diff --git a/openair2/PHY_INTERFACE/phy_stub_UE.c b/openair2/PHY_INTERFACE/phy_stub_UE.c
index 584618dac7..183cf77385 100644
--- a/openair2/PHY_INTERFACE/phy_stub_UE.c
+++ b/openair2/PHY_INTERFACE/phy_stub_UE.c
@@ -49,6 +49,7 @@ queue_t ul_config_req_queue;
 queue_t hi_dci0_req_queue;
 
 int current_sfn_sf;
+sem_t sfn_semaphore;
 
 static int ue_tx_sock_descriptor = -1;
 static int ue_rx_sock_descriptor = -1;
@@ -1204,6 +1205,12 @@ void *ue_standalone_pnf_task(void *context)
       uint16_t sfn_sf = 0;
       memcpy((void *)&sfn_sf, buffer, sizeof(sfn_sf));
       current_sfn_sf = sfn_sf;
+
+      if (sem_post(&sfn_semaphore) != 0)
+      {
+        LOG_E(MAC, "sem_post() error\n");
+        abort();
+      }
     }
     else
     {
diff --git a/openair2/PHY_INTERFACE/phy_stub_UE.h b/openair2/PHY_INTERFACE/phy_stub_UE.h
index 0ff3ce701b..c90dfe4429 100644
--- a/openair2/PHY_INTERFACE/phy_stub_UE.h
+++ b/openair2/PHY_INTERFACE/phy_stub_UE.h
@@ -14,6 +14,7 @@
 #include "nfapi_interface.h"
 #include "nfapi_pnf_interface.h"
 #include <pthread.h>
+#include <semaphore.h>
 #include "nfapi/oai_integration/vendor_ext.h"
 //#include "openair1/PHY/LTE_TRANSPORT/defs.h"
 //#include "openair1/PHY/defs.h"
@@ -156,4 +157,6 @@ extern nfapi_hi_dci0_request_t* hi_dci0_req;
 
 extern int current_sfn_sf;
 
+extern sem_t sfn_semaphore;
+
 #endif /* PHY_STUB_UE_H_ */
diff --git a/targets/RT/USER/lte-ue.c b/targets/RT/USER/lte-ue.c
index 4995ae028d..af2ea29ab4 100644
--- a/targets/RT/USER/lte-ue.c
+++ b/targets/RT/USER/lte-ue.c
@@ -1046,7 +1046,11 @@ static void *UE_phy_stub_standalone_pnf_task(void *arg)
     bool sent_any = false;
     int sfn_sf = current_sfn_sf;
     if (sfn_sf == last_sfn_sf) {
-      usleep(100);
+      if (sem_wait(&sfn_semaphore) != 0)
+      {
+        LOG_E(MAC, "sem_wait() error\n");
+        abort();
+      }
       continue;
     }
 
diff --git a/targets/RT/USER/lte-uesoftmodem.c b/targets/RT/USER/lte-uesoftmodem.c
index 55f167c3ac..218a337fd5 100644
--- a/targets/RT/USER/lte-uesoftmodem.c
+++ b/targets/RT/USER/lte-uesoftmodem.c
@@ -733,7 +733,13 @@ int main( int argc, char **argv ) {
     init_queue(&tx_req_pdu_queue);
     init_queue(&hi_dci0_req_queue);
     init_queue(&ul_config_req_queue);
+
     config_sync_var=0;
+    if (sem_init(&sfn_semaphore, 0, 0) != 0)
+    {
+      LOG_E(MAC, "sem_init() error\n");
+      abort();
+    }
     init_UE_stub_single_thread(NB_UE_INST,eMBMS_active,uecap_xer_in,emul_iface);
     init_UE_standalone_thread();
   } else {