diff --git a/hnodeb/HNBGW_ConnectionHandler.ttcn b/hnodeb/HNBGW_ConnectionHandler.ttcn
index 3c4bc6f..b069a11 100644
--- a/hnodeb/HNBGW_ConnectionHandler.ttcn
+++ b/hnodeb/HNBGW_ConnectionHandler.ttcn
@@ -34,8 +34,13 @@
 import from HNBLLIF_Types all;
 import from HNBLLIF_Templates all;
 
+import from GTP_Emulation all;
+import from GTP_Templates all;
+import from GTP_CodecPort all;
+import from GTPU_Types all;
+
 /* this component represents a single Iuh connection at the HNBGW. */
-type component HNBGW_ConnHdlr extends StatsD_ConnHdlr {
+type component HNBGW_ConnHdlr extends StatsD_ConnHdlr, GTP_ConnHdlr {
 	port TELNETasp_PT HNBVTY;
 	port HNBAP_PT HNBAP;
 	port RUA_PT RUA;
@@ -46,6 +51,10 @@
 	var RTP_Emulation_CT vc_RTPEM;
 	port RTPEM_CTRL_PT RTPEM_CTRL;
 	port RTPEM_DATA_PT RTPEM_DATA;
+
+	var GTP_Emulation_CT vc_GTP;
+
+
 	var TestHdlrParams g_pars;
 
 	var boolean g_vty_initialized := false;
@@ -60,11 +69,8 @@
 	}
 }
 
-/* initialize all parameters */
-function f_HNBGW_ConnHdlr_init(charstring id, TestHdlrParams pars) runs on HNBGW_ConnHdlr {
+private function f_HNBGW_ConnHdlr_init_iuh(charstring id) runs on HNBGW_ConnHdlr {
 	var Iuh_Emulation_CT vc_Iuh;
-
-	g_pars := valueof(pars);
 	vc_Iuh := Iuh_Emulation_CT.create(id & "-HNBGW");
 	connect(self:HNBAP, vc_Iuh:HNBAP);
 	connect(self:RUA, vc_Iuh:RUA);
@@ -75,7 +81,30 @@
 	iuh_pars.local_ip := g_pars.hnbgw_addr;
 	iuh_pars.local_sctp_port  := g_pars.hnbgw_port;
 	vc_Iuh.start(Iuh_Emulation.main(iuh_pars, id & "-Iuh"));
+}
 
+private function f_HNBGW_ConnHdlr_init_gtp(charstring id) runs on HNBGW_ConnHdlr {
+	id := id & "-GTP";
+
+	var GtpEmulationCfg gtp_cfg := {
+		gtpc_bind_ip := g_pars.hnbgw_addr,
+		gtpc_bind_port := GTP1C_PORT,
+		gtpu_bind_ip :=  g_pars.hnbgw_addr,
+		gtpu_bind_port := GTP1U_PORT,
+		sgsn_role := false
+	};
+
+	vc_GTP := GTP_Emulation_CT.create(id);
+	connect(self:GTP, vc_GTP:CLIENT);
+	connect(self:GTP_PROC, vc_GTP:CLIENT_PROC);
+	vc_GTP.start(GTP_Emulation.main(gtp_cfg));
+}
+
+/* initialize all parameters */
+function f_HNBGW_ConnHdlr_init(charstring id, TestHdlrParams pars) runs on HNBGW_ConnHdlr {
+	g_pars := valueof(pars);
+	f_HNBGW_ConnHdlr_init_iuh(id);
+	f_HNBGW_ConnHdlr_init_gtp(id);
 	f_HNBGW_ConnHdlr_init_vty();
 
 	/* Connect to HNB on LLSK and do HELLO ping-pong  */
@@ -115,6 +144,13 @@
 		Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Timeout waiting for HNBLLIF HELLO.REQ SAPI=AUDIO");
 		}
 	}
+	pt.send(t_SD_HNBLLIF(hnbllif_conn_id, ts_HNBLLIF_CTL_HELLO_REQ(HNBLL_IF_SAPI_GTP, 0)));
+	alt {
+	[] as_hnbllif_hello_cnf(pt, hnbllif_conn_id, last_hello_cnf, HNBLL_IF_SAPI_GTP, 0);
+	[] T.timeout {
+		Misc_Helpers.f_shutdown(__BFILE__, __LINE__, fail, "Timeout waiting for HNBLLIF HELLO.REQ SAPI=GTP");
+		}
+	}
 }
 
 type record TestHdlrParams {
@@ -151,6 +187,17 @@
 	sac := 4
 }
 
+template (value) GtpPeer ts_GtpPeerU(charstring ip) := {
+	connId := 1,
+	remName := ip,
+	remPort := GTP1U_PORT
+}
+
+function f_gtpu_send(uint32_t tei, octetstring payload) runs on HNBGW_ConnHdlr {
+	var GtpPeer peer := valueof(ts_GtpPeerU(g_pars.hnodeb_addr));
+	GTP.send(ts_GTP1U_GPDU(peer, 0 /*seq*/, int2oct(tei, 4),  payload));
+}
+
 /* HNBLLIF socket may at any time receive a new INFO.ind */
 altstep as_hnbllif_hello_cnf(HNBLLIF_CODEC_PT pt, integer hnbllif_conn_id,
 				out HNBLLIF_Message last_hello_cnf,
diff --git a/hnodeb/HNB_Tests.ttcn b/hnodeb/HNB_Tests.ttcn
index 05cd2bf..ca42e5c 100644
--- a/hnodeb/HNB_Tests.ttcn
+++ b/hnodeb/HNB_Tests.ttcn
@@ -52,6 +52,10 @@
 import from HNBLLIF_Types all;
 import from HNBLLIF_Templates all;
 
+import from GTPU_Types all;
+import from GTP_Templates all;
+import from GTP_Emulation all;
+
 modulepar {
 	/* IP address at which the HNodeB can be reached */
 	charstring mp_hnodeb_ip := "127.0.0.1";
@@ -359,12 +363,70 @@
 	f_shutdown_helper();
 }
 
+private function f_tc_ps_mo_gtp_ping_pong(charstring id) runs on HNBGW_ConnHdlr {
+	const integer context_id := 30;
+	const bitstring context_id_bstr := '000000000000000000011110'B; /* encoded context_id */
+	const Establishment_Cause est_cause := normal_call;
+	var uint32_t remote_tei := 8888;
+	var uint32_t local_tei;
+	var octetstring gtp_payload := f_rnd_octstring(40);
+	var HNBLLIF_send_data sd;
+
+	f_gtp_register_teid(int2oct(remote_tei, 4));
+
+	f_handle_hnbap_hnb_register_req();
+
+	LLSK.receive(f_llsk_rx(tr_HNBLLIF_IUH_CONFIGURE_IND(g_pars.mcc, g_pars.mnc, g_pars.cell_identity,
+						  g_pars.lac, g_pars.rac, g_pars.sac, g_pars.rnc_id)));
+
+	/* Now an UE attempts CM Service Request: */
+	LLSK.send(f_llsk_tx(ts_HNBLLIF_IUH_CONN_ESTABLISH_REQ(context_id, 1, enum2int(est_cause), hex2oct(ranap_cm_service_req))));
+	/* The related RUA Connect + RANAP message is received on Iuh: */
+	RUA.receive(tr_RUA_Connect(ps_domain, context_id_bstr, est_cause, hex2oct(ranap_cm_service_req)));
+
+	/* Now HNBGW answers with RUA-DirectTransfer(RANAP-RabASsReq) */
+	RUA.send(ts_RUA_DirectTransfer(ps_domain, context_id_bstr, hex2oct(ranap_rab_ass_req)));
+
+	/* Now on LLSK first the Conn establishment is confirmed and then we receive data */
+	LLSK.receive(f_llsk_rx(tr_HNBLLIF_IUH_CONN_ESTABLISH_CNF(context_id, 1, 0)));
+	LLSK.receive(f_llsk_rx(tr_HNBLLIF_IUH_CONN_DATA_IND(context_id, 1, hex2oct(ranap_rab_ass_req))));
+
+	/* Now LLSK provides the remote TransportLayerAddress from RabAssReq and asks SUT to provide a local address: */
+	LLSK.send(f_llsk_tx(ts_HNBLLIF_GTP_CONN_ESTABLISH_REQ(context_id, remote_tei, HNBLL_IF_ADDR_TYPE_IPV4,
+							      f_HNBLLIF_Addr(HNBLL_IF_ADDR_TYPE_IPV4, g_pars.hnbgw_addr))));
+	LLSK.receive(f_llsk_rx(tr_HNBLLIF_GTP_CONN_ESTABLISH_CNF(context_id, ?, 0,
+								 HNBLL_IF_ADDR_TYPE_IPV4, ?))) -> value sd;
+	local_tei := sd.data.u.gtp.u.conn_establish.u.cnf.local_tei;
+
+	/* Forward GTP data in both directions */
+	LLSK.send(f_llsk_tx(ts_HNBLLIF_GTP_CONN_DATA_REQ(context_id, remote_tei, gtp_payload)));
+	GTP.receive(tr_GTPU_GPDU(ts_GtpPeerU(g_pars.hnodeb_addr), int2oct(remote_tei, 4), gtp_payload));
+	f_gtpu_send(local_tei, gtp_payload);
+	LLSK.receive(f_llsk_rx(tr_HNBLLIF_GTP_CONN_DATA_IND(context_id, local_tei, gtp_payload)));
+
+	/* Done, release GTP conn */
+	LLSK.send(f_llsk_tx(ts_HNBLLIF_GTP_CONN_RELEASE_REQ(context_id, remote_tei)));
+
+	/* UE sends Iu Release Complete to release the conn */
+	LLSK.send(f_llsk_tx(ts_HNBLLIF_IUH_CONN_RELEASE_REQ(context_id, 1, 0, 0, hex2oct(iu_release_compl))));
+	RUA.receive(tr_RUA_Disconnect(ps_domain, context_id_bstr, ts_RUA_Cause(normal), hex2oct(iu_release_compl)));
+}
+testcase TC_ps_mo_gtp_ping_pong() runs on test_CT {
+	var HNBGW_ConnHdlr vc_conn;
+
+	f_init();
+	vc_conn := f_start_handler(refers(f_tc_ps_mo_gtp_ping_pong));
+	vc_conn.done;
+	f_shutdown_helper();
+}
+
 control {
 	execute( TC_hnb_register_request_accept() );
 	execute( TC_hnb_register_request_reject() );
 	execute( TC_mo_conn() );
 	execute( TC_paging() );
 	execute( TC_cs_mo_call() );
+	execute( TC_ps_mo_gtp_ping_pong() );
 }
 
 }
diff --git a/hnodeb/gen_links.sh b/hnodeb/gen_links.sh
index 6ddb4c0..84495e9 100755
--- a/hnodeb/gen_links.sh
+++ b/hnodeb/gen_links.sh
@@ -44,6 +44,10 @@
 FILES="TELNETasp_PT.cc  TELNETasp_PT.hh  TELNETasp_PortType.ttcn"
 gen_links $DIR $FILES
 
+DIR=$BASEDIR/titan.ProtocolModules.GTP_v13.5.0/src
+FILES="GTPC_EncDec.cc  GTPC_Types.ttcn  GTPU_EncDec.cc  GTPU_Types.ttcn"
+gen_links $DIR $FILES
+
 DIR=../library/hnbap
 FILES="HNBAP_CommonDataTypes.asn HNBAP_Constants.asn HNBAP_Containers.asn HNBAP_IEs.asn HNBAP_PDU_Contents.asn HNBAP_PDU_Descriptions.asn "
 FILES+="HNBAP_EncDec.cc  HNBAP_Types.ttcn  HNBAP_Templates.ttcn "
@@ -59,7 +63,7 @@
 FILES+="Iuh_Types.ttcn Iuh_CodecPort.ttcn Iuh_CodecPort_CtrlFunctDef.cc Iuh_CodecPort_CtrlFunct.ttcn Iuh_Emulation.ttcn DNS_Helpers.ttcn "
 FILES+="Misc_Helpers.ttcn General_Types.ttcn Osmocom_Types.ttcn Osmocom_VTY_Functions.ttcn Native_Functions.ttcn Native_FunctionDefs.cc IPA_Types.ttcn IPA_CodecPort.ttcn IPA_CodecPort_CtrlFunct.ttcn IPA_CodecPort_CtrlFunctDef.cc IPA_Emulation.ttcnpp Osmocom_CTRL_Types.ttcn Osmocom_CTRL_Functions.ttcn Osmocom_CTRL_Adapter.ttcn RTP_CodecPort.ttcn RTP_CodecPort_CtrlFunct.ttcn RTP_CodecPort_CtrlFunctDef.cc RTP_Emulation.ttcn IuUP_Types.ttcn IuUP_EncDec.cc IuUP_Emulation.ttcn "
 FILES+="StatsD_Types.ttcn StatsD_CodecPort.ttcn StatsD_CodecPort_CtrlFunct.ttcn StatsD_CodecPort_CtrlFunctdef.cc StatsD_Checker.ttcn "
-
+FILES+="GTP_CodecPort.ttcn GTP_CodecPort_CtrlFunct.ttcn GTP_CodecPort_CtrlFunctDef.cc GTP_Emulation.ttcn GTP_Templates.ttcn IPCP_Types.ttcn GSM_Types.ttcn "
 gen_links $DIR $FILES
 
 ignore_pp_results
diff --git a/hnodeb/regen_makefile.sh b/hnodeb/regen_makefile.sh
index 2d13504..10f5c21 100755
--- a/hnodeb/regen_makefile.sh
+++ b/hnodeb/regen_makefile.sh
@@ -25,6 +25,9 @@
 	HNBAP_EncDec.cc
 	RUA_EncDec.cc
 	UD_PT.cc
+	GTPC_EncDec.cc
+	GTPU_EncDec.cc
+	GTP_CodecPort_CtrlFunctDef.cc
 "
 
 export CPPFLAGS_TTCN3="
diff --git a/library/HNBLLIF_Templates.ttcn b/library/HNBLLIF_Templates.ttcn
index 3fa49b7..78cf89a 100644
--- a/library/HNBLLIF_Templates.ttcn
+++ b/library/HNBLLIF_Templates.ttcn
@@ -367,4 +367,131 @@
 		}
 	}
 }
+
+
+/**********************
+ * GTP SAPI
+ **********************/
+template (value) HNBLLIF_Message ts_HNBLLIF_GTP_CONN_ESTABLISH_REQ(template (value) uint32_t context_id,
+								     template (value) uint32_t remote_tei,
+								     template (value) HNBLLIF_AddrType remote_gtpu_address_type,
+								     template (value) HNBLLIF_Addr remote_gtpu_addr) := {
+	sapi := HNBLL_IF_SAPI_GTP,
+	u := {
+		gtp := {
+			prim := HNBLL_IF_GTP_MSG_CONN_ESTABLISH,
+			u := {
+				conn_establish := {
+					op := HNBLL_IF_OP_REQUEST,
+					u := {
+						req := {
+							context_id := context_id,
+							remote_tei := remote_tei,
+							reserved := 0,
+							remote_gtpu_address_type := remote_gtpu_address_type,
+							remote_gtpu_addr := remote_gtpu_addr
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
+template (present) HNBLLIF_Message tr_HNBLLIF_GTP_CONN_ESTABLISH_CNF(template (present) uint32_t context_id := ?,
+								     template (present) uint32_t local_tei := ?,
+								     template (present) uint8_t error_code := ?,
+								     template (present) HNBLLIF_AddrType local_gtpu_address_type := ?,
+								     template (present) HNBLLIF_Addr local_gtpu_addr := ?) := {
+	sapi := HNBLL_IF_SAPI_GTP,
+	u := {
+		gtp := {
+			prim := HNBLL_IF_GTP_MSG_CONN_ESTABLISH,
+			u := {
+				conn_establish := {
+					op := HNBLL_IF_OP_CONFIRM,
+					u := {
+						cnf := {
+							context_id := context_id,
+							local_tei := local_tei,
+							error_code := error_code,
+							local_gtpu_address_type := local_gtpu_address_type,
+							local_gtpu_addr := local_gtpu_addr
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
+template (value) HNBLLIF_Message ts_HNBLLIF_GTP_CONN_RELEASE_REQ(template (value) uint32_t context_id,
+								 template (value) uint32_t remote_tei) := {
+	sapi := HNBLL_IF_SAPI_GTP,
+	u := {
+		gtp := {
+			prim := HNBLL_IF_GTP_MSG_CONN_RELEASE,
+			u := {
+				conn_release := {
+					op := HNBLL_IF_OP_REQUEST,
+					u := {
+						req := {
+							context_id := context_id,
+							remote_tei := remote_tei
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
+template (present) HNBLLIF_Message tr_HNBLLIF_GTP_CONN_DATA_IND(template (present) uint32_t context_id := ?,
+							        template (present) uint32_t local_tei := ?,
+							        template (present) octetstring data := ?) := {
+	sapi := HNBLL_IF_SAPI_GTP,
+	u := {
+		gtp := {
+			prim := HNBLL_IF_GTP_MSG_CONN_DATA,
+			u := {
+				conn_data := {
+					op := HNBLL_IF_OP_INDICATION,
+					u := {
+						ind := {
+							context_id := context_id,
+							local_tei := local_tei,
+							data_len := ?,
+							data := data
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
+template (value) HNBLLIF_Message ts_HNBLLIF_GTP_CONN_DATA_REQ(template (value) uint32_t context_id,
+							      template (value) uint32_t remote_tei,
+							      template (value) octetstring data) := {
+	sapi := HNBLL_IF_SAPI_GTP,
+	u := {
+		gtp := {
+			prim := HNBLL_IF_GTP_MSG_CONN_DATA,
+			u := {
+				conn_data := {
+					op := HNBLL_IF_OP_REQUEST,
+					u := {
+						req := {
+							context_id := context_id,
+							remote_tei := remote_tei,
+							data_len := lengthof(data),
+							data := data
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
 } with { encode "RAW" variant "BYTEORDER(first)" };
diff --git a/library/HNBLLIF_Types.ttcn b/library/HNBLLIF_Types.ttcn
index befd7bb..95f91fc 100644
--- a/library/HNBLLIF_Types.ttcn
+++ b/library/HNBLLIF_Types.ttcn
@@ -330,6 +330,106 @@
 				other,	OTHERWISE)"
 };
 
+/**********************
+ * GTP SAPI
+ **********************/
+type enumerated HNBLLIF_GTP_MsgType {
+	HNBLL_IF_GTP_MSG_CONN_ESTABLISH	('0000'O),
+	HNBLL_IF_GTP_MSG_CONN_RELEASE		('0001'O),
+	HNBLL_IF_GTP_MSG_CONN_DATA		('0002'O)
+} with { variant "FIELDLENGTH(16)" };
+
+/* CONN_ESTABLISH */
+type record HNBLLIF_GTP_conn_establish_req {
+	uint32_t context_id,
+	uint32_t remote_tei,
+	uint8_t reserved,
+	HNBLLIF_AddrType remote_gtpu_address_type,
+	HNBLLIF_Addr remote_gtpu_addr
+} with { variant "" };
+
+type record HNBLLIF_GTP_conn_establish_cnf {
+	uint32_t context_id,
+	uint32_t local_tei,
+	uint8_t error_code,
+	HNBLLIF_AddrType local_gtpu_address_type,
+	HNBLLIF_Addr local_gtpu_addr
+} with { variant "" };
+
+type union HNBLLIF_GTP_PrimOpUnion_conn_establish {
+	HNBLLIF_GTP_conn_establish_req req,
+	HNBLLIF_GTP_conn_establish_cnf cnf,
+	octetstring		other
+} with { variant "" };
+type record HNBLLIF_GTP_PrimOp_conn_establish  {
+	HNBLLIF_Operation	op,
+	HNBLLIF_GTP_PrimOpUnion_conn_establish	u
+} with { variant (u) "CROSSTAG( req, 	op = HNBLL_IF_OP_REQUEST;
+				cnf, 	op = HNBLL_IF_OP_CONFIRM;
+				other,	OTHERWISE)"
+};
+
+/* CONN_RELEASE */
+type record HNBLLIF_GTP_conn_release_req {
+	uint32_t context_id,
+	uint32_t remote_tei
+} with { variant "" };
+
+type union HNBLLIF_GTP_PrimOpUnion_conn_release {
+	HNBLLIF_GTP_conn_release_req req,
+	octetstring		other
+} with { variant "" };
+type record HNBLLIF_GTP_PrimOp_conn_release  {
+	HNBLLIF_Operation	op,
+	HNBLLIF_GTP_PrimOpUnion_conn_release	u
+} with { variant (u) "CROSSTAG( req, 	op = HNBLL_IF_OP_REQUEST;
+				other,	OTHERWISE)"
+};
+
+/* CONN_DATA */
+type record HNBLLIF_GTP_conn_data_req {
+	uint32_t context_id,
+	uint32_t remote_tei,
+	uint32_t data_len,
+	octetstring data /* RANAP message */
+} with { variant (data_len) "LENGTHTO (data)" };
+
+type record HNBLLIF_GTP_conn_data_ind {
+	uint32_t context_id,
+	uint32_t local_tei,
+	uint32_t data_len,
+	octetstring data /* RANAP message */
+} with { variant (data_len) "LENGTHTO (data)" };
+
+type union HNBLLIF_GTP_PrimOpUnion_conn_data {
+	HNBLLIF_GTP_conn_data_req req,
+	HNBLLIF_GTP_conn_data_ind ind,
+	octetstring		other
+} with { variant "" };
+type record HNBLLIF_GTP_PrimOp_conn_data  {
+	HNBLLIF_Operation	op,
+	HNBLLIF_GTP_PrimOpUnion_conn_data	u
+} with { variant (u) "CROSSTAG( req, 	op = HNBLL_IF_OP_REQUEST;
+				ind, 	op = HNBLL_IF_OP_INDICATION;
+				other,	OTHERWISE)"
+};
+
+type union HNBLLIF_GTP_PrimUnion {
+	HNBLLIF_GTP_PrimOp_conn_establish	conn_establish,
+	HNBLLIF_GTP_PrimOp_conn_release		conn_release,
+	HNBLLIF_GTP_PrimOp_conn_data		conn_data,
+	octetstring		other
+} with { variant "" };
+
+type record HNBLLIF_GTP_PrimHdr  {
+	HNBLLIF_GTP_MsgType	prim,
+	HNBLLIF_GTP_PrimUnion	u
+} with { variant (u) "CROSSTAG( conn_establish,	prim = HNBLL_IF_GTP_MSG_CONN_ESTABLISH;
+				conn_release,	prim = HNBLL_IF_GTP_MSG_CONN_RELEASE;
+				conn_data,	prim = HNBLL_IF_GTP_MSG_CONN_DATA;
+				other,	OTHERWISE)"
+};
+
 
 /**********************
 * General
@@ -345,7 +445,7 @@
 type enumerated HNBLLIF_Sapi {
 	HNBLL_IF_SAPI_CTL		(-1),
 	HNBLL_IF_SAPI_IUH		('00000001'O),
-	//HNBLL_IF_SAPI_GTP		('00000002'O),
+	HNBLL_IF_SAPI_GTP		('00000002'O),
 	HNBLL_IF_SAPI_AUDIO		('00000003'O)
 } with { variant "FIELDLENGTH(32)"
 	 variant "COMP(2scompl)"
@@ -361,6 +461,7 @@
 type union HNBLLIF_SapiUnion {
 	HNBLLIF_CTL_PrimHdr		ctl,
 	HNBLLIF_IUH_PrimHdr		iuh,
+	HNBLLIF_GTP_PrimHdr		gtp,
 	HNBLLIF_AUDIO_PrimHdr		audio,
 	octetstring			other
 } with { variant "" };
@@ -370,6 +471,7 @@
 	HNBLLIF_SapiUnion u
 } with { variant (u) "CROSSTAG( ctl, 		sapi = HNBLL_IF_SAPI_CTL;
 				iuh, 		sapi = HNBLL_IF_SAPI_IUH;
+				gtp, 		sapi = HNBLL_IF_SAPI_GTP;
 				audio, 		sapi = HNBLL_IF_SAPI_AUDIO;
 				other,	OTHERWISE)"
 };