Merge branch 'ptrkrysik/trx' into development

36 files changed, 1636 insertions, 219 deletions

diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index db440e4..923de48 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -70,6 +70,7 @@ add_subdirectory(flow_control)
 add_subdirectory(misc_utils)
 add_subdirectory(qa_utils)
 add_subdirectory(receiver)
+add_subdirectory(transmitter)
 
 ########################################################################
 # Setup library
diff --git a/lib/decoding/sch.c b/lib/decoding/sch.c
index 9cf6ac4..fff82ea 100644
--- a/lib/decoding/sch.c
+++ b/lib/decoding/sch.c
@@ -21,7 +21,7 @@
  */
 
 #include <string.h>
-#include "gsm_constants.h"
+#include <grgsm/gsm_constants.h>
 
 #include <stdbool.h>
 #include <osmocom/coding/gsm0503_coding.h>
diff --git a/lib/flow_control/CMakeLists.txt b/lib/flow_control/CMakeLists.txt
index 30a5f50..b8f63f7 100644
--- a/lib/flow_control/CMakeLists.txt
+++ b/lib/flow_control/CMakeLists.txt
@@ -23,6 +23,7 @@ add_sources(
     burst_sdcch_subslot_splitter_impl.cc
     burst_timeslot_filter_impl.cc
     burst_timeslot_splitter_impl.cc
+    burst_type_filter_impl.cc
     dummy_burst_filter_impl.cc
     uplink_downlink_splitter_impl.cc
 )
diff --git a/lib/flow_control/burst_type_filter_impl.cc b/lib/flow_control/burst_type_filter_impl.cc
new file mode 100644
index 0000000..c8bbd7e
--- /dev/null
+++ b/lib/flow_control/burst_type_filter_impl.cc
@@ -0,0 +1,103 @@
+/* -*- c++ -*- */
+/* @file
+ * @author (C) 2017 by Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ *
+ * Gr-gsm 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.
+ *
+ * Gr-gsm 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 gr-gsm; 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 "burst_type_filter_impl.h"
+#include <stdio.h>
+#include <grgsm/endian.h>
+#include <grgsm/gsmtap.h>
+
+
+namespace gr {
+  namespace gsm {
+      
+    burst_type_filter::sptr
+    burst_type_filter::make(const std::vector<uint8_t> & selected_burst_types)
+    {
+      return gnuradio::get_initial_sptr
+        (new burst_type_filter_impl(selected_burst_types));
+    }
+
+    /*
+     * The private constructor
+     */
+    burst_type_filter_impl::burst_type_filter_impl(const std::vector<uint8_t> & selected_burst_types)
+      : gr::block("burst_type_filter",
+              gr::io_signature::make(0, 0, 0),
+              gr::io_signature::make(0, 0, 0)),
+        d_filter_policy(FILTER_POLICY_DEFAULT)
+    {
+        set_selected_burst_types(selected_burst_types);
+    
+        message_port_register_in(pmt::mp("bursts_in"));
+        message_port_register_out(pmt::mp("bursts_out"));
+        
+        set_msg_handler(pmt::mp("bursts_in"), boost::bind(&burst_type_filter_impl::process_burst, this, _1));
+    }
+
+    /*
+     * Our virtual destructor.
+     */
+    burst_type_filter_impl::~burst_type_filter_impl() {}
+
+    void burst_type_filter_impl::process_burst(pmt::pmt_t msg)
+    {
+        if (d_filter_policy == FILTER_POLICY_DROP_ALL)
+          return;
+
+        if (d_filter_policy == FILTER_POLICY_PASS_ALL) {
+          message_port_pub(pmt::mp("bursts_out"), msg);
+          return;
+        }
+
+        gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(pmt::cdr(msg));
+        if (std::find(d_selected_burst_types.begin(), d_selected_burst_types.end(), header->sub_type) != d_selected_burst_types.end()) //check if burst type is listed in burst types to pass
+        {
+            message_port_pub(pmt::mp("bursts_out"), msg);
+        }
+    }
+    
+    /* Filtering policy */
+    filter_policy
+    burst_type_filter_impl::get_policy(void)
+    {
+      return d_filter_policy;
+    }
+
+    filter_policy
+    burst_type_filter_impl::set_policy(filter_policy policy)
+    {
+      d_filter_policy = policy;
+      return d_filter_policy;
+    }
+    
+    void
+    burst_type_filter_impl::set_selected_burst_types(const std::vector<uint8_t> & selected_burst_types)
+    {
+      d_selected_burst_types.assign(selected_burst_types.begin(), selected_burst_types.end());
+    }
+  } /* namespace gsm */
+} /* namespace gr */
diff --git a/lib/flow_control/burst_type_filter_impl.h b/lib/flow_control/burst_type_filter_impl.h
new file mode 100644
index 0000000..5c6ad14
--- /dev/null
+++ b/lib/flow_control/burst_type_filter_impl.h
@@ -0,0 +1,55 @@
+/* -*- c++ -*- */
+/* @file
+ * @author (C) 2017 by Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ *
+ * Gr-gsm 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.
+ *
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef INCLUDED_GSM_BURST_TYPE_FILTER_IMPL_H
+#define INCLUDED_GSM_BURST_TYPE_FILTER_IMPL_H
+
+#define BURST_TYPE_LEN 148
+
+#include <grgsm/flow_control/burst_type_filter.h>
+
+namespace gr {
+  namespace gsm {
+
+    class burst_type_filter_impl : public burst_type_filter
+    {
+     private:
+      filter_policy d_filter_policy;
+      std::vector<uint8_t> d_selected_burst_types;
+     public:
+      burst_type_filter_impl(const std::vector<uint8_t> & selected_burst_types);
+      ~burst_type_filter_impl();
+      void process_burst(pmt::pmt_t msg);
+
+      /* External API */
+      /* Filtering policy */
+      filter_policy get_policy(void);
+      filter_policy set_policy(filter_policy policy);
+      
+      void set_selected_burst_types(const std::vector<uint8_t> & selected_burst_types);
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GSM_BURST_TYPE_FILTER_IMPL_H */
+
diff --git a/lib/flow_control/uplink_downlink_splitter_impl.cc b/lib/flow_control/uplink_downlink_splitter_impl.cc
index 691feb3..de5ae30 100644
--- a/lib/flow_control/uplink_downlink_splitter_impl.cc
+++ b/lib/flow_control/uplink_downlink_splitter_impl.cc
@@ -30,7 +30,7 @@
 #include <grgsm/endian.h>
 #define BURST_SIZE 148
 namespace gr {
-  namespace grgsm {
+  namespace gsm {
 
     uplink_downlink_splitter::sptr
     uplink_downlink_splitter::make()
@@ -71,6 +71,6 @@ namespace gr {
     uplink_downlink_splitter_impl::~uplink_downlink_splitter_impl()
     {
     }
-  } /* namespace grgsm */
+  } /* namespace gsm */
 } /* namespace gr */
 
diff --git a/lib/flow_control/uplink_downlink_splitter_impl.h b/lib/flow_control/uplink_downlink_splitter_impl.h
index fb8b2b8..5edfe5a 100644
--- a/lib/flow_control/uplink_downlink_splitter_impl.h
+++ b/lib/flow_control/uplink_downlink_splitter_impl.h
@@ -26,7 +26,7 @@
 #include <grgsm/flow_control/uplink_downlink_splitter.h>
 
 namespace gr {
-  namespace grgsm {
+  namespace gsm {
 
     class uplink_downlink_splitter_impl : public uplink_downlink_splitter
     {
@@ -36,7 +36,7 @@ namespace gr {
 
       void process_msg(pmt::pmt_t msg);
     };
-  } // namespace grgsm
+  } // namespace gsm
 } // namespace gr
 
 #endif /* INCLUDED_GRGSM_UPLINK_DOWNLINK_SPLITTER_IMPL_H */
diff --git a/lib/misc_utils/CMakeLists.txt b/lib/misc_utils/CMakeLists.txt
index 720eee3..e0fc818 100644
--- a/lib/misc_utils/CMakeLists.txt
+++ b/lib/misc_utils/CMakeLists.txt
@@ -33,5 +33,9 @@ add_sources(
     message_printer_impl.cc
     msg_to_tag_impl.cc
     tmsi_dumper_impl.cc
+    time_spec.cc
+    fn_time.cc
+    udp_socket.cc
+    trx_burst_if_impl.cc
 )
 
diff --git a/lib/misc_utils/controlled_fractional_resampler_cc_impl.cc b/lib/misc_utils/controlled_fractional_resampler_cc_impl.cc
index 3376c67..36cf170 100644
--- a/lib/misc_utils/controlled_fractional_resampler_cc_impl.cc
+++ b/lib/misc_utils/controlled_fractional_resampler_cc_impl.cc
@@ -177,6 +177,6 @@ namespace gr {
       set_relative_rate(1.0 / resamp_ratio);
     }
 
-  } /* namespace grgsm */
+  } /* namespace gsm */
 } /* namespace gr */
 
diff --git a/lib/misc_utils/controlled_fractional_resampler_cc_impl.h b/lib/misc_utils/controlled_fractional_resampler_cc_impl.h
index 24e00ed..1ca8082 100644
--- a/lib/misc_utils/controlled_fractional_resampler_cc_impl.h
+++ b/lib/misc_utils/controlled_fractional_resampler_cc_impl.h
@@ -64,7 +64,7 @@ namespace gr {
       void set_resamp_ratio(float resamp_ratio);
     };
 
-  } // namespace grgsm
+  } // namespace gsm
 } // namespace gr
 
 #endif /* INCLUDED_GRGSM_CONTROLLED_FRACTIONAL_RESAMPLER_CC_IMPL_H */
diff --git a/lib/misc_utils/fn_time.cc b/lib/misc_utils/fn_time.cc
new file mode 100644
index 0000000..2773f33
--- /dev/null
+++ b/lib/misc_utils/fn_time.cc
@@ -0,0 +1,94 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @author Vadim Yanitskiy <axilirator@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ * 
+ */
+
+#include <grgsm/misc_utils/fn_time.h>
+#include <grgsm/misc_utils/time_spec.h>
+#include <math.h>
+
+#define GSM_HYPER_FRAME (26 * 51 * 2048)
+#define GSM_SYM_RATE (13.0e6 / 48.0)
+
+#define GSM_TS_PERIOD (156.25 / GSM_SYM_RATE)
+#define GSM_FN_PERIOD (8 * GSM_TS_PERIOD)
+
+namespace gr {
+  namespace gsm {
+    /**
+     * Computes difference between two frame numbers modulo
+     * GSM_HYPER_FRAME / 2. The result is correct if difference
+     * between the frame numbers is not bigger than GSM_HYPER_FRAME / 2.
+     * @param  fn1 first frame number
+     * @param  fn2 second frame number
+     * @return     computed difference
+     */
+    static int fnmod_delta(uint32_t fn1, uint32_t fn2)
+    {
+      int delta, h2;
+
+      delta = (fn1 % GSM_HYPER_FRAME) - (fn2 % GSM_HYPER_FRAME);
+
+      h2 = GSM_HYPER_FRAME / 2;
+
+      if (delta >= h2) {
+        delta -= GSM_HYPER_FRAME;
+      } else if(delta < -h2) {
+        delta += GSM_HYPER_FRAME;
+      }
+
+      return delta;
+    }
+
+    static int fn_time_diff_delta(uint32_t fn, uint32_t fn_ref,
+      time_spec_t time_diff_hint)
+    {
+      int frames_diff, fn_delta;
+      frames_diff = int(round(time_diff_hint.get_real_secs() / GSM_FN_PERIOD));
+      fn_delta = fnmod_delta(fn, fn_ref + frames_diff) + frames_diff;
+
+      return fn_delta;
+    }
+
+    /**
+     * Computes difference between reference frame number
+     * and a second frame number. 
+     * @param  fn_ref    reference frame number modulo GSM_HYPER_FRAME
+     * @param  fn        second frame number modulo GSM_HYPER_FRAME
+     * @param  time_ref  precise timestamp of the first sample in the fn_ref
+     * @param  time_hint coarse time for fn that is used as a hint to avoid
+     *                   ambiguities caused by modulo operation applied to
+     *                   frame numbers
+     * @return           difference between fn_ref and fn
+     */
+    time_format fn_time_delta_cpp(uint32_t fn_ref, time_format time_ref, uint32_t fn_x, 
+      time_format time_hint, uint32_t ts_num, uint32_t ts_ref)
+    {
+      time_spec_t time_diff_hint = time_spec_t(time_hint.first, time_hint.second) - time_spec_t(time_ref.first, time_ref.second);
+      int fn_delta = fn_time_diff_delta(fn_x, fn_ref, time_diff_hint);
+      time_spec_t time_x_precise = fn_delta * GSM_FN_PERIOD + time_spec_t(time_ref.first, time_ref.second) + (static_cast<int>(ts_num) - static_cast<int>(ts_ref)) * GSM_TS_PERIOD;
+
+      return time_format(time_x_precise.get_full_secs(), time_x_precise.get_frac_secs());
+    }
+
+  } /* namespace gsm */
+} /* namespace gr */
+
diff --git a/lib/misc_utils/msg_to_tag_impl.cc b/lib/misc_utils/msg_to_tag_impl.cc
index 0ab65e7..e08c7e6 100644
--- a/lib/misc_utils/msg_to_tag_impl.cc
+++ b/lib/misc_utils/msg_to_tag_impl.cc
@@ -94,6 +94,6 @@ namespace gr {
       return noutput_items;
     }
 
-  } /* namespace grgsm */
+  } /* namespace gsm */
 } /* namespace gr */
 
diff --git a/lib/misc_utils/msg_to_tag_impl.h b/lib/misc_utils/msg_to_tag_impl.h
index 39c6ca3..55e1fae 100644
--- a/lib/misc_utils/msg_to_tag_impl.h
+++ b/lib/misc_utils/msg_to_tag_impl.h
@@ -44,7 +44,7 @@ namespace gr {
          gr_vector_void_star &output_items);
     };
 
-  } // namespace grgsm
+  } // namespace gsm
 } // namespace gr
 
 #endif /* INCLUDED_GRGSM_MSG_TO_TAG_IMPL_H */
diff --git a/lib/misc_utils/time_spec.cc b/lib/misc_utils/time_spec.cc
new file mode 100644
index 0000000..5293da2
--- /dev/null
+++ b/lib/misc_utils/time_spec.cc
@@ -0,0 +1,122 @@
+//
+// Copyright 2011-2013 Ettus Research LLC
+//
+// This program 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 of the License, or
+// (at your option) any later version.
+//
+// This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#include <grgsm/misc_utils/time_spec.h>
+
+namespace gr {
+  namespace gsm {
+
+    /***********************************************************************
+     * Time spec constructors
+     **********************************************************************/
+    #define time_spec_init(full, frac) { \
+        const time_t _full = time_t(full); \
+        const double _frac = double(frac); \
+        const int _frac_int = int(_frac); \
+        _full_secs = _full + _frac_int; \
+        _frac_secs = _frac - _frac_int; \
+        if (_frac_secs < 0) {\
+            _full_secs -= 1; \
+            _frac_secs += 1; \
+        } \
+    }
+
+    inline long long fast_llround(const double x){
+        return (long long)(x + 0.5); // assumption of non-negativity
+    }
+
+    time_spec_t::time_spec_t(const time_spec_t & spec){
+        time_spec_init(spec.get_full_secs(), spec.get_frac_secs());
+    }
+
+    time_spec_t::time_spec_t(double secs){
+        time_spec_init(0, secs);
+    }
+
+    time_spec_t::time_spec_t(time_t full_secs, double frac_secs){
+        time_spec_init(full_secs, frac_secs);
+    }
+
+    time_spec_t::time_spec_t(time_t full_secs, long tick_count, double tick_rate){
+        const double frac_secs = tick_count/tick_rate;
+        time_spec_init(full_secs, frac_secs);
+    }
+
+    time_spec_t time_spec_t::from_ticks(long long ticks, double tick_rate){
+        const long long rate_i = (long long)(tick_rate);
+        const double rate_f = tick_rate - rate_i;
+        const time_t secs_full = time_t(ticks/rate_i);
+        const long long ticks_error = ticks - (secs_full*rate_i);
+        const double ticks_frac = ticks_error - secs_full*rate_f;
+        return time_spec_t(secs_full, ticks_frac/tick_rate);
+    }
+
+    /***********************************************************************
+     * Time spec accessors
+     **********************************************************************/
+    long time_spec_t::get_tick_count(double tick_rate) const{
+        return long(fast_llround(this->get_frac_secs()*tick_rate));
+    }
+
+    long long time_spec_t::to_ticks(double tick_rate) const{
+        const long long rate_i = (long long)(tick_rate);
+        const double rate_f = tick_rate - rate_i;
+        const long long ticks_full = this->get_full_secs()*rate_i;
+        const double ticks_error = this->get_full_secs()*rate_f;
+        const double ticks_frac = this->get_frac_secs()*tick_rate;
+        return ticks_full + fast_llround(ticks_error + ticks_frac);
+    }
+
+    double time_spec_t::get_real_secs(void) const{
+        return this->get_full_secs() + this->get_frac_secs();
+    }
+
+    /***********************************************************************
+     * Time spec math overloads
+     **********************************************************************/
+    time_spec_t &time_spec_t::operator+=(const time_spec_t &rhs){
+        time_spec_init(
+            this->get_full_secs() + rhs.get_full_secs(),
+            this->get_frac_secs() + rhs.get_frac_secs()
+        );
+        return *this;
+    }
+
+    time_spec_t &time_spec_t::operator-=(const time_spec_t &rhs){
+        time_spec_init(
+            this->get_full_secs() - rhs.get_full_secs(),
+            this->get_frac_secs() - rhs.get_frac_secs()
+        );
+        return *this;
+    }
+
+    bool operator==(const time_spec_t &lhs, const time_spec_t &rhs){
+        return
+            lhs.get_full_secs() == rhs.get_full_secs() and
+            lhs.get_frac_secs() == rhs.get_frac_secs()
+        ;
+    }
+
+    bool operator<(const time_spec_t &lhs, const time_spec_t &rhs){
+        return (
+            (lhs.get_full_secs() < rhs.get_full_secs()) or (
+            (lhs.get_full_secs() == rhs.get_full_secs()) and
+            (lhs.get_frac_secs() < rhs.get_frac_secs())
+        ));
+    }
+  }
+}
diff --git a/lib/misc_utils/trx_burst_if_impl.cc b/lib/misc_utils/trx_burst_if_impl.cc
new file mode 100644
index 0000000..8f458b0
--- /dev/null
+++ b/lib/misc_utils/trx_burst_if_impl.cc
@@ -0,0 +1,231 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Vadim Yanitskiy <axilirator@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; 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 <boost/lexical_cast.hpp>
+
+#include "udp_socket.h"
+#include "trx_burst_if_impl.h"
+
+#define BURST_SIZE     148
+#define DATA_IF_MTU    160
+
+/**
+ * 41-bit RACH synchronization sequence
+ * GSM 05.02 Chapter 5.2.7 Access burst (AB)
+ */
+static uint8_t rach_synch_seq[] = {
+  0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
+  1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0,
+  1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0,
+};
+
+namespace gr {
+  namespace gsm {
+
+    trx_burst_if::sptr
+    trx_burst_if::make(
+      const std::string &remote_addr,
+      const std::string &base_port)
+    {
+      int base_port_int = boost::lexical_cast<int> (base_port);
+
+      return gnuradio::get_initial_sptr
+        (new trx_burst_if_impl(remote_addr, base_port_int));
+    }
+
+    /*
+     * The private constructor
+     */
+    trx_burst_if_impl::trx_burst_if_impl(
+      const std::string &remote_addr,
+      int base_port
+    ) : gr::block("trx_burst_if",
+        gr::io_signature::make(0, 0, 0),
+        gr::io_signature::make(0, 0, 0))
+    {
+        message_port_register_in(pmt::mp("bursts"));
+        message_port_register_out(pmt::mp("bursts"));
+
+        // Bind a port handler
+        set_msg_handler(pmt::mp("bursts"),
+          boost::bind(&trx_burst_if_impl::handle_dl_burst, this, _1));
+
+        // Prepare port numbers
+        std::string data_src_port = boost::lexical_cast<std::string> (base_port + 2);
+        std::string data_dst_port = boost::lexical_cast<std::string> (base_port + 102);
+
+        // Init DATA interface
+        d_data_sock = new udp_socket(remote_addr,
+          data_src_port, data_dst_port, DATA_IF_MTU);
+
+        // Bind DATA interface handler
+        d_data_sock->udp_rx_handler = boost::bind(
+          &trx_burst_if_impl::handle_ul_burst, this, _1, _2);
+    }
+
+    /*
+     * Our virtual destructor.
+     */
+    trx_burst_if_impl::~trx_burst_if_impl()
+    {
+        // Release all UDP sockets and free memory
+        delete d_data_sock;
+    }
+
+    /*
+     * Check if burst is a RACH burst
+     */
+    bool trx_burst_if_impl::detect_rach(uint8_t *burst)
+    {
+      // Compare synchronization sequence
+      for (int i = 0; i < 41; i++)
+        if (burst[i + 8] != rach_synch_seq[i])
+          return false;
+
+      // Make sure TB and GP are filled by 0x00
+      for (int i = 0; i < 63; i++)
+        if (burst[i + 85] != 0x00)
+          return false;
+
+      return true;
+    }
+
+    /*
+     * Create an UDP payload with burst bits
+     * and some channel data.
+     */
+    void
+    trx_burst_if_impl::burst_pack(pmt::pmt_t msg, uint8_t *buf)
+    {
+      pmt::pmt_t header_plus_burst = pmt::cdr(msg);
+
+      // Extract GSMTAP header from message
+      gsmtap_hdr *header = (gsmtap_hdr *)
+        pmt::blob_data(header_plus_burst);
+
+      // Pack timeslot index
+      buf[0] = header->timeslot;
+
+      // Extract frame number
+      uint32_t frame_nr = be32toh(header->frame_number);
+
+      // Pack frame number
+      buf[1] = (frame_nr >> 24) & 0xff;
+      buf[2] = (frame_nr >> 16) & 0xff;
+      buf[3] = (frame_nr >>  8) & 0xff;
+      buf[4] = (frame_nr >>  0) & 0xff;
+
+      // Pack RSSI (-dBm)
+      buf[5] = -(uint8_t) header->signal_dbm;
+
+      // Pack correlator timing offset (TOA)
+      // FIXME: where to find this value?
+      buf[6] = 0;
+      buf[7] = 0;
+
+      // Extract bits {0..1} from message
+      // Despite GR-GSM uses int8_t, they are not real sbits {-127..127}
+      uint8_t *burst = (uint8_t *)
+        (pmt::blob_data(header_plus_burst)) + sizeof(gsmtap_hdr);
+
+      // Convert to transceiver interface specific bits {255..0}
+      for (int i = 0; i < 148; i++)
+        buf[8 + i] = burst[i] ? 255 : 0;
+
+      // Fill two unused bytes
+      buf[156] = 0x00;
+      buf[157] = 0x00;
+    }
+
+    void
+    trx_burst_if_impl::handle_dl_burst(pmt::pmt_t msg)
+    {
+      // 8 bytes of header + 148 bytes of burst
+      // + two unused, but required bytes
+      // otherwise bursts would be rejected
+      uint8_t buf[158];
+
+      // Compose a new UDP payload with burst
+      burst_pack(msg, buf);
+
+      // Send a burst
+      d_data_sock->udp_send(buf, 158);
+    }
+
+    void
+    trx_burst_if_impl::handle_ul_burst(uint8_t *payload, size_t len)
+    {
+      // Check length according to the protocol
+      if (len != 154)
+        return;
+
+      /* Make sure TS index is correct */
+      if (payload[0] >= 8)
+        return;
+
+      /* Unpack and check frame number */
+      uint32_t fn = (payload[1] << 24)
+        | (payload[2] << 16)
+        | (payload[3] << 8)
+        | payload[4];
+
+      if (fn >= 2715648)
+        return;
+
+      // Prepare a buffer for GSMTAP header and burst
+      uint8_t buf[sizeof(gsmtap_hdr) + BURST_SIZE];
+
+      // Set up pointer to GSMTAP header structure
+      struct gsmtap_hdr *header = (struct gsmtap_hdr *) buf;
+      memset(header, 0x00, sizeof(struct gsmtap_hdr));
+
+      // Fill in basic info
+      header->version = GSMTAP_VERSION;
+      header->hdr_len = sizeof(gsmtap_hdr) / 4;
+      header->type = GSMTAP_TYPE_UM_BURST;
+
+      // Set timeslot index and frame number
+      header->timeslot = payload[0];
+      header->frame_number = htobe32(fn);
+
+      // Check if one is a RACH burst
+      header->sub_type = detect_rach(payload + 6) ?
+        GSMTAP_BURST_ACCESS : GSMTAP_BURST_NORMAL;
+
+      // Copy burst bits (0 & 1) for source message
+      memcpy(buf + sizeof(gsmtap_hdr), payload + 6, BURST_SIZE);
+
+      // Create a pmt blob
+      pmt::pmt_t blob = pmt::make_blob(buf, sizeof(gsmtap_hdr) + BURST_SIZE);
+      pmt::pmt_t msg = pmt::cons(pmt::PMT_NIL, blob);
+
+      /* Send a message to the output */
+      message_port_pub(pmt::mp("bursts"), msg);
+    }
+
+  } /* namespace gsm */
+} /* namespace gr */
diff --git a/lib/misc_utils/trx_burst_if_impl.h b/lib/misc_utils/trx_burst_if_impl.h
new file mode 100644
index 0000000..35f939c
--- /dev/null
+++ b/lib/misc_utils/trx_burst_if_impl.h
@@ -0,0 +1,54 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Vadim Yanitskiy <axilirator@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ * 
+ */
+
+#ifndef INCLUDED_GRGSM_TRX_BURST_IF_IMPL_H
+#define INCLUDED_GRGSM_TRX_BURST_IF_IMPL_H
+
+#include <stddef.h>
+
+#include <grgsm/gsmtap.h>
+#include <grgsm/misc_utils/trx_burst_if.h>
+
+namespace gr {
+  namespace gsm {
+
+    class trx_burst_if_impl : public trx_burst_if
+    {
+     private:
+      udp_socket *d_data_sock;
+
+      bool detect_rach(uint8_t *burst);
+      void burst_pack(pmt::pmt_t msg, uint8_t *buf);
+
+     public:
+      trx_burst_if_impl(const std::string &remote_addr, int base_port);
+      ~trx_burst_if_impl();
+
+      void handle_dl_burst(pmt::pmt_t msg);
+      void handle_ul_burst(uint8_t *payload, size_t len);
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GRGSM_TRX_BURST_IF_IMPL_H */
+
diff --git a/lib/misc_utils/udp_socket.cc b/lib/misc_utils/udp_socket.cc
new file mode 100644
index 0000000..5c689c7
--- /dev/null
+++ b/lib/misc_utils/udp_socket.cc
@@ -0,0 +1,119 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2013 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/thread/thread.h>
+#include <gnuradio/io_signature.h>
+#include <gnuradio/blocks/pdu.h>
+#include <pmt/pmt.h>
+
+#include <boost/lexical_cast.hpp>
+#include "udp_socket.h"
+
+using boost::asio::ip::udp;
+
+namespace gr {
+  namespace gsm {
+
+    udp_socket::udp_socket(
+      const std::string &remote_addr,
+      const std::string &src_port,
+      const std::string &dst_port,
+      size_t mtu)
+    {
+      // Resize receive buffer according to MTU value
+      d_rxbuf.resize(mtu);
+
+      // Resolve remote host address
+      udp::resolver resolver(d_io_service);
+
+      udp::resolver::query rx_query(
+        udp::v4(), remote_addr, src_port,
+        boost::asio::ip::resolver_query_base::passive);
+      udp::resolver::query tx_query(
+        udp::v4(), remote_addr, dst_port,
+        boost::asio::ip::resolver_query_base::passive);
+
+      d_udp_endpoint_rx = *resolver.resolve(rx_query);
+      d_udp_endpoint_tx = *resolver.resolve(tx_query);
+
+      // Create a socket
+      d_udp_socket.reset(new udp::socket(d_io_service, d_udp_endpoint_rx));
+
+      // Setup read handler
+      d_udp_socket->async_receive_from(
+        boost::asio::buffer(d_rxbuf), d_udp_endpoint_rx,
+        boost::bind(&udp_socket::handle_udp_read, this,
+          boost::asio::placeholders::error,
+          boost::asio::placeholders::bytes_transferred));
+
+      // Start server
+      d_thread = gr::thread::thread(
+        boost::bind(&udp_socket::run_io_service, this));
+    }
+
+    udp_socket::~udp_socket()
+    {
+      // Stop server
+      d_io_service.stop();
+      d_thread.interrupt();
+      d_thread.join();
+    }
+
+    void
+    udp_socket::run_io_service(void)
+    {
+      d_io_service.run();
+    }
+
+    void
+    udp_socket::udp_send(uint8_t *data, size_t len)
+    {
+      d_udp_socket->send_to(
+        boost::asio::buffer(data, len),
+        d_udp_endpoint_tx);
+    }
+
+    void
+    udp_socket::handle_udp_read(
+      const boost::system::error_code& error,
+      size_t bytes_transferred)
+    {
+      if (error)
+        return;
+
+      // Call incoming data handler
+      if (udp_rx_handler != NULL)
+        udp_rx_handler((uint8_t *) &d_rxbuf[0], bytes_transferred);
+
+      d_udp_socket->async_receive_from(
+        boost::asio::buffer(d_rxbuf), d_udp_endpoint_rx,
+        boost::bind(&udp_socket::handle_udp_read, this,
+          boost::asio::placeholders::error,
+          boost::asio::placeholders::bytes_transferred));
+    }
+
+  } /* namespace gsm */
+}/* namespace gr */
diff --git a/lib/misc_utils/udp_socket.h b/lib/misc_utils/udp_socket.h
new file mode 100644
index 0000000..15b2c66
--- /dev/null
+++ b/lib/misc_utils/udp_socket.h
@@ -0,0 +1,69 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2013 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_GRGSM_TRX_UDP_SOCKET_H
+#define INCLUDED_GRGSM_TRX_UDP_SOCKET_H
+
+#include <gnuradio/thread/thread.h>
+
+#include <boost/function.hpp>
+#include <boost/array.hpp>
+#include <boost/asio.hpp>
+#include <boost/bind.hpp>
+#include <pmt/pmt.h>
+
+namespace gr {
+  namespace gsm {
+
+    class udp_socket
+    {
+    private:
+      boost::asio::io_service d_io_service;
+      std::vector<char> d_rxbuf;
+      gr::thread::thread d_thread;
+      bool d_started;
+      bool d_finished;
+
+      boost::asio::ip::udp::endpoint d_udp_endpoint_rx;
+      boost::asio::ip::udp::endpoint d_udp_endpoint_tx;
+      boost::shared_ptr<boost::asio::ip::udp::socket> d_udp_socket;
+
+      void handle_udp_read(const boost::system::error_code& error,
+        size_t bytes_transferred);
+      void run_io_service(void);
+
+    public:
+      udp_socket(
+        const std::string &remote_addr,
+        const std::string &src_port,
+        const std::string &dst_port,
+        size_t mtu);
+      ~udp_socket();
+
+      void udp_send(uint8_t *data, size_t len);
+      boost::function<void (uint8_t *, size_t)> udp_rx_handler;
+    };
+
+  } /* namespace gsm */
+} /* namespace gr */
+
+#endif /* INCLUDED_GRGSM_TRX_UDP_SOCKET_H */
diff --git a/lib/qa_utils/burst_sink_impl.cc b/lib/qa_utils/burst_sink_impl.cc
index 102c5be..bdc2192 100644
--- a/lib/qa_utils/burst_sink_impl.cc
+++ b/lib/qa_utils/burst_sink_impl.cc
@@ -47,7 +47,8 @@ namespace gr {
     burst_sink_impl::burst_sink_impl()
       : gr::block("burst_sink",
               gr::io_signature::make(0, 0, 0),
-              gr::io_signature::make(0, 0, 0))
+              gr::io_signature::make(0, 0, 0)),
+        d_bursts(pmt::PMT_NIL)
     {
         message_port_register_in(pmt::mp("in"));
         set_msg_handler(pmt::mp("in"), boost::bind(&burst_sink_impl::process_burst, this, _1));
@@ -105,7 +106,10 @@ namespace gr {
     {
         return d_burst_data;
     }
-
+    pmt::pmt_t burst_sink_impl::get_bursts()
+    {
+        return d_bursts;
+    }
   } /* namespace gsm */
 } /* namespace gr */
 
diff --git a/lib/qa_utils/burst_sink_impl.h b/lib/qa_utils/burst_sink_impl.h
index 1035430..e87422d 100644
--- a/lib/qa_utils/burst_sink_impl.h
+++ b/lib/qa_utils/burst_sink_impl.h
@@ -35,6 +35,7 @@ namespace gr {
       std::vector<int> d_framenumbers;
       std::vector<int> d_timeslots;
       std::vector<std::string> d_burst_data;
+      pmt::pmt_t d_bursts;
      public:
       burst_sink_impl();
       ~burst_sink_impl();
@@ -42,6 +43,7 @@ namespace gr {
       virtual std::vector<int> get_framenumbers();
       virtual std::vector<int> get_timeslots();
       virtual std::vector<std::string> get_burst_data();
+      virtual pmt::pmt_t get_bursts();
     };
 
   } // namespace gsm
diff --git a/lib/receiver/CMakeLists.txt b/lib/receiver/CMakeLists.txt
index 343d2f8..123eba5 100644
--- a/lib/receiver/CMakeLists.txt
+++ b/lib/receiver/CMakeLists.txt
@@ -23,4 +23,5 @@ add_sources(
     receiver_config.cc
     receiver_impl.cc
     viterbi_detector.cc
+    time_sample_ref.cc
 )
diff --git a/lib/receiver/clock_offset_control_impl.cc b/lib/receiver/clock_offset_control_impl.cc
index 868cbc2..d62c801 100644
--- a/lib/receiver/clock_offset_control_impl.cc
+++ b/lib/receiver/clock_offset_control_impl.cc
@@ -25,7 +25,7 @@
 #endif
 
 #include <sch.h>
-#include <gsm_constants.h>
+#include <grgsm/gsm_constants.h>
 #include "clock_offset_control_impl.h"
 
 namespace gr
diff --git a/lib/receiver/gsm_constants.h b/lib/receiver/gsm_constants.h
deleted file mode 100644
index 9052290..0000000
--- a/lib/receiver/gsm_constants.h
+++ /dev/null
@@ -1,177 +0,0 @@
-/* -*- c++ -*- */
-/*
- * @file
- * @author (C) 2014 by Piotr Krysik <ptrkrysik@gmail.com>
- * @section LICENSE
- *
- * Gr-gsm 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.
- *
- * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
- * the Free Software Foundation, Inc., 51 Franklin Street,
- * Boston, MA 02110-1301, USA.
- */
- 
-#ifndef INCLUDED_GSM_CONSTANTS_H
-#define INCLUDED_GSM_CONSTANTS_H
-
-#define GSM_SYMBOL_RATE  (1625000.0/6.0) //symbols per second
-#define GSM_SYMBOL_PERIOD (1.0/GSM_SYMBOL_RATE) //seconds per symbol
-
-//Burst timing
-#define TAIL_BITS         3
-#define GUARD_BITS        8
-#define GUARD_FRACTIONAL  0.25 //fractional part of guard period
-#define GUARD_PERIOD      GUARD_BITS + GUARD_FRACTIONAL
-#define DATA_BITS         57   //size of 1 data block in normal burst
-#define STEALING_BIT      1
-#define N_TRAIN_BITS      26
-#define N_SYNC_BITS       64
-#define USEFUL_BITS       142  //(2*(DATA_BITS+STEALING_BIT) + N_TRAIN_BITS )
-#define FCCH_BITS         USEFUL_BITS
-#define BURST_SIZE        (USEFUL_BITS+2*TAIL_BITS)
-#define PROCESSED_CHUNK   BURST_SIZE+2*GUARD_PERIOD
-
-#define SCH_DATA_LEN      39
-#define TS_BITS           (TAIL_BITS+USEFUL_BITS+TAIL_BITS+GUARD_BITS)  //a full TS (156 bits)
-#define TS_PER_FRAME      8
-#define FRAME_BITS        (TS_PER_FRAME * TS_BITS + 2) // 156.25 * 8
-#define FCCH_POS          TAIL_BITS
-#define SYNC_POS          39
-#define TRAIN_POS         ( TAIL_BITS + (DATA_BITS+STEALING_BIT) + 5) //first 5 bits of a training sequence
-                                                       //aren't used for channel impulse response estimation
-#define TRAIN_BEGINNING   5
-#define SAFETY_MARGIN     6   //
-
-#define FCCH_HITS_NEEDED        (USEFUL_BITS - 4)
-#define FCCH_MAX_MISSES         1
-#define FCCH_MAX_FREQ_OFFSET    100
-
-#define CHAN_IMP_RESP_LENGTH  5
-
-#define MAX_SCH_ERRORS    10  //maximum number of subsequent sch errors after which gsm receiver goes to find_next_fcch state
-
-typedef enum {empty, fcch_burst, sch_burst, normal_burst, rach_burst, dummy, dummy_or_normal, normal_or_noise} burst_type;
-typedef enum {unknown, multiframe_26, multiframe_51} multiframe_type;
-
-static const unsigned char SYNC_BITS[] = {
-  1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0,
-  0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
-  0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1,
-  0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1
-};
-
-const unsigned FCCH_FRAMES[] = {0, 10, 20, 30, 40};
-const unsigned SCH_FRAMES[] = {1, 11, 21, 31, 41};
-
-const unsigned BCCH_FRAMES[] = {2, 3, 4, 5};          //!!the receiver shouldn't care about logical
-                                                      //!!channels so this will be removed from this header
-const unsigned TEST_CCH_FRAMES[] = {2, 3, 4, 5, 6, 7, 8, 9, 12, 13, 14, 15, 16, 17, 18, 19, 22, 23, 24, 25, 26, 27, 28, 29, 32, 33, 34, 35, 36, 37, 38, 39, 42, 43, 44, 45, 46, 47, 48, 49};
-const unsigned TRAFFIC_CHANNEL_F[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
-const unsigned TEST51[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50};
-
-
-#define TSC0  0
-#define TSC1  1
-#define TSC2  2
-#define TSC3  3
-#define TSC4  4
-#define TSC5  5
-#define TSC6  6
-#define TSC7  7
-#define TS_DUMMY 8
-
-#define TRAIN_SEQ_NUM 9
-
-#define TIMESLOT0  0
-#define TIMESLOT1  1
-#define TIMESLOT2  2
-#define TIMESLOT3  3
-#define TIMESLOT4  4
-#define TIMESLOT5  5
-#define TIMESLOT6  6
-#define TIMESLOT7  7
-
-
-static const unsigned char train_seq[TRAIN_SEQ_NUM][N_TRAIN_BITS] = {
-  {0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1},
-  {0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1},
-  {0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0},
-  {0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0},
-  {0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1},
-  {0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0},
-  {1, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 1, 1},
-  {1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0},
-  {0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1} // DUMMY
-};
-
-
-//Dummy burst 0xFB 76 0A 4E 09 10 1F 1C 5C 5C 57 4A 33 39 E9 F1 2F A8
-static const unsigned char dummy_burst[] = {
-  0, 0, 0, 
-  1, 1, 1, 1, 1, 0, 1, 1, 0, 1,
-  1, 1, 0, 1, 1, 0, 0, 0, 0, 0,
-  1, 0, 1, 0, 0, 1, 0, 0, 1, 1,
-  1, 0, 0, 0, 0, 0, 1, 0, 0, 1,
-  0, 0, 0, 1, 0, 0, 0, 0, 0, 0,
-  0, 1, 1, 1, 1, 1, 0, 0,
-
-  0, 1, 1, 1, 0, 0, 0, 1, 0, 1,
-  1, 1, 0, 0, 0, 1, 0, 1, 1, 1,
-  0, 0, 0, 1, 0, 1,
-
-  0, 1, 1, 1, 0, 1, 0, 0, 1, 0,
-  1, 0, 0, 0, 1, 1, 0, 0, 1, 1,
-  0, 0, 1, 1, 1, 0, 0, 1, 1, 1,
-  1, 0, 1, 0, 0, 1, 1, 1, 1, 1,
-  0, 0, 0, 1, 0, 0, 1, 0, 1, 1,
-  1, 1, 1, 0, 1, 0, 1, 0,
-  0, 0, 0
-};
-
-
-/*
- * The frequency correction burst is used for frequency synchronization
- * of the mobile.  This is broadcast in TS0 together with the SCH and
- * BCCH.
- *
- * Modulating the bits below causes a spike at 62.5kHz above (below for
- * COMPACT) the center frequency.  One can use this spike with a narrow
- * band filter to accurately determine the center of the channel.
- */
-static const unsigned char fc_fb[] = {
-  0, 0, 0,                                           //I don't use this tables,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,    //I copied this here from burst_types.h because
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,    //the description is very informative - p.krysik
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-  0, 0, 0
-};
-
-static const unsigned char fc_compact_fb[] = {
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,
-  1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0
-};
-
-
-#endif /* INCLUDED_GSM_CONSTANTS_H */
diff --git a/lib/receiver/receiver_config.h b/lib/receiver/receiver_config.h
index 6ad43a1..b3c0f49 100644
--- a/lib/receiver/receiver_config.h
+++ b/lib/receiver/receiver_config.h
@@ -25,7 +25,7 @@
 #include <vector>
 #include <algorithm>
 #include <stdint.h>
-#include <gsm_constants.h>
+#include <grgsm/gsm_constants.h>
 
 class multiframe_configuration
 {
diff --git a/lib/receiver/receiver_impl.cc b/lib/receiver/receiver_impl.cc
index c7626b5..ffaf9ee 100644
--- a/lib/receiver/receiver_impl.cc
+++ b/lib/receiver/receiver_impl.cc
@@ -73,10 +73,13 @@ namespace gr
     ) : gr::sync_block("receiver",
           gr::io_signature::make(1, -1, sizeof(gr_complex)),
           gr::io_signature::make(0, 0, 0)),
+        d_samples_consumed(0),
+        d_rx_time_received(false),
+        d_time_samp_ref(GSM_SYMBOL_RATE * osr),
         d_OSR(osr),
         d_process_uplink(process_uplink),
         d_chan_imp_length(CHAN_IMP_RESP_LENGTH),
-        d_counter(0),
+        d_counter(0),       //TODO: use nitems_read instead of d_counter
         d_fcch_start_pos(0),
         d_freq_offset_setting(0),
         d_state(fcch_search),
@@ -174,8 +177,13 @@ namespace gr
           d_freq_offset_tag_in_fcch = tag_offset < last_sample_nr;
         }
       }
+      
+      /* Obtaining current time with use of rx_time tag provided i.e. by UHD devices */
+      /* And storing it in time_sample_ref for sample number to time conversion */
+      std::vector<tag_t> rx_time_tags;
 
       /* Main state machine */
+      d_samples_consumed = 0;
       switch (d_state) {
       case fcch_search:
         fcch_search_handler(input, noutput_items);
@@ -188,7 +196,20 @@ namespace gr
         break;
       }
 
-      return 0;
+      get_tags_in_window(rx_time_tags, 0, 0, d_samples_consumed, pmt::string_to_symbol("rx_time"));
+      if(!rx_time_tags.empty()){
+        d_rx_time_received = true;
+        tag_t rx_time_tag = *(rx_time_tags.begin());
+
+        uint64_t rx_time_full_part = to_uint64(tuple_ref(rx_time_tag.value,0));
+        double rx_time_frac_part = to_double(tuple_ref(rx_time_tag.value,1));
+        
+        time_spec_t current_rx_time = time_spec_t(rx_time_full_part, rx_time_frac_part);
+        uint64_t current_start_offset = rx_time_tag.offset;
+        d_time_samp_ref.update(current_rx_time, current_start_offset);
+      }
+
+      return d_samples_consumed;
     }
 
     void
@@ -248,7 +269,9 @@ namespace gr
       d_burst_nr++;
 
       /* Consume samples up to the next guard period */
-      consume_each(burst_start + BURST_SIZE * d_OSR + 4 * d_OSR);
+      unsigned int to_consume = burst_start + BURST_SIZE * d_OSR + 4 * d_OSR;
+//      consume_each(to_consume);
+      d_samples_consumed += to_consume;
 
       /* Update current state */
       d_state = synchronized;
@@ -320,7 +343,7 @@ namespace gr
 
         case sch_burst:
         {
-          int d_ncc, d_bcc;
+          int ncc, bcc;
           int t1, t2, t3;
           int rc;
 
@@ -332,12 +355,8 @@ namespace gr
           detect_burst(input, &channel_imp_resp[0],
             d_c0_burst_start, output_binary);
 
-          /* Compose a message with GSMTAP header and bits */
-          send_burst(d_burst_nr, output_binary,
-            GSMTAP_BURST_SCH, input_nr);
-
           /* Attempt to decode SCH burst */
-          rc = decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc);
+          rc = decode_sch(&output_binary[3], &t1, &t2, &t3, &ncc, &bcc);
           if (rc) {
             if (++d_failed_sch >= MAX_SCH_ERRORS) {
               /* We have to resynchronize, change state */
@@ -352,6 +371,10 @@ namespace gr
             break;
           }
 
+          /* Compose a message with GSMTAP header and bits */
+          send_burst(d_burst_nr, output_binary,
+            GSMTAP_BURST_SCH, input_nr, d_c0_burst_start);
+
           /**
            * Decoding was successful, now
            * compute offset from burst_start,
@@ -380,7 +403,7 @@ namespace gr
 
           /* Compose a message with GSMTAP header and bits */
           send_burst(d_burst_nr, output_binary,
-            GSMTAP_BURST_NORMAL, input_nr);
+            GSMTAP_BURST_NORMAL, input_nr, d_c0_burst_start);
 
           break;
         }
@@ -404,13 +427,13 @@ namespace gr
 
             /* Compose a message with GSMTAP header and bits */
             send_burst(d_burst_nr, output_binary,
-              GSMTAP_BURST_NORMAL, input_nr); 
+              GSMTAP_BURST_NORMAL, input_nr, normal_burst_start); 
           } else {
             d_c0_burst_start = dummy_burst_start;
 
             /* Compose a message with GSMTAP header and bits */
             send_burst(d_burst_nr, dummy_burst,
-              GSMTAP_BURST_DUMMY, input_nr);
+              GSMTAP_BURST_DUMMY, input_nr, dummy_burst_start);
           }
 
           break;
@@ -462,7 +485,7 @@ namespace gr
             burst_start, output_binary);
 
           /* Compose a message with GSMTAP header and bits */
-          send_burst(d_burst_nr, output_binary, GSMTAP_BURST_NORMAL, input_nr);
+          send_burst(d_burst_nr, output_binary, GSMTAP_BURST_NORMAL, input_nr, burst_start);
 
           break;
         }
@@ -483,7 +506,8 @@ namespace gr
 
           /* Consume samples of the burst up to next guard period */
           to_consume += TS_BITS * d_OSR + d_burst_nr.get_offset();
-          consume_each(to_consume);
+//          consume_each(to_consume);
+          d_samples_consumed += to_consume;
         }
       }
     }
@@ -674,7 +698,8 @@ namespace gr
       }
 
       d_counter += to_consume;
-      consume_each(to_consume);
+//      consume_each(to_consume);
+      d_samples_consumed += to_consume;
 
       return result;
     }
@@ -725,7 +750,8 @@ namespace gr
       }
 
       d_counter += to_consume;
-      consume_each(to_consume);
+//      consume_each(to_consume);
+      d_samples_consumed += to_consume;
 
       return result;
     }
@@ -979,7 +1005,7 @@ namespace gr
     void
     receiver_impl::send_burst(burst_counter burst_nr,
       const unsigned char * burst_binary, uint8_t burst_type,
-      size_t input_nr)
+      size_t input_nr, unsigned int burst_start)
     {
       /* Buffer for GSMTAP header and burst */
       uint8_t buf[sizeof(gsmtap_hdr) + BURST_SIZE];
@@ -1018,12 +1044,26 @@ namespace gr
       tap_header->signal_dbm = static_cast<int8_t>(d_signal_dbm);
       tap_header->snr_db = 0; /* FIXME: Can we calculate this? */
 
+      pmt::pmt_t pdu_header = pmt::make_dict();
+
+      /* Add timestamp of the first sample - if available */
+      if(d_rx_time_received) {
+        time_spec_t time_spec_of_first_sample = d_time_samp_ref.offset_to_time(nitems_read(0)+burst_start);
+        uint64_t full = time_spec_of_first_sample.get_full_secs();
+        double   frac = time_spec_of_first_sample.get_frac_secs();
+        pdu_header = 
+          pmt::dict_add(pdu_header, pmt::mp("fn_time"), 
+            pmt::cons(
+              pmt::cons(pmt::from_uint64(be32toh(frame_number)), pmt::from_uint64(tn)),
+              pmt::cons(pmt::from_uint64(full), pmt::from_double(frac))));
+      }
+
       /* Copy burst to the buffer */
       memcpy(burst, burst_binary, BURST_SIZE);
 
       /* Allocate a new message */
       pmt::pmt_t blob = pmt::make_blob(buf, sizeof(gsmtap_hdr) + BURST_SIZE);
-      pmt::pmt_t msg = pmt::cons(pmt::PMT_NIL, blob);
+      pmt::pmt_t msg = pmt::cons(pdu_header, blob);
 
       /* Send message */
       if (input_nr == 0)
@@ -1092,6 +1132,5 @@ namespace gr
     {
       d_state = fcch_search;
     }
-
   } /* namespace gsm */
 } /* namespace gr */
diff --git a/lib/receiver/receiver_impl.h b/lib/receiver/receiver_impl.h
index 0b032db..b880837 100644
--- a/lib/receiver/receiver_impl.h
+++ b/lib/receiver/receiver_impl.h
@@ -25,16 +25,20 @@
 
 #include <grgsm/receiver/receiver.h>
 #include <grgsm/gsmtap.h>
-#include <gsm_constants.h>
+#include <grgsm/gsm_constants.h>
 #include <receiver_config.h>
 #include <vector>
+#include "time_sample_ref.h"
 
 namespace gr {
   namespace gsm {
     class receiver_impl : public receiver
     {
      private:
-        unsigned int d_c0_burst_start;
+        unsigned int d_samples_consumed;
+        bool d_rx_time_received;
+        time_sample_ref d_time_samp_ref;
+        int d_c0_burst_start;
         float d_c0_signal_dbm;
         
         /**@name Configuration of the receiver */
@@ -195,7 +199,7 @@ namespace gr {
          * @param burst_binary - content of the burst
          * @b_type - type of the burst
          */
-        void send_burst(burst_counter burst_nr, const unsigned char * burst_binary, uint8_t burst_type, size_t input_nr);
+        void send_burst(burst_counter burst_nr, const unsigned char * burst_binary, uint8_t burst_type, size_t input_nr, unsigned int burst_start=-1);
 
         /**
          * Configures burst types in different channels
@@ -209,13 +213,13 @@ namespace gr {
             gr_vector_const_void_star &input_items, int noutput_items);
 
      public:
-       receiver_impl(int osr, const std::vector<int> &cell_allocation, const std::vector<int> &tseq_nums, bool process_uplink);
-      ~receiver_impl();
+        receiver_impl(int osr, const std::vector<int> &cell_allocation, const std::vector<int> &tseq_nums, bool process_uplink);
+        ~receiver_impl();
       
-      int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items);
-      virtual void set_cell_allocation(const std::vector<int> &cell_allocation);
-      virtual void set_tseq_nums(const std::vector<int> & tseq_nums);
-      virtual void reset();
+        int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items);
+        virtual void set_cell_allocation(const std::vector<int> &cell_allocation);
+        virtual void set_tseq_nums(const std::vector<int> & tseq_nums);
+        virtual void reset();
     };
   } // namespace gsm
 } // namespace gr
diff --git a/lib/receiver/time_sample_ref.cc b/lib/receiver/time_sample_ref.cc
new file mode 100644
index 0000000..0cf85ed
--- /dev/null
+++ b/lib/receiver/time_sample_ref.cc
@@ -0,0 +1,60 @@
+/* -*- c++ -*- */
+/*
+ * @file
+ * @author (C) 2017 by Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ *
+ * Gr-gsm 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.
+ *
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <math.h>
+#include "time_sample_ref.h"
+
+namespace gr {
+  namespace gsm {
+    time_sample_ref::time_sample_ref(double samp_rate): d_samp_rate(samp_rate)
+    {
+    }
+    
+    time_sample_ref::~time_sample_ref()
+    {
+    }
+    
+    void time_sample_ref::update(time_spec_t last_rx_time, uint64_t current_start_offset)
+    {
+        d_last_rx_time = last_rx_time;
+        d_current_start_offset = current_start_offset;
+    }
+    
+    time_spec_t time_sample_ref::offset_to_time(uint64_t offset)
+    {
+      uint64_t samples_from_last_rx_time = offset - d_current_start_offset;
+      time_spec_t time = time_spec_t(static_cast<double>(samples_from_last_rx_time)/d_samp_rate) + d_last_rx_time;
+      
+      return time;
+    }
+
+    uint64_t time_sample_ref::time_to_offset(time_spec_t time)
+    {
+      double samples_since_last_rx_time_tag = (time-d_last_rx_time).get_real_secs()*d_samp_rate;
+//      double fractional_part = round(samples_since_last_rx_time_tag) - samples_since_last_rx_time_tag;
+      uint64_t offset = static_cast<uint64_t>(round(samples_since_last_rx_time_tag)) + d_current_start_offset;
+      
+      return offset;
+    }
+  } // namespace gsm
+} // namespace gr
+
diff --git a/lib/receiver/time_sample_ref.h b/lib/receiver/time_sample_ref.h
new file mode 100644
index 0000000..793944d
--- /dev/null
+++ b/lib/receiver/time_sample_ref.h
@@ -0,0 +1,49 @@
+/* -*- c++ -*- */
+/*
+ * @file
+ * @author (C) 2017 by Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ *
+ * Gr-gsm 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.
+ *
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef INCLUDED_TIME_SAMPLE_REF_IMPL_H
+#define INCLUDED_TIME_SAMPLE_REF_IMPL_H
+
+#include <stdint.h>
+#include <grgsm/misc_utils/time_spec.h>
+
+namespace gr {
+  namespace gsm {
+    /*
+    Class for storing time reference and for conversions time<->sample number 
+    */
+    class time_sample_ref
+    {
+     private:
+        double d_samp_rate;
+        time_spec_t d_last_rx_time;
+        uint64_t d_current_start_offset;
+     public:
+        time_sample_ref(double samp_rate);
+        ~time_sample_ref();
+        void update(time_spec_t last_rx_time, uint64_t current_start_offset);
+        time_spec_t offset_to_time(uint64_t offset);
+        uint64_t time_to_offset(time_spec_t time);
+    };
+  } // namespace gsm
+} // namespace gr
+#endif// INCLUDED_TIME_SAMPLE_REF_IMPL_H
diff --git a/lib/receiver/viterbi_detector.cc b/lib/receiver/viterbi_detector.cc
index 6a64a2c..3dce379 100644
--- a/lib/receiver/viterbi_detector.cc
+++ b/lib/receiver/viterbi_detector.cc
@@ -56,7 +56,8 @@
  */
 
 #include <gnuradio/gr_complex.h>
-#include <gsm_constants.h>
+#include <grgsm/gsm_constants.h>
+#include <cmath>
 
 #define PATHS_NUM (1 << (CHAN_IMP_RESP_LENGTH-1))
 
diff --git a/lib/transmitter/CMakeLists.txt b/lib/transmitter/CMakeLists.txt
new file mode 100644
index 0000000..eb53162
--- /dev/null
+++ b/lib/transmitter/CMakeLists.txt
@@ -0,0 +1,24 @@
+# Copyright 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.
+
+add_sources(
+   txtime_setter_impl.cc
+   preprocess_tx_burst_impl.cc
+   gen_test_ab_impl
+)
diff --git a/lib/transmitter/gen_test_ab_impl.cc b/lib/transmitter/gen_test_ab_impl.cc
new file mode 100644
index 0000000..bb9c9f6
--- /dev/null
+++ b/lib/transmitter/gen_test_ab_impl.cc
@@ -0,0 +1,107 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; 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 <grgsm/gsmtap.h>
+#include <grgsm/gsm_constants.h>
+#include "gen_test_ab_impl.h"
+
+namespace gr {
+  namespace gsm {
+
+    static uint8_t rach_synch_seq[] = {
+      0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
+      1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0  ,
+      1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0,
+    };
+  
+    static uint8_t AB[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+//    static uint8_t AB[] = {0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1};
+// static uint8_t AB[] = { 1, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1};
+//  static uint8_t AB[] = {1,1,1,1,1,1,1,1,1,0,1,1,0,1,0,0,1,0,0,0,0,0,0,0,0,1,1,0,0,1,1,0,0,1,0,1,0,1,0,1,1,1,0,0,0,0,1,1,1,0,0,1,0,0,0,1,0,1,0,1,0,0,1,0,1,0,1,1,0,1,1,0,0,1,0,1,0,0,0,1,1,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
+//  ,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1};
+    gen_test_ab::sptr
+    gen_test_ab::make()
+    {
+      return gnuradio::get_initial_sptr
+        (new gen_test_ab_impl());
+    }
+
+    /*
+     * The private constructor
+     */
+    gen_test_ab_impl::gen_test_ab_impl()
+      : gr::block("gen_test_ab",
+              gr::io_signature::make(0, 0, 0),
+              gr::io_signature::make(0, 0, 0))
+    {
+        message_port_register_in(pmt::intern("bursts_in"));
+        message_port_register_out(pmt::intern("bursts_out"));
+
+        set_msg_handler(pmt::intern("bursts_in"),  boost::bind(&gen_test_ab_impl::generate_ab,   this, _1));
+    }
+
+    /*
+     * Our virtual destructor.
+     */
+    gen_test_ab_impl::~gen_test_ab_impl()
+    {
+    }
+    
+    void gen_test_ab_impl::generate_ab(pmt::pmt_t burst)
+    {
+        uint8_t buf[sizeof(gsmtap_hdr) + 148];
+        struct gsmtap_hdr *tap_header = (struct gsmtap_hdr *) buf;
+        uint8_t *access_burst = buf + sizeof(gsmtap_hdr);
+
+//        memset(access_burst, 0, 8); /* TB */
+//        memcpy(access_burst + 8, rach_synch_seq, 41); /* sync seq */
+//        memcpy(access_burst + 49, AB, 36); /* payload */
+//        memset(access_burst + 85, 0, 63); /* TB + GP */
+        
+        memcpy(access_burst, AB, 148);
+        
+        gsmtap_hdr * header = (gsmtap_hdr *)(pmt::blob_data(pmt::cdr(burst)));
+        uint32_t frame_nr = be32toh(header->frame_number);
+        frame_nr = (frame_nr+51)% (26*51*2048);
+        
+        tap_header->version = GSMTAP_VERSION;
+        tap_header->hdr_len = sizeof(gsmtap_hdr) / 4;
+        tap_header->type = GSMTAP_TYPE_UM_BURST;
+        tap_header->sub_type = GSMTAP_BURST_ACCESS;
+        tap_header->frame_number = htobe32(frame_nr);
+        tap_header->timeslot = header->timeslot;
+        tap_header->arfcn = 0;
+        
+        pmt::pmt_t blob = pmt::make_blob(buf, sizeof(gsmtap_hdr) + BURST_SIZE);
+        pmt::pmt_t pdu_header = pmt::make_dict();
+        
+        pmt::pmt_t new_msg = pmt::cons(pdu_header, blob);
+        message_port_pub(pmt::intern("bursts_out"), new_msg);
+    }
+  } /* namespace gsm */
+} /* namespace gr */
+
diff --git a/lib/transmitter/gen_test_ab_impl.h b/lib/transmitter/gen_test_ab_impl.h
new file mode 100644
index 0000000..366481e
--- /dev/null
+++ b/lib/transmitter/gen_test_ab_impl.h
@@ -0,0 +1,47 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ * 
+ */
+
+#ifndef INCLUDED_GSM_GEN_TEST_AB_IMPL_H
+#define INCLUDED_GSM_GEN_TEST_AB_IMPL_H
+
+#include <grgsm/transmitter/gen_test_ab.h>
+#include <grgsm/misc_utils/time_spec.h>
+#include <grgsm/misc_utils/fn_time.h>
+
+namespace gr {
+  namespace gsm {
+
+    class gen_test_ab_impl : public gen_test_ab
+    {
+     private:
+      void generate_ab(pmt::pmt_t burst);
+      
+     public:
+      gen_test_ab_impl();
+      ~gen_test_ab_impl();
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GSM_GEN_TEST_AB_IMPL_H */
+
diff --git a/lib/transmitter/preprocess_tx_burst_impl.cc b/lib/transmitter/preprocess_tx_burst_impl.cc
new file mode 100644
index 0000000..5fbac98
--- /dev/null
+++ b/lib/transmitter/preprocess_tx_burst_impl.cc
@@ -0,0 +1,96 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @author Vadim Yanitskiy <axilirator@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; 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 <assert.h>
+
+#include <gnuradio/io_signature.h>
+#include <grgsm/gsm_constants.h>
+#include <grgsm/gsmtap.h>
+
+#include "preprocess_tx_burst_impl.h"
+
+namespace gr {
+  namespace gsm {
+
+    preprocess_tx_burst::sptr
+    preprocess_tx_burst::make()
+    {
+      return gnuradio::get_initial_sptr
+        (new preprocess_tx_burst_impl());
+    }
+
+    /*
+     * The private constructor
+     */
+    preprocess_tx_burst_impl::preprocess_tx_burst_impl()
+      : gr::block("preprocess_tx_burst",
+        gr::io_signature::make(0, 0, 0),
+        gr::io_signature::make(0, 0, 0))
+    {
+        message_port_register_in(pmt::mp("bursts_in"));
+        message_port_register_out(pmt::mp("bursts_out"));
+
+        set_msg_handler(pmt::mp("bursts_in"),
+          boost::bind(&preprocess_tx_burst_impl::process_burst, this, _1));
+    }
+
+    /*
+     * Our virtual destructor.
+     */
+    preprocess_tx_burst_impl::~preprocess_tx_burst_impl()
+    {
+    }
+    
+    void preprocess_tx_burst_impl::process_burst(pmt::pmt_t msg_in)
+    {
+      pmt::pmt_t blob_in = pmt::cdr(msg_in);
+
+      // Extract GSMTAP header from message
+      gsmtap_hdr *burst_hdr = (gsmtap_hdr *) pmt::blob_data(blob_in);
+
+      // Extract burst bits from message
+      uint8_t *burst_bits = (uint8_t *)
+        (pmt::blob_data(blob_in)) + sizeof(gsmtap_hdr);
+
+      // Determine and check burst length
+      size_t burst_len = pmt::blob_length(blob_in) - sizeof(gsmtap_hdr);
+      assert(burst_len == BURST_SIZE);
+
+      // The Access Burst last has reduced length
+      if (burst_hdr->sub_type == GSMTAP_BURST_ACCESS)
+        burst_len = ACCESS_BURST_SIZE;
+
+      // Prepare an output message
+      pmt::pmt_t blob_out = pmt::make_blob(burst_bits, burst_len);
+      pmt::pmt_t msg_out = pmt::cons(pmt::car(msg_in), blob_out);
+
+      /* Send a message to the output */
+      message_port_pub(pmt::mp("bursts_out"), msg_out);
+    }
+
+  } /* namespace gsm */
+} /* namespace gr */
diff --git a/lib/transmitter/preprocess_tx_burst_impl.h b/lib/transmitter/preprocess_tx_burst_impl.h
new file mode 100644
index 0000000..27fc508
--- /dev/null
+++ b/lib/transmitter/preprocess_tx_burst_impl.h
@@ -0,0 +1,47 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ * 
+ */
+
+#ifndef INCLUDED_GSM_PREPROCESS_TX_BURST_IMPL_H
+#define INCLUDED_GSM_PREPROCESS_TX_BURST_IMPL_H
+
+#include <grgsm/transmitter/preprocess_tx_burst.h>
+#include <grgsm/misc_utils/time_spec.h>
+#include <grgsm/misc_utils/fn_time.h>
+
+namespace gr {
+  namespace gsm {
+
+    class preprocess_tx_burst_impl : public preprocess_tx_burst
+    {
+     private:
+      void process_burst(pmt::pmt_t burst);
+      
+     public:
+      preprocess_tx_burst_impl();
+      ~preprocess_tx_burst_impl();
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GSM_PREPROCESS_TX_BURST_IMPL_H */
+
diff --git a/lib/transmitter/txtime_setter_impl.cc b/lib/transmitter/txtime_setter_impl.cc
new file mode 100644
index 0000000..33bc994
--- /dev/null
+++ b/lib/transmitter/txtime_setter_impl.cc
@@ -0,0 +1,196 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @author Vadim Yanitskiy <axilirator@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; 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 <grgsm/gsmtap.h>
+
+#include "txtime_setter_impl.h"
+
+#define UNKNOWN_FN 0xffffffff
+#define MAX_EARLY_TIME_DIFF 10.0
+
+namespace gr {
+  namespace gsm {
+
+    txtime_setter::sptr
+    txtime_setter::make(
+      uint32_t init_fn, uint64_t init_time_secs,
+      double init_time_fracs, uint64_t time_hint_secs,
+      double time_hint_fracs, double timing_advance,
+      double delay_correction)
+    {
+      return gnuradio::get_initial_sptr
+        (new txtime_setter_impl(init_fn, init_time_secs,
+          init_time_fracs, time_hint_secs, time_hint_fracs,
+          timing_advance, delay_correction));
+    }
+
+    /*
+     * The private constructor
+     */
+    txtime_setter_impl::txtime_setter_impl(
+      uint32_t init_fn, uint64_t init_time_secs,
+      double init_time_fracs, uint64_t time_hint_secs,
+      double time_hint_fracs, double timing_advance,
+      double delay_correction
+    ) : gr::block("txtime_setter",
+          gr::io_signature::make(0, 0, 0),
+          gr::io_signature::make(0, 0, 0)),
+        d_time_hint(time_hint_secs,time_hint_fracs),
+        d_time_ref(init_time_secs,init_time_fracs),
+        d_delay_correction(delay_correction),
+        d_timing_advance(timing_advance),
+        d_fn_ref(init_fn),
+        d_ts_ref(0)
+    {
+        // Register I/O ports
+        message_port_register_in(pmt::mp("fn_time"));
+        message_port_register_in(pmt::mp("bursts_in"));
+        message_port_register_out(pmt::mp("bursts_out"));
+
+        // Bind message handlers
+        set_msg_handler(pmt::mp("fn_time"),
+          boost::bind(&txtime_setter_impl::process_fn_time_reference,
+            this, _1));
+        set_msg_handler(pmt::mp("bursts_in"),
+          boost::bind(&txtime_setter_impl::process_txtime_of_burst,
+            this, _1));
+    }
+
+    /*
+     * Our virtual destructor.
+     */
+    txtime_setter_impl::~txtime_setter_impl()
+    {
+    }
+    
+    void txtime_setter_impl::process_fn_time_reference(pmt::pmt_t msg)
+    {
+      pmt::pmt_t not_found = pmt::intern("not_found");
+      pmt::pmt_t fn_time, time_hint;
+
+      fn_time = pmt::dict_ref(msg,
+        pmt::intern("fn_time"), not_found);
+      time_hint = pmt::dict_ref(msg,
+        pmt::intern("fn_time"), not_found);
+
+      if (fn_time != not_found) {
+        uint32_t fn_ref = static_cast<uint32_t>
+          (pmt::to_uint64(pmt::car(pmt::car(fn_time))));
+        uint32_t ts = static_cast<uint32_t>
+          (pmt::to_uint64(pmt::cdr(pmt::car(fn_time))));
+        uint64_t time_secs = pmt::to_uint64(
+          pmt::car(pmt::cdr(fn_time)));
+        double time_fracs = pmt::to_double(
+          pmt::cdr(pmt::cdr(fn_time)));
+
+        set_fn_time_reference(fn_ref, ts, time_secs, time_fracs);
+      } else if (time_hint != not_found) {
+        set_time_hint(pmt::to_uint64(pmt::car(fn_time)),
+          pmt::to_double(pmt::cdr(fn_time)));
+      }
+    }
+
+    void txtime_setter_impl::process_txtime_of_burst(pmt::pmt_t msg_in)
+    {
+      if (d_fn_ref != UNKNOWN_FN)
+      {
+        pmt::pmt_t blob = pmt::cdr(msg_in);
+
+        // Extract GSMTAP header from message
+        gsmtap_hdr *header = (gsmtap_hdr *) pmt::blob_data(blob);
+        uint32_t frame_nr = be32toh(header->frame_number);
+        uint32_t ts_num = header->timeslot;
+
+        time_format txtime = fn_time_delta_cpp(d_fn_ref, d_time_ref,
+          frame_nr, d_time_hint, ts_num, d_ts_ref);
+
+        time_spec_t txtime_spec = time_spec_t(txtime.first, txtime.second);
+        txtime_spec -= d_delay_correction;
+        txtime_spec -= d_timing_advance;
+
+        time_spec_t current_time_estimate = time_spec_t(d_time_hint.first, d_time_hint.second);
+
+        if (txtime_spec <= current_time_estimate) { // Drop too late bursts
+          std::cout << "lB" << std::flush;
+        } else if (txtime_spec > current_time_estimate + MAX_EARLY_TIME_DIFF) { // Drop too early bursts
+          std::cout << "eB" << std::flush;      //TODO: too early condition might happen when changing BTSes.
+                                                //Wrong fn_time is applied to new or old bursts in such situation.
+                                                //This solution is not perfect as MS might be blocked upto 
+                                                //MAX_EARLY_TIME_DIFF seconds.
+                                                //Better solution would be to indentify fn_time and burst coming
+                                                //from given BTS (i.e. based on ARFCN) and dropping bursts for which
+                                                //the bts_id doesn't match with bts_id of fn_time.
+        } else { //process bursts that are in the right time-frame
+          pmt::pmt_t tags_dict = pmt::dict_add(
+            pmt::make_dict(),
+            pmt::intern("tx_time"),
+            pmt::make_tuple(
+              pmt::from_uint64(txtime_spec.get_full_secs()),
+              pmt::from_double(txtime_spec.get_frac_secs()))
+          );
+
+          tags_dict = pmt::dict_add(tags_dict,
+            pmt::intern("fn"), pmt::from_uint64(frame_nr));
+          tags_dict = pmt::dict_add(tags_dict,
+            pmt::intern("ts"), pmt::from_uint64(ts_num));
+
+          // Send a message to the output
+          pmt::pmt_t msg_out = pmt::cons(tags_dict, pmt::cdr(msg_in));
+          message_port_pub(pmt::mp("bursts_out"), msg_out);
+        }
+      }
+    }
+
+    void txtime_setter_impl::set_fn_time_reference(
+      uint32_t fn, uint32_t ts, uint64_t time_secs,
+      double time_fracs)
+    {
+      d_fn_ref = fn;
+      d_ts_ref = ts;
+      d_time_ref = std::make_pair(time_secs, time_fracs);
+      set_time_hint(time_secs, time_fracs);
+    }
+
+    void txtime_setter_impl::set_time_hint(
+      uint64_t time_hint_secs, double time_hint_fracs)
+    {
+      d_time_hint = std::make_pair(time_hint_secs, time_hint_fracs);
+    }
+
+    void txtime_setter_impl::set_delay_correction(double delay_correction)
+    {
+      d_delay_correction = delay_correction;
+    }
+
+    void txtime_setter_impl::set_timing_advance(double timing_advance)
+    {
+      d_timing_advance = timing_advance;
+    }
+
+  } /* namespace gsm */
+} /* namespace gr */
diff --git a/lib/transmitter/txtime_setter_impl.h b/lib/transmitter/txtime_setter_impl.h
new file mode 100644
index 0000000..62f500a
--- /dev/null
+++ b/lib/transmitter/txtime_setter_impl.h
@@ -0,0 +1,64 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Piotr Krysik <ptrkrysik@gmail.com>
+ * @section LICENSE
+ * 
+ * Gr-gsm 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.
+ * 
+ * Gr-gsm 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 gr-gsm; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ * 
+ */
+
+#ifndef INCLUDED_GSM_TXTIME_SETTER_IMPL_H
+#define INCLUDED_GSM_TXTIME_SETTER_IMPL_H
+
+#include <grgsm/transmitter/txtime_setter.h>
+#include <grgsm/misc_utils/time_spec.h>
+#include <grgsm/misc_utils/fn_time.h>
+
+namespace gr {
+  namespace gsm {
+
+    class txtime_setter_impl : public txtime_setter
+    {
+     private:
+      uint32_t d_fn_ref;
+      uint32_t d_ts_ref;
+      time_format d_time_ref;
+      time_format d_time_hint;
+      double d_timing_advance;
+      double d_delay_correction;
+
+      void process_fn_time_reference(pmt::pmt_t msg);
+      void process_txtime_of_burst(pmt::pmt_t msg);
+
+     public:
+      txtime_setter_impl(uint32_t init_fn, uint64_t init_time_secs,
+        double init_time_fracs, uint64_t time_hint_secs,
+        double time_hint_fracs, double timing_advance,
+        double delay_correction);
+      ~txtime_setter_impl();
+
+      // Where all the action really happens
+      void set_fn_time_reference(uint32_t fn, uint32_t ts,
+        uint64_t time_secs, double time_fracs);
+      void set_time_hint(uint64_t time_hint_secs, double time_hint_fracs);
+      void set_delay_correction(double delay_correction);
+      void set_timing_advance(double timing_advance);
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GSM_TXTIME_SETTER_IMPL_H */