(19)
(11)EP 2 710 836 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
18.04.2018 Bulletin 2018/16

(21)Application number: 12723923.4

(22)Date of filing:  03.05.2012
(51)International Patent Classification (IPC): 
H04W 36/02(2009.01)
H04W 88/16(2009.01)
H04W 36/14(2009.01)
(86)International application number:
PCT/IB2012/052231
(87)International publication number:
WO 2012/156855 (22.11.2012 Gazette  2012/47)

(54)

INTER-RAT HANDOVER CONTROL USING EMPTY GRE PACKETS

STEUERUNG DER WEITERLEITUNG ZWISCHEN FUNKZUGANGSTECHNOLOGIEN MIT LEEREN GRE-DATENPAKETEN

CONTRÔLE DE TRANSFERT INTER-RAT UTILISANT DES PAQUETS GRE VIDES


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 19.05.2011 US 201113111141

(43)Date of publication of application:
26.03.2014 Bulletin 2014/13

(60)Divisional application:
18151364.9

(73)Proprietor: Telefonaktiebolaget LM Ericsson (publ)
164 83 Stockholm (SE)

(72)Inventors:
  • JAISWAL, Suraj
    Santa Clara, California 95054 (US)
  • WEN, Renhua
    San Ramon, California 94583 (US)

(74)Representative: Ericsson 
Patent Development Torshamnsgatan 21-23
164 80 Stockholm
164 80 Stockholm (SE)


(56)References cited: : 
WO-A1-2010/069985
  
  • ERICSSON ET AL: "Solutions to minimize packet losses for handover between E-UTRAN and HRPD", 3GPP DRAFT; S2-074114 MINIMIZE_PACKET_LOSSES_REV5, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCE, vol. SA WG2, no. Kobe; 20071002, 2 October 2007 (2007-10-02), XP050260956, [retrieved on 2007-10-02]
  • KITATSUJI Y ET AL: "On Handover Procedure with Data Forwarding for Reducing Buffered User Data in Base Stations", GLOBAL TELECOMMUNICATIONS CONFERENCE, 2009. GLOBECOM 2009. IEEE, IEEE, PISCATAWAY, NJ, USA, 30 November 2009 (2009-11-30), pages 1-8, XP031646436, ISBN: 978-1-4244-4148-8
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

TECHNICAL FIELD



[0001] The invention disclosed herein generally relates to handover of a mobile station, and more particularly to in-order delivery of data packets during inter-RAT handover using empty Generic Routing Encapsulation (GRE) packets.

BACKGROUND



[0002] The 3rd Generation Partnership Project (3GPP) oversees and governs 3rd Generation (3G) networks, including 3G Long Term Evolution (LTE) networks. 3G LTE provides mobile broadband to User Equipment (UEs) within the 3G LTE network at higher data rates than generally available with other networks. For example, the air interface for 3G LTE, Evolved Universal Mobile Telecommunication System (UMTS) Terrestrial Radio Access Network (E-UTRAN), utilizes multi-antenna and multi-user coding techniques to achieve downlink data rates of 100s of Mbps and uplink data rates of 10s of Mbps.

[0003] In LTE, user mobility is controlled by the network with assistance from the UE. Handover decisions, as well as the choices for the target cell and technology (when applicable), are made by the current serving eNodeB (equivalent to Base Station in 2G/3G network) based on measurements made by the eNodeB, and based on measurements reported by the UE to the eNodeB. Due to the nature of E-UTRAN, the number of packets buffered before scheduled transmissions occur may not be negligible. For that reason, packet forwarding mechanisms may be used (when applicable) between a source node and a target node so as to limit packet loss during handover from the source node to the target node.

[0004] Due to various delays, e.g., those caused by the forwarding process, the target node may receive forwarded data packets after receiving post-handover data packets. Such delays may cause the target node to deliver data packets to the UE out of order. Procedures currently exist to guarantee in-order packet delivery to the UE during handover of a UE between network nodes within the same Radio Access Network (RAN) and/or associated with the same Radio Access Technology (RAT). However, because no such procedures exist for handover of a UE between network nodes associated with some RATs, i.e., handover from 3GPP to HRPD (High Rate Packet Data), there is a risk of out-of-order packet delivery.

[0005] WO-A1-2010/069985 discloses a packet data network gateway (PDN-GW) on a wireless telecommunications network having a target radio access network (RAN) and a Serving (GW) which includes a processing unit which generates an end marker packet. The PDN-GW includes a network interface which sends the end marker packet onto the network to assist the target RAN in reordering of downlink data. A method for a packet data network gateway (PDN-GW) on a wireless telecommunications network having a target radio access network (RAN) and a Serving (GW) includes the steps of generating an end marker packet with a processing unit. There is the step of sending the end marker packet onto the network with a network interface to assist the target RAN in reordering of downlink data.

SUMMARY



[0006] The present invention provides a method implemented by a target gateway according to Claim 1.

[0007] The present invention also provides a target gateway according to Claim 6. Preferred embodiments are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS



[0008] 

Figure 1 shows a block diagram of a 3GPP network and HRPD network interfacing with a mobile station.

Figure 2 shows a simplified block diagram of the source and target networks interfacing with the mobile station during inter-RAT handover according to one exemplary embodiment disclosed herein.

Figure 3 shows a block diagram of an exemplary network gateway.

Figure 4 shows an exemplary method of inter-RAT handover as implemented by the network gateway of Figure 3.

Figure 5 shows a block diagram of an exemplary source gateway.

Figure 6 shows an exemplary method of inter-RAT handover as implemented by the source gateway of Figure 5.

Figure 7 shows a block diagram of an exemplary target gateway.

Figure 8 shows an exemplary method of inter-RAT handover as implemented by the target gateway of Figure 7.

Figure 9 shows another exemplary method of inter-RAT handover as implemented by the network gateway of Figure 3.

Figure 10 shows another exemplary method of inter-RAT handover as implemented by the source gateway of Figure 5.

Figure 11 shows another exemplary method of inter-RAT handover as implemented by the target gateway of Figure 7.

Figure 12 shows an example of inter-RAT handover between 3GPP and HRPD networks according to one exemplary embodiment disclosed herein.

Figure 13 shows an example of a call flow diagram for the inter-RAT handover of Figure 2.


DETAILED DESCRIPTION



[0009] The following discloses the use of empty GRE (Generic Routing Encapsulation) packets to provide in-order delivery of data packets for a session to a UE (User Equipment) during inter-RAT (Radio Access Technology) handover. In particular, an empty GRE packet sent from a source gateway in a source RAN (Radio Access Network) to a target gateway in a target RAN indicates to the target gateway the end of forwarded data packets from the source gateway. The target gateway sends data packets received from the source gateway to the UE until the empty GRE packet is received. Upon receipt of the empty GRE packet, the target gateway begins sending data packets received directly from a home network gateway to the UE.

[0010] The network gateway, source gateway, and target gateway each play a part in implementing the inter-RAT handover described herein. After receiving handover instructions, the network gateway sends an end-marker packet to the source gateway to indicate the end of the data packets being sent by the network gateway to the source gateway. If the session includes more than one bearer stream, the network gateway sends an end-marker packet for each bearer stream. The network gateway subsequently sends one or more data packets for the session directly to the target gateway, where the direct data packets are sequentially ordered relative to the data packets sent to the source gateway. The network gateway may also send an empty GRE packet to the target gateway before sending the data packets to the target gateway. The empty GRE packet indicates the start of the transmission of data packets for the session from the network gateway directly to the target gateway.

[0011] The source gateway forwards the data packets to the target gateway in the target RAN. Responsive to receiving an end-marker packet, the source gateway generates and sends an empty GRE packet to the target gateway. If the session includes multiple bearer streams, the source gateway sends the empty GRE packet after receiving the end-marker packet for each bearer stream. The empty GRE packet indicates to the target gateway the end of the forwarded packets for the session.

[0012] The target gateway sends data packets to the UE based on the received data packets and the received empty GRE packet(s). More particularly, the target gateway sends the forwarded data packets received from the source gateway to the UE. Responsive to receiving the empty GRE packet from the source gateway, the target gateway sends the data packets received directly from the network gateway to the UE.

[0013] The embodiments disclosed herein use empty GRE (Generic Routing Encapsulation) packets to deliver packets for a session in-order to a UE (User Equipment) during inter-RAT (Radio Access Technology) handover. In particular, an empty GRE packet sent from a source gateway in a source RAN (Radio Access Network) to a target gateway in a target RAN indicates the end of the data packets from the source gateway. The target gateway sends data packets received from the source gateway to the UE until the empty GRE packet is received. After receipt of the empty GRE packet, the target gateway sends data packets received directly from the network gateway to the UE. While the embodiments are described herein in terms of 3GPP and HRPD networks, the embodiments of the invention disclosed herein may generally apply to any downlink inter-RAT handover.

[0014] Before describing further details, the following first generally describes inter-RAT handover. Figure 1 shows a wireless network including elements associated with a home mobile network, 3GPP RAN, and HRPD RAN during inter-RAT handover of the UE between 3GPP and HRPD. The wireless network applies to both roaming and non-roaming scenarios, where the S5 interface between the Packet Data Network (PDN) Gateway (PGW) and the Serving Gateway (SGW) applies to non-roaming scenarios, and the S8 interface between the PGW and SGW applies to roaming scenarios. It will be appreciated that Figure 1 omits various elements, e.g., the PCRF, AAA servers, etc., for simplicity.

[0015] The home mobile network represents one or more external networks, and includes an IP node, a Home Subscriber Server (HSS), and a PGW. The IP node provides data associated with IP services, e.g., IMS, PSS, etc., to the PGW. The HSS comprises a central database containing user-related and subscription-related information. In addition, the HSS provides mobility management, call and session establishment support, user authentication, and access authorization. The PGW provides connectivity between the UE and the home mobile network. Further, the PGW serves as an anchor for mobility between 3GPP and non-3GPP technologies.

[0016] The PGW provides data packets for a session to the SGW via the S5 (non-roaming) or S8 (roaming) interface. The SGW routes GTP data packets to an eNodeB of the E-UTRAN via the S1 -U interface for transmission to the UE according to the 3GPP standard. After the eNodeB makes the decision to handover the UE to a non-3GPP network, e.g., the HRPD network, the eNodeB returns any received GTP data packets for the session back to the SGW. The SGW forwards the returned data packets to the HSGW via the S103 interface as GRE data packets.

[0017] To complete the handover, the PGW sends a GTP-U end-marker packet to the SGW to indicate the end of the data packets being sent to the SGW. Subsequently, the PGW sends GRE data packets for the session to the HSGW via the S2a interface. After the downlink path is switched at the PGW, forwarded data packets on the S103 interface and GRE data packets on the S2a interface may arrive interchanged at the HSGW, which may hinder or otherwise prevent the HSGW from delivering the data packets for the session via the HRPD AN to the UE in order.

[0018] One possible solution to this problem is to insert sequence numbers in the header of each data packet. While such sequence numbers would enable the HSGW to determine the correct order for the data packets, using such sequence numbers also undesirably increases the overhead and signal processing associated with the transmission of each data packet.

[0019] The inter-RAT handover described herein solves this problem by using an empty GRE packet to indicate the end of the forwarded packets to the HSGW. Figure 2 shows a simplified block diagram of the wireless network implementing the inter-RAT handover described herein. The wireless network includes a network gateway 100 in a home mobile network, a source gateway 200 in a source network, and a target gateway 300 in a target network. The source network sends data packets from the SGW 200 to the UE 400 via the source AN 260. The target network sends data packets from the target gateway 300 to the UE 400 via the target AN 360. While not required, examples of the network gateway 100, source gateway 200, source AN 260, target gateway 300, and target AN 360 respectively comprise the PGW, SGW, eNodeB/E-UTRAN, HSGW, and HRPD AN shown in Figure 1.

[0020] SGW 200 sends an empty GRE packet to the HSGW 300 based on an end-marker packet originating at the PGW 100 and returned to the SGW 200 from the source AN 260. The empty GRE packet indicates to the HSGW 300 the end of the data packets from the SGW 200. The HSGW 300 sends data packets received from the SGW 200 to the UE 400 until the empty GRE packet is received. Upon receipt of the empty GRE packet, HSGW 300 begins sending data packets received directly from the PGW 100 to the UE 400.

[0021] Figures 3 and 4 respectively describe handover operations from the perspective of the PGW 100 and a method 180 implemented by the PGW 100. PGW 100 comprises a transmitter 110 and a control unit 120. Transmitter 110 sends source RAN data packets, e.g., GTP data packets, for the session to the SGW 200 according to 3GPP protocols (block 182). Control unit 120 generally controls the operation of the PGW 100, and includes a packet router 122 to control packet transmissions before, during, and after handover. More particularly, after the transmitter 110 sends the last GTP data packet, packet router 122 controls the transmitter 110 to send an end-marker packet, e.g., a GTP-U end-marker packet, indicating the end of the GTP data packets to the SGW 200 for the session (block 184). If the session includes multiple bearer streams, the packet router 122 controls the transmitter to send an end-marker packet for each bearer stream.

[0022] After the end-marker packet(s) are sent to the SGW 200, the packet router 122 controls the transmitter 110 to send target RAN data packets for the session, e.g., GRE data packets, to the UE 400 according to HRPD protocols. In some embodiments, the packet router 122 generates an empty GRE packet and controls the transmitter 110 to send the empty GRE packet to the HSGW 300 (block 186) after sending the end-marker packet(s) to the SGW 200 and before sending the GRE data packets to the HSGW 300. The empty GRE packet indicates the beginning of the subsequent transmission of the GRE data packets for the session to the HSGW 300. After sending the empty GRE packet, the transmitter 110 sends the subsequent GRE data packets for the session to the HSGW 300 (block 188). The subsequent GRE data packets are sequentially ordered relative to the GTP data packets.

[0023] Figures 5 and 6 respectively describe the handover operations from the perspective of the SGW 200 and a method 280 implemented by the SGW 200. The SGW 200 comprises a receiver 210, control unit 220, and transmitter 230. Receiver 210 receives source RAN data packets, e.g., GTP data packets, for the session from the PGW 100. During handover, the receiver 210 also receives an end-marker packet for each of the one or more bearer streams of the session. Control unit 220 comprises a packet router 222 configured to direct the received GTP data packets to the transmitter 230 for transmission to the eNodeB 260. Before handover, the eNodeB 260 transmits the GTP data packets to the UE 400. After eNodeB 260 breaks the connection with the UE 400 during handover, the eNodeB 260 returns any received GTP data packets, including any GTP-U end-marker packet(s) to the SGW 200.

[0024] Responsive to receiving returned GTP data packets from the eNodeB 260, the packet router 222 controls the transmitter 230 to forward the data packets as target RAN data packets, e.g., GRE data packets, to the HSGW 300 (block 282). In addition, packet router 222 generates an empty GRE packet responsive to the end-marker packet, e.g., the end-marker packet returned by the eNodeB 260 (blocks 284, 286). If the session includes multiple bearer streams, the packet router 222 generates the empty GRE packet responsive to receiving an end-marker packet for each bearer stream. Subsequently, the packet router 222 controls the transmitter 230 to send the empty GRE packet to the HSGW 300 to indicate to the HSGW 300 the end of the GRE data packets from the SGW 200 (block 288).

[0025] Figures 7 and 8 respectively describe the handover operations from the perspective of the HSGW 300 and a method implemented by the HSGW 300. HSGW 300 includes a receiver 310, control unit 320, and transmitter 330. During handover, receiver 310 receives target RAN data packets for the session, e.g., GRE data packets, from both the SGW 200 and the PGW 100, where the GRE data packets received from the SGW 200 contain payload that is the same as the payload of the GTP data packets originating at the PGW 100 and forwarded by the SGW 200 (block 382). Until the HSGW 300 receives the empty GRE packet from the SGW 200 (block 384), packet router 322 controls the transmitter 320 to send the forwarded data packets from the SGW 200 to the UE 400 via the Access Node (AN) 360 (blocks 384, 386). Once the HSGW 300 receives the empty GRE packet from the SGW 200, the packet router 322 controls the transmitter to send the data packets received directly from the PGW 100 to the UE 400 via AN 360 (blocks 384, 388).

[0026] In some embodiments, the HSGW 300 may also include a buffer 340. Buffer 340 buffers the data packets received directly from the PGW 100 until receiver 310 receives the empty GRE packet from the SGW 200. Upon receipt of the empty GRE packet, the packet router 322 controls the transmitter 330 to send the buffered data packets to the UE 400. Once the buffer is empty 340, the packet router 322 controls the transmitter 330 to send the data packets received from the PGW 100.

[0027] The HSGW 300 may also include a timer 350 to ensure that the buffered data packets are eventually delivered to the UE 400, even if the empty GRE packet is never received. For example, the packet router 322 may control the transmitter 330 to send the buffered data packets upon expiration of the timer 350. Thus, if the empty GRE packet is lost or damaged, the HSGW 300 will still send the buffered data packets upon expiration of the timer. The timer 350 may be set based on an expected duration of the handover process. In one embodiment, timer 350 starts responsive to receipt of an empty GRE packet from the PGW 100. In anther embodiment, the timer 350 starts responsive to receipt of the first data packet from the PGW 100.

[0028] The embodiments described above rely on empty GRE packets to indicate the end of the session data packets being sent from the SGW 200 to the HSGW 300. In some instances, an empty GRE packet may also be used to indicate the beginning of session data packets being sent from the PGW 100 to the HSGW 300 during handover. Other embodiments may also or alternatively use one or more sequence numbers in a header of an empty packet or a data packet to indicate the end and/or beginning of the data packets. Figures 9-11 provide exemplary methods for a PGW 100, SGW 200, and HSGW 300, respectively, when sequence numbers are used to indicate the beginning and/or end of data packet transmissions.

[0029] Figure 9 shows an exemplary method 190 from the perspective of the PGW 100 for handling inter-RAT handover using sequence numbers. Transmitter 110 sends GTP data packets for the session to the SGW 200 (block 192). After the transmitter 110 sends the last GTP data packet, the packet router 122 controls the transmitter 110 to send an end-marker packet indicating the end of the GTP data packets for the session (block 194). The header of the end-marker packet includes a sequence number field containing a first sequence number. If the session includes multiple bearer streams, the packet router 122 controls the transmitter to send an end-marker packet for each bearer stream, where each end-marker packet includes a first sequence number in the header. In one embodiment, the end-marker packet for each bearer stream includes a different sequence number. It will be appreciated, however, that some or all of the end-marker packets may include the same sequence number.

[0030] After sending the end-marker packet, the packet router 122 controls the transmitter 110 to send an initial GRE data packet with a second sequence number in the header to the HSGW 300 (block 196). The second sequence number indicates the beginning of the GRE data packets being sent from the PGW 100 directly to the HSGW 300. The initial data packet may contain payload data in the body of the packet. Alternatively, the initial data packet may comprise an empty GRE packet. After sending the initial data packet, transmitter 110 sends the subsequent GRE data packets for the session to the HSGW (block 198). The subsequent GRE data packets are sequentially ordered relative to the GTP data packets sent to the SGW 200.

[0031] Figure 10 shows an exemplary method 290 from the perspective of the SGW 200 for handling inter-RAT handover using sequence numbers. Responsive to receiving returned GTP data packets from the eNodeB, the packet router 222 controls the transmitter 230 to forward the data to the HSGW 300 in GRE data packets (block 292). In addition, packet router 222 generates an empty GRE packet responsive to an end-marker packet, e.g., the end-marker packet returned from the eNodeB 260 (blocks 294, 296). The header of the empty GRE packet includes the sequence number in the returned end-marker packet. If the session includes multiple bearer streams, an end-marker packet containing a sequence number is received for each bearer stream. The packet router 222 selects one of the sequence numbers in the received end-marker packets, e.g., the largest sequence number, and generates the empty GRE packet with the selected sequence number. After the end-marker packet for each bearer stream is received, the packet router 222 controls the transmitter 230 to send the empty GRE packet to the HSGW 300 to indicate to the HSGW 300 the end of the data packets for the session sent by the SGW 200 (block 298).

[0032] Figure 11 shows an exemplary method 390 from the perspective of the HSGW 300 for handling inter-RAT handover using sequence numbers. During handover, receiver 310 receives GRE data packets for the session from both the SGW 200 and the PGW 100, where the GRE data packets received from the SGW 200 contain payload that is the same as the payload of the GTP data packets originating at the PGW 100 and forwarded by the SGW 200 (block 392). Until the HSGW 300 receives the empty GRE packet with the sequence number from the SGW 200 (block 384), the packet router 322 controls the transmitter 320 to send the forwarded GRE data packets from the SGW 200 to the UE 400 via the HRPD AN 360 (blocks 394, 396). Once the HSGW 300 receives the empty GRE packet with the sequence number from the SGW 200, the packet router 322 controls the transmitter to send the GRE data packets received directly from the PGW 100 to the UE 400 via the HRPD AN 360 (blocks 394, 398).

[0033] In some embodiments, the HSGW 300 receives an empty GRE packet having a first sequence number from the SGW 200 and an initial data packet having a second sequence number from the PGW 100. In this case, the HSGW 300 determines whether or not the empty GRE packet and initial GRE data packet are being used to indicate the end and beginning of the data packets from the respective gateways by comparing the first and second sequence numbers. If the sequence numbers have the expected relationship, e.g., the second sequence number is greater than the first sequence number, the first and second sequence numbers are equal, etc., control unit 320 determines that the HSGW 300 has received the indication of the end and start of the data packets from the respective SGW 200 and PGW 100. Based on this information, packet router 322 determines whether or not to have the transmitter 330 begin sending the direct data packets from the PGW 100 to the UE 400.

[0034] When a buffer 340 and timer 350 are included in the HSGW 300, the packet router 322 may also control the transmitter 330 to send the buffered data packets upon expiration of the timer 350. Thus, if the empty GRE packet is lost or damaged, the HSGW 300 will still send the buffered data packets upon expiration of the timer. The timer 350 may be set based on an expected duration of the handover process. In one embodiment, timer 350 starts responsive to receipt of the empty GRE packet with the sequence number from the PGW 100. In anther embodiment, the timer 350 starts responsive to receipt of the first data packet containing a sequence number from the PGW 100.

[0035] When the empty GRE packet sent from the SGW 200 includes a sequence number, the previously sent data packets generally do not include a sequence number. Similarly, when the initial data packet sent form the PGW 100 includes a sequence number, the subsequently sent data packets generally do not include sequence numbers. It will be appreciated, however, that the embodiments disclosed herein do not preclude the use of sequence numbers in the other data packets.

[0036] Figures 12 and 13 respectively show an exemplary block diagram and call flow diagram implementing handover from a 3GPP network to an HRPD network according to one exemplary embodiment. PGW 100 sends user payload packets a, b, and c to the SGW 200 via the S5/S8 GTP tunnel. SGW 200 sends the user payload packets a, b, and c to the eNodeB 260 in the E-UTRAN via the S1-U GTP tunnel. Because eNodeB 260 has already disconnected from the UE 400 and the HRPD AN 360 has connected to the UE 400, the eNodeB 260 returns the user payload packets a, b, and c to the SGW 200 via an indirect GTP tunnel.

[0037] After sending the last data packet (data packet c), the PGW 100 sends an end-marker packet for each bearer stream (call flow item 14c.i). In the example in Figure 12, there is only one bearer stream, and the associated end-marker packet includes sequence number 100. SGW 200 sends the end-marker packet to the eNodeB 260 (call flow item 14c.ii), which returns it to the SGW 200 as part of the data packet forwarding process (call flow item 14c.iii). Responsive to the returned end-marker packet, the SGW 200 generates an empty GRE packet that includes sequence number 100. After SGW 200 forwards the user payload packets a, b, and c to the HSGW 300 via the S103 GRE tunnel, the SGW 200 sends the empty GRE packet to the HSGW (call flow item 14c.v).

[0038] After PGW 100 sends the end-marker packet(s) to SGW 200 (call flow item 14c.i), the PGW 100 sends an initial packet followed by user payload packets d, e, and f to the HSGW 300 via the S2a GRE tunnel. In the example shown in Figure 12, the initial packet comprises an empty GRE packet that includes sequence number 101 (call flow item 14c.iv). The HSGW 300 receives user payload packets a, b, and c and sends them to the HRPD AN 360 for transmission to the UE 400. Upon receipt of the empty GRE packet, the control unit 320 compares the sequence number in the empty GRE packet received from the SGW 200 to the sequence number in the empty GRE packet received from the PGW 100. Because sequence number 101 is greater than sequence number 100, as expected by the HSGW 300, the HSGW sends user payload packets d, e, and f to the HRPD AN 360. If the HSGW 300 receives user payload packets d, e, or f before receiving the empty GRE packet with sequence number 100, the HSGW 300 buffers user payload packets d, e, and/or f in buffer 340 until the empty GRE packet is received, and sends the buffered user payload packets to the HRPD AN 360 after the empty GRE packet is received. After the buffer is emptied, the HSGW 300 sends user payload packets received from the PGW 100 via the S2a GRE tunnel in the order they are received.

[0039] While the embodiments are generally described herein in terms of handover of a UE 400 from 3GPP to HRPD, it will be appreciated that the various embodiments and details also apply to handover of a UE 400 from HRPD to 3GPP, where the source, target, and network gateways respectively comprise the HSGW 300, SGW 200, and PGW 100. In particular, an empty GRE packet sent from the HSGW 300 to the SGW 200 indicates the end of the data packets from the HSGW 300. The SGW 200 sends data packets received from the HSGW 300 to the UE 400 until the empty GRE packet is received. After receipt of the empty GRE packet, the SGW 200 sends data packets received directly from the PGW 100 to the UE 400.

[0040] The embodiments disclosed herein facilitate inter-RAT handover by ensuring in-order delivery of data packets to the UE during the handover. The inter-RAT handover disclosed herein may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning of the appended claims are intended to be embraced therein.


Claims

1. A method (380) implemented by a target gateway, GW, for delivering data packets of a session to a mobile station during inter-RAT handover of said mobile station from a source Radio Access Network, RAN, of a source Radio Access Technology, RAT, to a target RAN of a target RAT different than the source RAT, wherein the target GW is associated with the target RAN and wherein either the source and target RANs are an Evolved UMTS RAN E-UTRAN and an High Rate Data Packet HRPD RAN, respectively, or the source and target RANs are an HRPD RAN and an E-UTRAN, respectively, the method comprising:

receiving (382) one or more forwarded packets for the session from a source gateway associated with the source RAN;

receiving (384) a first empty Generic Routing Encapsulation, GRE, packet from the source gateway indicating the end of the forwarded packets for the session, said first empty GRE packet generated by the source gateway responsive to the source gateway receiving an end marker packet from a network gateway;

sending (388) the forwarded packets to the mobile station via the target RAN;

receiving one or more direct packets for the session from the network gateway, said direct packets sequentially ordered relative to the forwarded packets;

sending the direct packets to the mobile station via the target RAN responsive to receiving the first empty GRE packet;

receiving a second empty GRE packet from the network gateway indicating the start of the direct packets for the session; and

starting a timer responsive to receiving the second empty GRE packet, wherein sending the direct packets comprises sending the direct packets to the mobile station responsive to expiration of the timer.


 
2. The method of claim 1 further comprising starting a timer responsive to receiving a first one of the direct packets, wherein sending the direct packets comprises sending the direct packets to the mobile station responsive to expiration of the timer.
 
3. The method of claim 1 wherein receiving (384) the first empty GRE packet comprises receiving the first empty GRE packet before receiving the direct packets for the session, and wherein sending the direct packets to the mobile station responsive to receiving the first empty GRE packet comprises sending the direct packets to the mobile station upon receipt of the direct packets at the target gateway.
 
4. The method of claim 1 further comprising buffering, in the target gateway, the direct packets received from the network gateway before receipt of the first empty GRE packet, wherein sending the direct packets comprises sending the buffered packets after receiving the first empty GRE packet.
 
5. The method of claim 1 wherein the source gateway comprises one of a 3rd Generation Partnership Project, 3GPP, serving gateway and a High Rate Packet Data, HRPD, serving gateway, the target gateway comprises the other of the 3GPP serving gateway and the HRPD serving gateway, and the network gateway comprises a Packet Data Network, PDN, Gateway, PGW.
 
6. A target gateway (300), GW, for delivering data packets of a session to a mobile station during inter-RAT handover of said mobile station from a source Radio Access Network, RAN, of a source Radio Access Technology, RAT, to a target RAN of a target RAT different than the source RAT, wherein the target GW is associated with the target RAN and wherein either the source and target RANs are an Evolved UMTS RAN E-UTRAN and an High Rate Data Packet HRPD RAN, respectively, or the source and target RANs are an HRPD RAN and an E-UTRAN, respectively, said target gateway comprising:

a receiver (310) configured to:

receive one or more forwarded packets for the session from a source gateway associated with the source RAN;

receive a first empty Generic Routing Encapsulation, GRE, packet from the source gateway indicating the end of the forwarded packets for the session, said first empty GRE packet generated by the source gateway responsive to the source gateway receiving an end marker packet from a network gateway;

receive one or more direct packets for the session from the network gateway, said direct packets sequentially ordered relative to the forwarded packets; and

receive a second empty GRE packet from the network gateway indicating the start of the direct packets;

a transmitter (320) configured to send the forwarded packets to the mobile station via the target RAN;

a control unit (320) coupled to the transmitter (330) and comprising a packet router (322) configured to control the transmitter (330) to send the direct packets to the mobile station via the target RAN responsive to receipt of the first empty GRE packet; and

a timer (350), wherein said control unit (320) is further configured to start the timer (350) responsive to receipt of the second empty GRE packet, and wherein the packet router (322) is configured to control the transmitter (330) by controlling the transmitter (330) to send the direct packets to the mobile station responsive to expiration of the timer (350).


 
7. The target gateway (300) of claim 6 further comprising a timer (350), wherein said control unit (320) is further configured to start the timer (350) responsive to receipt of a first one of the direct packets at the receiver (310), and wherein the packet router (322) is configured to control the transmitter (330) by controlling the transmitter (330) to send the direct packets to the mobile station responsive to expiration of the timer (350).
 
8. The target gateway (300) of claim 6 wherein when the receiver (310) receives the first empty GRE packet before receiving the direct packets for the session, the packet router (322) is configured to control the transmitter (330) to send the direct packets to the mobile station upon receipt of the direct packets by the receiver (310).
 
9. The target gateway (300) of claim 6 further comprising a buffer (340) configured to buffer the direct packets received before receipt of the first empty GRE packet, wherein the packet router (322) is configured to control the transmitter (330) by controlling the transmitter (330) to send the buffered packets after receipt of the first empty GRE packet.
 
10. The target gateway (300) of claim 6 wherein the source gateway comprises one of a 3rd Generation Partnership Project, 3GPP, serving gateway and a High Rate Packet Data, HRPD, serving gateway, the target gateway comprises the other of the 3GPP serving gateway and the HRPD serving gateway, and the network gateway comprises a Packet Data Network, PDN, Gateway, PGW.
 


Ansprüche

1. Verfahren (380), das von einem Ziel-Gateway, GW, implementiert wird, zur Zustellung von Datenpaketen einer Sitzung an eine Mobilstation während eines Inter-RAT-Handovers der Mobilstation von einem Ursprungs-Funkzugangsnetzwerk, RAN, einer Ursprungs-Funkzugangstechnologie, RAT, zu einem Ziel-RAN einer von der Ursprungs-RAT verschiedenen Ziel-RAT, wobei das Ziel-GW mit dem Ziel-RAN assoziiert ist, und wobei die Ursprungs- und Ziel-RANs entweder ein E-UTRAN (Evolved UMTS) bzw. ein HRPD (High Rate Data Packet)-RAN sind oder die Ursprungs- und Ziel-RANs ein HRPD-RAN bzw. ein E-UTRAN sind, wobei das Verfahren umfasst:

Empfangen (382) eines oder mehrerer weitergeleiteter Pakete für die Sitzung von einem Ursprungs-Gateway, das mit dem Ursprungs-RAN assoziiert ist;

Empfangen (384) eines ersten leeren GRE (generische Routing-Verkapselung)-Pakets vom Ursprungs-Gateway, welches das Ende der weitergeleiteten Pakete für die Sitzung anzeigt, wobei das erste leere GRE-Paket durch das Ursprungs-Gateway in Reaktion darauf erzeugt wird, dass das Ursprungs-Gateway ein Ende-Markierungspaket von einem Netzwerk-Gateway empfängt;

Senden (388) der weitergeleiteten Pakete über das Ziel-RAN an die Mobilstation;

Empfangen eines oder mehrerer direkter Pakete für die Sitzung vom Netzwerk-Gateway, wobei die direkten Pakete in Bezug auf die weitergeleiteten Pakete sequenziell geordnet sind;

Senden der direkten Pakete in Reaktion auf den Empfang des ersten leeren GRE-Pakets über das Ziel-RAN an die Mobilstation;

Empfangen eines zweiten leeren GRE-Pakets vom Netzwerk-Gateway, das den Start der direkten Pakete für die Sitzung anzeigt;

Starten eines Zeitgebers in Reaktion auf den Empfang des zweiten leeren GRE-Pakets, wobei das Senden der direkten Pakete ein Senden der direkten Pakete in Reaktion auf den Ablauf des Zeitgebers an die Mobilstation umfasst.


 
2. Verfahren nach Anspruch 1, ferner umfassend ein Starten eines Zeitgebers in Reaktion auf den Empfang eines ersten der direkten Pakete, wobei das Senden der direkten Pakete ein Senden der direkten Pakete in Reaktion auf den Ablauf des Zeitgebers an die Mobilstation umfasst.
 
3. Verfahren nach Anspruch 1, wobei das Empfangen (384) des ersten leeren GRE-Pakets ein Empfangen des ersten leeren GRE-Pakets vor dem Empfangen der direkten Pakete für die Sitzung umfasst, und wobei das Senden der direkten Pakete in Reaktion auf den Empfang des ersten leeren GRE-Pakets an die Mobilstation ein Senden der direkten Pakete bei Empfang der direkten Pakete am Ziel-Gateway an die Mobilstation umfasst.
 
4. Verfahren nach Anspruch 1, ferner umfassend ein Puffern der direkten Pakete im Ziel-Gateway, die vom Netzwerk-Gateway vor dem Empfang des ersten leeren GRE-Pakets empfangen werden, wobei das Senden der direkten Pakete ein Senden der gepufferten Pakete nach dem Empfang des ersten leeren GRE-Pakets umfasst.
 
5. Verfahren nach Anspruch 1, wobei das Ursprungs-Gateway ein versorgendes 3GPP (Partnerschaftsprojekt der 3. Generation)-Gateway oder ein versorgendes HRPD (High Rate Packet Data)-Gateway umfasst, wobei das Ziel-Gateway das andere des versorgenden 3GPP-Gateways oder des versorgenden HRPD-Gateways umfasst, und das Netzwerk-Gateway ein Paketdatennetzwerk, PDN,-Gateway, PGW, umfasst.
 
6. Ziel-Gateway, GW, (300) zum Zustellen von Datenpaketen einer Sitzung an eine Mobilstation während eines Inter-RAT-Handovers der Mobilstation von einem Ursprungs-Funkzugangsnetzwerk, RAN, einer Ursprungs-Funkzugangstechnologie, RAT, zu einem Ziel-RAN einer von der Ursprungs-RAT verschiedenen Ziel-RAT, wobei das Ziel-GW mit dem Ziel-RAN assoziiert ist, und wobei die Ursprungs- und Ziel-RANs entweder ein E-UTRAN (Evolved UMTS) bzw. ein HRPD (High Rate Data Packet)-RAN sind oder die Ursprungs- und Ziel-RANs ein HRPD-RAN bzw. ein E-UTRAN sind, wobei das Ziel-Gateway umfasst:

einen Empfänger (310), der konfiguriert ist zum:

Empfangen eines oder mehrerer weitergeleiteter Pakete für die Sitzung von einem Ursprungs-Gateway, das mit dem Ursprungs-RAN assoziiert ist;

Empfangen eines ersten leeren GRE (generische Routing-Verkapselung)-Pakets vom Ursprungs-Gateway, welches das Ende der weitergeleiteten Pakete für die Sitzung anzeigt, wobei das erste leere GRE-Paket durch das Ursprungs-Gateway in Reaktion darauf erzeugt wird, dass das Ursprungs-Gateway ein Ende-Markierungspaket von einem Netzwerk-Gateway empfängt;

Empfangen eines oder mehrerer direkter Pakete für die Sitzung vom Netzwerk-Gateway, wobei die direkten Pakete in Bezug auf die weitergeleiteten Pakete sequenziell geordnet sind; und

Empfangen eines zweiten leeren GRE-Pakets vom Netzwerk-Gateway, das den Start der direkten Pakete anzeigt;

einen Sender (320), der zum Senden der weitergeleiteten Pakete über das Ziel-RAN an die Mobilstation konfiguriert ist;

eine Steuereinheit (320), die mit dem Sender (330) gekoppelt ist und einen Paket-Router (322) umfasst, der so konfiguriert ist, dass er den Sender (330) zum Senden der direkten Pakete in Reaktion auf den Empfang des ersten leeren GRE-Pakets über das Ziel-RAN an die Mobilstation steuert; und

einen Zeitgeber (350), wobei die Steuereinheit (320) ferner so konfiguriert ist, dass sie den Zeitgeber (350) in Reaktion auf den Empfang des zweiten leeren GRE-Pakets startet, und wobei der Paket-Router (322) so konfiguriert ist, dass er den Sender (330) steuert, indem er den Sender (330) zum Senden der direkten Pakete in Reaktion auf den Ablauf des Zeitgebers (350) an die Mobilstation steuert.


 
7. Ziel-Gateway (300) nach Anspruch 6, ferner umfassend einen Zeitgeber (350), wobei die Steuereinheit (320) ferner so konfiguriert ist, dass sie den Zeitgeber (350) in Reaktion auf den Empfang eines ersten der direkten Pakete am Empfänger (310) startet, und wobei der Paket-Router (322) so konfiguriert ist, dass er den Sender (330) steuert, indem er den Sender (330) zum Senden der direkten Pakete in Reaktion auf den Ablauf des Zeitgebers (350) an die Mobilstation steuert.
 
8. Ziel-Gateway (300) nach Anspruch 6, wobei der Paket-Router so konfiguriert ist, dass er, wenn der Empfänger (310) das erste leere GRE-Paket vor dem Empfangen der direkten Pakete für die Sitzung empfängt, den Sender (330) zum Senden der direkten Pakete bei Empfang der direkten Pakete durch den Empfänger (310) an die Mobilstation steuert.
 
9. Ziel-Gateway (300) nach Anspruch 6, ferner umfassend einen Puffer (340), der so konfiguriert ist, dass er die vor dem Empfang des ersten leeren GRE-Pakets empfangenen direkten Pakete puffert, wobei der Paket-Router (322) so konfiguriert ist, dass er den Sender (330) steuert, indem er den Sender (330) zum Senden der gepufferten Pakete nach Empfang des ersten leeren GRE-Pakets steuert.
 
10. Ziel-Gateway (300) nach Anspruch 6, wobei das Ursprungs-Gateway ein versorgendes 3GPP (Partnerschaftsprojekt der 3. Generation)-Gateway oder ein versorgendes HRPD (High Rate Packet Data)-Gateway umfasst, wobei das Ziel-Gateway das andere des versorgenden 3GPP-Gateways oder des versorgenden HRPD-Gateways umfasst, und das Netzwerk-Gateway ein Paketdatennetzwerk, PDN,-Gateway, PGW, umfasst.
 


Revendications

1. Procédé (380) mis en oeuvre par une passerelle, GW, cible pour délivrer des paquets de données d'une session à une station mobile au cours d'un transfert intercellulaire inter-RAT de ladite station mobile d'un réseau d'accès radio, RAN, source d'une technologie d'accès radio, RAT, source à un RAN cible d'une RAT cible différente de la RAT source, dans lequel la GW cible est associée au RAN cible et dans lequel les RAN source et cible sont respectivement un RAN UMTS évolué, E-UTRAN, et un RAN de paquets de données à haut débit, HRPD, ou les RAN source et cible sont respectivement un RAN HRPD et un E-UTRAN, le procédé comprenant :

la réception (382) d'un ou plusieurs paquets transférés pour la session en provenance d'une passerelle source associée au RAN source ;

la réception (384) d'un premier paquet d'encapsulation d'acheminement générique, GRE, vide en provenance de la passerelle source indiquant la fin des paquets transférés pour la session, ledit premier paquet GRE vide étant généré par la passerelle source en réponse à la réception, par la passerelle source, d'un paquet de marqueur de fin en provenance d'une passerelle de réseau ;

l'envoi (388) des paquets transférés à la station mobile par l'intermédiaire du RAN cible ;

la réception d'un ou plusieurs paquets directs pour la session en provenance de la passerelle de réseau, lesdits paquets directs étant ordonnés en séquence par rapport aux paquets transférés ;

l'envoi des paquets directs à la station mobile par l'intermédiaire du RAN cible en réponse à la réception du premier paquet GRE vide ;

la réception d'un deuxième paquet GRE vide en provenance de la passerelle de réseau indiquant le début des paquets directs pour la session ; et

le démarrage d'une minuterie en réponse à la réception du deuxième paquet GRE vide, dans lequel l'envoi des paquets directs comprend l'envoi des paquets directs à la station mobile en réponse à l'expiration de la minuterie.


 
2. Procédé selon la revendication 1, comprenant en outre le démarrage d'une minuterie en réponse à la réception d'un premier paquet direct parmi les paquets directs, dans lequel l'envoi des paquets directs comprend l'envoi des paquets directs à la station mobile en réponse à l'expiration de la minuterie.
 
3. Procédé selon la revendication 1, dans lequel la réception (384) du premier paquet GRE vide comprend la réception du premier paquet GRE vide avant la réception des paquets directs pour la session, et dans lequel l'envoi des paquets directs à la station mobile en réponse à la réception du premier paquet GRE vide comprend l'envoi des paquets directs à la station mobile à la réception des paquets directs à la passerelle cible.
 
4. Procédé selon la revendication 1, comprenant en outre la mise en mémoire tampon, dans la passerelle cible, des paquets directs reçus en provenance de la passerelle de réseau avant la réception du premier paquet GRE vide, dans lequel l'envoi des paquets directs comprend l'envoi des paquets mis en mémoire tampon après la réception du premier paquet GRE vide.
 
5. Procédé selon la revendication 1, dans lequel la passerelle source comprend l'une d'une passerelle de desserte de projet de partenariat de troisième génération, 3GPP, et d'une passerelle de desserte de données en paquets à haut débit, HRPD, la passerelle cible comprend l'autre de la passerelle de desserte 3GPP et de la passerelle de desserte HRPD, et la passerelle de réseau comprend une passerelle de réseau de données en paquets, PDN, PGW.
 
6. Passerelle cible, GW, (300) pour délivrer des paquets de données d'une session à une station mobile au cours d'un transfert intercellulaire inter-RAT de ladite station mobile d'un réseau d'accès radio, RAN, source d'une technologie d'accès radio, RAT, source à un RAN cible d'une RAT cible différente de la RAT source, dans laquelle la GW cible est associée au RAN cible et dans laquelle les RAN source et cible sont respectivement un RAN UMTS évolué, E-UTRAN, et un RAN de paquets de données à haut débit, HRPD, ou les RAN source et cible sont respectivement un RAN HRPD et un E-UTRAN, ladite passerelle cible comprenant :

un récepteur (310) configuré pour effectuer :

la réception d'un ou plusieurs paquets transférés pour la session en provenance d'une passerelle source associée au RAN source ;

la réception d'un premier paquet d'encapsulation d'acheminement générique, GRE, vide en provenance de la passerelle source indiquant la fin des paquets transférés pour la session, ledit premier paquet GRE vide étant généré par la passerelle source en réponse à la réception, par la passerelle source, d'un paquet de marqueur de fin en provenance d'une passerelle de réseau ;

la réception d'un ou plusieurs paquets directs pour la session en provenance de la passerelle de réseau, lesdits paquets directs étant ordonnés en séquence par rapport aux paquets transférés ; et

la réception d'un deuxième paquet GRE vide en provenance de la passerelle de réseau indiquant le début des paquets directs ;

un émetteur (320) configuré pour effectuer l'envoi des paquets transférés à la station mobile par l'intermédiaire du RAN cible ;

une unité de commande (320) couplée à l'émetteur (330) et comprenant un routeur de paquets (322) configuré pour commander à l'émetteur (330) d'effectuer l'envoi des paquets directs à la station mobile par l'intermédiaire du RAN cible en réponse à la réception du premier paquet GRE vide ; et

une minuterie (350), dans laquelle ladite unité de commande (320) est en outre configurée pour effectuer le démarrage de la minuterie (350) en réponse à la réception du deuxième paquet GRE vide, et dans laquelle le routeur de paquets (322) est configuré pour commander l'émetteur (330) en commandant à l'émetteur (330) d'effectuer l'envoi des paquets directs à la station mobile en réponse à l'expiration de la minuterie (350).


 
7. Passerelle cible (300) selon la revendication 6, comprenant en outre une minuterie (350), dans laquelle ladite unité de commande (320) est en outre configurée pour effectuer le démarrage de la minuterie (350) en réponse à la réception d'un premier paquet direct parmi les paquets directs au récepteur (310), et dans laquelle le routeur de paquets (322) est configuré pour commander l'émetteur (330) en commandant à l'émetteur (330) d'effectuer l'envoi des paquets directs à la station mobile en réponse à l'expiration de la minuterie (350).
 
8. Passerelle cible (300) selon la revendication 6, dans laquelle, lorsque le récepteur (310) effectue la réception du premier paquet GRE vide avant la réception des paquets directs pour la session, le routeur de paquets (322) est configuré pour commander à l'émetteur (330) d'effectuer l'envoi des paquets directs à la station mobile à la réception des paquets directs par le récepteur (310).
 
9. Passerelle cible (300) selon la revendication 6, comprenant en outre une mémoire tampon (340) configurée pour effectuer la mise en mémoire tampon des paquets directs reçus avant la réception du premier paquet GRE vide, dans laquelle le routeur de paquets (322) est configuré pour commander l'émetteur (330) en commandant à l'émetteur (330) d'effectuer l'envoi des paquets mis en mémoire tampon après la réception du premier paquet GRE vide.
 
10. Passerelle cible (300) selon la revendication 6, dans laquelle la passerelle source comprend l'une d'une passerelle de desserte de projet de partenariat de troisième génération, 3GPP, et d'une passerelle de desserte de données en paquets à haut débit, HRPD, la passerelle cible comprend l'autre de la passerelle de desserte 3GPP et de la passerelle de desserte HRPD, et la passerelle de réseau comprend une passerelle de réseau de données en paquets, PDN, PGW.
 




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Cited references

REFERENCES CITED IN THE DESCRIPTION



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Patent documents cited in the description