diff --git a/lib/include/srslte/interfaces/ue_interfaces.h b/lib/include/srslte/interfaces/ue_interfaces.h
index a05f117a4..41b90bf9f 100644
--- a/lib/include/srslte/interfaces/ue_interfaces.h
+++ b/lib/include/srslte/interfaces/ue_interfaces.h
@@ -230,6 +230,31 @@ public:
 };
 
 
+//BSR interface for MUX
+class bsr_interface_mux
+{
+public:
+  typedef enum {
+    LONG_BSR,
+    SHORT_BSR,
+    TRUNC_BSR
+  } bsr_format_t;
+
+  typedef struct {
+    bsr_format_t format;
+    uint32_t buff_size[4];
+  } bsr_t;
+
+  /* MUX calls BSR to check if it can fit a BSR into PDU */
+  virtual bool need_to_send_bsr_on_ul_grant(uint32_t grant_size, bsr_t *bsr) = 0;
+
+  /* MUX calls BSR to let it generate a padding BSR if there is space in PDU */
+  virtual bool generate_padding_bsr(uint32_t nof_padding_bytes, bsr_t *bsr) = 0;
+
+  /* MAX calls BSR to set the Tx TTI */
+  virtual void set_tx_tti(uint32_t tti) = 0;
+};
+
 
 /** MAC interface 
  *
diff --git a/srsue/hdr/mac/mux.h b/srsue/hdr/mac/mux.h
index db98ebe78..b33cf0d19 100644
--- a/srsue/hdr/mac/mux.h
+++ b/srsue/hdr/mac/mux.h
@@ -57,7 +57,7 @@ class mux
 public:
   mux();
   void     reset();
-  void     init(rlc_interface_mac *rlc, srslte::log *log_h, bsr_proc *bsr_procedure, phr_proc *phr_procedure_);
+  void     init(rlc_interface_mac *rlc, srslte::log *log_h, bsr_interface_mux *bsr_procedure, phr_proc *phr_procedure_);
 
   bool     is_pending_any_sdu();
   bool     is_pending_sdu(uint32_t lcid); 
@@ -94,7 +94,7 @@ private:
 
   srslte::log       *log_h;
   rlc_interface_mac *rlc; 
-  bsr_proc          *bsr_procedure;
+  bsr_interface_mux *bsr_procedure;
   phr_proc          *phr_procedure;
   uint16_t           pending_crnti_ce;
   
diff --git a/srsue/hdr/mac/proc_bsr.h b/srsue/hdr/mac/proc_bsr.h
index bbfaa1c90..21f278e29 100644
--- a/srsue/hdr/mac/proc_bsr.h
+++ b/srsue/hdr/mac/proc_bsr.h
@@ -37,7 +37,7 @@
 
 namespace srsue {
 
-class bsr_proc : public srslte::timer_callback
+class bsr_proc : public srslte::timer_callback, public bsr_interface_mux
 {
 public:
   bsr_proc();
@@ -48,18 +48,6 @@ public:
   void set_priority(uint32_t lcid, uint32_t priority); 
   void timer_expired(uint32_t timer_id);
   uint32_t get_buffer_state();
-  
-  typedef enum {
-    LONG_BSR, 
-    SHORT_BSR, 
-    TRUNC_BSR    
-  } bsr_format_t;
-  
-  typedef struct {
-    bsr_format_t format; 
-    uint32_t buff_size[4];
-  } bsr_t; 
-
   bool need_to_send_bsr_on_ul_grant(uint32_t grant_size, bsr_t *bsr); 
   bool generate_padding_bsr(uint32_t nof_padding_bytes, bsr_t *bsr);
   bool need_to_send_sr(uint32_t tti); 
diff --git a/srsue/src/mac/mux.cc b/srsue/src/mac/mux.cc
index 58ba3d57f..38a71649a 100644
--- a/srsue/src/mac/mux.cc
+++ b/srsue/src/mac/mux.cc
@@ -51,7 +51,7 @@ mux::mux() : pdu_msg(MAX_NOF_SUBHEADERS)
   msg3_flush();
 }
 
-void mux::init(rlc_interface_mac *rlc_, srslte::log *log_h_, bsr_proc *bsr_procedure_, phr_proc *phr_procedure_)
+void mux::init(rlc_interface_mac *rlc_, srslte::log *log_h_, bsr_interface_mux *bsr_procedure_, phr_proc *phr_procedure_)
 {
   log_h      = log_h_;
   rlc        = rlc_;