Abstract:
A system and method for mobility support of a mobile node having a home network in a heterogeneous roaming environment is presented. The method comprises the steps of authenticating the mobile node in a visited network and obtaining an address for the mobile node in the visited network, establishing a security connection between a functional component in the visited network and an agent in the home network, creating a home address for the mobile node, and using the home address to generate a SIP signaling address, a SIP media address, and a non-SIP media address, such that SIP non-media is transmitted using the security connection to the SIP signaling address, SIP media is transmitted using the security connection to the SIP media address, and non-SIP media is transmitted using the security connection to the non-SIP media address.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present invention claims the benefit of U.S. provisional patent application 60/876,765 filed Dec. 22, 2006, and of U.S. provisional patent application 60/930,412 filed May 16, 2007, the entire contents and disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to next generation wireless networks, and more specifically to a framework for heterogeneous roaming of mobile nodes in such networks. 
       BACKGROUND OF THE INVENTION 
       [0003]    Ubiquitous roaming support for real-time traffic, such as interactive VoIP, streaming, and the non-real-time data transfer of FTP and e-mail in an access independent manner, is becoming increasingly important. For example, the evolution of the mobility protocols of Mobile IPv4 (MIPv4) and Mobile IPv6 (MIPv6) has made it easier to support ubiquitous roaming. Carriers in the wireless Internet have different mobility capabilities, and mobile clients may also have a variety of mobility capabilities. For example, some operators or carriers may support mobile assisted mobility protocol, such as MIPv6 and Client Mobile IPv6 (CMIPv6), while others may support network assisted mobile protocol, such as Proxy Mobile IPv6 (PMIPv6). In some cases, often the mobile assisted mobility protocols, a mobile node or mobile client may be equipped with a mobility stack, and the mobile node may use an application layer mobility protocol in certain situations. 
         [0004]    In a typical roaming environment, two domains can belong to two separate carriers with different mobility support and security and authentication procedures. Accordingly, a mobile node in the Next Generation Wireless Networks may be subjected to roaming that may involve different kinds of movement scenarios. These movement types can be confined to home domain or visited domain. When the mobile node is away from home and is in the visited domain, the mobile node is defined to be in roaming mode. When in the roaming mode, the mobile node can move between two sub-networks that may belong to the same carrier domain, or it can move from one carrier domain to another carrier domain. Any mobile node in roaming scenario may be subjected to several degrees of heterogeneity, such as types of mobility being supported in the network elements and in the mobile node&#39;s stack, the type of application supported in the mobile node and type of movement both in the local domain or in the visited domain that might involve changing bearer manager. Also, while in the visited domain, avoiding exposure of a subscriber&#39;s permanent IP address in the visited carrier networks is important to maintain security. 
         [0005]    Several existing standards bodies are attempting to define the core network architecture for next generation wireless networks. Third Generation Partnership Project (3GPP) defined an IP Multimedia Subsystem (IMS) architecture, and 3GPP2 defined the Multimedia Domain (MMD) architecture. Recently, Advances to IMS (A-IMS) architecture, which enhances existing IMS and MMD networks, has been proposed to support a variety of services such as Session Initiation Protocol (SIP)-based and non-SIP-based applications. SIP-based applications are typically set up by SIP and provide services such as VoIP. On the other hand, non-SIP-based applications provide services such as IPTV and FTP without using SIP. Similarly, International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is working on defining the Next Generation Network (NGN) under the premises of a Global Standards Initiative, i.e. NGN-GSI. All these architectures include heterogeneous access networks, such as CDMA, WiMAX, and 802.11 technologies, and include support for roaming. 
         [0006]    At present, however, the inventors know of no flexible framework that can support seamless mobility between networks with different mobility support. 
         [0007]    The following abbreviations are used throughout.
   3GPP: Third Generation Partnership Project   AAA: Authentication, Authorization and Accounting   AGW: Access GateWays   AN: Access Network   AS: Application Servers   CDMA: Code Division Multiple Access   CMIPv6: Client Mobile IPv6   CN: Correspondent Node   DAD: Duplicate Address Detection   DHCP: Dynamic Host Configuration Protocol   FTP: File Transfer Protocol   GGSN: Gateway GPRS Support Node   GSM: Global System for Mobile communications   HA: Home Agent   hHoA: Home Address of node in home domain   I-CSCF: Interrogating Call Session Control Function   IETF: Internet Engineering Task Force   IMS: IP Multimedia Subsystem   IMS/MMD—combination of IMS and MMD   IPTV: Internet Protocol TeleVision   ITU-T: International Telecommunication Union Telecommunication Standardization Sector   LCP: Link Control Protocol   LMA: Local Mobility Anchor   LTE: Long Term Evolution   MAG: Mobile Access Gateway   MIPv4: Mobile IPv4   MIPv6: Mobile IPv6   MMD: Multimedia Domain   MN: Mobile Node   NAI: Network Access Identifier   NGN: Next Generation Network   NGN-GSI: Next Generation Network-Global Standards Initiative   PCF: Packet Control Function   P-CSCF—Proxy Call Session Control Function   PDSN—Packet Data Serving Node   PMA: Proxy Mobile Agents   PMIPv6: Proxy Mobile IPv6   PPP: Point to Point Protocol   SAE: System Architecture Evolution   S-CSCF—Serving Call Session Control Function   SDP: Session Description Protocol   SIP: Session Initiation Protocol   URI: Universal Resource Identifier   vHoA: Home Address of node in visited domain   VoIP: Voice over IP   WiMAX: IEEE 802.16 wireless specification   
 
       BRIEF SUMMARY OF THE INVENTION 
       [0054]    The present invention advantageously provides a solution to the problems of mobility management, that is, roaming and service continuity, in next generation wireless networks. This invention benefits different types of roaming, such as home local, visited local, global mobility and combinations thereof, as well as Simple IP, CMIPv6 and PMIPv6 mobility operation, and also addresses heterogeneity of application, e.g., SIP, non-SIP based, being supported on a mobile node. A combination of application layer, network layer and local mobility protocol can be used based on the mobile&#39;s movement pattern, the mobile&#39;s and the network&#39;s mobility capability, and the type of application being supported. The solution provides a framework useful for supporting inter-carrier roaming involving global and local mobility between domains and within domains. 
         [0055]    In one embodiment, a system and method for mobility support of a mobile node having a home network in a heterogeneous roaming environment, includes a method comprising the steps of authenticating the mobile node in a visited network and obtaining an address for the mobile node in the visited network, establishing a security connection between a functional component in the visited network and an agent in the home network, creating a home address for the mobile node, and using the home address to generate an SIP signaling address, an SIP media address, and a non-SIP media address, such that SIP non-media is transmitted using the security connection to the SIP signaling address, SIP media is transmitted using the security connection to the SIP media address, and non-SIP media is transmitted using the security connection to the non-SIP media address. 
         [0056]    In another embodiment, the method comprises the steps of authenticating the mobile node in a visited network and obtaining an address for the mobile node in the visited network, establishing more than one security connection between a functional component in the visited network and an agent in the home network, creating a home address for the mobile node, and using the home address to generate a SIP signaling address for SIP, a SIP media address for SIP media, and a non-SIP media address for non-SIP media, such that SIP signaling is transmitted using one of the security connections to the SIP media address, SIP media is transmitted using another of the security connections to the SIP media address, and non-SIP media is transmitted using yet another of the security connections to the non-SIP media address. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0057]    The invention is further described in the detailed description that follows, by reference to the noted drawings by way of non-limiting illustrative embodiments of the invention, in which like reference numerals represent similar parts throughout the drawings. As should be understood, however, the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
           [0058]      FIG. 1  illustrates generic network architecture for next generation wireless networks; 
           [0059]      FIG. 2  illustrates network elements associated with PMIPv6; 
           [0060]      FIG. 3  illustrates roaming in one embodiment of the invention; 
           [0061]      FIG. 4  illustrates a flow of home local mobility; and 
           [0062]      FIG. 5  illustrates a flow of mobility with home and visited domains. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0063]    An inventive solution to the problem of mobility management in next generation wireless networks is presented. This solution is a framework for supporting inter-carrier roaming involving global and local mobility between domains and within domains. When a mobile node changes its network point of attachment, traffic is disrupted due to the handover process, which can be mobile-node-controlled or network-controlled. Depending on the type of movement, mobility can be handled at the link layer, the network layer, or the application layer. Link layer mobility is access specific, so that it cannot solve the problem of heterogeneity and therefore is not discussed. 
         [0064]    In network layer mobility, mobility involves heterogeneous access technologies, and can be controlled either by the mobile node or the network. In a mobile-controlled scenario of network layer mobility, the mobile node is usually equipped with a mobility stack and interacts with a remote entity such as a Home Agent (HA). An example of mobile-node-controlled mobility is CMIPv6. In the network layer mobility, when the mobility protocol is network-controlled, other networking elements in the middle of the network interact with the remote entity, typically an HA, and perform handoff related functions. 
         [0065]      FIG. 1  illustrates the functional components of generic network architecture for next generation wireless networks for providing ubiquitous services that need mobility support along with quality of service, security and charging. This generic network comprises a home network  10  and a visited network  12 , which can also be considered another home network. In addition, it includes IP core entities of MN or mobile node  14 , access gateways (AGW)  16 , home agents (HA)  18 , and authentication, authorization and accounting (AAA)  20 . It also has IMS/MMD entities of Proxy Call Session Control Function (P-CSCF)  22 , Interrogating Call Session Control Function (I-CSCF)  24 , Serving Call Session Control Function (S-CSCF)  26 , home subscriber service (HSS)  28 , application server (AS)  30  and policy and charging rules function (PCRF)  32 . Details of these functions components are as follows. 
         [0066]    Home agent or entity HA  18  provides media packet transfer in the home domain or network  10  as Home Agent (hHA), and in the visited domain or network  12  as Visited Home Agent (vHA). The HAs  18  map the home addresses with the temporary care-of-addresses, and route the media and signaling messages to the mobile node  14 . 
         [0067]    SIP servers or entities, such as S-CSCF  26  and P-CSCF  22 , take care of routing SIP signaling messages from and to the mobile node  14 . S-CSCF  26  is always located in the home network  10  and assists with user or MN  14  registration regardless of the user location. In MMD network, either the P-CSCF  22  located in the home network  10  or the P-CSCF  22  in the visited network  12  can be used for registration. Dynamic Host Configuration Protocol (DHCP) servers (not shown) in each network help assign the P-CSCF  22  address to the mobile node  14 . 
         [0068]    AAA  20  servers in both the home network  10  and visited network  12  are used for user profile verification. However, each of the visited networks  12  and the home network  10  can have different mobility capabilities and requirements depending on the verification policy defined by the individual network operators. 
         [0069]    In addition, there are both SIP-based and non-SIP-based ASs  30  that are responsible for providing advanced multimedia services beyond voice over internet protocol (VoIP). PCRF  32  controls the media based on the policy in each home and/or visited network  10 ,  12 , and helps to provide feature interaction between SIP-based and non-SIP-based services. Depending on the type of access network, e.g., CDMA, 802.11, etc., the architecture can have AGWs  16  that may act as Gateway GPRS Support Node (GGSN), Packet Data Serving Node (PDSN) or Packet Data Interworking Function (PDIF). 
         [0070]    Home local mobility is a scenario in which the mobile node  14  moves between two different access routers within a home domain  10 . A similar type of movement in the visited domain  12  is called visited local mobility. Correspondingly, there can be several types of global mobility. The first form of global mobility occurs when the mobile node  14  moves from its home network  10  to the visited domain  12  of a new carrier network. The second form of global mobility involves the mobile node  14  moving from one visited domain  12  to another visited domain  12  within the same carrier network. The third form of global mobility happens when the mobile node  14  moves from one carrier network to another carrier network while away from the home domain  10 . 
         [0071]    Table 1 shows the possible combination of movement patterns that involve different types of mobility support in the home domain  10  and in the visited domain  12 . The mobile node&#39;s stack can have either Simple IP or CMIPv6, and can move from the home domain  10  to the visited domain  12 , where the home domain  10  and the visited domain  12  may offer different mobility support. The grey areas are situations that are unlikely to happen. 
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         [0072]    In order to reduce the load on the mobile node  14  and handle local mobility, the Internet Engineering Task Force (IETF) has been developing network-based localized mobility management protocols. These protocols are designed to take care of local mobility and are controlled by the network elements in the access routers. One such protocol is PMIPv6, which does not use any mobility stack on the mobile node  14  but rather uses functions or proxies on the access routers to help perform the mobility functions, such as the binding update to the HA  18 . These functions or functional components are called Mobile Access Gateway (MAG) and can co-locate with the access routers. As long as the mobile node  14  moves within the same domain that has MAGs, the mobile node  14  assumes that it is in a home link. The MAG is responsible for sending the proper mobile prefix as part of the router advertisement for stateless auto-configuration, or it can also act as a DHCP relay agent for stateful auto-configuration. 
         [0073]      FIG. 2  describes the network elements associated with PMIPv6 operation, and illustrates mobile node  14  handoff from visited network  1   12  to visited network  2   12 . The mobile node  14  is in communication with a correspondent node (CN)  34 . AGW 1   16  and AGW 2   16  each include a mobile proxy or MAG  38 , and each has a tunnel  36  with HA  18 . 
         [0074]    After the mobile node  14  connects to the new point-of-attachment as part of the initial bootstrapping process or after the movement to a new domain, access is authenticated with the designated AAA  20  server. During this process, MAG  38  sends the binding update to the HA  18  with the address of the MAG  38  that is specific to the home prefix of the mobile node  14 . In the absence of a pre-existing tunnel, this process helps to set up a tunnel  36  between the HA  18  and the respective MAG  38 . The mobile node  14  configures its address using the prefix included in the router advertisement and interface-id, which can be assigned by MAG  38  or created by itself. The PMIPv6-based mobility protocol is preferred when mobility is confined within a domain and wireless service providers do not want to overload the mobile node&#39;s stack by setting up a tunnel  36  between the mobile node  14  and the HA  18 . A tunnel is not desirable on the mobile node  14  because it adds extra processing and bandwidth constraints to the wireless hop. 
         [0075]      FIG. 3  illustrates roaming according to one embodiment of the invention. A home domain  10  includes entities or functional components of hP-CSCF  22 , hS-CSCF  26 , hI-CSCF  24 , hHA  18  and hDHCP  40 . In addition, the home domain  10  includes hPDSN routers each having a proxy mobile agent  38 . The visited domain  12  includes entities of vP-CSCF  22 , vS-CSCF  26 , vI-CSCF  24 , vHA  18  and vDHCP  40 . The visited domain  12  also includes vPDSN routers, each having a mobile agent gateway  38 . MN 1   14  and MN 2   14  are in visited domain  12 . A tunnel  36  is established between each MAG  38  and hHA  18  in the home domain  10 . Tunnels  36  are also created between each MAG  38  and vHA  18  in the visited domain  12 . During session enablement, when the end nodes are notified of the signaling address and Session Description Protocol (SDP) address, media and signaling splitting is performed. The tunnels  36  carry the split traffic, so that SIP signaling is transmitted over one tunnel, and media for SIP as well as non-SIP application is sent over another tunnel. Each application specific media uses different contact address for transport. 
         [0076]      FIG. 4  shows the case of home local mobility when the mobile node  14  has a Simple IP stack, and the home network  10  is equipped with PMIPv6. Generic network architecture having access routers that behave as 3GPP2 PDSN are assumed, and a Local Mobility Anchor (LMA) serves as HA  18 . As the mobile node  14  initially bootstraps in PDSN# 1 , it goes through an access authentication phase. With a Point-to-Point Protocol (PPP) link, access authentication takes place at the lower layer during the Link Control Protocol (LCP) and authentication phase. Since the PDSNs are equipped with MAG  38 , the Network Access Identifier (NAI) is passed to the LMA  18  as part of the binding update, during which a tunnel  36  is created between MAG  38  and LMA  18 . MAG  38  may also receive the home prefix and the interface-id for the specific mobile node  14  from the LMA  18 . These are used for creating the hHoA# 1  address. 
         [0077]    The mobile node  14  interacts with the DHCP server to obtain the address of the P-CSCF  22 . It then sends a SIP registration to the P-CSCF  22 , and the P-CSCF  22  sends this registration to S-CSCF  26 . Since hHoA# 1  is used for the purpose of SIP signaling, the mobile node  14  uses the HoA&#39;s prefix and locally generated random interface-id to generate the new media addresses, hHoA# 2  and hHoA# 3 , for SIP-based and non-SIP-based traffic, respectively. The mobile node  14  uses hHoA# 2  as the media contact address in its SDP when the mobile node  14  invites another user or correspondent node  34 . Consequently, the mobile node  14  receives media for the SIP-based application using a different IP address than for SIP signaling. 
         [0078]    Since there is already a tunnel  36  established between the MAG  38  and LMA  18 , any SIP signaling traffic destined for hHoA# 1 , SIP media destined for hHoA# 2 , and non-SIP media destined for hHoA# 3  are tunneled via the PMIPv6 tunnel  36  setup between the MAG  38  and LMA  18 . In one embodiment (not shown), separate tunnels are established for each of SIP signaling traffic, SIP media and non-SIP media. In all cases, even if the mobile node  14  moves to a new PDSN# 2 , and hence changes to a new MAG  38 , hHoA# 1 , hHoA# 2 , and hHoA# 3  do not change. 
         [0079]      FIG. 5  shows the flows for the case in which the mobile node  14  has a Simple IP stack, and both the home domain  10  and visited domain  12  support PMIPv6. As in  FIG. 3 , LMA serves as a form of HA  18 . The first time the mobile node  14  moves to the visited domain  12 , access is authenticated along with the PMIPv6 binding update procedure with MAG  38 . During the access authentication, the MAG  38  sends two binding update messages to two LMAs  18 . One binding update message is sent to the visited LMA  18  and the other is sent to the home LMA  18  according to the authentication response message from the visited AAA  20  and home AAA  20 . MAG  38  sends the interface-id during the IPv6CP procedure, and sends both the vHoA&#39;s prefix and hHoA&#39;s prefix as part of the router advertisement message. Based upon these three parameters, the mobile node  14  generates hHoA# 1  used for SIP signaling, and vHoA# 1  used for media packets. The mobile node  14  then obtains the address of home P-CSCF  22  from the home DHCP server through the PMIPv6 tunnel  36  between the MAG  38  and home LMA  18 , and sends SIP registration to the home P-CSCF  22 . The home P-CSCF  22  forwards it to home S-CSCF  26  to update the user information. After a successful SIP signaling setup, the mobile node  14  receives traffic using the vHoA# 1  address. In order to send the non-SIP media packets, the mobile node  14  creates vHoA# 2  using a self-generated interface-id and vHoA&#39;s prefix. During handoff, the mobile node  14  obtains the same prefixes from the visited LMA  18  and home LMA  18 . Therefore, the mobile node  14  does not have to send an SIP registration message unless the assigned P-CSCF  22  changes. 
         [0080]    While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the claims below.