diff --git a/lib/demapping/universal_ctrl_chans_demapper_impl.cc b/lib/demapping/universal_ctrl_chans_demapper_impl.cc
index c711928..cbbbc32 100644
--- a/lib/demapping/universal_ctrl_chans_demapper_impl.cc
+++ b/lib/demapping/universal_ctrl_chans_demapper_impl.cc
@@ -36,16 +36,16 @@
   namespace gsm {
 
     universal_ctrl_chans_demapper::sptr
-    universal_ctrl_chans_demapper::make(unsigned int timeslot_nr, const std::vector<int> &starts_fn_mod51, const std::vector<int> &channel_types)
+    universal_ctrl_chans_demapper::make(unsigned int timeslot_nr, const std::vector<int> &downlink_starts_fn_mod51, const std::vector<int> &downlink_channel_types, const std::vector<int> &uplink_starts_fn_mod51, const std::vector<int> &uplink_channel_types)
     {
       return gnuradio::get_initial_sptr
-        (new universal_ctrl_chans_demapper_impl(timeslot_nr, starts_fn_mod51, channel_types));
+        (new universal_ctrl_chans_demapper_impl(timeslot_nr, downlink_starts_fn_mod51, downlink_channel_types, uplink_starts_fn_mod51, uplink_channel_types));
     }
 
     /*
      * The private constructor
      */
-    universal_ctrl_chans_demapper_impl::universal_ctrl_chans_demapper_impl(unsigned int timeslot_nr, const std::vector<int> &starts_fn_mod51, const std::vector<int> &channel_types)
+    universal_ctrl_chans_demapper_impl::universal_ctrl_chans_demapper_impl(unsigned int timeslot_nr, const std::vector<int> &downlink_starts_fn_mod51, const std::vector<int> &downlink_channel_types, const std::vector<int> &uplink_starts_fn_mod51, const std::vector<int> &uplink_channel_types)
       : gr::block("universal_ctrl_chans_demapper",
               gr::io_signature::make(0, 0, 0),
               gr::io_signature::make(0, 0, 0)),
@@ -56,75 +56,137 @@
         
         for(int ii=0; ii<51; ii++)
         {
-            d_starts_fn_mod51[ii]=0;
-            d_channel_types[ii]=0;
-	    d_subslots[ii] = 0;
-	    d_subslots[ii+51] = 0;
+            d_downlink_starts_fn_mod51[ii]=0;
+            d_downlink_channel_types[ii]=0;
+            d_downlink_subslots[ii] = 0;
+            d_downlink_subslots[ii+51] = 0;
+
+            d_uplink_starts_fn_mod51[ii]=0;
+            d_uplink_channel_types[ii]=0;
+            d_uplink_subslots[ii] = 0;
+            d_uplink_subslots[ii+51] = 0;
         }
         
         std::vector<int>::const_iterator s;
         std::vector<int>::const_iterator ch_type;
         
-        for(s=starts_fn_mod51.begin(), ch_type=channel_types.begin();s != starts_fn_mod51.end(); s++)
+        for(s=downlink_starts_fn_mod51.begin(), ch_type=downlink_channel_types.begin();s != downlink_starts_fn_mod51.end(); s++)
         {
             if((*s >= 0) and (*s <= (51-4)))
             {
                 for(int ii=0; ii<4; ii++){
-                    d_starts_fn_mod51[*s+ii] = *s;
-                    if(ch_type!=channel_types.end())
+                    d_downlink_starts_fn_mod51[*s+ii] = *s;
+                    if(ch_type!=downlink_channel_types.end())
                     {
-                        d_channel_types[*s+ii] = *ch_type;
+                        d_downlink_channel_types[*s+ii] = *ch_type;
                     }
                 }
-                if(ch_type!=channel_types.end())
+                if(ch_type!=downlink_channel_types.end())
                 {
                     ch_type++;
                 }
             }
         }
         
-        std::set<int> distinct_channels(channel_types.begin(), channel_types.end());
-	std::set<int>::iterator it;
-        unsigned int subslot;
-	
-	for (it=distinct_channels.begin(); it != distinct_channels.end(); it++)
-	{
-	    subslot = 0;
-	    for(s=starts_fn_mod51.begin();s != starts_fn_mod51.end(); s++)
-	    {
-		if ((d_channel_types[*s] == *it) and (*s >= 0) and (*s <= (51-4)))
-		{
-		    for(int ii=0; ii<4; ii++)
-		    {
-			d_subslots[*s+ii] = subslot;
-			d_subslots[*s+ii+51] = subslot;
-		    }
-		    subslot++;
-		}
-	    }
-	    
-	    if (*it == GSMTAP_CHANNEL_ACCH or 
-		*it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH) or
-		*it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH4) or
-		*it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH8) or
-		*it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_F) or
-		*it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_H)
-	    )
-	    {
-		for(s=starts_fn_mod51.begin();s != starts_fn_mod51.end(); s++)
-		{
-		    if ((d_channel_types[*s] == *it) and (*s >= 0) and (*s <= (51-4)))
-		    {
-			for(int ii=0; ii<4; ii++)
-			{
-			    d_subslots[*s+ii+51] = subslot;
-			}
-			subslot++;
-		    }
-		}
-	    }
-	}
+        for(s=uplink_starts_fn_mod51.begin(), ch_type=uplink_channel_types.begin();s != uplink_starts_fn_mod51.end(); s++)
+        {
+            if((*s >= 0) and (*s <= (51-4)))
+            {
+                for(int ii=0; ii<4; ii++){
+                    d_uplink_starts_fn_mod51[*s+ii] = *s;
+                    if(ch_type!=uplink_channel_types.end())
+                    {
+                        d_uplink_channel_types[*s+ii] = *ch_type;
+                    }
+                }
+                if(ch_type!=uplink_channel_types.end())
+                {
+                    ch_type++;
+                }
+            }
+        }
         
+        std::set<int> distinct_downlink_channels(downlink_channel_types.begin(), downlink_channel_types.end());
+        std::set<int>::iterator it;
+        unsigned int subslot;
+        
+        for (it=distinct_downlink_channels.begin(); it != distinct_downlink_channels.end(); it++)
+        {
+            subslot = 0;
+            for(s=downlink_starts_fn_mod51.begin();s != downlink_starts_fn_mod51.end(); s++)
+            {
+                if ((d_downlink_channel_types[*s] == *it) and (*s >= 0) and (*s <= (51-4)))
+                {
+                    for(int ii=0; ii<4; ii++)
+                    {
+                        d_downlink_subslots[*s+ii] = subslot;
+                        d_downlink_subslots[*s+ii+51] = subslot;
+                    }
+                    subslot++;
+                }
+            }
+            
+            if (*it == GSMTAP_CHANNEL_ACCH or 
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH4) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH8) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_F) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_H)
+            )
+            {
+                for(s=downlink_starts_fn_mod51.begin();s != downlink_starts_fn_mod51.end(); s++)
+                {
+                    if ((d_downlink_channel_types[*s] == *it) and (*s >= 0) and (*s <= (51-4)))
+                    {
+                        for(int ii=0; ii<4; ii++)
+                        {
+                            d_downlink_subslots[*s+ii+51] = subslot;
+                        }
+                        subslot++;
+                    }
+                }
+            }
+        }
+        
+        std::set<int> distinct_uplink_channels(uplink_channel_types.begin(), uplink_channel_types.end());
+        for (it=distinct_uplink_channels.begin(); it != distinct_uplink_channels.end(); it++)
+        {
+            subslot = 0;
+            for(s=uplink_starts_fn_mod51.begin();s != uplink_starts_fn_mod51.end(); s++)
+            {
+                if ((d_uplink_channel_types[*s] == *it) and (*s >= 0) and (*s <= (51-4)))
+                {
+                    for(int ii=0; ii<4; ii++)
+                    {
+                        d_uplink_subslots[*s+ii] = subslot;
+                        d_uplink_subslots[*s+ii+51] = subslot;
+                    }
+                    subslot++;
+                }
+            }
+            
+            if (*it == GSMTAP_CHANNEL_ACCH or 
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH4) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_SDCCH8) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_F) or
+                *it == (GSMTAP_CHANNEL_ACCH|GSMTAP_CHANNEL_TCH_H)
+            )
+            {
+                for(s=uplink_starts_fn_mod51.begin();s != uplink_starts_fn_mod51.end(); s++)
+                {
+                    if ((d_uplink_channel_types[*s] == *it) and (*s >= 0) and (*s <= (51-4)))
+                    {
+                        for(int ii=0; ii<4; ii++)
+                        {
+                            d_uplink_subslots[*s+ii+51] = subslot;
+                        }
+                        subslot++;
+                    }
+                }
+            }
+        }
+
         
         message_port_register_in(pmt::mp("bursts"));
         set_msg_handler(pmt::mp("bursts"), boost::bind(&universal_ctrl_chans_demapper_impl::filter_ctrl_chans, this, _1));
@@ -142,52 +204,102 @@
     {
         pmt::pmt_t header_plus_burst = pmt::cdr(msg);
         gsmtap_hdr * header = (gsmtap_hdr *)pmt::blob_data(header_plus_burst);
-            
+
         uint32_t frame_nr = be32toh(header->frame_number);
         uint32_t fn_mod51 = frame_nr % 51;
-        uint32_t fn51_start = d_starts_fn_mod51[fn_mod51];
-        uint32_t fn51_stop = fn51_start + 3;
-        uint32_t ch_type = d_channel_types[fn_mod51];
         
+        bool uplink_burst = (be16toh(header->arfcn) & 0x4000) ? true : false;
+
         if(header->timeslot==d_timeslot){
             int8_t new_msg[sizeof(gsmtap_hdr)+BURST_SIZE];
             gsmtap_hdr * new_hdr = (gsmtap_hdr*)new_msg;
             memcpy(new_msg, header, sizeof(gsmtap_hdr)+BURST_SIZE);
-            new_hdr->sub_type = ch_type;
-            new_hdr->sub_slot = d_subslots[fn_mod51 + (51 * (frame_nr % 2))];
             pmt::pmt_t msg_binary_blob = pmt::make_blob(new_msg,sizeof(gsmtap_hdr)+BURST_SIZE);
             pmt::pmt_t msg_out = pmt::cons(pmt::PMT_NIL, msg_binary_blob);
 	    
-            if(fn_mod51>=fn51_start && fn_mod51<=fn51_stop)
+            if(uplink_burst)
             {
-                uint32_t ii = fn_mod51 - fn51_start;
-                d_frame_numbers[ii] = frame_nr;
-                d_bursts[ii] = msg_out;
-            }
-            
-            if(fn_mod51==fn51_stop)
-            {
-                //check for a situation where some bursts were lost
-                //in this situation frame numbers won't be consecutive
-                bool frames_are_consecutive = true;
-                for(int jj=1; jj<4; jj++)
+                uint32_t fn51_start = d_uplink_starts_fn_mod51[fn_mod51];
+                uint32_t fn51_stop = fn51_start + 3;
+                uint32_t ch_type = d_uplink_channel_types[fn_mod51];
+
+                if(ch_type != 0)
                 {
-                    if((d_frame_numbers[jj]-d_frame_numbers[jj-1])!=1)
-                    {
-                        frames_are_consecutive = false;
-                    }
+                    new_hdr->sub_type = ch_type;
                 }
-                if(frames_are_consecutive)
+                new_hdr->sub_slot = d_uplink_subslots[fn_mod51 + (51 * (frame_nr % 2))];
+                
+                if(fn_mod51>=fn51_start && fn_mod51<=fn51_stop)
                 {
-                    //send bursts to the output
-                    for(int jj=0; jj<4; jj++)
+                    uint32_t ii = fn_mod51 - fn51_start;
+                    d_uplink_frame_numbers[ii] = frame_nr;
+                    d_uplink_bursts[ii] = msg_out;
+                }
+                
+                if(fn_mod51==fn51_stop)
+                {
+                    //check for a situation where some bursts were lost
+                    //in this situation frame numbers won't be consecutive
+                    bool frames_are_consecutive = true;
+                    for(int jj=1; jj<4; jj++)
                     {
-                        message_port_pub(pmt::mp("bursts"), d_bursts[jj]);
+                        if((d_uplink_frame_numbers[jj]-d_uplink_frame_numbers[jj-1])!=1)
+                        {
+                            frames_are_consecutive = false;
+                        }
                     }
-                } 
+                    if(frames_are_consecutive)
+                    {
+                        //send bursts to the output
+                        for(int jj=0; jj<4; jj++)
+                        {
+                            message_port_pub(pmt::mp("bursts"), d_uplink_bursts[jj]);
+                        }
+                    } 
+                }
+            }
+            else 
+            {
+                uint32_t fn51_start = d_downlink_starts_fn_mod51[fn_mod51];
+                uint32_t fn51_stop = fn51_start + 3;
+                uint32_t ch_type = d_downlink_channel_types[fn_mod51];
+
+                if(ch_type != 0)
+                {
+                    new_hdr->sub_type = ch_type;
+                }
+                new_hdr->sub_slot = d_downlink_subslots[fn_mod51 + (51 * (frame_nr % 2))];
+                
+                if(fn_mod51>=fn51_start && fn_mod51<=fn51_stop)
+                {
+                    uint32_t ii = fn_mod51 - fn51_start;
+                    d_downlink_frame_numbers[ii] = frame_nr;
+                    d_downlink_bursts[ii] = msg_out;
+                }
+                
+                if(fn_mod51==fn51_stop)
+                {
+                    //check for a situation where some bursts were lost
+                    //in this situation frame numbers won't be consecutive
+                    bool frames_are_consecutive = true;
+                    for(int jj=1; jj<4; jj++)
+                    {
+                        if((d_downlink_frame_numbers[jj]-d_downlink_frame_numbers[jj-1])!=1)
+                        {
+                            frames_are_consecutive = false;
+                        }
+                    }
+                    if(frames_are_consecutive)
+                    {
+                        //send bursts to the output
+                        for(int jj=0; jj<4; jj++)
+                        {
+                            message_port_pub(pmt::mp("bursts"), d_downlink_bursts[jj]);
+                        }
+                    } 
+                }
             }
         }
     }
   } /* namespace gsm */
 } /* namespace gr */
-