diff --git a/executables/nr-ue.c b/executables/nr-ue.c
index d744b6e780..1ad0ddd50a 100644
--- a/executables/nr-ue.c
+++ b/executables/nr-ue.c
@@ -705,8 +705,7 @@ void *UE_thread(void *arg) {
       UE->rx_offset_diff = computeSamplesShift(UE);
       readBlockSize=get_readBlockSize(slot_nr, &UE->frame_parms) -
                     UE->rx_offset_diff;
-      writeBlockSize=UE->frame_parms.get_samples_per_slot((slot_nr + DURATION_RX_TO_TX - RX_NB_TH) % nb_slot_frame, &UE->frame_parms)-
-                     UE->rx_offset_diff;
+      writeBlockSize=UE->frame_parms.get_samples_per_slot((slot_nr + DURATION_RX_TO_TX - RX_NB_TH) % nb_slot_frame, &UE->frame_parms)- UE->rx_offset_diff;
     }
 
     AssertFatal(readBlockSize ==
@@ -765,14 +764,28 @@ void *UE_thread(void *arg) {
       timing_advance = UE->timing_advance;
     }
 
-    AssertFatal( writeBlockSize ==
-                 UE->rfdevice.trx_write_func(&UE->rfdevice,
-                     writeTimestamp,
-                     txp,
-                     writeBlockSize,
-                     UE->frame_parms.nb_antennas_tx,
-                     1),"");
+    int flags = 0;
+    int slot_tx_usrp = slot_nr + DURATION_RX_TO_TX - RX_NB_TH;
+    uint8_t tdd_period = mac->phy_config.config_req.tdd_table.tdd_period_in_slots;
+    uint8_t num_UL_slots = mac->scc->tdd_UL_DL_ConfigurationCommon->pattern1.nrofUplinkSlots +
+                           (mac->scc->tdd_UL_DL_ConfigurationCommon->pattern1.nrofUplinkSymbols!=0);
+    uint8_t first_tx_slot = tdd_period - num_UL_slots;
+    if (slot_tx_usrp%tdd_period==first_tx_slot)
+      flags=2;
+    else     if (slot_tx_usrp%tdd_period==first_tx_slot+num_UL_slots-1)
+      flags = 3;
+    else     if (slot_tx_usrp%tdd_period>first_tx_slot)
+      flags = 1;
 
+    if (flags || IS_SOFTMODEM_RFSIM)
+      AssertFatal( writeBlockSize ==
+                 UE->rfdevice.trx_write_func(&UE->rfdevice,
+					       writeTimestamp,
+					       txp,
+					       writeBlockSize,
+					       UE->frame_parms.nb_antennas_tx,
+					       flags),"");
+    
     for (int i=0; i<UE->frame_parms.nb_antennas_tx; i++)
       memset(txp[i], 0, writeBlockSize);
 
@@ -780,7 +793,7 @@ void *UE_thread(void *arg) {
     msgToPush->key=slot_nr;
     pushTpool(&(get_nrUE_params()->Tpool), msgToPush);
 
-    if ( IS_SOFTMODEM_RFSIM || IS_SOFTMODEM_NOS1) {  //getenv("RFSIMULATOR")
+    if (IS_SOFTMODEM_RFSIM) {  //getenv("RFSIMULATOR")
       // FixMe: Wait previous thread is done, because race conditions seems too bad
       // in case of actual RF board, the overlap between threads mitigate the issue
       // We must receive one message, that proves the slot processing is done