diff --git a/src/algorithms/PVT/libs/rtklib_solver.cc b/src/algorithms/PVT/libs/rtklib_solver.cc
index 726225998..93685eb24 100644
--- a/src/algorithms/PVT/libs/rtklib_solver.cc
+++ b/src/algorithms/PVT/libs/rtklib_solver.cc
@@ -349,7 +349,7 @@ bool rtklib_solver::get_PVT(const std::map<int,Gnss_Synchro> & gnss_observables_
             result = rtkpos(&rtk_, obs_data, valid_obs, &nav_data);
             if(result == 0)
                 {
-                    LOG(INFO) << "RTKLIB rtkpos error message: " << rtk_.errbuf;
+                    DLOG(INFO) << "RTKLIB rtkpos error message: " << rtk_.errbuf;
                     this->set_time_offset_s(0.0); //reset rx time estimation
                     this->set_num_valid_observations(0);
                 }
diff --git a/src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition_cc.h b/src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition_cc.h
index bb3db1e43..17fa90689 100644
--- a/src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition_cc.h
+++ b/src/algorithms/acquisition/gnuradio_blocks/pcps_acquisition_cc.h
@@ -58,6 +58,7 @@
 #include <gnuradio/gr_complex.h>
 #include <gnuradio/fft/fft.h>
 #include "gnss_synchro.h"
+#include <glog/logging.h>
 
 class pcps_acquisition_cc;
 
diff --git a/src/algorithms/channel/adapters/channel.cc b/src/algorithms/channel/adapters/channel.cc
index 425dbb968..e66074b7a 100644
--- a/src/algorithms/channel/adapters/channel.cc
+++ b/src/algorithms/channel/adapters/channel.cc
@@ -40,7 +40,7 @@ using google::LogMessage;
 Channel::Channel(ConfigurationInterface *configuration, unsigned int channel,
         std::shared_ptr<GNSSBlockInterface> pass_through, std::shared_ptr<AcquisitionInterface> acq,
         std::shared_ptr<TrackingInterface> trk, std::shared_ptr<TelemetryDecoderInterface> nav,
-        std::string role, std::string implementation, boost::shared_ptr<gr::msg_queue> queue)
+        std::string role, std::string implementation, gr::msg_queue::sptr queue)
 {
     pass_through_ = pass_through;
     acq_ = acq;
@@ -50,6 +50,7 @@ Channel::Channel(ConfigurationInterface *configuration, unsigned int channel,
     implementation_ = implementation;
     channel_ = channel;
     queue_ = queue;
+    channel_fsm_ = std::make_shared<ChannelFsm>();
 
     flag_enable_fpga = configuration->property("Channel.enable_FPGA", false);
     acq_->set_channel(channel_);
@@ -89,24 +90,21 @@ Channel::Channel(ConfigurationInterface *configuration, unsigned int channel,
     repeat_ = configuration->property("Acquisition_" + implementation_ + boost::lexical_cast<std::string>(channel_) + ".repeat_satellite", false);
     DLOG(INFO) << "Channel " << channel_ << " satellite repeat = " << repeat_;
 
-    channel_fsm_.set_acquisition(acq_);
-    channel_fsm_.set_tracking(trk_);
-    channel_fsm_.set_channel(channel_);
-    channel_fsm_.set_queue(queue_);
+    channel_fsm_->set_acquisition(acq_);
+    channel_fsm_->set_tracking(trk_);
+    channel_fsm_->set_channel(channel_);
+    channel_fsm_->set_queue(queue_);
 
     connected_ = false;
 
     gnss_signal_ = Gnss_Signal(implementation_);
 
-    channel_msg_rx = channel_msg_receiver_make_cc(&channel_fsm_, repeat_);
+    channel_msg_rx = channel_msg_receiver_make_cc(channel_fsm_, repeat_);
 }
 
 
 // Destructor
-Channel::~Channel()
-{
-    channel_fsm_.terminate();
-}
+Channel::~Channel(){}
 
 
 void Channel::connect(gr::top_block_sptr top_block)
@@ -139,7 +137,6 @@ void Channel::connect(gr::top_block_sptr top_block)
     top_block->msg_connect(nav_->get_left_block(), pmt::mp("preamble_timestamp_s"), trk_->get_right_block(), pmt::mp("preamble_timestamp_s"));
     DLOG(INFO) << "MSG FEEDBACK CHANNEL telemetry_decoder -> tracking";
 
-    //std::cout<<"has port: "<<trk_->get_right_block()->has_msg_port(pmt::mp("events"))<<std::endl;
     top_block->msg_connect(acq_->get_right_block(), pmt::mp("events"), channel_msg_rx, pmt::mp("events"));
     top_block->msg_connect(trk_->get_right_block(), pmt::mp("events"), channel_msg_rx, pmt::mp("events"));
 
@@ -187,6 +184,7 @@ gr::basic_block_sptr Channel::get_right_block()
 
 void Channel::set_signal(const Gnss_Signal& gnss_signal)
 {
+    std::lock_guard<std::mutex> lk(mx);
     gnss_signal_ = gnss_signal;
     std::string str_aux = gnss_signal_.get_signal_str();
     const char * str = str_aux.c_str(); // get a C style null terminated string
@@ -201,6 +199,14 @@ void Channel::set_signal(const Gnss_Signal& gnss_signal)
 
 void Channel::start_acquisition()
 {
-    channel_fsm_.Event_start_acquisition();
+    std::lock_guard<std::mutex> lk(mx);
+    bool result = false;
+    result = channel_fsm_->Event_start_acquisition();
+    if(!result)
+        {
+            LOG(WARNING) << "Invalid channel event";
+            return;
+        }
+    DLOG(INFO) << "Channel start_acquisition()";
 }
 
diff --git a/src/algorithms/channel/adapters/channel.h b/src/algorithms/channel/adapters/channel.h
index a05697eed..8740b5ad9 100644
--- a/src/algorithms/channel/adapters/channel.h
+++ b/src/algorithms/channel/adapters/channel.h
@@ -37,6 +37,7 @@
 
 #include <memory>
 #include <string>
+#include <mutex>
 #include <gnuradio/msg_queue.h>
 #include <gnuradio/block.h>
 #include "channel_interface.h"
@@ -63,8 +64,7 @@ public:
     Channel(ConfigurationInterface *configuration, unsigned int channel,
             std::shared_ptr<GNSSBlockInterface> pass_through, std::shared_ptr<AcquisitionInterface> acq,
             std::shared_ptr<TrackingInterface> trk, std::shared_ptr<TelemetryDecoderInterface> nav,
-            std::string role, std::string implementation,
-            boost::shared_ptr<gr::msg_queue> queue);
+            std::string role, std::string implementation, gr::msg_queue::sptr queue);
     //! Virtual destructor
     virtual ~Channel();
 
@@ -79,6 +79,7 @@ public:
     inline std::string implementation() override { return implementation_; }
 
     inline size_t item_size() override { return 0; }
+
     inline Gnss_Signal get_signal() const override { return gnss_signal_; }
 
     void start_acquisition() override;   //!< Start the State Machine
@@ -104,8 +105,9 @@ private:
     Gnss_Signal gnss_signal_;
     bool connected_;
     bool repeat_;
-    ChannelFsm channel_fsm_;
-    boost::shared_ptr<gr::msg_queue> queue_;
+    std::shared_ptr<ChannelFsm> channel_fsm_;
+    gr::msg_queue::sptr queue_;
+    std::mutex mx;
 };
 
 #endif /*GNSS_SDR_CHANNEL_H_*/
diff --git a/src/algorithms/channel/libs/channel_fsm.cc b/src/algorithms/channel/libs/channel_fsm.cc
index 187d419f4..b6f23cbeb 100644
--- a/src/algorithms/channel/libs/channel_fsm.cc
+++ b/src/algorithms/channel/libs/channel_fsm.cc
@@ -1,11 +1,12 @@
 /*!
  * \file channel_fsm.cc
- * \brief Implementation of a State Machine for channel using boost::statechart
- * \author Luis Esteve, 2011. luis(at)epsilon-formacion.com
+ * \brief Implementation of a State Machine for channel
+ * \authors Antonio Ramos, 2017. antonio.ramos(at)cttc.es
+ *          Luis Esteve,   2011. luis(at)epsilon-formacion.com
  *
  * -------------------------------------------------------------------------
  *
- * Copyright (C) 2010-2015  (see AUTHORS file for a list of contributors)
+ * Copyright (C) 2010-2017  (see AUTHORS file for a list of contributors)
  *
  * GNSS-SDR is a software defined Global Navigation
  *          Satellite Systems receiver
@@ -29,109 +30,16 @@
  */
 
 #include "channel_fsm.h"
-#include <memory>
-#include <boost/statechart/simple_state.hpp>
-#include <boost/statechart/state.hpp>
-#include <boost/statechart/transition.hpp>
-#include <boost/statechart/custom_reaction.hpp>
-#include <boost/mpl/list.hpp>
 #include <glog/logging.h>
 #include "control_message_factory.h"
 
 
-struct Ev_channel_start_acquisition: sc::event<Ev_channel_start_acquisition>
-{};
-
-struct Ev_channel_valid_acquisition: sc::event<Ev_channel_valid_acquisition>
-{};
-
-struct Ev_channel_failed_acquisition_repeat: sc::event<Ev_channel_failed_acquisition_repeat>
-{};
-
-struct Ev_channel_failed_acquisition_no_repeat: sc::event<Ev_channel_failed_acquisition_no_repeat>
-{};
-
-struct Ev_channel_failed_tracking_standby: sc::event<Ev_channel_failed_tracking_standby>
-{};
-
-//struct Ev_channel_failed_tracking_reacq: sc::event<Ev_channel_failed_tracking_reacq>
-//{};
-
-struct channel_idle_fsm_S0: public sc::state<channel_idle_fsm_S0, ChannelFsm>
-{
-public:
-    // sc::transition(event, next state)
-    typedef sc::transition<Ev_channel_start_acquisition, channel_acquiring_fsm_S1> reactions;
-    channel_idle_fsm_S0(my_context ctx) : my_base(ctx)
-    {
-        //std::cout << "Enter Channel_Idle_S0 " << std::endl;
-    }
-};
-
-
-struct channel_acquiring_fsm_S1: public sc::state<channel_acquiring_fsm_S1, ChannelFsm>
-{
-public:
-    typedef mpl::list<sc::transition<Ev_channel_failed_acquisition_no_repeat, channel_waiting_fsm_S3>,
-                      sc::transition<Ev_channel_failed_acquisition_repeat, channel_acquiring_fsm_S1>,
-                      sc::transition<Ev_channel_valid_acquisition, channel_tracking_fsm_S2> > reactions;
-
-    channel_acquiring_fsm_S1(my_context ctx) : my_base(ctx)
-    {
-        //std::cout << "Enter Channel_Acq_S1 " << std::endl;
-        context<ChannelFsm> ().start_acquisition();
-    }
-    ~channel_acquiring_fsm_S1()
-    {
-        //std::cout << "Exit Channel_Acq_S1 " << std::endl;
-    }
-};
-
-
-struct channel_tracking_fsm_S2: public sc::state<channel_tracking_fsm_S2, ChannelFsm>
-{
-public:
-    typedef mpl::list<sc::transition<Ev_channel_failed_tracking_standby, channel_idle_fsm_S0>,
-                      sc::transition<Ev_channel_start_acquisition, channel_acquiring_fsm_S1>> reactions;
-
-    channel_tracking_fsm_S2(my_context ctx) : my_base(ctx)
-    {
-       //std::cout << "Enter Channel_tracking_S2 " << std::endl;
-        context<ChannelFsm> ().start_tracking();
-    }
-
-    ~channel_tracking_fsm_S2()
-    {
-        //std::cout << "Exit Channel_tracking_S2 " << std::endl;
-        context<ChannelFsm> ().notify_stop_tracking();
-    }
-
-};
-
-
-struct channel_waiting_fsm_S3: public sc::state<channel_waiting_fsm_S3, ChannelFsm>
-{
-public:
-    typedef sc::transition<Ev_channel_start_acquisition,
-            channel_acquiring_fsm_S1> reactions;
-
-    channel_waiting_fsm_S3(my_context ctx) :
-        my_base(ctx)
-    {
-        //std::cout << "Enter Channel_waiting_S3 " << std::endl;
-        context<ChannelFsm> ().request_satellite();
-    }
-   // ~channel_waiting_fsm_S3(){}
-};
-
-
-
 ChannelFsm::ChannelFsm()
 {
     acq_ = nullptr;
     trk_ = nullptr;
     channel_ = 0;
-    initiate(); //start the FSM
+    d_state = 0;
 }
 
 
@@ -141,62 +49,115 @@ ChannelFsm::ChannelFsm(std::shared_ptr<AcquisitionInterface> acquisition) :
 {
     trk_ = nullptr;
     channel_ = 0;
-    initiate(); //start the FSM
+    d_state = 0;
 }
 
 
-
-void ChannelFsm::Event_start_acquisition()
+bool ChannelFsm::Event_start_acquisition()
 {
-    this->process_event(Ev_channel_start_acquisition());
-    //std::cout<<"Ev_channel_start_acquisition launched"<<std::endl;
+    std::lock_guard<std::mutex> lk(mx);
+    if((d_state == 1) || (d_state == 2))
+        {
+            return false;
+        }
+    else
+        {
+            d_state = 1;
+            start_acquisition();
+            DLOG(INFO) << "CH = " << channel_ << ". Ev start acquisition";
+            return true;
+        }
 }
 
 
-void ChannelFsm::Event_valid_acquisition()
+bool ChannelFsm::Event_valid_acquisition()
 {
-    this->process_event(Ev_channel_valid_acquisition());
+    std::lock_guard<std::mutex> lk(mx);
+    if(d_state != 1)
+        {
+            return false;
+        }
+    else
+        {
+            d_state = 2;
+            start_tracking();
+            DLOG(INFO) << "CH = " << channel_ << ". Ev valid acquisition";
+            return true;
+        }
 }
 
 
-void ChannelFsm::Event_failed_acquisition_repeat()
+bool ChannelFsm::Event_failed_acquisition_repeat()
 {
-    this->process_event(Ev_channel_failed_acquisition_repeat());
+    std::lock_guard<std::mutex> lk(mx);
+    if(d_state != 1)
+        {
+            return false;
+        }
+    else
+        {
+            d_state = 1;
+            start_acquisition();
+            DLOG(INFO) << "CH = " << channel_ << ". Ev failed acquisition repeat";
+            return true;
+        }
 }
 
-void ChannelFsm::Event_failed_acquisition_no_repeat()
+
+bool ChannelFsm::Event_failed_acquisition_no_repeat()
 {
-    this->process_event(Ev_channel_failed_acquisition_no_repeat());
+    std::lock_guard<std::mutex> lk(mx);
+    if(d_state != 1)
+        {
+            return false;
+        }
+    else
+        {
+            d_state = 3;
+            request_satellite();
+            DLOG(INFO) << "CH = " << channel_ << ". Ev failed acquisition no repeat";
+            return true;
+        }
 }
 
 
-// Something is wrong here, we are using a memory after it ts freed
-void ChannelFsm::Event_failed_tracking_standby()
+bool ChannelFsm::Event_failed_tracking_standby()
 {
-    this->process_event(Ev_channel_failed_tracking_standby());
+    std::lock_guard<std::mutex> lk(mx);
+    if(d_state != 2)
+        {
+            return false;
+        }
+    else
+        {
+            d_state = 0;
+            notify_stop_tracking();
+            DLOG(INFO) << "CH = " << channel_ << ". Ev failed tracking standby";
+            return true;
+        }
 }
 
-//void ChannelFsm::Event_failed_tracking_reacq() {
-//    this->process_event(Ev_channel_failed_tracking_reacq());
-//}
-
 void ChannelFsm::set_acquisition(std::shared_ptr<AcquisitionInterface> acquisition)
 {
+    std::lock_guard<std::mutex> lk(mx);
     acq_ = acquisition;
 }
 
 void ChannelFsm::set_tracking(std::shared_ptr<TrackingInterface> tracking)
 {
+    std::lock_guard<std::mutex> lk(mx);
     trk_ = tracking;
 }
 
-void ChannelFsm::set_queue(boost::shared_ptr<gr::msg_queue> queue)
+void ChannelFsm::set_queue(gr::msg_queue::sptr queue)
 {
+    std::lock_guard<std::mutex> lk(mx);
     queue_ = queue;
 }
 
 void ChannelFsm::set_channel(unsigned int channel)
 {
+    std::lock_guard<std::mutex> lk(mx);
     channel_ = channel;
 }
 
diff --git a/src/algorithms/channel/libs/channel_fsm.h b/src/algorithms/channel/libs/channel_fsm.h
index 868388b7b..23b92c394 100644
--- a/src/algorithms/channel/libs/channel_fsm.h
+++ b/src/algorithms/channel/libs/channel_fsm.h
@@ -1,12 +1,12 @@
 /*!
  * \file channel_fsm.h
- * \brief Interface of the State Machine for channel using boost::statechart
- * \author Luis Esteve, 2011. luis(at)epsilon-formacion.com
- *
+ * \brief Interface of the State Machine for channel
+ * \authors Antonio Ramos, 2017. antonio.ramos(at)cttc.es
+ *          Luis Esteve,   2011. luis(at)epsilon-formacion.com
  *
  * -------------------------------------------------------------------------
  *
- * Copyright (C) 2010-2015  (see AUTHORS file for a list of contributors)
+ * Copyright (C) 2010-2017  (see AUTHORS file for a list of contributors)
  *
  * GNSS-SDR is a software defined Global Navigation
  *          Satellite Systems receiver
@@ -32,26 +32,17 @@
 #ifndef GNSS_SDR_CHANNEL_FSM_H
 #define GNSS_SDR_CHANNEL_FSM_H
 
-
-#include <boost/statechart/state_machine.hpp>
+#include <mutex>
+#include <memory>
 #include <gnuradio/msg_queue.h>
 #include "acquisition_interface.h"
 #include "tracking_interface.h"
 #include "telemetry_decoder_interface.h"
 
-
-namespace sc = boost::statechart;
-namespace mpl = boost::mpl;
-
-struct channel_idle_fsm_S0;
-struct channel_acquiring_fsm_S1;
-struct channel_tracking_fsm_S2;
-struct channel_waiting_fsm_S3;
-
 /*!
- * \brief This class implements a State Machine for channel using boost::statechart
+ * \brief This class implements a State Machine for channel
  */
-class ChannelFsm: public sc::state_machine<ChannelFsm, channel_idle_fsm_S0>
+class ChannelFsm
 {
 public:
     ChannelFsm();
@@ -59,26 +50,29 @@ public:
 
     void set_acquisition(std::shared_ptr<AcquisitionInterface> acquisition);
     void set_tracking(std::shared_ptr<TrackingInterface> tracking);
-    void set_queue(boost::shared_ptr<gr::msg_queue> queue);
+    void set_queue(gr::msg_queue::sptr queue);
     void set_channel(unsigned int channel);
+
+    //FSM EVENTS
+    bool Event_start_acquisition();
+    bool Event_valid_acquisition();
+    bool Event_failed_acquisition_repeat();
+    bool Event_failed_acquisition_no_repeat();
+    bool Event_failed_tracking_standby();
+
+private:
+
     void start_acquisition();
     void start_tracking();
     void request_satellite();
     void notify_stop_tracking();
 
-    //FSM EVENTS
-    void Event_start_acquisition();
-    void Event_valid_acquisition();
-    void Event_failed_acquisition_repeat();
-    void Event_failed_acquisition_no_repeat();
-    //void Event_gps_failed_tracking_reacq();
-    void Event_failed_tracking_standby();
-
-private:
     std::shared_ptr<AcquisitionInterface> acq_;
     std::shared_ptr<TrackingInterface> trk_;
-    boost::shared_ptr<gr::msg_queue> queue_;
+    gr::msg_queue::sptr queue_;
     unsigned int channel_;
+    unsigned int d_state;
+    std::mutex mx;
 };
 
 #endif /*GNSS_SDR_CHANNEL_FSM_H*/
diff --git a/src/algorithms/channel/libs/channel_msg_receiver_cc.cc b/src/algorithms/channel/libs/channel_msg_receiver_cc.cc
index 573c1aa84..7a80cfceb 100644
--- a/src/algorithms/channel/libs/channel_msg_receiver_cc.cc
+++ b/src/algorithms/channel/libs/channel_msg_receiver_cc.cc
@@ -37,37 +37,34 @@
 using google::LogMessage;
 
 
-channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(ChannelFsm* channel_fsm,  bool repeat)
+channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(std::shared_ptr<ChannelFsm> channel_fsm,  bool repeat)
 {
     return channel_msg_receiver_cc_sptr(new channel_msg_receiver_cc(channel_fsm, repeat));
 }
 
 void channel_msg_receiver_cc::msg_handler_events(pmt::pmt_t msg)
 {
+    bool result = false;
     try
     {
             long int message = pmt::to_long(msg);
             switch (message)
             {
             case 1: //positive acquisition
-                //DLOG(INFO) << "Channel " << channel_ << " ACQ SUCCESS satellite " <<
-                //    gnss_synchro_.System << " " << gnss_synchro_.PRN;
-                d_channel_fsm->Event_valid_acquisition();
+                result = d_channel_fsm->Event_valid_acquisition();
                 break;
             case 2: //negative acquisition
-                //DLOG(INFO) << "Channel " << channel_
-                //    << " ACQ FAILED satellite " << gnss_synchro_.System << " " << gnss_synchro_.PRN;
                 if (d_repeat == true)
                     {
-                        d_channel_fsm->Event_failed_acquisition_repeat();
+                        result = d_channel_fsm->Event_failed_acquisition_repeat();
                     }
                 else
                     {
-                        d_channel_fsm->Event_failed_acquisition_no_repeat();
+                        result = d_channel_fsm->Event_failed_acquisition_no_repeat();
                     }
                 break;
             case 3: // tracking loss of lock event
-                d_channel_fsm->Event_failed_tracking_standby();
+                result = d_channel_fsm->Event_failed_tracking_standby();
                 break;
             default:
                 LOG(WARNING) << "Default case, invalid message.";
@@ -78,10 +75,14 @@ void channel_msg_receiver_cc::msg_handler_events(pmt::pmt_t msg)
     {
             LOG(WARNING) << "msg_handler_telemetry Bad any cast!";
     }
+    if(!result)
+        {
+            LOG(WARNING) << "msg_handler_telemetry invalid event";
+        }
 }
 
 
-channel_msg_receiver_cc::channel_msg_receiver_cc(ChannelFsm* channel_fsm, bool repeat) :
+channel_msg_receiver_cc::channel_msg_receiver_cc(std::shared_ptr<ChannelFsm> channel_fsm, bool repeat) :
     gr::block("channel_msg_receiver_cc", gr::io_signature::make(0, 0, 0), gr::io_signature::make(0, 0, 0))
 {
     this->message_port_register_in(pmt::mp("events"));
diff --git a/src/algorithms/channel/libs/channel_msg_receiver_cc.h b/src/algorithms/channel/libs/channel_msg_receiver_cc.h
index 195d41e7c..77a91379a 100644
--- a/src/algorithms/channel/libs/channel_msg_receiver_cc.h
+++ b/src/algorithms/channel/libs/channel_msg_receiver_cc.h
@@ -38,7 +38,7 @@ class channel_msg_receiver_cc;
 
 typedef boost::shared_ptr<channel_msg_receiver_cc> channel_msg_receiver_cc_sptr;
 
-channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(ChannelFsm* channel_fsm, bool repeat);
+channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(std::shared_ptr<ChannelFsm> channel_fsm, bool repeat);
 
 /*!
  * \brief GNU Radio block that receives asynchronous channel messages from acquisition and tracking blocks
@@ -46,11 +46,11 @@ channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(ChannelFsm* channel_fs
 class channel_msg_receiver_cc : public gr::block
 {
 private:
-    ChannelFsm* d_channel_fsm;
+    std::shared_ptr<ChannelFsm> d_channel_fsm;
     bool d_repeat; // todo: change FSM to include repeat value
-    friend channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(ChannelFsm* channel_fsm, bool repeat);
+    friend channel_msg_receiver_cc_sptr channel_msg_receiver_make_cc(std::shared_ptr<ChannelFsm> channel_fsm, bool repeat);
     void msg_handler_events(pmt::pmt_t msg);
-    channel_msg_receiver_cc(ChannelFsm* channel_fsm, bool repeat);
+    channel_msg_receiver_cc(std::shared_ptr<ChannelFsm> channel_fsm, bool repeat);
 
 public:
     ~channel_msg_receiver_cc (); //!< Default destructor
diff --git a/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_cc.cc b/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_cc.cc
index 7ccb0c825..003bc8bd1 100644
--- a/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_cc.cc
+++ b/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l1_ca_telemetry_decoder_cc.cc
@@ -404,7 +404,7 @@ int gps_l1_ca_telemetry_decoder_cc::general_work (int noutput_items __attribute_
  void gps_l1_ca_telemetry_decoder_cc::set_satellite(const Gnss_Satellite & satellite)
  {
      d_satellite = Gnss_Satellite(satellite.get_system(), satellite.get_PRN());
-     LOG(INFO) << "Setting decoder Finite State Machine to satellite "  << d_satellite;
+     DLOG(INFO) << "Setting decoder Finite State Machine to satellite "  << d_satellite;
      d_GPS_FSM.i_satellite_PRN = d_satellite.get_PRN();
      DLOG(INFO) << "Navigation Satellite set to " << d_satellite;
  }
diff --git a/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l2c_telemetry_decoder_cc.cc b/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l2c_telemetry_decoder_cc.cc
index 242aca3ac..01b4bed0b 100644
--- a/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l2c_telemetry_decoder_cc.cc
+++ b/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l2c_telemetry_decoder_cc.cc
@@ -154,7 +154,7 @@ int gps_l2c_telemetry_decoder_cc::general_work (int noutput_items __attribute__(
             //* The time of the last input symbol can be computed from the message ToW and
             //* delay by the formulae:
             //* \code
-            //* symbolTime_ms = msg->tow * 6000 + *pdelay * 20
+            //* symbolTime_ms = msg->tow * 6000 + *pdelay * 20 + (12 * 20); 12 symbols of the encoder's transitory
             d_TOW_at_current_symbol = static_cast<double>(msg.tow) * 6.0 + static_cast<double>(delay) * GPS_L2_M_PERIOD + 12 * GPS_L2_M_PERIOD;
             d_TOW_at_current_symbol = floor(d_TOW_at_current_symbol * 1000.0) / 1000.0;
             d_flag_valid_word = true;
diff --git a/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l5_telemetry_decoder_cc.cc b/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l5_telemetry_decoder_cc.cc
index 30d549508..2d604b221 100644
--- a/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l5_telemetry_decoder_cc.cc
+++ b/src/algorithms/telemetry_decoder/gnuradio_blocks/gps_l5_telemetry_decoder_cc.cc
@@ -192,7 +192,7 @@ int gps_l5_telemetry_decoder_cc::general_work (int noutput_items __attribute__((
             //* The time of the last input symbol can be computed from the message ToW and
             //* delay by the formulae:
             //* \code
-            //* symbolTime_ms = msg->tow * 6000 + *pdelay * 10
+            //* symbolTime_ms = msg->tow * 6000 + *pdelay * 10 + (12 * 10); 12 symbols of the encoder's transitory
             d_TOW_at_current_symbol = (static_cast<double>(msg.tow) * 6.0) + (static_cast<double>(delay) + 12.0) * GPS_L5i_SYMBOL_PERIOD;
             d_TOW_at_current_symbol = floor(d_TOW_at_current_symbol * 1000.0) / 1000.0;
             d_flag_valid_word = true;
diff --git a/src/algorithms/tracking/gnuradio_blocks/gps_l1_ca_dll_pll_tracking_cc.cc b/src/algorithms/tracking/gnuradio_blocks/gps_l1_ca_dll_pll_tracking_cc.cc
index b90860ada..d3cbb6310 100644
--- a/src/algorithms/tracking/gnuradio_blocks/gps_l1_ca_dll_pll_tracking_cc.cc
+++ b/src/algorithms/tracking/gnuradio_blocks/gps_l1_ca_dll_pll_tracking_cc.cc
@@ -185,6 +185,7 @@ Gps_L1_Ca_Dll_Pll_Tracking_cc::Gps_L1_Ca_Dll_Pll_Tracking_cc(
 
 void Gps_L1_Ca_Dll_Pll_Tracking_cc::start_tracking()
 {
+    gr::thread::scoped_lock lk(d_setlock);
     /*
      *  correct the code phase according to the delay between acq and trk
      */
@@ -521,6 +522,7 @@ Gps_L1_Ca_Dll_Pll_Tracking_cc::~Gps_L1_Ca_Dll_Pll_Tracking_cc()
 int Gps_L1_Ca_Dll_Pll_Tracking_cc::general_work (int noutput_items __attribute__((unused)), gr_vector_int &ninput_items __attribute__((unused)),
         gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
 {
+    gr::thread::scoped_lock lk(d_setlock);
     // process vars
     double carr_error_hz = 0.0;
     double carr_error_filt_hz = 0.0;
diff --git a/src/core/interfaces/acquisition_interface.h b/src/core/interfaces/acquisition_interface.h
index 722b99777..b6d9e4e72 100644
--- a/src/core/interfaces/acquisition_interface.h
+++ b/src/core/interfaces/acquisition_interface.h
@@ -53,7 +53,6 @@ template<typename Data>class concurrent_queue;
 class AcquisitionInterface: public GNSSBlockInterface
 {
 public:
-    //virtual void set_active(bool active) = 0;
     virtual void set_gnss_synchro(Gnss_Synchro* gnss_synchro) = 0;
     virtual void set_channel(unsigned int channel) = 0;
     virtual void set_threshold(float threshold) = 0;
diff --git a/src/core/receiver/control_message_factory.cc b/src/core/receiver/control_message_factory.cc
index 6f7994c29..a7da90ab1 100644
--- a/src/core/receiver/control_message_factory.cc
+++ b/src/core/receiver/control_message_factory.cc
@@ -44,18 +44,18 @@ ControlMessageFactory::~ControlMessageFactory()
 {}
 
 
-boost::shared_ptr<gr::message> ControlMessageFactory::GetQueueMessage(unsigned int who, unsigned int what)
+gr::message::sptr ControlMessageFactory::GetQueueMessage(unsigned int who, unsigned int what)
 {
     std::shared_ptr<ControlMessage> control_message = std::make_shared<ControlMessage>();
     control_message->who = who;
     control_message->what = what;
-    boost::shared_ptr<gr::message> queue_message = gr::message::make(0, 0, 0, sizeof(ControlMessage));
+    gr::message::sptr queue_message = gr::message::make(0, 0, 0, sizeof(ControlMessage));
     memcpy(queue_message->msg(), control_message.get(), sizeof(ControlMessage));
     return queue_message;
 }
 
 
-std::shared_ptr<std::vector<std::shared_ptr<ControlMessage>>>  ControlMessageFactory::GetControlMessages(boost::shared_ptr<gr::message> queue_message)
+std::shared_ptr<std::vector<std::shared_ptr<ControlMessage>>>  ControlMessageFactory::GetControlMessages(gr::message::sptr queue_message)
 {
     std::shared_ptr<std::vector<std::shared_ptr<ControlMessage>>>  control_messages = std::make_shared<std::vector<std::shared_ptr<ControlMessage>>>();
     unsigned int control_messages_count = queue_message->length() / sizeof(ControlMessage);
diff --git a/src/core/receiver/control_message_factory.h b/src/core/receiver/control_message_factory.h
index 2ff294a8c..9bdd49d32 100644
--- a/src/core/receiver/control_message_factory.h
+++ b/src/core/receiver/control_message_factory.h
@@ -58,7 +58,7 @@ public:
     //! Virtual destructor
     virtual ~ControlMessageFactory();
 
-    boost::shared_ptr<gr::message> GetQueueMessage(unsigned int who, unsigned int what);
+    gr::message::sptr GetQueueMessage(unsigned int who, unsigned int what);
     std::shared_ptr<std::vector<std::shared_ptr<ControlMessage>>> GetControlMessages(gr::message::sptr queue_message);
 };
 
diff --git a/src/core/receiver/control_thread.cc b/src/core/receiver/control_thread.cc
index 44cdc36d3..73b05651c 100644
--- a/src/core/receiver/control_thread.cc
+++ b/src/core/receiver/control_thread.cc
@@ -158,7 +158,7 @@ void ControlThread::run()
 }
 
 
-void ControlThread::set_control_queue(boost::shared_ptr<gr::msg_queue> control_queue)
+void ControlThread::set_control_queue(gr::msg_queue::sptr control_queue)
 {
     if (flowgraph_->running())
         {
@@ -445,7 +445,7 @@ void ControlThread::init()
 void ControlThread::read_control_messages()
 {
     DLOG(INFO) << "Reading control messages from queue";
-    boost::shared_ptr<gr::message> queue_message = control_queue_->delete_head();
+    gr::message::sptr queue_message = control_queue_->delete_head();
     if (queue_message != 0)
         {
             control_messages_ = control_message_factory_->GetControlMessages(queue_message);
diff --git a/src/core/receiver/control_thread.h b/src/core/receiver/control_thread.h
index 1580695df..ea0decec8 100644
--- a/src/core/receiver/control_thread.h
+++ b/src/core/receiver/control_thread.h
@@ -89,7 +89,7 @@ public:
      *
      * \param[in] boost::shared_ptr<gr::msg_queue> control_queue
      */
-    void set_control_queue(boost::shared_ptr<gr::msg_queue> control_queue);
+    void set_control_queue(gr::msg_queue::sptr control_queue);
 
 
     unsigned int processed_control_messages()
@@ -146,7 +146,7 @@ private:
     void apply_action(unsigned int what);
     std::shared_ptr<GNSSFlowgraph> flowgraph_;
     std::shared_ptr<ConfigurationInterface> configuration_;
-    boost::shared_ptr<gr::msg_queue> control_queue_;
+    gr::msg_queue::sptr control_queue_;
     std::shared_ptr<ControlMessageFactory> control_message_factory_;
     std::shared_ptr<std::vector<std::shared_ptr<ControlMessage>>> control_messages_;
     bool stop_;
diff --git a/src/core/receiver/gnss_block_factory.cc b/src/core/receiver/gnss_block_factory.cc
index c3e3889fb..bdf34dc22 100644
--- a/src/core/receiver/gnss_block_factory.cc
+++ b/src/core/receiver/gnss_block_factory.cc
@@ -151,7 +151,7 @@ GNSSBlockFactory::~GNSSBlockFactory()
 
 
 std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetSignalSource(
-        std::shared_ptr<ConfigurationInterface> configuration, boost::shared_ptr<gr::msg_queue> queue, int ID)
+        std::shared_ptr<ConfigurationInterface> configuration, gr::msg_queue::sptr queue, int ID)
 {
     std::string default_implementation = "File_Signal_Source";
     std::string role = "SignalSource"; //backwards compatibility for old conf files
@@ -264,7 +264,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetPVT(std::shared_ptr<Con
 std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_1C(
         std::shared_ptr<ConfigurationInterface> configuration,
         std::string acq, std::string trk, std::string tlm, int channel,
-        boost::shared_ptr<gr::msg_queue> queue)
+        gr::msg_queue::sptr queue)
 {
     //"appendix" is added to the "role" with the aim of Acquisition, Tracking and Telemetry Decoder adapters
     //can find their specific configurations when they read the config
@@ -332,7 +332,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_1C(
 std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_2S(
         std::shared_ptr<ConfigurationInterface> configuration,
         std::string acq, std::string trk, std::string tlm, int channel,
-        boost::shared_ptr<gr::msg_queue> queue)
+        gr::msg_queue::sptr queue)
 {
 
     LOG(INFO) << "Instantiating Channel " << channel << " with Acquisition Implementation: "
@@ -397,7 +397,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_2S(
 std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_1B(
         std::shared_ptr<ConfigurationInterface> configuration,
         std::string acq, std::string trk, std::string tlm, int channel,
-        boost::shared_ptr<gr::msg_queue> queue)
+        gr::msg_queue::sptr queue)
 {
     std::stringstream stream;
     stream << channel;
@@ -464,7 +464,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_1B(
 std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_5X(
         std::shared_ptr<ConfigurationInterface> configuration,
         std::string acq, std::string trk, std::string tlm, int channel,
-        boost::shared_ptr<gr::msg_queue> queue)
+        gr::msg_queue::sptr queue)
 {
     std::stringstream stream;
     stream << channel;
@@ -531,7 +531,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_5X(
 std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_L5(
         std::shared_ptr<ConfigurationInterface> configuration,
         std::string acq, std::string trk, std::string tlm, int channel,
-        boost::shared_ptr<gr::msg_queue> queue)
+        gr::msg_queue::sptr queue)
 {
     std::stringstream stream;
     stream << channel;
@@ -597,7 +597,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetChannel_L5(
 
 
 std::unique_ptr<std::vector<std::unique_ptr<GNSSBlockInterface>>> GNSSBlockFactory::GetChannels(
-        std::shared_ptr<ConfigurationInterface> configuration, boost::shared_ptr<gr::msg_queue> queue)
+        std::shared_ptr<ConfigurationInterface> configuration, gr::msg_queue::sptr queue)
 {
     std::string default_implementation = "Pass_Through";
     std::string tracking_implementation;
@@ -783,7 +783,7 @@ std::unique_ptr<GNSSBlockInterface> GNSSBlockFactory::GetBlock(
         std::shared_ptr<ConfigurationInterface> configuration,
         std::string role,
         std::string implementation, unsigned int in_streams,
-        unsigned int out_streams, boost::shared_ptr<gr::msg_queue> queue)
+        unsigned int out_streams, gr::msg_queue::sptr queue)
 {
     std::unique_ptr<GNSSBlockInterface> block;
 
diff --git a/src/core/receiver/gnss_block_factory.h b/src/core/receiver/gnss_block_factory.h
index 516b9e8e9..bba584d7a 100644
--- a/src/core/receiver/gnss_block_factory.h
+++ b/src/core/receiver/gnss_block_factory.h
@@ -57,7 +57,7 @@ public:
     GNSSBlockFactory();
     virtual ~GNSSBlockFactory();
     std::unique_ptr<GNSSBlockInterface> GetSignalSource(std::shared_ptr<ConfigurationInterface> configuration,
-            boost::shared_ptr<gr::msg_queue> queue, int ID = -1);
+            gr::msg_queue::sptr queue, int ID = -1);
 
     std::unique_ptr<GNSSBlockInterface> GetSignalConditioner(std::shared_ptr<ConfigurationInterface> configuration, int ID = -1);
 
@@ -66,7 +66,7 @@ public:
     std::unique_ptr<GNSSBlockInterface> GetObservables(std::shared_ptr<ConfigurationInterface> configuration);
 
     std::unique_ptr<std::vector<std::unique_ptr<GNSSBlockInterface>>> GetChannels(std::shared_ptr<ConfigurationInterface> configuration,
-            boost::shared_ptr<gr::msg_queue> queue);
+            gr::msg_queue::sptr queue);
 
     /*
      * \brief Returns the block with the required configuration and implementation
@@ -74,29 +74,29 @@ public:
     std::unique_ptr<GNSSBlockInterface> GetBlock(std::shared_ptr<ConfigurationInterface> configuration,
             std::string role, std::string implementation,
             unsigned int in_streams, unsigned int out_streams,
-            boost::shared_ptr<gr::msg_queue> queue = nullptr);
+            gr::msg_queue::sptr queue = nullptr);
 
 private:
 
     std::unique_ptr<GNSSBlockInterface> GetChannel_1C(std::shared_ptr<ConfigurationInterface> configuration,
             std::string acq, std::string trk, std::string tlm, int channel,
-            boost::shared_ptr<gr::msg_queue> queue);
+            gr::msg_queue::sptr queue);
 
     std::unique_ptr<GNSSBlockInterface> GetChannel_2S(std::shared_ptr<ConfigurationInterface> configuration,
             std::string acq, std::string trk, std::string tlm, int channel,
-            boost::shared_ptr<gr::msg_queue> queue);
+            gr::msg_queue::sptr queue);
 
     std::unique_ptr<GNSSBlockInterface> GetChannel_1B(std::shared_ptr<ConfigurationInterface> configuration,
             std::string acq, std::string trk, std::string tlm, int channel,
-            boost::shared_ptr<gr::msg_queue> queue);
+            gr::msg_queue::sptr queue);
 
     std::unique_ptr<GNSSBlockInterface> GetChannel_5X(std::shared_ptr<ConfigurationInterface> configuration,
             std::string acq, std::string trk, std::string tlm, int channel,
-            boost::shared_ptr<gr::msg_queue> queue);
+            gr::msg_queue::sptr queue);
 
     std::unique_ptr<GNSSBlockInterface> GetChannel_L5(std::shared_ptr<ConfigurationInterface> configuration,
-                std::string acq, std::string trk, std::string tlm, int channel,
-                boost::shared_ptr<gr::msg_queue> queue);
+            std::string acq, std::string trk, std::string tlm, int channel,
+            gr::msg_queue::sptr queue);
 
     std::unique_ptr<AcquisitionInterface> GetAcqBlock(
             std::shared_ptr<ConfigurationInterface> configuration,
diff --git a/src/core/receiver/gnss_flowgraph.cc b/src/core/receiver/gnss_flowgraph.cc
index ed505b5f9..a59d4e5d1 100644
--- a/src/core/receiver/gnss_flowgraph.cc
+++ b/src/core/receiver/gnss_flowgraph.cc
@@ -33,7 +33,6 @@
  */
 
 #include "gnss_flowgraph.h"
-#include <memory>
 #include <algorithm>
 #include <exception>
 #include <iostream>
@@ -51,8 +50,7 @@
 
 using google::LogMessage;
 
-GNSSFlowgraph::GNSSFlowgraph(std::shared_ptr<ConfigurationInterface> configuration,
-        boost::shared_ptr<gr::msg_queue> queue)
+GNSSFlowgraph::GNSSFlowgraph(std::shared_ptr<ConfigurationInterface> configuration, gr::msg_queue::sptr queue)
 {
     connected_ = false;
     running_ = false;
@@ -91,12 +89,6 @@ void GNSSFlowgraph::start()
 
 void GNSSFlowgraph::stop()
 {
-    //    for (unsigned int i = 0; i < channels_count_; i++)
-    //        {
-    //            channels_.at(i)->stop_channel();
-    //            LOG(INFO) << "Channel " << i << " in state " << channels_state_[i];
-    //        }
-    //    LOG(INFO) << "Threads finished. Return to main program.";
     top_block_->stop();
     running_ = false;
 }
@@ -291,18 +283,13 @@ void GNSSFlowgraph::connect()
             }
 
             std::string gnss_signal = channels_.at(i)->get_signal().get_signal_str(); // use channel's implicit signal!
-            while (gnss_signal.compare(available_GNSS_signals_.front().get_signal_str()) != 0 )
-                {
-                    available_GNSS_signals_.push_back(available_GNSS_signals_.front());
-                    available_GNSS_signals_.pop_front();
-                }
-            channels_.at(i)->set_signal(available_GNSS_signals_.front());
+            channels_.at(i)->set_signal(search_next_signal(gnss_signal, false));
 
             if (channels_state_[i] == 1)
                 {
                     channels_.at(i)->start_acquisition();
                     available_GNSS_signals_.pop_front();
-                    LOG(INFO) << "Channel " << i << " assigned to " << available_GNSS_signals_.front();
+                    LOG(INFO) << "Channel " << i << " assigned to " << channels_.at(i)->get_signal();
                     LOG(INFO) << "Channel " << i << " connected to observables and ready for acquisition";
                 }
             else
@@ -373,77 +360,59 @@ bool GNSSFlowgraph::send_telemetry_msg(pmt::pmt_t msg)
  */
 void GNSSFlowgraph::apply_action(unsigned int who, unsigned int what)
 {
-    DLOG(INFO) << "received " << what << " from " << who;
-
+    DLOG(INFO) << "Received " << what << " from " << who << ". Number of applied actions = " << applied_actions_;
     switch (what)
     {
     case 0:
-        LOG(INFO) << "Channel " << who << " ACQ FAILED satellite " << channels_.at(who)->get_signal().get_satellite() << ", Signal " << channels_.at(who)->get_signal().get_signal_str();
+        DLOG(INFO) << "Channel " << who << " ACQ FAILED satellite " << channels_.at(who)->get_signal().get_satellite() << ", Signal " << channels_.at(who)->get_signal().get_signal_str();
         available_GNSS_signals_.push_back(channels_.at(who)->get_signal());
-        //TODO: Optimize the channel and signal matching!
-        while ( channels_.at(who)->get_signal().get_signal_str().compare(available_GNSS_signals_.front().get_signal_str()) != 0 )
-            {
-                available_GNSS_signals_.push_back(available_GNSS_signals_.front());
-                available_GNSS_signals_.pop_front();
-            }
-        channels_.at(who)->set_signal(available_GNSS_signals_.front());
-        available_GNSS_signals_.pop_front();
-        usleep(100);
-        LOG(INFO) << "Channel "<< who << " Starting acquisition " << channels_.at(who)->get_signal().get_satellite() << ", Signal " << channels_.at(who)->get_signal().get_signal_str();
+        channels_.at(who)->set_signal(search_next_signal(channels_.at(who)->get_signal().get_signal_str(), true));
+        DLOG(INFO) << "Channel "<< who << " Starting acquisition " << channels_.at(who)->get_signal().get_satellite() << ", Signal " << channels_.at(who)->get_signal().get_signal_str();
         channels_.at(who)->start_acquisition();
         break;
+
     case 1:
         LOG(INFO) << "Channel " << who << " ACQ SUCCESS satellite " << channels_.at(who)->get_signal().get_satellite();
         channels_state_[who] = 2;
         acq_channels_count_--;
-        if (!available_GNSS_signals_.empty() && acq_channels_count_ < max_acq_channels_)
+        for (unsigned int i = 0; i < channels_count_; i++)
             {
-                for (unsigned int i = 0; i < channels_count_; i++)
+                if(!available_GNSS_signals_.empty() && (acq_channels_count_ < max_acq_channels_) && (channels_state_[i] == 0))
                     {
-                        if (channels_state_[i] == 0)
-                            {
-                                channels_state_[i] = 1;
-                                while (channels_.at(i)->get_signal().get_signal_str().compare(available_GNSS_signals_.front().get_signal_str()) != 0 )
-                                    {
-                                        available_GNSS_signals_.push_back(available_GNSS_signals_.front());
-                                        available_GNSS_signals_.pop_front();
-                                    }
-                                channels_.at(i)->set_signal(available_GNSS_signals_.front());
-                                available_GNSS_signals_.pop_front();
-                                acq_channels_count_++;
-                                channels_.at(i)->start_acquisition();
-                                break;
-                            }
-                        DLOG(INFO) << "Channel " << i << " in state " << channels_state_[i];
+                        channels_state_[i] = 1;
+                        channels_.at(i)->set_signal(search_next_signal(channels_.at(i)->get_signal().get_signal_str(), true));
+                        acq_channels_count_++;
+                        DLOG(INFO) << "Channel "<< i << " Starting acquisition " << channels_.at(i)->get_signal().get_satellite() << ", Signal " << channels_.at(i)->get_signal().get_signal_str();
+                        channels_.at(i)->start_acquisition();
                     }
+                DLOG(INFO) << "Channel " << i << " in state " << channels_state_[i];
             }
-
         break;
 
     case 2:
         LOG(INFO) << "Channel " << who << " TRK FAILED satellite " << channels_.at(who)->get_signal().get_satellite();
+        DLOG(INFO) << "Number of channels in acquisition = " << acq_channels_count_;
+
         if (acq_channels_count_ < max_acq_channels_)
             {
                 channels_state_[who] = 1;
                 acq_channels_count_++;
+                LOG(INFO) << "Channel "<< who << " Starting acquisition " << channels_.at(who)->get_signal().get_satellite() << ", Signal " << channels_.at(who)->get_signal().get_signal_str();
                 channels_.at(who)->start_acquisition();
             }
         else
             {
                 channels_state_[who] = 0;
+                LOG(INFO) << "Channel "<< who << " Idle state";
                 available_GNSS_signals_.push_back( channels_.at(who)->get_signal() );
             }
-
-        // for (unsigned int i = 0; i < channels_count_; i++)
-        //    {
-        //        LOG(INFO) << "Channel " << i << " in state " << channels_state_[i] << std::endl;
-        //    }
         break;
 
     default:
         break;
     }
     DLOG(INFO) << "Number of available signals: " << available_GNSS_signals_.size();
+    applied_actions_++;
 }
 
 
@@ -555,7 +524,6 @@ void GNSSFlowgraph::init()
     set_signals_list();
     set_channels_state();
     applied_actions_ = 0;
-
     DLOG(INFO) << "Blocks instantiated. " << channels_count_ << " channels.";
 }
 
@@ -704,7 +672,7 @@ void GNSSFlowgraph::set_signals_list()
     if (configuration_->property("Channels_1B.count", 0) > 0)
         {
             /*
-             * Loop to create the list of Galileo E1 B signals
+             * Loop to create the list of Galileo E1B signals
              */
             for (available_gnss_prn_iter = available_galileo_prn.cbegin();
                     available_gnss_prn_iter != available_galileo_prn.cend();
@@ -718,7 +686,7 @@ void GNSSFlowgraph::set_signals_list()
     if (configuration_->property("Channels_5X.count", 0) > 0 )
         {
             /*
-             * Loop to create the list of Galileo E1 B signals
+             * Loop to create the list of Galileo E5a signals
              */
             for (available_gnss_prn_iter = available_galileo_prn.cbegin();
                     available_gnss_prn_iter != available_galileo_prn.cend();
@@ -754,14 +722,6 @@ void GNSSFlowgraph::set_signals_list()
                     gnss_it = available_GNSS_signals_.insert(gnss_it, signal_value);
                 }
         }
-
-    //    **** FOR DEBUGGING THE LIST OF GNSS SIGNALS ****
-    //    std::list<Gnss_Signal>::const_iterator available_gnss_list_iter;
-    //    for (available_gnss_list_iter = available_GNSS_signals_.cbegin(); available_gnss_list_iter
-    //    != available_GNSS_signals_.cend(); available_gnss_list_iter++)
-    //        {
-    //            std::cout << *available_gnss_list_iter << std::endl;
-    //        }
 }
 
 
@@ -776,14 +736,22 @@ void GNSSFlowgraph::set_channels_state()
     channels_state_.reserve(channels_count_);
     for (unsigned int i = 0; i < channels_count_; i++)
         {
-            if (i < max_acq_channels_)
-                {
-                    channels_state_.push_back(1);
-                }
-            else
-                channels_state_.push_back(0);
+            if (i < max_acq_channels_) {channels_state_.push_back(1);}
+            else {channels_state_.push_back(0);}
             DLOG(INFO) << "Channel " << i << " in state " << channels_state_[i];
         }
     acq_channels_count_ = max_acq_channels_;
     DLOG(INFO) << acq_channels_count_ << " channels in acquisition state";
 }
+
+Gnss_Signal GNSSFlowgraph::search_next_signal(std::string searched_signal, bool pop)
+{
+    while(searched_signal.compare(available_GNSS_signals_.front().get_signal_str()) != 0)
+        {
+            available_GNSS_signals_.push_back(available_GNSS_signals_.front());
+            available_GNSS_signals_.pop_front();
+        }
+    Gnss_Signal result = available_GNSS_signals_.front();
+    if(pop){available_GNSS_signals_.pop_front();}
+    return result;
+}
diff --git a/src/core/receiver/gnss_flowgraph.h b/src/core/receiver/gnss_flowgraph.h
index d765d3cf4..abb4a6ef5 100644
--- a/src/core/receiver/gnss_flowgraph.h
+++ b/src/core/receiver/gnss_flowgraph.h
@@ -63,8 +63,7 @@ public:
     /*!
      * \brief Constructor that initializes the receiver flowgraph
      */
-    GNSSFlowgraph(std::shared_ptr<ConfigurationInterface> configuration,
-                  boost::shared_ptr<gr::msg_queue> queue);
+    GNSSFlowgraph(std::shared_ptr<ConfigurationInterface> configuration, gr::msg_queue::sptr queue);
 
     /*!
      * \brief Virtual destructor
@@ -119,6 +118,7 @@ private:
     void set_signals_list();
     void set_channels_state(); // Initializes the channels state (start acquisition or keep standby)
                                // using the configuration parameters (number of channels and max channels in acquisition)
+    Gnss_Signal search_next_signal(std::string searched_signal, bool pop);
     bool connected_;
     bool running_;
     int sources_count_;
@@ -139,7 +139,7 @@ private:
     std::vector<std::shared_ptr<ChannelInterface>> channels_;
     gnss_sdr_sample_counter_sptr ch_out_sample_counter;
     gr::top_block_sptr top_block_;
-    boost::shared_ptr<gr::msg_queue> queue_;
+    gr::msg_queue::sptr queue_;
     std::list<Gnss_Signal> available_GNSS_signals_;
     std::vector<unsigned int> channels_state_;
 };
diff --git a/src/core/system_parameters/gnss_signal.h b/src/core/system_parameters/gnss_signal.h
index 4922e5399..25288a704 100644
--- a/src/core/system_parameters/gnss_signal.h
+++ b/src/core/system_parameters/gnss_signal.h
@@ -51,7 +51,7 @@ public:
     Gnss_Signal(const std::string& signal_);
     Gnss_Signal(const Gnss_Satellite& satellite_, const std::string& signal_);
     ~Gnss_Signal();
-    std::string get_signal_str() const; //!<  Get the satellite signal {"1C" for GPS L1 C/A, "2S" for GPS L2C (M), "1B" for Galileo E1B, "5X" for Galileo E5a}
+    std::string get_signal_str() const; //!<  Get the satellite signal {"1C" for GPS L1 C/A, "2S" for GPS L2C (M), "1B" for Galileo E1B, "5X" for Galileo E5a, "L5" for GPS L5}
     Gnss_Satellite get_satellite() const;    //!< Get the Gnss_Satellite associated to the signal
     friend bool operator== (const Gnss_Signal &, const Gnss_Signal &);    //!< operator== for comparison
     friend std::ostream& operator<<(std::ostream &, const Gnss_Signal &); //!< operator<< for pretty printing