing_recovery_cc> sptr;
+
+      /*!
+       * \brief Make an MSK timing recovery block.
+       *
+       * \param sps: Samples per symbol
+       * \param gain: Loop gain of timing error filter (try 0.05)
+       * \param limit: Relative limit of timing error (try 0.1 for 10% error max)
+       * \param osps: Output samples per symbol
+       *
+       */
+      static sptr make(float sps, float gain, float limit, int osps);
+
+      virtual void set_gain(float gain)=0;
+      virtual float get_gain(void)=0;
+
+      virtual void set_limit(float limit)=0;
+      virtual float get_limit(void)=0;
+
+      virtual void set_sps(float sps)=0;
+      virtual float get_sps(void)=0;
+    };
+
+  } // namespace digital
+} // namespace gr
+
+#endif /* INCLUDED_DIGITAL_MSK_TIMING_RECOVERY_CC_H */
+
diff --git a/gr-digital/lib/CMakeLists.txt b/gr-digital/lib/CMakeLists.txt
index 0c213d7ac8..c5591e8c91 100644
--- a/gr-digital/lib/CMakeLists.txt
+++ b/gr-digital/lib/CMakeLists.txt
@@ -90,6 +90,7 @@ list(APPEND digital_sources
     mpsk_receiver_cc_impl.cc
     mpsk_snr_est.cc
     mpsk_snr_est_cc_impl.cc
+    msk_timing_recovery_cc_impl.cc
     ofdm_carrier_allocator_cvc_impl.cc
     ofdm_chanest_vcvc_impl.cc
     ofdm_cyclic_prefixer_impl.cc
diff --git a/gr-digital/lib/msk_timing_recovery_cc_impl.cc b/gr-digital/lib/msk_timing_recovery_cc_impl.cc
new file mode 100644
index 0000000000..a567357019
--- /dev/null
+++ b/gr-digital/lib/msk_timing_recovery_cc_impl.cc
@@ -0,0 +1,210 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2014 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <gnuradio/io_signature.h>
+#include <gnuradio/math.h>
+#include "msk_timing_recovery_cc_impl.h"
+#include <gnuradio/filter/firdes.h>
+
+namespace gr {
+  namespace digital {
+
+    msk_timing_recovery_cc::sptr
+    msk_timing_recovery_cc::make(float sps, float gain, float limit, int osps=1)
+    {
+      return gnuradio::get_initial_sptr
+        (new msk_timing_recovery_cc_impl(sps, gain, limit, osps));
+    }
+
+    /*
+     * The private constructor
+     */
+    msk_timing_recovery_cc_impl::msk_timing_recovery_cc_impl(float sps, float gain, float limit, int osps)
+      : gr::block("msk_timing_recovery_cc",
+              gr::io_signature::make(1, 1, sizeof(gr_complex)),
+              gr::io_signature::make3(1, 3, sizeof(gr_complex), sizeof(float), sizeof(float))),
+      d_limit(limit),
+      d_interp(new filter::mmse_fir_interpolator_cc()),
+      d_dly_conj_1(0),
+      d_dly_conj_2(0),
+      d_dly_diff_1(0),
+      d_mu(0.5),
+      d_div(0),
+      d_osps(osps)
+    {
+        set_sps(sps);
+        enable_update_rate(true); //fixes tag propagation through variable rate blox
+        set_gain(gain);
+        if(d_osps != 1 && d_osps != 2) throw std::out_of_range("osps must be 1 or 2");
+    }
+
+    msk_timing_recovery_cc_impl::~msk_timing_recovery_cc_impl()
+    {
+        delete d_interp;
+    }
+
+    void msk_timing_recovery_cc_impl::set_sps(float sps) {
+        d_sps = sps/2.0; //loop runs at 2x sps
+        d_omega = d_sps;
+        set_relative_rate(d_osps/sps);
+//        set_history(d_sps);
+    }
+
+    float msk_timing_recovery_cc_impl::get_sps(void) {
+        return d_sps;
+    }
+
+    void msk_timing_recovery_cc_impl::set_gain(float gain) {
+        d_gain = gain;
+        if(d_gain <= 0) throw std::out_of_range("Gain must be positive");
+        d_gain_omega = d_gain*d_gain*0.25;
+    }
+
+    float msk_timing_recovery_cc_impl::get_gain(void) {
+        return d_gain;
+    }
+
+    void msk_timing_recovery_cc_impl::set_limit(float limit) {
+        d_limit = limit;
+    }
+
+    float msk_timing_recovery_cc_impl::get_limit(void) {
+        return d_limit;
+    }
+
+    void
+    msk_timing_recovery_cc_impl::forecast (int noutput_items, gr_vector_int &ninput_items_required)
+    {
+        unsigned ninputs = ninput_items_required.size();
+        for(unsigned i=0; i<ninputs; i++) {
+            ninput_items_required[i] = (int)ceil((noutput_items*d_sps*2) + 3.0*d_sps + d_interp->ntaps());
+        }
+    }
+
+    int
+    msk_timing_recovery_cc_impl::general_work (int noutput_items,
+                       gr_vector_int &ninput_items,
+                       gr_vector_const_void_star &input_items,
+                       gr_vector_void_star &output_items)
+    {
+        const gr_complex *in = (const gr_complex *) input_items[0];
+        gr_complex *out = (gr_complex *) output_items[0];
+        float *out2, *out3;
+        if(output_items.size() >= 2) out2 = (float *) output_items[1];
+        if(output_items.size() >= 3) out3 = (float *) output_items[2];
+        int oidx=0, iidx=0;
+        int ninp=ninput_items[0] - 3.0*d_sps;
+        if(ninp <= 0) {
+            consume_each(0);
+            return(0);
+        }
+
+        std::vector<tag_t> tags;
+        get_tags_in_range(tags,
+                          0,
+                          nitems_read(0),
+                          nitems_read(0)+ninp,
+                          pmt::intern("time_est"));
+
+        gr_complex sq,        //Squared input
+                   dly_conj,  //Input delayed sps and conjugated
+                   nlin_out,  //output of the nonlinearity
+                   in_interp; //interpolated input
+        float      err_out=0; //error output
+
+        while(oidx < noutput_items && iidx < ninp) {
+            //check to see if there's a tag to reset the timing estimate
+            if(tags.size() > 0) {
+                int offset = tags[0].offset - nitems_read(0);
+                if((offset >= iidx) && (offset < (iidx+d_sps))) {
+                    float center = (float) pmt::to_double(tags[0].value);
+                    if(center != center) { //test for NaN, it happens somehow
+                       tags.erase(tags.begin());
+                       goto out;
+                    }
+                    d_mu = center;
+                    iidx = offset;
+                    if(d_mu<0) {
+                        d_mu++;
+                        iidx--;
+                    }
+                    d_div = 0;
+                    d_omega = d_sps;
+                    d_dly_conj_2 = d_dly_conj_1;
+                    //this keeps the block from outputting an odd number of
+                    //samples and throwing off downstream blocks which depend
+                    //on proper alignment -- for instance, a decimating FIR
+                    //filter.
+//                    if(d_div == 0 and d_osps == 2) oidx++;
+                    tags.erase(tags.begin());
+                }
+            }
+
+out:
+            //the actual equation for the nonlinearity is as follows:
+            //e(n) = in[n]^2 * in[n-sps].conj()^2
+            //we then differentiate the error by subtracting the sample delayed by d_sps/2
+            in_interp = d_interp->interpolate(&in[iidx], d_mu);
+            sq = in_interp*in_interp;
+            //conjugation is distributive.
+            dly_conj = std::conj(d_dly_conj_2*d_dly_conj_2);
+            nlin_out = sq*dly_conj;
+            //TODO: paper argues that some improvement can be had
+            //if you either operate at >2sps or use a better numeric
+            //differentiation method.
+            err_out = std::real(nlin_out - d_dly_diff_1);
+            if(d_div % 2) { //error loop calc once per symbol
+                err_out = gr::branchless_clip(err_out, 3.0);
+                d_omega += d_gain_omega*err_out;
+                d_omega  = d_sps + gr::branchless_clip(d_omega-d_sps, d_limit);
+                d_mu    += d_gain*err_out;
+            }
+            //output every other d_sps by default.
+            if(!(d_div % 2) or d_osps==2) {
+                out[oidx] = in_interp;
+                if(output_items.size() >= 2) out2[oidx] = err_out;
+                if(output_items.size() >= 3) out3[oidx] = d_mu;
+                oidx++;
+            }
+            d_div++;
+
+            d_dly_conj_1 = in_interp;
+            d_dly_conj_2 = d_dly_conj_1;
+            d_dly_diff_1 = nlin_out;
+
+            //update interpolator twice per symbol
+            d_mu += d_omega;
+            iidx    += (int)floor(d_mu);
+            d_mu    -= floor(d_mu);
+        }
+
+        consume_each (iidx);
+        return oidx;
+    }
+
+  } /* namespace digital */
+} /* namespace gr */
+
diff --git a/gr-digital/lib/msk_timing_recovery_cc_impl.h b/gr-digital/lib/msk_timing_recovery_cc_impl.h
new file mode 100644
index 0000000000..02c29dc6ec
--- /dev/null
+++ b/gr-digital/lib/msk_timing_recovery_cc_impl.h
@@ -0,0 +1,72 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2014 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_MSK_TIMING_RECOVERY_CC_IMPL_H
+#define INCLUDED_DIGITAL_MSK_TIMING_RECOVERY_CC_IMPL_H
+
+#include <gnuradio/digital/msk_timing_recovery_cc.h>
+#include <gnuradio/filter/mmse_fir_interpolator_cc.h>
+#include <boost/circular_buffer.hpp>
+#include <gnuradio/filter/fir_filter_with_buffer.h>
+
+namespace gr {
+  namespace digital {
+
+    class msk_timing_recovery_cc_impl : public msk_timing_recovery_cc
+    {
+     private:
+        float d_sps;
+        float d_gain;
+        float d_limit;
+        filter::mmse_fir_interpolator_cc *d_interp;
+        filter::kernel::fir_filter_with_buffer_fff *d_decim;
+        gr_complex d_dly_conj_1, d_dly_conj_2, d_dly_diff_1;
+        float d_mu, d_omega, d_gain_omega;
+        int d_div;
+        int d_osps;
+        int d_loop_rate;
+
+     public:
+      msk_timing_recovery_cc_impl(float sps, float gain, float limit, int osps);
+      ~msk_timing_recovery_cc_impl();
+
+      // Where all the action really happens
+      void forecast (int noutput_items, gr_vector_int &ninput_items_required);
+
+      int general_work(int noutput_items,
+                       gr_vector_int &ninput_items,
+                       gr_vector_const_void_star &input_items,
+                       gr_vector_void_star &output_items);
+      void set_gain(float gain);
+      float get_gain(void);
+
+      void set_limit(float limit);
+      float get_limit(void);
+
+      void set_sps(float sps);
+      float get_sps(void);
+    };
+  } // namespace digital
+} // namespace gr
+
+#endif /* INCLUDED_DIGITAL_MSK_TIMING_RECOVERY_CC_IMPL_H */
+
diff --git a/gr-digital/swig/digital_swig.i b/gr-digital/swig/digital_swig.i
index 675c9b02b5..9797e797cf 100644
--- a/gr-digital/swig/digital_swig.i
+++ b/gr-digital/swig/digital_swig.i
@@ -83,6 +83,7 @@
 #include "gnuradio/digital/mpsk_receiver_cc.h"
 #include "gnuradio/digital/mpsk_snr_est.h"
 #include "gnuradio/digital/mpsk_snr_est_cc.h"
+#include "gnuradio/digital/msk_timing_recovery_cc.h"
 #include "gnuradio/digital/ofdm_carrier_allocator_cvc.h"
 #include "gnuradio/digital/ofdm_chanest_vcvc.h"
 #include "gnuradio/digital/ofdm_cyclic_prefixer.h"
@@ -161,6 +162,7 @@
 %include "gnuradio/digital/mpsk_receiver_cc.h"
 %include "gnuradio/digital/mpsk_snr_est.h"
 %include "gnuradio/digital/mpsk_snr_est_cc.h"
+%include "gnuradio/digital/msk_timing_recovery_cc.h"
 %include "gnuradio/digital/ofdm_carrier_allocator_cvc.h"
 %include "gnuradio/digital/ofdm_chanest_vcvc.h"
 %include "gnuradio/digital/ofdm_cyclic_prefixer.h"
@@ -229,6 +231,7 @@ GR_SWIG_BLOCK_MAGIC2(digital, lms_dd_equalizer_cc);
 GR_SWIG_BLOCK_MAGIC2(digital, map_bb);
 GR_SWIG_BLOCK_MAGIC2(digital, mpsk_receiver_cc);
 GR_SWIG_BLOCK_MAGIC2(digital, mpsk_snr_est_cc);
+GR_SWIG_BLOCK_MAGIC2(digital, msk_timing_recovery_cc);
 GR_SWIG_BLOCK_MAGIC2(digital, ofdm_carrier_allocator_cvc);
 GR_SWIG_BLOCK_MAGIC2(digital, ofdm_chanest_vcvc);
 GR_SWIG_BLOCK_MAGIC2(digital, ofdm_cyclic_prefixer);