Abstract:
Supporting an optimized idle mode handoff of user equipment from a 3GPP to a non-3GPP system. Namely, during an idle mode registration of the user equipment with the non-3GPP system, the user equipment may provide an indication to the access node on the non-3GPP system so that the access point in that non-3GPP system contacts the appropriate entity (HSS or AAA) on the home network for the user equipment to download the addresses of the multiple PDN gateway addresses that are currently in use by the user equipment. This indication to the non-3GPP access node, the contact message from the access node to the home network, and the response from the home network to the access node on the non-3GPP system provide the access node with sufficient information to maintain multiple PDN connectivity to the user equipment during an idle mode handover.

Description:
RELATED APPLICATION DATA 
     This application is a continuation of U.S. patent application Ser. No. 12/934,452, filed Sep. 24, 2010 which is a Submission Under 35 U.S.C. §371 for U.S. National Stage Patent Application PCT/IB2009/005654, filed Mar. 25, 2009, which claims priority to Provisional Patent Application Serial No.61/039,252 filed on Mar. 25, 2008, all of which are incorporated by reference in their entirety as if fully and completely set forth herein. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     A method and system for maintaining multiple PDN network connections during inter-technology wireless handover in idle mode. 
     BACKGROUND OF THE INVENTION 
     When a mobile unit is traveling, it may need to be handed off from one network to another. There are different types of wireless communication systems, such as general packet radio service (GPRS), global system for mobile (GSM)/enhanced data rates for GSM evolution (EDGE) radio access network (GERAN), and long term evolution (LTE) evolved universal terrestrial radio access network (EUTRAN). LTE/EUTRAN system has a different physical layer and a different architecture from those systems preceding it, i.e., GPRS, GERAN, or UTRAN. Since not all networks are identical, a method for supporting the handoff between systems would be beneficial. 
     United States Patent Publication Nos. US 2008/0268846A1 and 2008/0192697A1 describe a prior art method and system for supporting a handoff of user equipment from a GPRS/GERAN system to an LTE EUTRAN system, and vice versa, respectively. These references include a  FIG. 1  exemplary diagram of a system including an LTE system architecture shown by an LTE/EUTRAN and its evolved packet core interworking with an existing GERAN, UTRAN, and their GPRS Core. The LTE/EUTRAN comprises an E-Node B that is connected (S 1 ) to an evolved packet core containing a mobility management entity/user plane entity (MME/UPE) and an inter AS anchor Gateway. The Evolved Packet Core connects (S 6 ) to a home subscriber service (HSS), and connects (S 7 ) to a Policy and Charging Rules (PCRF). The inter AS Anchor gateway connects (Gi) to Operator IP Servers (such as IMS, PSS), connects (S 2 ) to a Non-3GPP IP Access network  108 , and connects (S 2 ) to a WLAN 3GPP IP Access network  109 . 
     The GPRS Core shown in  FIG. 1  of these prior art references comprises a Serving GPRS Support Node (SGSN) which is responsible for Mobility Management, Access Procedures, and User Plane Control. The GPRS Core also comprises a Gateway GPRS Support Node (GGSN), where the network is connected to external networks and other operator servers. The Non-3GPP IP access network  108  includes connections to other technologies that are developed in other standard Forums such as 3GPP2 (CDMA2000) and WiMAX (IEEE 802.16 system). The WLAN 3GPP IP access network has WLANs incorporated into 3GPP systems via interworking architecture defined in 3GPP. These identified patent references, however, do not address the optimized handover procedures and system for an idle mode handover of user equipment from a 3GPP (EUTRAN) to a non-3GPP (HRPD cdma2000) system where the user equipment wishes to maintain connectivity with multiple PDN networks. 
     The Technical Specification 3GPP TS 23.402 V8.1.1 (2008-03) describes a 3rd Generation Partnership Project (3GPP) Technical Specification for enhancements and interactions with non-3GPP accesses. The particular version of the Technical Specification is Release 8, which describes the general network resources, entities, functions, and handover procedures for certain inter-technology combination handover systems, protocols, and procedures. Like the above-identified references, this Technical Specification also fails to address the optimized handover procedures and system for an idle mode handoff of user equipment from a 3GPP (EUTRAN) to a non-3GPP system (HRPD cdma 2000) where the user equipment wishes to maintain connectivity with multiple PDN networks. It would be beneficial to have a method and system that could support such an idle mode handover while maintaining the user equipment&#39;s connectivity to multiple PDN networks. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and system for supporting an optimized idle mode handoff of user equipment from a 3GPP (EUTRAN) to a non-3GPP system (HRPD, cdma2000) where the user equipment wishes to maintain connectivity with multiple PDN networks. Namely, when the user equipment establishes its presence with the non-3GPP system in idle mode, the user equipment will provide an indication to the access node on the non-3GPP system so that the access node in that non-3GPP system contacts the appropriate entity (HSS or AAA) on the home network for the user equipment to download the addresses of the multiple PDN gateway that are currently in use by the user equipment. This indication to the non-3GPP access node, the contact message from the access node to the home network, and the response from the home network to the access node on the non-3GPP system are novel features that are not shown in the prior art, and provide the access node with sufficient information to maintain multiple PDN connectivity to the user equipment during an idle mode handover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings in which like numerals represent like elements and in which: 
         FIG. 1  is a mobile IP-based communication system showing the user equipment, the 3GPP based network, the non-3GPP network and the multiple PDN connections to the user equipment, and, 
         FIG. 2  is a handover protocol of the user equipment to the non-3GPP system with the disclosure of the indication message, the access node request message to the home network, and the response to the access node. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , the present invention proposes a solution to the idle mode handover of user equipment from a 3GPP network to a non-3GPP network that includes providing the access node on the non-3GPP network with the addresses for the multiple PDN gateway connections currently being used by the user equipment, which are shown as PDN Gateway 1  110  and PDN Gateway 2  115 . The handover occurs in  FIG. 1  from the E-UTRAN network  102  to the HRPD network  120  in the present invention so that multiple PDN network connectivity can be maintained with the user equipment  101  during the idle mode handover. In this example, the E-UTRAN network  102  is a 3GPP network called the source network, and the HRPD network  120  is a non-3GPP network called the target network. 
     In the prior art, the HSS on the home network (not shown in  FIG. 1 ) receives the values of the addresses of all allocated PDN Gateways ( 110  and  115 ) and the corresponding PDN information for a given user equipment  101  assigned to the HSS&#39;s home network from both the 3GPP AAA (not shown) and also from the MME  135 , depending on the currently in-use access. The HSS on the home network is responsible for the storage of PDN Gateway address information. In an active mode handover in the prior art, if user equipment is attached to a non-3GPP access and it already has assigned PDN Gateways ( 110  and  115 ) due to a previous attach in a 3GPP access, the HSS on the home network provides the IP address(es) of the already allocated PDN Gateway(s) ( 110  and  115 ) with the corresponding PDN information to the 3GPP AAA server over the SWx reference point. The PDN gateway&#39;s address(es) is sent during the attach procedure in the non-3GPP access. Also in active mode, if user equipment  101  attaches to a 3GPP access and it already has an assigned PDN Gateway(s)  110  and  115  due to a previous attach in a non-3GPP access, the HSS provides the IP address(es) of the already allocated PDN Gateway(s) ( 110  and  115 ) with the corresponding PDN information to the MME over the S 6   a  reference point, and the PDN gateway address(es) is sent during the attach procedure in the 3GPP access. 
     No prior art procedures support the handover of user equipment in a non-active, idle mode so that connectivity can be maintained with multiple PDN connections, and no prior art procedures allow for the direct interaction between the access node of the non-3GPP network and the HSS entity/AAA server on the home entity to acquire the multiple PDN gateway addresses. By “idle mode,” the applicant means that the system is not operating in an active or connected mobility mode procedure, and the “idle mode” can be characterized by an idle mobility procedure or a radio link failure scenario. The present invention supports such an “idle mode” transfer of user equipment with multiple PDN gateway connections. 
     Referring to  FIG. 1 , the network  100  shows the various network components involved with the idle mode inter-technology handover with connectivity to multiple PDN networks. The user equipment  101  is coupled to the E-UTRAN network (3GPP)  102  through connection  103 . When referred to hereafter, the terminology user equipment (UE) includes, but is not limited to, a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. 
     The E-UTRAN network  102  is coupled through SI-U connection  112  to the Serving Gateway  105 , which is coupled to PDN Gateway 1  110  and PDN Gateway 2  115  through connections S 5   116  and  117 , respectively. The PDN Gateway 1  110  and PDN Gateway 2  115  couple the multiple PDN networks  150  and  151 , which are coupled by connections  143  and  144 , respectively. SGi1  142  and SGi2  141  interfaces are coupled to PDN sources of data located on the Internet  150  through connections  151  and  152 , respectively. Maintaining these multiple PDN connections during an idle handover of the user equipment  101  from the E-UTRAN  102  system to a non-3GPP system, such as the HRPD system  120  shown in  FIG. 1  is the primary focus of the present invention. 
     The E-UTRAN network  102  is coupled through S 1 -MME connection  137  to the Mobility Management Entity (MME)  135 , which has an internal S 10  connection  113 . The MME  135  is coupled to the Serving Gateway  105  through connection S 11   111 , and the MME  135  is couple to the HRPD Access Node  130  on the HRPD system  120  through S 101  connection  132 . The HRPD Access Node  130  is coupled to the Packet Data Switching Node (PDSN)  125  through the Interoperability Specification (IOS) connection  127 . The PDSN  125  is sometimes called the HRPD Serving Gateway (HSGW), which is coupled to the PDN Gateway  1   110  and PDN Gateway  2   115  through the S 2   a  connections  122  and  121 , respectively. 
     The HRPD Access Node  130  will be provided with a connection request in idle mode from the user equipment  101 , and the connection request will include an indication from the user equipment  101  that multiple PDN connections are in use by the user equipment  101 . This indication will prompt the HRPD Access Node  130  to send a request to the home subscriber storage (HSS) entity and/or Authentication, Authorization and Accounting (AAA) server located on the home network (not shown in  FIG. 1 ) assigned to the user equipment  101  to request the addresses of all PDN gateways ( 110  and  115 ) currently in use by the user equipment. The HSS entity and/or AAA server on the home network will respond to the request with the addresses of all PDN gateways currently in use by the user equipment  101  so the multiple PDN connectivity with the user equipment  101  can be maintained during the idle mode handover. 
     In  FIG. 2 , the handover communication protocol is shown starting at step  310  when the user equipment is designated as being in idle mode. The user equipment makes a decision to “re-select” its cell location in step  315  to the non-3GPP network, and the user equipment  101  sends a HRPD Connection Request message in step  320  to the HRPD Access Node  130 . This HRPD Connection Request message in step  320  would include an indication that the user equipment  101  is currently using multiple PDN connections. 
     In response to this indication, the HRPD Access Node  130  will send a request message  322  to the AAA server/HSS entity  175  located on the home network assigned to the user equipment in step  322 . In step  322 , the AAA server/HSS entity  175  will respond to that request with the addresses for the multiple PDN gateways and any other relevant information regarding the PDN connections currently in use by the user equipment  101 , such as IP addresses of the already allocated PDN Gateway(s) ( 110  and  115 ) and corresponding PDN information. 
     The HRPD Access Node will transmit an A11 registration request message to the PDSN  125  on the non-3GPP network in step  325 , which will include the address information for the multiple PDN gateways  110  and  115  currently in use by the user equipment. The PDSN  125  will use the address information to send a PMIP message to the PDN gateways  110  and  115  in step  330 , which will be acknowledged by response messages to the PDSN  125  from the PDN gateways  110  and  115  in step  335 . The PDN gateways  110  and  115  will send messages to the PCRF entities in step  340 , and receive a response from the PCRF entities in step  345 . 
     After receiving the response from the PDN gateways  110  and  115  in step  335 , the PDSN on the non-3GPP network will send an A11 registration reply to the HRPD Access Node  130  in step  350 . The HRPD Access Node will send the user equipment  101  an HRPD Traffic Channel Assignment in step  360  to establish the connection with the user equipment  101 . The user equipment  101  will then send an HRPD TCC (traffic channel complete) message to the HRPD Access Node  130  in step  370 . The user equipment  101  may also send an HRPD Connection Release message to the HRPD Access Node  130  in step  380 . After these connections are established, any future user equipment  101  communication traffic may flow in both the uplink and downlink directions via the non-3GPP network, including traffic through the multiple PDN connections which have been maintained after the handover to the non-3GPP network. 
     While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention.