diff --git a/lib/flow_control/burst_sdcch_subslot_filter_impl.h b/lib/flow_control/burst_sdcch_subslot_filter_impl.h
new file mode 100644
index 0000000..05038d7
--- /dev/null
+++ b/lib/flow_control/burst_sdcch_subslot_filter_impl.h
@@ -0,0 +1,55 @@
+/* -*- c++ -*- */
+/* @file
+ * @author Roman Khassraf <rkhassraf@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_SDCCH_SUBSLOT_FILTER_IMPL_H
+#define INCLUDED_GSM_BURST_SDCCH_SUBSLOT_FILTER_IMPL_H
+
+#include <grgsm/flow_control/burst_sdcch_subslot_filter.h>
+
+namespace gr {
+  namespace gsm {
+
+    class burst_sdcch_subslot_filter_impl : public burst_sdcch_subslot_filter
+    {
+     private:
+      // hardcoded subslots of the channels, both SDCCH and the associated SACCH
+      // -1 means that the particular position in the frame is not SDCCH
+      const int8_t d_subslots_sdcch4[102] = {
+          -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, 0, 0, 0, 0, 1, 1, 1, 1,-1,-1, 2, 2, 2, 2, 3, 3, 3, 3,-1,-1, 0, 0, 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, 0, 0, 0, 0, 1, 1, 1, 1,-1,-1, 2, 2, 2, 2, 3, 3, 3, 3,-1,-1, 2, 2, 2, 2, 3, 3, 3, 3,-1
+      };
+      const int8_t d_subslots_sdcch8[102] = {
+          0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3,-1,-1,-1,
+          0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7,-1,-1,-1
+      };
+      subslot_filter_mode d_mode;
+      unsigned int d_subslot;
+     public:
+      burst_sdcch_subslot_filter_impl(subslot_filter_mode mode, unsigned int subslot);
+      ~burst_sdcch_subslot_filter_impl();
+      void process_burst(pmt::pmt_t msg);
+    };
+
+  } // namespace gsm
+} // namespace gr
+
+#endif /* INCLUDED_GSM_BURST_SDCCH_SUBSLOT_FILTER_IMPL_H */