diff --git a/lib/include/srslte/interfaces/ue_interfaces.h b/lib/include/srslte/interfaces/ue_interfaces.h
index 41b90bf9f..3cffaae1e 100644
--- a/lib/include/srslte/interfaces/ue_interfaces.h
+++ b/lib/include/srslte/interfaces/ue_interfaces.h
@@ -300,6 +300,7 @@ public:
     uint32_t                rv;
     uint16_t                rnti; 
     uint32_t                current_tx_nb;
+    int32_t                 tti_offset;     // relative offset between grant and UL tx/HARQ rx
     srslte_softbuffer_tx_t *softbuffer;
     srslte_phy_grant_t      phy_grant;
     uint8_t                *payload_ptr; 
diff --git a/srsue/hdr/mac/ul_harq.h b/srsue/hdr/mac/ul_harq.h
index 107683ebb..2ef1ed2b6 100644
--- a/srsue/hdr/mac/ul_harq.h
+++ b/srsue/hdr/mac/ul_harq.h
@@ -128,13 +128,13 @@ public:
 
   void new_grant_ul_ack(Tgrant grant, bool ack, Taction *action)
   {
-    set_ack(grant.tti, ack);
+    set_ack(grant.tti, ack, action);
     new_grant_ul(grant, action);
   }
 
   void harq_recv(uint32_t tti, bool ack, Taction *action)
   {
-    set_ack(tti, ack);
+    set_ack(tti, ack, action);
     run_tti(tti, NULL, action);
   }
 
@@ -385,13 +385,13 @@ private:
   // Called with UL grant
   void run_tti(uint32_t tti, Tgrant *grant, Taction* action)
   {
-    uint32_t tti_tx = (tti+4)%10240;
+    uint32_t tti_tx = (tti+action->tti_offset)%10240;
     proc[pidof(tti_tx)].run_tti(tti_tx, grant, action);
   }
 
-  void set_ack(uint32_t tti, bool ack)
+  void set_ack(uint32_t tti, bool ack, Taction *action)
   {
-    int tti_harq = (int) tti - 4;
+    int tti_harq = (int) tti - action->tti_offset;
     if (tti_harq < 0) {
       tti_harq += 10240;
     }
diff --git a/srsue/src/phy/phch_worker.cc b/srsue/src/phy/phch_worker.cc
index 14de9b51a..c2796e2ad 100644
--- a/srsue/src/phy/phch_worker.cc
+++ b/srsue/src/phy/phch_worker.cc
@@ -240,6 +240,9 @@ void phch_worker::work_imp()
     set_uci_periodic_cqi();
   }
 
+  /* TTI offset for UL is always 4 for LTE */
+  ul_action.tti_offset = 4;
+
   /* Send UL grant or HARQ information (from PHICH) to MAC */
   if (ul_grant_available         && ul_ack_available)  {    
     phy->mac->new_grant_ul_ack(ul_mac_grant, ul_ack, &ul_action);