diff --git a/openair1/PHY/defs_eNB.h b/openair1/PHY/defs_eNB.h
index 271d54fdce..0c41328f32 100644
--- a/openair1/PHY/defs_eNB.h
+++ b/openair1/PHY/defs_eNB.h
@@ -312,6 +312,8 @@ typedef struct RU_t_s{
   LTE_DL_FRAME_PARMS frame_parms;
   ///timing offset used in TDD
   int              N_TA_offset; 
+  /// SF extension used in TDD (unit: number of samples at 30.72MHz) (this is an expert option)
+  int              sf_extension;
   /// RF device descriptor
   openair0_device rfdevice;
   /// HW configuration
diff --git a/openair2/ENB_APP/enb_paramdef.h b/openair2/ENB_APP/enb_paramdef.h
index b44ec9de16..edbb34461a 100644
--- a/openair2/ENB_APP/enb_paramdef.h
+++ b/openair2/ENB_APP/enb_paramdef.h
@@ -101,6 +101,7 @@ typedef enum {
 #define CONFIG_STRING_RU_NBIOTRRC_LIST            "NbIoT_RRC_instances"
 #define CONFIG_STRING_RU_SDR_ADDRS                "sdr_addrs"
 #define CONFIG_STRING_RU_SDR_CLK_SRC              "clock_src"
+#define CONFIG_STRING_RU_SF_EXTENSION             "sf_extension"
 
 #define RU_LOCAL_IF_NAME_IDX          0
 #define RU_LOCAL_ADDRESS_IDX          1
@@ -122,6 +123,7 @@ typedef enum {
 #define RU_NBIOTRRC_LIST_IDX          17
 #define RU_SDR_ADDRS                  18
 #define RU_SDR_CLK_SRC                19
+#define RU_SF_EXTENSION_IDX           20
 
 
 
@@ -149,7 +151,8 @@ typedef enum {
 {CONFIG_STRING_RU_ATT_RX,                   	 NULL,       0,       uptr:NULL,       defintval:0,		TYPE_UINT,	  0}, \
 {CONFIG_STRING_RU_NBIOTRRC_LIST,                 NULL,       0,       uptr:NULL,       defintarrayval:DEFENBS,  TYPE_INTARRAY,    1}, \
 {CONFIG_STRING_RU_SDR_ADDRS,                 	 NULL,       0,       strptr:NULL,     defstrval:"type=b200",   TYPE_STRING,      0}, \
-{CONFIG_STRING_RU_SDR_CLK_SRC,               	 NULL,       0,       strptr:NULL,     defstrval:"internal",   TYPE_STRING,      0}, \
+{CONFIG_STRING_RU_SDR_CLK_SRC,               	 NULL,       0,       strptr:NULL,     defstrval:"internal",    TYPE_STRING,      0}, \
+{CONFIG_STRING_RU_SF_EXTENSION,                  NULL,       0,       uptr:NULL,       defuintval:312,          TYPE_UINT,        0}, \
 }
 
 /*---------------------------------------------------------------------------------------------------------------------------------------*/
diff --git a/targets/RT/USER/lte-ru.c b/targets/RT/USER/lte-ru.c
index 787e630d17..002190ec53 100644
--- a/targets/RT/USER/lte-ru.c
+++ b/targets/RT/USER/lte-ru.c
@@ -835,7 +835,7 @@ void tx_rf(RU_t *ru) {
         (prevSF_type == SF_UL) &&
         (nextSF_type == SF_DL)) {
       flags = 2; // start of burst
-      sf_extension = ru->N_TA_offset;
+      sf_extension = ru->sf_extension;
     }
 
     if ((fp->frame_type == TDD) &&
@@ -843,7 +843,7 @@ void tx_rf(RU_t *ru) {
         (prevSF_type == SF_UL) &&
         (nextSF_type == SF_UL)) {
       flags = 4; // start of burst and end of burst (only one DL SF between two UL)
-      sf_extension = ru->N_TA_offset;
+      sf_extension = ru->sf_extension;
     }
 
 #if defined(__x86_64) || defined(__i386__)
@@ -1386,6 +1386,14 @@ int setup_RU_buffers(RU_t *ru) {
        * TODO: find a proper cleaner solution
        */
       ru->N_TA_offset = 0;
+
+    if      (frame_parms->N_RB_DL == 100) /* no scaling to do */;
+    else if (frame_parms->N_RB_DL == 50)  ru->sf_extension /= 2;
+    else if (frame_parms->N_RB_DL == 25)  ru->sf_extension /= 4;
+    else { printf("not handled, todo\n"); exit(1); }
+  } else {
+    ru->N_TA_offset = 0;
+    ru->sf_extension = 0;
   }
 
   if (ru->openair0_cfg.mmapped_dma == 1) {
@@ -2883,6 +2891,8 @@ void RCconfig_RU(void) {
         RC.ru[j]->max_pdschReferenceSignalPower     = *(RUParamList.paramarray[j][RU_MAX_RS_EPRE_IDX].uptr);;
         RC.ru[j]->max_rxgain                        = *(RUParamList.paramarray[j][RU_MAX_RXGAIN_IDX].uptr);
         RC.ru[j]->num_bands                         = RUParamList.paramarray[j][RU_BAND_LIST_IDX].numelt;
+        /* sf_extension is in unit of samples for 30.72MHz here, has to be scaled later */
+        RC.ru[j]->sf_extension                      = *(RUParamList.paramarray[j][RU_SF_EXTENSION_IDX].uptr);
 
         for (i=0; i<RC.ru[j]->num_bands; i++) RC.ru[j]->band[i] = RUParamList.paramarray[j][RU_BAND_LIST_IDX].iptr[i];
       } //strcmp(local_rf, "yes") == 0