diff --git a/pcu_l1_if.cpp b/pcu_l1_if.cpp
index 18e8d5be..c3d1b12d 100644
--- a/pcu_l1_if.cpp
+++ b/pcu_l1_if.cpp
@@ -28,6 +28,18 @@
 // TODO: We should take ports and IP from config.
 UDPSocket pcu_gsmtap_socket(5077, "127.0.0.1", 4729);
 
+// Variable for storage current FN.
+int frame_number;
+
+int get_current_fn()
+{
+	return frame_number;
+}
+
+void set_current_fn(int fn)
+{
+	frame_number = fn;
+}
 
 struct msgb *l1p_msgb_alloc(void)
 {
@@ -39,11 +51,27 @@ struct msgb *l1p_msgb_alloc(void)
 	return msg;
 }
 
+struct msgb *gen_dummy_msg(void)
+{
+	int ofs = 0;
+	struct msgb *msg = l1p_msgb_alloc();
+	GsmL1_Prim_t *prim = msgb_l1prim(msg);
+	// RLC/MAC filler with USF=1
+	BitVector filler("0100000110010100001010110010101100101011001010110010101100101011001010110010101100101011001010110010101100101011001010110010101100101011001010110010101100101011001010110010101100101011");
+	prim->id = GsmL1_PrimId_PhDataReq;
+	filler.pack((unsigned char*)&(prim->u.phDataReq.msgUnitParam.u8Buffer[ofs]));
+	ofs += filler.size() >> 3;
+	prim->u.phDataReq.msgUnitParam.u8Size = ofs;
+	return msg;
+}
+
 // Send RLC/MAC block to OpenBTS.
 void pcu_l1if_tx(BitVector * block)
 {
 	int ofs = 0;
 	struct msgb *msg = l1p_msgb_alloc();
+	struct osmo_wqueue * queue;
+	queue = &((l1fh->fl1h)->write_q);
 	GsmL1_Prim_t *prim = msgb_l1prim(msg);
 	
 	prim->id = GsmL1_PrimId_PhDataReq;
@@ -51,21 +79,37 @@ void pcu_l1if_tx(BitVector * block)
 	ofs += block->size() >> 3;
 	prim->u.phDataReq.msgUnitParam.u8Size = ofs;
 	
-	COUT("Send to OpenBTS: " << *block);
-	osmo_wqueue_enqueue(&l1fh->udp_wq, msg);
+	COUT("Add Block to WRITE QUEUE: " << *block);
+	osmo_wqueue_enqueue(queue, msg);
 }
 
 int pcu_l1if_rx_pdch(GsmL1_PhDataInd_t *data_ind)
 {
 	BitVector *block = new BitVector(23*8);
 	block->unpack((const unsigned char*)data_ind->msgUnitParam.u8Buffer);
-	COUT("Recieve from OpenBTS (MS): " << *block);
+	COUT("RX: " << *block);
 	
 	gprs_rlcmac_rcv_block(block);
 }
 
-static int handle_ph_data_ind(struct femtol1_hdl *fl1, GsmL1_PhDataInd_t *data_ind,
-			struct msgb *l1p_msg)
+static int handle_ph_readytosend_ind(struct femtol1_hdl *fl1, GsmL1_PhReadyToSendInd_t *readytosend_ind)
+{
+	struct msgb *resp_msg;
+	struct osmo_wqueue * queue;
+	queue = &((l1fh->fl1h)->write_q);
+	
+	set_current_fn(readytosend_ind->u32Fn);
+	resp_msg = msgb_dequeue(&queue->msg_queue);
+	if (!resp_msg) {
+		resp_msg = gen_dummy_msg();
+		if (!resp_msg)
+			return 0;
+	}
+	osmo_wqueue_enqueue(&l1fh->udp_wq, resp_msg);
+	return 1;
+}
+
+static int handle_ph_data_ind(struct femtol1_hdl *fl1, GsmL1_PhDataInd_t *data_ind)
 {
 	int rc = 0;
 	switch (data_ind->sapi) {
@@ -97,16 +141,14 @@ int pcu_l1if_handle_l1prim(struct femtol1_hdl *fl1, struct msgb *msg)
 	int rc = 0;
 
 	switch (l1p->id) {
-	case GsmL1_PrimId_MphTimeInd:
-		break;
-	case GsmL1_PrimId_MphSyncInd:
-		break;
 	case GsmL1_PrimId_PhConnectInd:
 		break;
 	case GsmL1_PrimId_PhReadyToSendInd:
+		rc = handle_ph_readytosend_ind(fl1, &l1p->u.phReadyToSendInd);
 		break;
 	case GsmL1_PrimId_PhDataInd:
-		rc = handle_ph_data_ind(fl1, &l1p->u.phDataInd, msg);
+		COUT("RX GsmL1_PrimId_PhDataInd ");
+		rc = handle_ph_data_ind(fl1, &l1p->u.phDataInd);
 		break;
 	case GsmL1_PrimId_PhRaInd:
 		break;
diff --git a/pcu_l1_if.h b/pcu_l1_if.h
index ec56a951..cdd36424 100644
--- a/pcu_l1_if.h
+++ b/pcu_l1_if.h
@@ -23,6 +23,7 @@
 
 #include <BitVector.h>
 #include <gsmL1prim.h>
+#include <sys/socket.h>
 extern "C" {
 #include <osmocom/core/write_queue.h>
 #include <osmocom/core/socket.h>
@@ -59,6 +60,8 @@ struct l1fwd_hdl {
 
 extern struct l1fwd_hdl *l1fh;
 
+int get_current_fn();
+
 void pcu_l1if_tx(BitVector * block);
 
 int pcu_l1if_handle_l1prim(struct femtol1_hdl *fl1h, struct msgb *msg);