Patent Publication Number: US-2023164653-A1

Title: Inter-system mobility in integrated wireless networks

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/801,783 filed Feb. 26, 2020 which is a continuation of U.S. patent application Ser. No. 15/321,365 filed Dec. 22, 2016 which is a National Stage Application filed under 35 U.S.C. 371 of International Application No. PCT/US2015/037186, filed Jun. 23, 2015, which claims benefit under 37 U.S.C. § 119(e) of Provisional U.S. Patent Application No. 62/015,763, filed on Jun. 23, 2014, the contents of which are hereby incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     As wireless communications technologies have evolved, additional demands have been placed on wireless systems to support more extensive use of diverse wireless networks. For example, mobile network operators (MNOs) have begun incorporating “carrier-grade” WiFi in ways that complement their cellular and core network services. For instance, MNOs have sought to employ WiFi to offload Internet traffic from their cellular and core networks. MNOs have also sought to provide users of WiFi networks with access to the evolved packet core (EPC) of cellular systems. 
     While demand continues to increase for inter-system integration of cellular and WiFi networks, existing methods of providing such integration have proven to be resource intensive and too often result in interruptions in ongoing communications. 
     SUMMARY 
     Applicants disclose herein systems and methods for inter-system mobility in integrated long term evolution (LTE) and trusted wireless local area network (WLAN) access networks (TWAN). A control plane interface, referred to as the S1a-C interface, is defined between a trusted WLAN access network (TWAN) and a mobility management entity (MME) comprised in a 3GPP core network. A user plane interface, referred to as the S1a-U interface, is defined between the TWAN and a serving gateway (SGW) in the 3GPP core network. The MME operates as a common control plane entity for both LTE and TWAN access, while the SGW operates as a user plane serving gateway for both LTE and TWAN access network. The integrated MME and SGW allow for user equipment (UE) to access the capabilities of a 3GPP packet data network (PDN) through either the LTE or TWAN access network. Moreover, an existing communication connection between a UE and a 3GPP PDN may be handed over from one of the LTE or TWAN access network to the other. Still further, the MME and SGW provide for simultaneously maintaining two accessing communication paths, one via the LTE and one via the TWAN, between a UE and a 3GPP packet core network. 
     In an example scenario, user equipment (UE) such as, for example, a wireless phone or other computing system, may attempt to attach to the evolved packet core (EPC) of a 3GPP network via a TWAN access network. The processing may be initiated, for example, when a UE associates with a WiFi access point. In response to this association with the WiFi access point, the TWAN generates and transmits an authentication request to a 3GPP AAA server. A trusted WLAN AAA proxy (TWAP) comprised in the TWAN generates and transmits the authentication request. In response to the authentication request, the TWAN, and in particular, the TWAP, receives an answer from the 3GPP AAA server indicating communication between the TWAN and a mobility management entity (MME) via a first interface is authorized. In an example scenario, the received answer identifies that communication over the S1a-C interface is authorized. 
     The TWAN generates and transmits a request to create a session to the MME over the S1a-C interface. In an example embodiment, a WLAN access node (AN) comprised in the TWAN generates and transmits the request. In response to receiving the request, the MME generates and transmits a create session request to the SGW. In an example embodiment, the MME communicates the create session request to the SGW over an S11 interface that is adapted to accommodate the request. 
     The SGW generates and transmits a request to create a session to a selected packet data network (PDN) gateway (PGW). Upon receipt of the request, the PGW coordinates the requested attachment of the UE within the 3GPP network and, assuming the request is authorized, generates and transmits a create session response. 
     The SGW receives the create session response, which, in an example embodiment, includes an IP address for the UE. The SGW forwards the response to the MME, which transmits the create session response including the IP address for the UE to the TWAN over the S1a-C interface. The response may be received at the WLAN AN within the TWAN and communicated to the TWAP along with an indication that a second interface, the S1a-U interface, has been successfully established. The TWAN, and in particular, the TWAP, communicates to the UE that the attach procedure is completed. The UE receives the IP address from the WLAN. Thereafter, the TWAN routes packets between the UE and the PGW via the SGW and the S1a-U interface. 
     According to another aspect of the disclosed systems and methods, the communication path used by a UE to a PDN may be handed over from one of the wireless networks to the other. For example, in a situation where a UE has an established communication path to a PDN network via a WiFi connection through a TWAN, the connection to the PDN may be handed over for routing through the LTE access network. Analogously, where a UE has an established connection to a PDN via the LTE access network, the connection may be handed over for routing through the TWAN instead of the LTE access network. In an example scenario, a UE discovers a WiFi access point (AP) associated with a TWAN that has been integrated with an LTE access network with which the UE has an existing connection. The UE associates with the WiFi access point using the attach procedure as described above. The association results in the establishment of an S1a-C interface between the TWAN and an MME in the 3GPP network, as well as the identification of an S1a-U interface between the TWAN and an SGW in the 3GPP network. 
     With a connection established to the PDN via the TWAN, the UE generates, and the TWAN receives, a connection request that indicates a request to hand over control from the existing LTE connection. In an example embodiment, the handover request is received at the WLAN AN which forwards the request to the trusted WLAN access gateway (TWAG). In an example embodiment, the TWAG forwards the request over the established S1a-C interface to the MME. The MME generates and transmits a request to the SGW over an S11 interface. 
     The SGW generates and transmits a request for a handover to the PGW. Upon receipt of the request, the PGW coordinates the handover of the existing connection of the UE within the 3GPP network and, assuming the request is authorized, generates and transmits a create session response. The response includes information regarding the existing communication path between the SGW and the PDN that was previously established to service access through the LTE access network. 
     The SGW receives the response including the information regarding the existing communication path and forwards the response to the MME. The MME transmits the responsive information to the TWAN over the S1a-C interface. The response may be received at TWAG which forwards the information to the WLAN AN. The WLAN communicates that the connection to the PDN via the TWAN has been established. In other words, the TWAN communicates information to the PDN that was previously routed through the LTE network. The UE may then initiate to release the LTE connection. 
     According to another aspect of the disclosed systems and methods, two communication paths—one via the LTE access network and one via the TWAN between a UE and a 3GPP PDN—may be established and maintained. For example, in a situation where a UE has an established communication path to a 3GPP PDN network via a WiFi connection through a TWAN, a communication path may be added and maintained through the LTE access network. Analogously, where a UE has an established communication path to a 3GPP PDN network via the LTE access network, a communication path through the TWAN may be added and maintained. In an example scenario, a UE that has an established connection to a 3GPP PDN via LTE discovers a WiFi access point (AP) associated with a TWAN that has been integrated with the LTE access network. The UE associates with the WiFi access point using the attach procedure as described above. The association results in the establishment of an S1a-C interface between the TWAN and an MME in the 3GPP network, and an S1a-U interface between the TWAN and an SGW in the 3GPP network. 
     With a connection established to the PDN via the TWAN, the UE generates, and the TWAN receives, a multi-connection request that indicates a request to assign the same IP address for the UE access to the PDN through the TWAN as has been assigned for communication via the LTE access network. In an example embodiment, the multi-connection request is received at the WLAN AN, which forwards the request to the TWAG. In an example embodiment, the TWAG forwards the request over the established S1a-C interface to the MME. The MME generates and transmits a request for a multi-connection session to the SGW over an S11 interface. 
     The SGW generates and transmits a request for a multi-connection session to the PGW. Upon receipt of the request, the PGW coordinates multi-connectivity of the UE within the 3GPP network and, assuming the request is authorized, generates and transmits a response. The response includes information regarding the existing communication path between the SGW and the PDN that was previously established to service access through the LTE access network including the IP address for the UE. 
     The SGW receives the response including the information regarding the existing communication path and forwards the response to the MME. The MME transmits the responsive information to the TWAN over the S1a-C interface. The response may be received at the TWAG which forwards the information to the WLAN AN. The WLAN communicates to the UE that the connection to the PDN via the TWAN has been established. Thereafter, the TWAG can route packets between the UE and the PGW via the SGW. The UE may route packets via the SGW over either the TWAN or the LTE access network. The SGW may route packets to the UE over either the TWAN or the LTE access network. 
     As described in greater detail below, there may be many variations of the above embodiments. For example in some instances, the TWAN that is integrated with the LTE access network may be adapted to provide single-PDN connectivity. While in other instances, the TWAN may be adapted to provide multi-PDN connectivity. By way of further example, the functionality that is traditionally associated with a TWAG portion of a TWAN may be integrated into the SGW in the 3GPP processing network. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description of Illustrative Embodiments. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other features are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary and the following additional description of the illustrative embodiments may be better understood when read in conjunction with the appended drawings. It is understood that potential embodiments of the disclosed systems and methods are not limited to those depicted. 
         FIG.  1    depicts existing architecture for providing TWAN and 3GPP LTE access to a PDN. 
         FIG.  2    depicts an example architecture for integrated LTE and TWAN access to a PDN. 
         FIG.  3    depicts an example architecture for integrated LTE and TWAN access to a PDN where the TWAG is integrated with the SGW. 
         FIGS.  4 A-B  provide a diagram depicting, for a single-PDN connection, example processing associated with a UE attaching via a TWAN to a PDN where the TWAG is integrated with the SGW. 
         FIGS.  5 A-B  provide a diagram depicting, for a single-PDN connection, example processing associated with a UE attaching via a TWAN to a PDN where the TWAG is separated from the SGW. 
         FIGS.  6 A-B  provide a diagram depicting, for a multi-PDN connection, example processing associated with a UE attaching via a TWAN to a PDN where the TWAG is integrated with the SGW. 
         FIGS.  7 A-B  provide a diagram depicting, for a multi-PDN connection, example processing associated with a UE attaching via a TWAN to a PDN where the TWAG is separated from SGW. 
         FIGS.  8 A-C  provide a diagram depicting example processing associated with a handover of a connection from an LTE access network to TWAN. 
         FIGS.  9 A-C  provide a diagram depicting example processing associated with establishing multi-connection communication with a PDN between LTE and TWAN access. 
         FIGS.  10 A-B  provide a diagram depicting example processing associated with a handover of a connection from a TWAN to an LTE access network. 
         FIGS.  11 A-B  provide a diagram depicting example processing associated with establishing multi-connection communication with a PDN between TWAN and LTE access. 
         FIG.  12 A  is a system diagram of an example UE with which one or more disclosed embodiments may be implemented. 
         FIG.  12 B  is a system diagram of an example computing system that may be used to implement the systems and methods described herein. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Applicants disclose herein systems and methods for inter-system mobility in integrated LTE and trusted WLAN access networks (TWAN). An S1a-C control plane interface is defined between a trusted WLAN access network (TWAN) and a mobility management entity (MME) comprised in a 3GPP core network. An S1-U user plane interface is defined between the TWAN and a server gateway (SGW) in the 3GPP core network. The MME operates as a common control plane entity for both LTE and TWAN access, while the SGW operates as a user plane serving gateway for both LTE and TWAN. The integrated MME and SGW allow for user equipment (UE) to access the capabilities of a packet data network (PDN) through either the LTE access network or TWAN. Moreover, an existing communication connection between a UE and a PDN may be handed over from one of the LTE access network or TWAN to the other. Still further, the MME and SGW provide for simultaneously maintaining two communication paths, one via the LTE access network and one via the TWAN, between a UE and a packet network. 
     Example Mobile Network Operations 
     Under current practices, mobile network operators (MNOs) typically employ WiFi for offloading “best effort” Internet traffic from their cellular and core networks. However, increased interest in operator deployment of “small cells,” i.e., localized geographic areas providing wireless network access via 3GPP, and “carrier WiFi” is expected to encourage MNOs to seek better inter-operability across local cellular and WiFi networks. 
     As operators adopt “carrier WiFi” to optimize their networks and reduce expenses, it is expected that there will be a greater deployment of “Trusted” WLAN Access Networks (TWAN) that can interface directly with an operator&#39;s Mobile Core Network (MCN). Similarly, it is expected that there will be greater integration of MNO deployed small cell and WiFi access networks within common geographical areas such as high-traffic urban metropolitan hotspot locations. Such integration is motivated by the growing number of smartphones that support both cellular and WiFi access. 
     In this context, the term “trusted WLAN (TWAN) access” refers to the circumstances wherein appropriate measures have been taken to safeguard the EPC from access via the WLAN. Such measures are left to the discretion of the MNO and may, for example, include establishment of a tamper-proof fiber connection between the WLAN and EPC, or establishment of an IPSec security association between the WLAN and a Security Gateway at the EPC edge. In contrast, if the WLAN access is deemed “untrusted,” the WLAN may interface with an evolved Packet Data Gateway (ePDG) at the EPC edge, and the ePDG must establish an IPSec security association directly with each UE accessing the EPC through the WLAN. 
     3GPP Activities Related to WLAN Access 
     The GPRS Tunneling Protocol (GTP) has been the standard transport protocol for packet data in 3GPP networks. In terms of inter-working with a wide assortment of non-3GPP networks, use of the IETF Proxy Mobile IP (PMIP) protocol has been standardized as a general solution for a variety of IP-based access networks such as WiMAX. With respect to WLAN access networks, in particular, there has been activity directed at standardizing procedures for 3GPP access using the GTP protocol. The activities were intended to enable subscriber access to the MNO&#39;s core network via lower cost unlicensed 802.11 spectrum in lieu of expensive cellular spectrum. Although operator adoption of generic access network (GAN), I-WLAN, and Untrusted WLAN has been very limited, interest in Trusted WLAN seems to be gaining momentum, especially with respect to the GTP-based option. 
     The 3GPP Release 11 SA2 work item for “S2a Mobility based on GTP &amp; WLAN access to EPC” (SaMOG) focused on enabling a GTP-based S2a interface to the PDN Gateway (PGW) for “Trusted WLAN Access Networks” (TWANs). This item precluded any solutions that would impact the UE. The Release 11 architectures, functional descriptions, and procedures for GTP-based S2a over trusted WLAN access were subsequently standardized. The applicable GTP control plane protocol for tunnel management (GTPv2-C) and the GTP user plane have also been standardized. SaMOG may be extended to address the Release 11 limitations and may include solutions requiring UE enhancements for UE-initiated PDN connectivity, multi-PDN connectivity, and seamless inter-system handover. 
     3GPP Release 10 standardized a GTP-based S2b interface for Untrusted WLAN access to the EPC. This included the associated support for a GTP-based S2b interface between an evolved Packet Data Gateway (ePDG) and the PGW. Untrusted WLAN solutions may require UE support for IPSec as well as EPC support of an ePDG for establishing an IPSec tunnel with the UE. 
     3GPP Release 6 provided a standardized WLAN Interworking (I-WLAN) solution by introducing a Packet Data Gateway (PDG) for WLAN access to the “pre-EPC” packet-switched core network. This release additionally described how to reuse existing GGSN deployments to implement the PDG functionality using a subset of the Gn interface (denoted as Gn′) via a “Tunnel Termination Gateway” (TTG) using GTP towards the GGSN. Again, these solutions may require UE support for IPSec as well as PDG/TTG support for establishing an IPSec tunnel with the UE. 
     3GPP Release 6 also standardized Generic Access Network (GAN) support for 2G/WiFi dual-mode handsets. Release 8 added support for 3G/WiFi handsets. Unlicensed Mobile Access (UMA) is the commercial name used by mobile carriers for GAN access via WiFi. GAN-enabled UEs can use WiFi to interface with a “GAN Controller” (GANC) that presents itself as a 2G BSC or 3G RNC to the core network. GANC provides a circuit-switched (CS) interface to the MSC, a packet-switched (PS) interface to the SGSN, and a Diameter EAP interface to the AAA Server/Proxy. It also includes a Security Gateway (SeGW) that terminates IPSec tunnels from the UE. Table 2 below illustrates the basic requirements for each GTP-based WLAN solution. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                 GAN/UMA  
                   
                 Untrusted 
                 Trusted  
               
               
                   
                 (PS only shown) 
                 I-WLAN 
                 WLAN 
                 WLAN 
               
               
                   
               
             
            
               
                 Network 
                 GANC 
                 PDG/TTG 
                 ePDG 
                 TWAN 
               
               
                 Element 
                   
                   
                   
                   
               
               
                 CN Interface 
                 SGSN (or GGSN for 
                 SGSN or GGSN 
                 PGW 
                 PGW 
               
               
                   
                 Direct Tunnel support) 
                   
                   
                   
               
               
                 CN Protocols 
                 GTP 
                 GTP 
                 GTP or PMIP 
                 GTP or PMIP 
               
               
                 UE Protocols 
                 IKEv2/IPSec, 
                 IKEv2/IPSec, 
                 IKEv2/IPSec, 
                 EAP-AKA’, 
               
               
                   
                 EAP-AKA, 
                 EAP-AKA 
                 EAP-AKA 
                 WLAN Control 
               
               
                   
                 Generic Access Radio 
                   
                   
                 Protocol (WLCP) 
               
               
                   
                 Resource Control  
                   
                   
                 as defined for 
               
               
                   
                 (GA-RRC), 
                   
                   
                 SaMOG Phase 2. 
               
               
                   
                 NAS protocols 
                   
                   
                   
               
               
                   
                 tunneled between UE 
                   
                   
                   
               
               
                   
                 and SGSN 
               
               
                   
               
            
           
         
       
     
     Each of the above activities were intended to enable subscriber access to an operator&#39;s mobile core network via lower cost unlicensed 802.11 access points in lieu of expensive cellular base stations. Although operator adoption of GAN, I-WLAN, and Untrusted WLAN has been very limited, interest in Trusted WLAN is growing. 
     Existing Architecture for Cellular LTE and TWAN Access to EPC 
       FIG.  1    depicts an existing 3GPP architecture that provides cellular LTE and Trusted WLAN access to an EPC  114 . As described in section 16.1.1 of 3GPP Technical Specification (TS) 23.402, the contents of which are hereby incorporated herein by reference, when a WLAN 110 is considered trusted by the operator, the Trusted WLAN Access Network (TWAN)  112  can be connected to the Evolved Packet Core (EPC)  114  via the STa interface  116  toward the 3GPP AAA Server  118  for authentication, authorization, and accounting via the S2a interface  120  toward the PDN Gateway (PGW)  122  for user plane traffic flows. 
     The 3GPP LTE access network  130  (i.e., evolved Node B) is connected to the EPC  114  via the S1-MME interface  132  which provides a communication path with the Mobility Management Entity (MME)  134 . The S1-U interface  136  provides a communication path with the Serving Gateway (SGW)  138 , which interfaces with the PDN Gateway (PGW)  122  via the S5 interface  140 . 
     An optional “local gateway” function (L-GW)  150  provides small cell LTE access, e.g., for Home eNB (HeNB) deployments. Similarly, an optional “HeNB Gateway” (HeNB GW)  152  may be used to concentrate control plane signaling for multiple HeNBs toward the MME  134  and could also be used to handle HeNB user plane traffic toward the SGW  138 . 
     Trusted WLAN Access Network (TWAN) 
     WLAN Access Network (WLAN AN)  110  comprises one or more WLAN Access Points (APs). An AP terminates the UE&#39;s WLAN IEEE 802.11 link via the SWw interface  156 . The APs may be deployed as standalone APs or as “thin” APs connected to a Wireless LAN Controller (WLC) using, for example, the IETF CAPWAP protocols. 
     Trusted WLAN Access Gateway (TWAG)  160  terminates the GTP-based S2a interface  120  with the PGW  122  and may act as the default IP router for the UE  162  on its WLAN access link. It also may act as a DHCP server for the UE  162 . The TWAG  160  typically maintains a UE MAC address association for forwarding packets between the UE  162  (via the WLAN AP) and the associated S2a  120  GTP-U tunnel (via the PGW). 
     Trusted WLAN AAA Proxy (TWAP)  164  terminates the Diameter-based STa interface  116  with the 3GPP AAA Server  118 . The TWAP 164 relays the AAA information between the WLAN AN  110  and the 3GPP AAA Server  118  (or Proxy in case of roaming). The TWAP 164 can inform the TWAG  160  of the occurrence of layer  2  attach and detach events. The TWAP 164 establishes the binding of UE subscription data (including IMSI) with UE MAC address and can provide such information to the TWAG  160 . 
     Authentication and Security over TWAN in Existing Systems 
     In existing systems, the UE  162  can leverage Universal Subscriber Identity Module (USIM) features for both 3GPP and non-3GPP WLAN access. Processing for authentication and security is described in section 4.9.1 of 3GPP TS 23.402, the contents of which are hereby incorporated by reference in its entirety. As described therein, non-3GPP access authentication, such as that which takes place via a WLAN, defines the process that is used for access control and thereby permits or denies a subscriber from attaching to and using the resources of a non-3GPP IP access which is interworked with the EPC network. Non-3GPP access authentication signaling is executed between the UE and the 3GPP AAA server  118  and HSS  170 . The authentication signaling may pass through AAA proxies. 
     Trusted 3GPP-based access authentication is executed across an STa reference point  116 . The 3GPP based access authentication signaling is based on IETF protocols, e.g., Extensible Authentication Protocol (EAP). The STa interface  116  and Diameter application are used for authenticating and authorizing the UE  162  for EPC access via trusted non-3GPP accesses. 3GPP TS 29.273, the contents of which are hereby incorporated by reference in its entirety, describes the standard TWAN procedures currently supported on the STa interface. 
     IP Address Allocation over TWAN in Existing Systems 
     For EPC access via GTP-based TWAN, the IPv4 address and/or IPv6 prefix is allocated to the UE  162  when a new PDN connection is established with the EPC  114  over the TWAN  112 . A separate IP address may also be allocated by the TWAN  112  for local network traffic and/or direct Internet offload. 
     For PDN connectivity through EPC  114  via the TWAN  112 , the TWAN  112  receives relevant PDN information via EAP/Diameter or WLCP signaling. The TWAN  112  may request an IPv4 address for the UE  162  from the PGW  122  via the GTP Create Session Request. The IPv4 address is delivered to the TWAN  112  during the GTP tunnel establishment via the GTP Create Session Response. When the UE  162  requests an IPv4 address for PDN connectivity via DHCPv4, the TWAN  112  delivers the received IPv4 address to the UE  162  within DHCPv4 signaling. Corresponding procedures are also defined for IPv6. 
     Existing Procedures for Access via LTE 
     For 3GPP LTE access, the UE  162  automatically triggers a PDN connection as part of its initial attachment to the EPC network  114 . The UE  162  may subsequently establish additional PDN connections as needed. 
     When a UE  162  attempts to attach to the EPC  114  via an (H)eNB LTE access network  130 , it first establishes an RRC connection with the (H)eNB LTE access network  130  and encapsulates the Attach Request within the RRC signaling. The (H)eNB LTE access network  130  then forwards the attach request to the MME  134  via S1-AP signaling on the S1-MME interface  132 . The MME  134  retrieves subscription information from the HSS  170  via the S6a interface  172  in order to authenticate the UE  162  and allow attachment to the EPC  114 . 
     After successfully authenticating the UE  162 , the MME  134  selects an SGW  138  (e.g., based on proximity to the (H)eNB LTE access network  130 ), and also selects a PGW  122  (e.g., based on the default APN retrieved from HSS  170  or a specific APN requested by UE  162 ). The MME  134  communicates with the SGW  138  over the S11 interface  174  and requests creation of the PDN connection. The SGW  138  executes the signaling to establish a GTP user plane tunnel with the designated PGW  122  over the S5 interface  140 . 
     “GTP control” signaling takes place within the S1-AP protocol between the MME  134  and (H)eNB  130 . This ultimately leads to the establishment of a GTP user plane tunnel on the S1-U interface  136  between (H)eNB  130  and SGW  138 . The path for the PDN connection between the UE  162  and PGW  122  is thus completed through the (H)eNB  130  and SGW  138 . 
     Existing Procedures for EPC Access via TWAN 
     In existing systems where communications take place via the TWAN  112 , UE  162  authentication and EPC  114  attachment is accomplished via EAP signaling between the UE  162  and 3GPP AAA Server  118 . The PDN connectivity service is provided by the point-to-point connectivity between the UE  162  and the TWAN  112 , concatenated with S2a bearer(s)  120  between the TWAN  112  and the PGW  122 . 
     When a UE  162  attempts to attach to the EPC  114  via a TWAN  112 , it first establishes a Layer  2  connection with the WLAN 110 and encapsulates EAP messages within EAPoL signaling. The WLAN 110 forwards the EAP messages to a TWAP 164 which encapsulates the messages within Diameter signaling and forwards the messages to the 3GPP AAA Server  118  via the STa interface  116 . The 3GPP AAA Server  118  retrieves subscription information from the HSS  170  via the SWx interface  180  in order to authenticate the UE  162  and allow attachment to the EPC  114 . 
     For 3GPP Release 11, the 3GPP AAA Server  118  also provides the TWAN  112  with information via STa interface  116  for establishing a PDN connection to the default PDN provisioned in the HSS  170 . The TWAN  112  then exercises GTP control plane (GTP-C) and user plane (GTP-U) protocols over the S2a interface  120  directly toward the PGW  122 , thereby completing the PDN connection between the UE  162  and PGW  122  through the TWAN  112 . 
     For 3GPP Release 12, the SaMOG phase-2 work item defines additional procedures for UE-initiated PDN connectivity, multi-PDN connectivity, and seamless inter-system handover. For the case of single-PDN capable TWAN connection scenarios, EAP extensions are defined to support UE-initiated PDN requests and seamless inter-system handover requests. For the case of multi-PDN capable TWAN scenarios, a WLAN Control Protocol (WLCP) is defined between the UE and TWAN to enable one or more UE PDN connection requests and seamless handover procedures. However, separate procedures are still utilized between the UE and 3GPP AAA Server for UE authentication. 
     Inter-System Mobility in Integrated Wireless Networks 
     As the above description illustrates, under current practices, cellular network and WiFi interworking occurs in the PGW. Such interworking is typically slow as it requires access and control by devices within the core of the EPC. Furthermore, communications that are reliant upon processing at the core of the network have an increased opportunity to be disrupted as the communications travel to and from the network core. 
     Given the anticipated deployment of many co-located small cell and WiFi access points, Applicants have noted that it would be beneficial to standardize some inter-working functionality closer to the small cell and WiFi access points. In some mobility and multi-access scenarios, such a capability could reduce user plane switching delays across access technologies and minimize the amount of signaling through the MCN, i.e., to the PGW. 
     Applicants disclose herein improved systems and methods for inter-system mobility in integrated wireless networks. More particularly, applicants disclose herein systems and methods for inter-system integration of small cell and WiFi networks. According to one aspect of the disclosed embodiments, the MME existing in the control network of the EPC has been extended to provide a common control plane entity for both LTE and WiFi access, while the SGW, which is also located in the EPC, has been extended to function as a common user plane gateway for both LTE and WiFi access. The disclosed combination of an MME and SGW with corresponding interfaces to the WiFi and LTE access networks may be referred to as an “Integrated Small Cell and WiFi Network” (ISWN). An ISWN may include enhancements to multi-RAT terminal capabilities, small cell and WiFi access capabilities, EPC network elements, and policy/traffic management functions. 
     The enhanced MME and SGW functionality as disclosed herein result in GTP-based integrated small-cell and WiFi (ISW) connectivity and mobility. In one embodiment, the MME may interact with separate gateways for LTE and WiFi access, i.e., SGW and TWAG respectively, or with an “ISW-enabled” SGW, including a combined SGW/TWAG. The UE interacts with the 3GPP AAA Server for EPC attachment via the TWAN, while the TWAN established connectivity to the PDN according to the procedures described herein. 
     The disclosed systems and methods improve performance by enabling execution of inter-system mobility procedures close to the edge of the network. Latency is reduced by minimizing the need for signaling procedures deep in the core network, i.e., toward the PGW. The improved performance and reduced latency resulting from the disclosed systems and methods is especially beneficial in environments where an MNO deploys both small cell and WiFi access in a common geographic area. The disclosed systems and methods, by distributing some inter-system mobility functions to the MME and SGW, improve scalability by reducing the processing burden placed on the PGW. 
     According to one aspect of the disclosed embodiments, communication of an IP data stream or “IP flow” to/from a single PDN may be switched or handed over to another of the LTE or TWAN connections based on local conditions and policies. The “handover” feature allows for selective use of connections for the purpose of optimizing throughput and minimizing resource expense. 
     According to another aspect of the disclosed embodiments, two concurrent connections to the PDN may be established, one via the LTE and one via WiFi. A “multi-connection” connection feature in the MME/SGW results in improved mobility robustness and reduce handover ping-ponging. The multi-connection aspect of the disclosed embodiments allows for an alternate path to the PDN to be made available as needed without incurring handover setup delays. The availability of alternate communication paths improves the user experience by reducing session interruptions when the primary data path is degraded (which can be a common occurrence given the limited coverage of small cell and WiFi access points). 
     Architecture for Inter-System Mobility in Integrated WLAN and LTE Access Networks 
       FIGS.  2  and  3    depict example embodiments of systems for providing inter-system mobility in integrated WLAN and LTE access networks. As shown in  FIGS.  2  and  3   , both example embodiments comprise a new “S1a-C” control plane interface ( 290 ,  390 ) between the MME ( 234 ,  334 ) and the TWAN ( 212 ,  312 ), and a new “S1a-U” user plane interface ( 292 ,  392 ) between SGW ( 238 ,  338 ) and TWAN ( 212 ,  312 ). With the S1a-C and S1a-U interfaces in place, the MME ( 234 ,  334 ) operates as a common control plane entity for both LTE access network ( 295 ,  395 ) and TWAN ( 212 ,  312 ) access, while the SGW ( 238 ,  338 ) operates as a user plane gateway for both LTE access network ( 295 ,  395 ) and TWAN ( 212 ,  312 ). As described in detail below in connection with  FIGS.  4 - 7   , the integrated MME ( 234 ,  334 ) and SGW ( 238 ,  338 ), which continue to be comprised in the core EPC network ( 214 ,  314 ), allow for user equipment (UE) ( 262 ,  362 ) to access the capabilities of a packet data network (PDN) through either the LTE access network ( 295 ,  395 ) or TWAN ( 212 ,  312 ). Moreover, and as described in detail in connection with  FIGS.  8  and  10   , an existing communication connection between a UE ( 262 ,  362 ) and a PDN ( 222 ,  322 ) may be handed over from one of the LTE access network ( 295 ,  395 ) or TWAN ( 212 ,  312 ) to the other. Still further, and as described below in connection with  FIGS.  9  and  11   , the MME ( 234 ,  334 ) and SGW ( 238 ,  338 ) provide for simultaneously maintain two communication paths, one via the LTE access network ( 295 ,  395 ) and one via the TWAN ( 212 ,  312 ), between a UE ( 262 ,  362 ) and a PDN ( 222 ,  322 ). 
     In the embodiment of  FIG.  2   , the S1a-C  290  and S1a-U  292  interfaces terminate in the TWAG  260  comprised in the TWAN  212 .  FIG.  3    depicts an alternative embodiment, wherein the functionality that had traditionally been provided by TWAG has been combined with the SGW  338 . The combined SGW and TWAG  338  offer the benefit of reducing the number of devices that a communication must traverse between the UE  362  to the PGW  322 . In the embodiment of  FIG.  3   , the S1a-C  390  and S1a-U  392  interfaces terminate in the TWAN  312 , but terminate specifically in the WLAN AN  310  rather than the TWAG  260  as in  FIG.  2   . 
     In one embodiment of the disclosed systems and methods, the transport network connection on the S1a-C interface between MME and TWAN is established using extensions to Operation, Administration, and Maintenance (OAM) procedures. In embodiments where GTPv2-C is employed as the baseline protocol stack, a User Datagram Protocol (UDP) is established over an IP path for the exchange of subsequent signaling messages on the “S1a-C” interface. In another embodiment, a Stream Control Transport Protocol (SCTP) over IP path may be used. 
     TWAN, MME and SGW Extensions 
     The disclosed systems and methods for inter-system mobility support both “single-PDN capable” and “multi-PDN capable” connections ( 212 ,  312 ). In the case of a single-PDN connection, the UE ( 262 ,  362 ) and the core network ( 214 ,  314 ) support one PDN connection via the TWAN ( 212 ,  312 ) or LTE access ( 295 ,  395 ). With respect to a multi-PDN connection, the UE ( 262 ,  362 ) and network ( 214 ,  314 ) support multiple simultaneous PDN connections via the TWAN ( 212 ,  312 ) and LTE access network ( 295 ,  395 ). 
     For the single-PDN connection scenario, the UE ( 262 ,  262 ) initiates both attach and PDN connection establishment via EAP signaling with the 3GPP AAA Server ( 218 ,  318 ). In one embodiment, the 3GPP AAA Server ( 218 ,  318 ) provides a new ISW-based indication via Diameter signaling extensions to the TWAN ( 212 ,  312 ) (based on reported UE ( 262 ,  362 ) and TWAN ( 212 ,  312 ) capabilities), allowing it to communicate with an enhanced MME ( 234 ,  334 ) via the new S1a-C interface. 
     For the multi-PDN connection scenario, the UE ( 262 ,  362 ) initiates the attach procedure via EAP signaling with the 3GPP AAA Server ( 218 ,  318 ). However, the PDN connection establishment procedure(s) are initiated via WLCP signaling with the TWAN ( 212 ,  312 ). The TWAN ( 212 ,  312 ) communicates with the enhanced MME ( 234 ,  334 ) to continue the PDN connection setup via the new S1a-C interface. 
     In addition to establishing the new S1a-C( 290 ,  390 ) and S1a-U interfaces ( 292 .  392 ), the disclosed embodiments extend existing protocols. For example, according to an aspect of the disclosed embodiments, the UE ( 262 ,  362 ) and the 3GPP AAA Server ( 218 ,  318 ) may be extended to support exchange of additional EAP signaling information for TWAN access in both single-PDN and multi-PDN capable scenarios. Similarly, the UE ( 262 ,  362 ) and TWAN ( 212 ,  312 ) may be extended to support exchange of additional WLCP signaling for TWAN access in multi-PDN capable scenarios. Also, the MME ( 234 ,  334 ) and TWAN ( 212 ,  312 ) may be extended to support new GTPv2-C based control plane procedures over the new “S1a-C” interface for TWAN PDN connection and bearer establishment. By way of further example, the SGW ( 238 ,  338 ) and TWAN ( 212 ,  312 ) may be extended to support new GTP-U based user plane procedures over the new “S1a-U” interface for bearer traffic between TWAN ( 212 ,  312 ) and SGW ( 238 ,  338 ). In yet another example, the MME ( 234 ,  334 ) and SGW ( 238 ,  338 ) may be extended to support new GTPv2-C based control plane procedures over the S11 (S11′) interface for TWAN PDN connection and bearer establishment through the SGW ( 238 ,  338 ). 
     According to an aspect of the disclosed embodiments, authentication and security procedures are performed consistent with existing standard mechanisms using the STa, SWx, and S6b interfaces that may have been enhanced. For example, the STa (STa′) interface between 3GPP AAA Server ( 218 ,  318 ) and TWAN ( 212 ,  312 ) may be extended to enable exchange of additional ISW-based information. Similarly, the SWx (SWx′) interface between HSS and 3GPP AAA Server ( 218 ,  318 ) may be extended to enable exchange of additional ISW-based information. Further, the S6a (S6a′) interface between the HSS ( 270 ,  370 ) and the MME ( 234 ,  334 ) may be enhanced to enable exchange of additional ISW-based information. 
     Protocol Extensions 
     In the disclosed systems and methods, existing protocols and messages may be extended to support the new functionality. For example, existing messages may be extended in order to convey new UE ( 262 ,  362 ) and TWAN ( 212 ,  312 ) capabilities to the 3GPP AAA Server ( 218 ,  318 ). By way of further example, existing messaging may be extended in order to convey UE ( 262 ,  362 ) to PDN connectivity requests to the MME ( 234 ,  334 ) via TWAN ( 212 ,  312 ). Additionally, existing messages may be extended in order to support “multi-connection” indications for an existing UE ( 262 ,  362 ) to PDN connection. The “multi-connection” feature allows a UE ( 262 ,  362 ) to request PDN connectivity via simultaneous access over both cellular and WiFi. In order to support this feature, the UE ( 262 ,  362 ) must be assigned the same IP address for routing of packets to/from the PDN via either access. This is accomplished by adding a “multi-connection” indicator to the EAP, WLCP, NAS, S1-AP and GTP protocols. The UE ( 262 ,  362 ) implementation is responsible for mapping the IP packet to the intended Layer  2  access. 
     Specific EAP/Diameter Protocol Extensions 
     According to an aspect of one disclosed embodiment, the EAP and Diameter signaling are extended to allow the UE ( 262 ,  362 ) and TWAN ( 212 ,  312 ) to indicate their expanded capabilities to the 3GPP AAA Server ( 218 ,  318 ). 
     For the case of inter-system handover in the “single-PDN” connection scenario, the extended EAP signaling described for SaMOG phase-2 already supports use of the “handover” indication along with the “APN” for the PDN connection to be handed over. For the case of inter-system multi-connection, a new indicator for “multi-connection” is defined which provides the “APN” of the PDN to which the connection is being made. 
     According to an aspect of the disclosed embodiments, with respect to the Diameter protocol elements, the “Access Type” information element is extended to include “ISW-enabled TWAN” as one of the potential access types. The TWAN ( 212 ,  312 ) capability indicates support for local and/or remote TWAG ( 260 ) functionality, as well as identifying its connections to ISW-enabled MMEs, if any. 
     The following chart summarizes various EAP extensions that may be incorporated into the disclosed embodiments. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                 Message 
                   
                 New Information 
                   
                   
               
               
                 Direction 
                 EAP Message 
                 Element 
                 Purpose 
                 Comment 
               
               
                   
               
             
            
               
                 UE to 3GPP AAA 
                 EAP- 
                 Multi-connection 
                 Indicates to the 
                 Applies to both 
               
               
                 Server 
                 Response/Identity 
                 capability 
                 network that UE 
                 “single-PDN” 
               
               
                   
                   
                   
                 is capable of 
                 and “multi- 
               
               
                   
                   
                   
                 maintain a PDN 
                 PDN” TWAN 
               
               
                   
                   
                   
                 connection 
                 scenarios 
               
               
                   
                   
                   
                 simultaneously 
                   
               
               
                   
                   
                   
                 over both LTE and 
                   
               
               
                   
                   
                   
                 WiFi access 
                   
               
               
                 3GPP AAA Server 
                 EAP- 
                 Allow/deny use of 
                 Allow/deny use of 
                 Indicates whether 
               
               
                 to UE 
                 Request/AKA- 
                 multi-connection 
                 multi-connection 
                 or not the UE is 
               
               
                   
                 Challenge or 
                   
                   
                 allowed to 
               
               
                   
                 EAP- 
                   
                   
                 request multi- 
               
               
                   
                 Request/AKA- 
                   
                   
                 connectivity on 
               
               
                   
                 Notification 
                   
                   
                 this network 
               
               
                 UE to 3GPP AAA 
                 EAP- 
                 Multi-connection 
                 Indicates to the 
                 For “single- 
               
               
                 Server 
                 Response/AKA- 
                 Indication, APN 
                 network that UE 
                 PDN” TWAN 
               
               
                   
                 Challenge 
                   
                 want to establish 
                 scenario 
               
               
                   
                   
                   
                 a WiFi connection 
                   
               
               
                   
                   
                   
                 to support IP flow 
                   
               
               
                   
                   
                   
                 mobility with a 
                   
               
               
                   
                   
                   
                 simultaneous LTE 
                   
               
               
                   
                   
                   
                 connection to the 
                   
               
               
                   
                   
                   
                 PDN 
               
               
                   
               
            
           
         
       
     
     According to another aspect of the disclosed embodiments, the STa interface and Diameter application may be used for authenticating and authorizing the UE for EPC access. The STa interface may also be used to transport GTPv2 related mobility parameters when the UE attaches to the EPC. 
     The following chart summarizes various Diameter extensions that may be incorporated into aspects of the disclosed embodiments. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 New/Modified 
                   
                   
               
               
                 Message 
                 Diameter 
                 Information 
                   
                   
               
               
                 Direction 
                 Message 
                 Element (IE) 
                 Purpose 
                 Comment 
               
               
                   
               
             
            
               
                 TWAN to 
                 Diameter-EAP- 
                 EAP Payload 
                 Modified to support 
                   
               
               
                 3GPP AAA 
                 Request (DER) 
                   
                 EAP extensions listed 
                   
               
               
                 Server 
                   
                   
                 in the above table 
                   
               
               
                 (STa) 
                   
                   
                 relating to EAP 
                   
               
               
                   
                   
                   
                 extensions 
                   
               
               
                   
                   
                 Access Type: 
                 May define “ISW- 
                   
               
               
                   
                   
                 “ISW TWAN” 
                 TWAN” as a new 
                   
               
               
                   
                   
                   
                 Access Type; 
                   
               
               
                   
                   
                   
                 alternatively, the 
                   
               
               
                   
                   
                   
                 ISW-TWAN capability 
                   
               
               
                   
                   
                   
                 may be included in a 
                   
               
               
                   
                   
                   
                 new “ISW capability” 
                   
               
               
                   
                   
                   
                 IE as shown below 
                   
               
               
                   
                   
                 ISW Capabilities 
                 New IE providing the 
                   
               
               
                   
                   
                   
                 following info: 
                   
               
               
                   
                   
                   
                 ISW-capable 
                   
               
               
                   
                   
                   
                 Connected MME(s) 
                   
               
               
                   
                   
                   
                 Local and/or remote 
                   
               
               
                   
                   
                   
                 TWAG support 
                   
               
               
                 3GPP AAA 
                 Diameter-EAP- 
                 EAP Payload 
                 Modified to support 
                   
               
               
                 Server to 
                 Answer (DEA) 
                   
                 EAP extensions listed 
                   
               
               
                 TWAN 
                   
                   
                 in the above table 
                   
               
               
                 (STa) 
                   
                   
                 relating to EAP 
                   
               
               
                   
                   
                   
                 extensions 
                   
               
               
                   
                   
                 ISW Usage 
                 New IE providing the 
                   
               
               
                   
                   
                 Authorization 
                 following info: 
                   
               
               
                   
                   
                   
                 Use ISW-enabled 
                   
               
               
                   
                   
                   
                 MME (S1a-C) or 
                   
               
               
                   
                   
                   
                 legacy PGW (S2a) 
                   
               
               
                   
                   
                   
                 If using S1a-C, use 
                   
               
               
                   
                   
                   
                 local or remote TWAG 
               
               
                   
               
            
           
         
       
     
     WLCP Protocol Extensions 
     Generally, the NAS Session Management (SM) protocol defined in 3GPP TS 24.008, the contents of which are hereby incorporated herein by reference, discloses the WLCP protocol that may be used to implement the systems and methods disclosed herein. According to one embodiment, the Activate PDP Context Request/Accept/Reject and Deactivate PDP Context Request/Accept message types may be adapted as needed to accommodate the described processing. The WLCP Stage  3  specification is 3GPP TS 24.244, the contents of which are hereby incorporated by reference herein in their entirety. 
     With respect to inter-system handover in the “multi-PDN” scenario, the WLCP signaling described for SaMOG phase-2 supports use of a “handover” request type along with an identification of the “APN” for the PDN connection to be handed over. In connection with processing of a request for an inter-system multi-connection, a new indicator for “multi-connection” may be defined which includes the “APN” for the PDN connection with which the connection is to be made. 
     The following chart summarizes WCLP extensions that may incorporated into embodiments of the disclosed systems and methods. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 New/Modified 
                   
                   
               
               
                 Message 
                 WLCP  
                 Information 
                   
                   
               
               
                 Direction 
                 Message 
                 Element 
                 Purpose 
                 Comment 
               
               
                   
               
             
            
               
                 UE to 
                 PDN 
                 Request Type- 
                 Indicates to the 
                 Applies only to 
               
               
                 TWAN 
                 Connectivity 
                 add “multi- 
                 network that UE 
                 “multi-PDN” 
               
               
                   
                 Request 
                 connection” to 
                 wants to maintain a 
                 TWAN scenarios 
               
               
                   
                   
                 existing “initial” 
                 PDN connection 
                   
               
               
                   
                   
                 and “handover” 
                 simultaneously 
                   
               
               
                   
                   
                 request types 
                 over both LTE and 
                   
               
               
                   
                   
                   
                 WiFi access 
               
               
                   
               
            
           
         
       
     
     NAS Protocol Extensions 
     With respect to the non-access stratum (NAS) protocol, a new indicator for “multi-connection” is defined. When the UE has an existing PDN connection via TWAN, the UE may request a “multi-access connection” via extensions to the LTE attach and PDN connection procedures specified in 3GPP TS 23.401, the contents of which are hereby incorporated herein by reference. In addition to the initial attach and handover indication, the disclosed systems and methods may employ a multi-connection indication. 
     The following chart summarizes the NAS extensions that may incorporated into embodiments of the disclosed systems and methods. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 New/Modified 
                   
                   
               
               
                 Message 
                 NAS  
                 Information 
                   
                   
               
               
                 Direction 
                 Message 
                 Element 
                 Purpose 
                 Comment 
               
               
                   
               
             
            
               
                 UE to 
                 Attach Request 
                 ESM Message 
                 Indicates to the 
                 Applies to initial 
               
               
                 MME 
                   
                 Container/Request 
                 network that UE 
                 PDN connection 
               
               
                   
                   
                 Type-add “multi- 
                 wants to maintain a 
                 triggered by Attach 
               
               
                   
                   
                 connection” to 
                 PDN connection 
                 Request 
               
               
                   
                   
                 existing “initial” 
                 simultaneously 
                   
               
               
                   
                   
                 and “handover” 
                 over both LTE and 
                   
               
               
                   
                   
                 request types 
                 WiFi access 
                   
               
               
                 UE to 
                 PDN 
                 Request Type- 
                 Indicates to the 
                 Applies to 
               
               
                 MME 
                 Connectivity 
                 add “multi- 
                 network that UE 
                 subsequent PDN 
               
               
                   
                 Request 
                 connection” to 
                 wants to maintain a 
                 connections 
               
               
                   
                   
                 existing “initial” 
                 PDN connection 
                 established after 
               
               
                   
                   
                 and “handover” 
                 simultaneously 
                 initial attach 
               
               
                   
                   
                 request types 
                 over both LTE and 
                   
               
               
                   
                   
                   
                 WiFi access 
               
               
                   
               
            
           
         
       
     
     GTPv2-C Protocol Extensions 
     The GTPv2-C protocol may also be extended in connection with the systems and methods disclosed herein. For example, the indication flags in the GTP-C “Create Session Request” may be expanded to include a value for “multi-connection” in addition to the existing “handover indication”. 
     As noted above in connection with  FIG.  3   , in an embodiment where the SGW and TWAG functionality have been combined, the S1a-C interface terminates in the WLAN AN function of the “TWAN.” In such embodiments, additional information such as a UE MAC address and a VLAN ID may need to be conveyed via the GTPv2-C signaling to the ISW-enabled combined SGW+TWAG. 
     The following chart summarizes the GTPv2-C extensions that may be incorporated into embodiments of the disclosed systems and methods. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                   
                 New/Modified 
                   
                   
               
               
                 Message 
                 GTPv2-C 
                 Information 
                   
                   
               
               
                 Direction 
                 Message 
                 Element 
                 Purpose 
                 Comment 
               
               
                   
               
             
            
               
                 TWAN to 
                 Create Session 
                 Indication Flags-add 
                 Indicates to the 
                   
               
               
                 MME 
                 Request 
                 “multi-connection” 
                 network that UE 
                   
               
               
                 (S1a-C) 
                   
                 indication in addition 
                 wants to maintain a 
                   
               
               
                   
                   
                 to existing “handover” 
                 PDN connection 
                   
               
               
                   
                   
                 indication 
                 simultaneously 
                   
               
               
                   
                   
                   
                 over both LTE and 
                   
               
               
                   
                   
                   
                 WiFi access 
                   
               
               
                   
                   
                 WLAN 802.11 MAC 
                 Facilitates packet 
                   
               
               
                   
                   
                 Address, UE 802.11 
                 routing and tunnel 
                   
               
               
                   
                   
                 MAC Address, 
                 management when 
                   
               
               
                   
                   
                 Session VLAN ID 
                 WLAN interfaces 
                   
               
               
                   
                   
                   
                 directly with 
                   
               
               
                   
                   
                   
                 combined SGW + 
                   
               
               
                   
                   
                   
                 TWAG 
                   
               
               
                 MME to 
                 Create Session 
                 Indication Flags-add 
                 Indicates to the 
                   
               
               
                 SGW 
                 Request 
                 “multi-connection” 
                 network that UE 
                   
               
               
                 (S11) 
                   
                 indication in addition 
                 wants to maintain a 
                   
               
               
                   
                   
                 to existing “handover” 
                 PDN connection 
                   
               
               
                   
                   
                 indication 
                 simultaneously 
                   
               
               
                   
                   
                   
                 over both LTE and 
                   
               
               
                   
                   
                   
                 WiFi access 
                   
               
               
                   
                   
                 WLAN 802.11 MAC 
                 Facilitates packet 
                   
               
               
                   
                   
                 Address, UE 802.11 
                 routing and tunnel 
                   
               
               
                   
                   
                 MAC Address, 
                 management when 
                   
               
               
                   
                   
                 Session VLAN ID 
                 WLAN interfaces 
                   
               
               
                   
                   
                   
                 directly with 
                   
               
               
                   
                   
                   
                 combined SGW + 
                   
               
               
                   
                   
                   
                 TWAG 
                   
               
               
                   
                   
                 Access routing 
                 In case of multi- 
                   
               
               
                   
                   
                 policy 
                 connection, MME 
                   
               
               
                   
                   
                   
                 includes this IE to 
                   
               
               
                   
                   
                   
                 indicate IP routing 
                   
               
               
                   
                   
                   
                 preferences to SGW 
               
               
                   
               
            
           
         
       
     
     Network Element Extensions 
     TWAN and 3GPP AAA Server Extensions 
     The TWAN ( 212 ,  312 ) and 3GPP AAA server ( 218 ,  318 ) may be extended in order to provide the processing as described herein. For example, according to one embodiment, the 3GPP AAA Server ( 218 ,  318 ) becomes aware of the TWAN&#39;s ISW network capabilities via new Diameter signaling information that is received from the TWAN ( 212 ,  312 ) over the STa interface. In an example scenario, the “Access Type” information element in the STa “Access Authentication and Authorization Request,” which is described in 3GPP TS 29.273, the contents of which are hereby incorporated by reference, may be extended to include “ISW-TWAN” in the instance that the TWAN supports the MME/SGW interworking capability. Additionally, the “Access Type” information may indicate support for a local TWAG or a remote SGW/TWAG, and identify a list of MMEs connected via S1a-C. 
     In an example embodiment, the 3GPP AAA Server ( 218 ,  318 ) allows use of an ISW-enabled MME by the TWAN using a new Diameter signaling indication over the STa interface. Relying upon considerations such as TWAN capabilities, UE connection status, known network topology, etc., the 3GPP AAA Server ( 218 ,  318 ) determines whether or not the TWAN ( 212 ,  312 ) connection should be established directly over the existing S2a interface with the PGW per legacy procedures, or via an ISW-enabled MME ( 234 ,  334 ) and SGW ( 238 ,  338 ) per new procedures over the proposed “S1a-C” and “S1a-U” interfaces, respectively. 
     According to an aspect of the disclosed embodiments, the HSS ( 270 ,  370 ) is updated with the latest UE connectivity information such as, for example, the MME address, SGW address, PGW address, etc. In the example scenario where the UE ( 262 ,  362 ) attempts to attach via TWAN ( 212 ,  312 ), the 3GPP AAA Server ( 218 ,  318 ) retrieves the latest UE subscription and connection information. If the UE ( 262 ,  362 ) is already connected to an ISW-enabled MME ( 234 ,  334 ) and SGW ( 238 ,  338 ) via LTE access, the same MME ( 234 ,  334 ) and/or SGW ( 238 ,  338 ) may be preferred for use via the TWAN access. In the scenario where the UE ( 262 ,  362 ) is in the vicinity of LTE and TWAN access points capable of sharing the same MME and/or SGW, the ISW-enabled MME and/or SGW may be preferred. 
     MME Extensions 
     The MME ( 234 ,  334 ) is adapted to provide integrated small-cell and WiFi (ISW) capabilities. For example, in the scenario where the S1a-C interface option is selected, the TWAN ( 212 ,  312 ) uses the ISW-enabled MME ( 234 ,  334 ) to establish a PDN connection from the TWAN ( 212 ,  312 ) to the PGW ( 222 ,  322 ) via an ISW-enabled SGW ( 238 ,  338 ). This processing involves new GTP-based signaling between the TWAN ( 212 ,  312 ) and MME ( 234 ,  334 ) via the newly proposed “S1a-C” interface and a new user plane path between the TWAN ( 2312 ,  312 ) and SGW ( 238 ,  338 ) via the newly proposed “S1a-U” interface. 
     The MME ( 234 ,  334 ) is adapted to handle the new information elements provided in the extended GTP-C protocols over the S1a-C interface with the TWAN. 
     In an embodiment wherein the SGW and TWAG have been combined, the S1a-C interface terminates in the WLAN AN  310  function of the TWAN  312 . As such, the MME  334  processes any new information elements from the extended GTP-C signaling (e.g., UE MAC address, VLAN ID) in order to facilitate routing of packets between the UE  362  and SGW  338 . This information, along with possible access routing policies, are conveyed to the ISW-enabled SGW  338  via modified GTPv2-C signaling on the S11′ interface. In the scenario wherein the purpose or reason for the session request includes a “multi-connection” indication, the SGW  338  may perform IP flow mobility procedures based on the MME-provided policy as further described below. 
     SGW Extensions 
     The SGW ( 238 ,  338 ) has likewise been adapted to provide integrated small-cell and WiFi (ISW) capabilities. In particular, the SGW ( 238 ,  338 ) is adapted to process new ISW-related information provided by the MME ( 234 ,  334 ) via extended GTPv2-C signaling over the S11′ interface. 
     In an embodiment such as depicted in  FIG.  3   , where the S1a-U interface terminates in the WLAN AN  310  function of the TWAN  312 , the SGW  338  supports or provides some of the functionality that typically has been provided by the TWAG. In such embodiments, the SGW  338  processes any new information elements from the extended GTPv2-C signaling (e.g., UE MAC address, VLAN ID) in order to facilitate routing of packets between the PGW  332  and UE  362 . 
     In scenario where a session request signaled by the extended GTPv2-C signaling includes a “multi-connection” indication, the SGW  338  performs IP flow mobility procedures, possibly based on new access routing policies provided by the MME  334 . For instance, in an example embodiment, the SGW  338  policy may be configured to send downlink packets via the same access for which the corresponding uplink packets were received. In this case, the SGW  338  may associate the “5-tuple” for each uplink packet flow with the access network on which they were received (LTE or WiFi), and send the corresponding downlink packets via the same access. The 5-tuple consists of the Source IP Address, Source Port Number, Destination IP Address, Destination Port Number, and Transport Protocol Type (e.g., UDP, TCP). For example, if previous uplink UDP packets with source IP address=“a”, source port number=“b”, destination IP address=“x”, and destination port number=“y” were received via WiFi, subsequent downlink UDP packets with source IP address=“x”, source port number=“y”, destination IP address=“a”, and destination port number=“b” will also be sent via WiFi. Alternatively, the downlink packets may be sent via any available access independently from uplink packets. 
     HSS Extensions 
     In an example embodiment, the HSS ( 270 ,  370 ) is adapted to store information identifying that the MME ( 234 ,  334 ) and SGW ( 238 ,  338 ) are “ISW-enabled”. 
     UE Extensions 
     The UE ( 262 ,  362 ) is adapted to initiate attach, handover, and multi-connection requests based on ANDSF policies, ANQP information, local conditions, etc. With respect to providing simultaneous connectivity over multiple networks, i.e. TWAN and LTE, the UE is adapted to handle the mapping of IP packets to the appropriate Layer  2  interface, i.e., LTE or WiFi. 
     Integrated Small-Cell and WiFi (ISW) Processing 
     The system architectures described above in connection with  FIGS.  2  and  3    are adapted to provide inter-system mobility in integrated WLAN and LTE access networks. The disclosed example embodiments comprise a new “S1a-C” control plane interface ( 290 ,  390 ) between the MME ( 234 ,  334 ) and the TWAN ( 212 ,  312 ), and a new “S1a-U” user plane interface ( 292 ,  392 ) between SGW ( 238 ,  338 ) and TWAN ( 212 ,  312 ). With the S1a-C and S1a-U interfaces in place, the MME ( 234 ,  334 ) operates as a common control plane entity for both LTE access network ( 295 ,  395 ) and TWAN ( 212 ,  312 ) access, while the SGW ( 238 ,  338 ) operates as a user plane gateway for both LTE ( 295 ,  395 ) and TWAN ( 212 ,  312 ). 
       FIGS.  4 - 11    provide flow diagrams for example processing performed by the systems depicted in  FIGS.  2  and  3    in providing inter-system mobility. More particularly,  FIGS.  4 - 7    depict processing relating to a UE attaching to PDN through either a TWAN or LTE access network.  FIGS.  8  and  10    depict processing relating to handing over an existing communication connection between a UE and a PDN from one of the LTE access network or TWAN to the other.  FIGS.  9  and  11    depict processing relating to establishing two simultaneous communication paths, one via the LTE access network and one via the TWAN, between a UE and a packet network. 
     TWAN Connections via ISW-enabled TWAN, MME and SGW 
     The disclosed systems are adapted to establish a communication path to a PDN via a TWAN. In one embodiment of the disclosed systems and methods, the TWAN connection may be a “single-PDN” TWAN connection. In another embodiment, the TWAN connection may be a “multi-PDN” TWAN connection as used in SaMOG phase-2. 
     In an embodiment where the TWAN services a multi-PDN connection, separate “attach” and “PDN connection establishment” procedures are employed consistent with section 16 of 3GPP TS 23.402 v 12.3.0, the contents of which are hereby incorporated herein by reference. The “attach” procedures (attach, detach) are performed via extended EAP signaling while the “PDN connection” procedures (activation, deactivation) are performed by the SaMOG phase-2 WLAN Control Protocol (WLCP). 
     In addition to supporting standard SaMOG phase-2 capabilities (UE-initiated PDN connection, multiple PDN connections, concurrent NSWO and TWAN PDN connections, IP address preservation for seamless inter-system handover), the disclosed systems and methods are also adapted to support establishing TWAN to PDN connections via ISW-enabled MMEs and ISW-enabled SGWs. 
     Initial Attach via TWAN 
     Before a UE may communicate with a PDN or EPC, the UE must attach to the PDN or EPC. The disclosed systems and methods support attaching via the TWAN. The procedures for attaching may vary depending upon whether the TWAN supports a “single-PDN” or “multi-PDN” connection, or whether the TWAG functionality is located in the TWAN or the SGW. The disclosed systems and methods are adapted to support all such embodiments. Processing associated with attaching via the TWAN under various different conditions is described below in connection with  FIGS.  4 - 7   . 
     Initial TWAN attach with single-PDN connection capability via extended MME and combined SGW+TWAG 
       FIGS.  4 A-B  depict a flow diagram depicting example processing associated with a UE attaching to a PDN via a TWAN. More particularly, the processing corresponds to an example system embodiment such as is depicted in  FIG.  3    wherein the TWAN  312  supports a single-PDN connection  322  and wherein the TWAG functionality is located in the SGW  338 . In the processing depicted in  FIGS.  4 A-B , an ISW-enabled MME  334  and ISW-enabled combined SGW+TWAG  338  provide attachment to PDN gateway (PGW)  322  via TWAN  312 . During processing, the 3GPP AAA Server  318  provides the TWAN  312  with an indication that an ISW-enabled MME  334  may be used if available. The WLAN AN  310  exchanges control signaling directly with the MME  334 , while user plane traffic is exchanged directly between WLAN AN  310  and the combined SGW+TWAG  338 . 
     Anchoring the UE  362  on a combined SGW+TWAG  338  may provide benefits when the UE  362  requests a handover or an inter-system multi-connection to the same PDN. Allowing the MME  334  to control the TWAN connection via the ISW-enabled combined SGW+TWAG  338  enables the MME  334  to perform new inter-system mobility management functions thereby reducing the signaling load on the PGW  332 . 
     Referring to  FIG.  4 A , at step 0, as a preliminary matter, the transport network layer (TNL) connection is or previously has been established between TWAN  312  and MME  334  which may be performed using, for example, using OAM. In an example scenario, OAM procedures, such as TR-069, may be used to configure UDP over an IP transport network layer connection on the S1a-c interface between TWAN  312  and MME  334 . Also at step 0, the 3GPP AAA Server  318  is configured with and maintains information about the ISW-enabled MMEs  334 , ISW-enabled SGWs  338 , and ISW-enabled TWANs  312 . In previously existing systems, 3GPP AAA servers manage WLAN network access but do not manage or track MMEs and SGWs as they currently pertain to LTE access only. 
     Referring to  FIG.  4 A , at step 1, the UE  362  associates to a WiFi access point (AP) that is part of an operator&#39;s Trusted WLAN Access Network (TWAN)  312 . The association occurs via standard IEEE 802.11 procedures via the SWw interface  356 . The UE  362  may discover and attempt association with this WiFi AP based on pre-configured information, ANDSF policies, ANQP signaling, etc. In the scenario where the UE  362  has an existing PDN connection via LTE access, the requested connection results in multiple access PDN connectivity “MAPCON,” i.e., simultaneous use of cellular and WiFi access for PDN connectivity. 
     The attach-related processing may be initiated by the UE  362  via EAP per the current SaMOG phase-2 “single-PDN connection” solution. In this scenario, the attach procedure is combined with establishment of a PDN connection to the UE-specified APN, or to the default APN if none was specified by the UE  362 . 
     Referring again to  FIG.  4   , at step 2, an internal message triggered by the WLAN AN  310  within the TWAN  312  may initiate the authentication procedure via the Trusted WLAN AAA Proxy (TWAP)  364 . 
     At step 3, the UE  362  determines the type of connection that should be requested based on its capabilities. In the scenario depicted in  FIG.  4 A , it is assumed that a SaMOG phase-2 “single-PDN” connection type is requested. Also at step 3, the TWAN  312  identifies its capabilities such as, for example, its local/remote TWAG support, MME connectivity, etc. 
     At step 4, the TWAP 364 retrieves identity information from the UE  362  using standard EAPoL procedures over the SWw interface  356 . 
     At step 5, the TWAP 364 generates and transmits a Diameter-EAP-Request to the 3GPP AAA Server  318  over the STa interface  316 . The request may comprise any suitable information including, for example: mandatory information elements for User Identity, EAP Payload, Authentication Request Type, UE Layer  2  Address, Access Type, and Access Network Identity; conditional information elements for Mobility Capabilities; and optional information elements for Terminal Information and WLAN Identifier. 
     In an example scenario, the EAP Payload of the request may contain an indication of the UE&#39;s  362  “single-PDN” support per the SaMOG phase-2 solution described in 3GPP TR 23.852 v12.0.0, the contents of which are hereby incorporated by reference herein in its entirety. 
     In an example scenario, the request values for Access Type that may be included in the request may include “ISW-WLAN” for the case where the TWAN  312  supports integration with 3GPP access as described herein. In another scenario, the definition of the Access Network Identifier is extended to allow inclusion of the value “ISW-WLAN” as the Access Network ID (ANID) Prefix. 
     In an example scenario, Additional TWAN capabilities may be included in the request. For example, the request may specify support for local TWAG or remote combined TWAG+SGW along with a list of connected MMEs, if any. 
     Still further, in an example scenario, the request may include an optional Terminal Information element which includes additional information about the UE&#39;s ISW capability. The Terminal Information element may not be needed if all the relevant UE capability information is exchanged via extensions to the EAP payload. 
     Referring to  FIG.  4 A , at step 6, in the situation the 3GPP AAA Server  318  requires additional information about the subscriber such as, for example, previous connectivity status, it retrieves this information from the HSS  370  using the Diameter protocol on the SWx interface  380 . 
     At step 7, using the information regarding the ISW-enabled SGWs and TWAN that was provided in the request or retrieved from HSS, the 3GPP AAA Server  318  determines to allow the TWAN  312  to utilize its S1a-C connection  392  with the MME  334  for establishment of the PDN connection. 
     At step 8, the 3GPP AAA Server  318  generates and transmits the Diameter-EAP-Answer to the TWAP 364 over the STa interface  316  including an indication allowing for PDN connection establishment via the ISW-enabled MME  334 . 
     At step 9, the TWAP 364 generates and transmits an internal message to the WLAN AN  310  informing it to set up a GTP tunnel with an SGW  338  via the ISW-enabled MME  334 . 
     At step 10 shown on  FIG.  4 B , the WLAN AN  310  sends a GTP-C Create Session Request message to the ISW-enable MME  334  over the S1a-C interface  390 . The message may comprise, for example, APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc. 
     A step 11, the MME  334  sends the Create Session Request message to the selected SGW  338  via the S11′ (“prime”) interface  374  which has been modified or extended to support the communications between MME  334  and SGW  338  as described herein. In an example scenario, the MME  334  chooses the combined ISW-enabled SGW+TWAG  338 . In an alternative scenario, such as one described in connection with  FIG.  2   , the MME may select a TWAG located within TWAN  312 . 
     Referring to step 12 of  FIG.  4 B , the combined SGW+TWAG  338  uses the received information to select the PGW  322 . The SGW+TWAG  338  transmits a GTP-C Create Session Request message to the selected PGW  322  over the S5 interface  340 . 
     At step 13, if dynamic policy and charging control (PCC) is implemented, the PGW  322  communicates the session establishment to the Policy and Charging Rules Function (PCRF)  394  in order to retrieve the QoS and charging rules. The PGW  322  enforces these rules as needed. If dynamic PCC is not implemented, such rules may be pre-configured in the PGW  322 . 
     At step 14, the PGW  322  uses the S6b interface  396  to update the 3GPP AAA Server  318  with the associated PGW  322  connectivity information for the UE  362 . In addition, it also provides the associated information for the combined SGW+TWAN  338 . The 3GPP AAA Server  318  subsequently updates the Home Subscriber System (HSS)  370  with this information via the SWx interface  380 . 
     At step 15, the PGW  322  generates and transmits a GTP-C Create Session Response message to the SGW  338  over the S5 interface  340 . The response message comprises any information that is needed for further processing including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. The GTP tunnel between the PGW  322  and SGW  338  is thereby established. 
     At step 16, the SGW  338  transmits the GTP-C Create Session Response message to the MME  334  over the modified S11′ (“prime”) interface  374 . The message comprises any information needed for further processing including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. 
     At step 17, the MME  334  transmits the GTP-C Create Session Response message to the WLAN AN  310  over the S1a-C interface  390 . The message comprises any suitable information including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. 
     At step 18, the WLAN AN  310  generates and transmits an internal message to the TWAP 364 informing it that the S1a-U  392  bearer has been successfully established. 
     At step 19, the TWAP 364 communicates the completion of the attach procedure to the UE  362  via an EAP Success indication in the EAPoL message transmitted over the SWw interface  356 . 
     At step 20, the UE  362  may receive its IPv4 address from the WLAN AN  310  via DHCPv4. The WLAN AN  310  provides the UE  362  with its IP address as previously delivered in the GTP-C Create Session Response. Thereafter, the WLAN AN  310  routes packets between UE  362  and PGW  322  via the ISW-enabled combined SGW+TWAG  338 . 
     Initial TWAN attach with single-PDN connection capability via extended MME, standalone TWAG and standalone SGW 
     In the example architecture of  FIG.  2   , the TWAG  260  is located in the TWAN  212  rather than in the SGW as in  FIG.  3   .  FIGS.  5 A-B  provide a flow diagram depicting example processing associated with a UE attaching to a PDN via a TWAN in a system such as depicted in  FIG.  2   . More particularly,  FIGS.  5 A-B  depict processing in an example system embodiment wherein the TWAN  212  supports a single-PDN connection  222  and wherein the TWAG functionality is located in the TWAN  212 . TWAG functionality in this embodiment is analogous to the HeNB Gateway function in LTE access networks. Namely the TWAG  260  carries control plane signaling between the WLAN AN  210  and MME  234 , and user plane traffic between the WLAN AN  210  and SGW  238 . 
     Referring to  FIG.  5 A , at step 0, as a preliminary matter, the transport network layer (TNL) connection is, or previously has been, established between TWAN  212  and MME  234  which may be performed using, for example, using OAM. The 3GPP AAA Server  218  is configured with and maintains information about the ISW-enabled MMEs  234 , ISW-enabled SGWs  238 , and ISW-enabled TWANs  212 . 
     Referring to  FIG.  5 A , at step 1, the UE  262  associates to a WiFi access point (AP) that is part of an operator&#39;s Trusted WLAN Access Network (TWAN)  212 . The association occurs via standard IEEE 802.11 procedures via the SWw interface  256 . The UE  262  may discover and attempt association with this WiFi AP based on pre-configured information, ANDSF policies, ANQP signaling, etc. In the scenario where the UE  262  has an existing PDN connection via LTE access, the requested results in multiple access PDN connectivity “MAPCON,” i.e., simultaneous use of cellular and WiFi access for PDN connectivity. 
     The attach-related processing may be initiated by the UE  262  via EAP per the current SaMOG phase-2 “single-PDN connection” solution. In this scenario, the attach procedure is combined with establishment of a PDN connection to the UE-specified APN, or to the default APN if none was specified by the UE  262 . 
     Referring again to  FIG.  5 A , at step 2, an internal message triggered by the WLAN AN  310  within the TWAN  212  may initiate the authentication procedure via the Trusted WLAN AAA Proxy (TWAP)  264 . 
     At step 3, the UE  262  determines the type of connection that should be requested based on its capabilities. In the scenario depicted in  FIG.  5 A , it is assumed that a SaMOG phase-2 “single-PDN” connection type is requested. Also at step 3, the TWAN  212  identifies its capabilities such as, for example, its local/remote TWAG support, MME connectivity, etc. 
     At step 4, the TWAP 264 retrieves identity information from the UE  262  using standard EAPoL procedures over the SWw interface  256 . 
     At step 5, the TWAP 264 generates and transmits a Diameter-EAP-Request to the 3GPP AAA Server  218  over the STa interface  216 . The request may comprise any suitable information including, for example: mandatory information elements for User Identity such as EAP Payload, Authentication Request Type, UE Layer  2  Address, Access Type, and Access Network Identity; conditional information elements for Mobility Capabilities; and optional information elements for Terminal Information and WLAN Identifier. 
     In an example scenario, the EAP Payload of the request may contain an indication of the UE&#39;s  362  “single-PDN” support per the SaMOG phase-2 solution described in 3GPP TR 23.852 v 12.0.0. 
     In an example scenario, the request values for Access Type that may be included in the request may include “ISW-WLAN” for the case where the TWAN  212  supports integration with 3GPP access as described herein. In another scenario, the definition of the Access Network Identifier is also extended to allow inclusion of the value “ISW-WLAN” as the Access Network ID (ANID) Prefix. 
     In an example scenario, Additional TWAN capabilities may be included in the request. For example, the request may specify support for local TWAG or remote TWAG+SGW along with a list of connected MMEs, if any. 
     Still further, in an example scenario, the request may include an optional Terminal Information element which includes additional information about the UE&#39;s ISW capability. The Terminal Information element may not be needed if all the relevant UE capability information is exchanged via extensions to the EAP payload. 
     Referring to  FIG.  5 A , at step 6, in the situation the 3GPP AAA Server  218  requires additional information about the subscriber such as, for example, previous connectivity status, it retrieves this information from the HSS  270  using the Diameter protocol on the SWx interface  280 . 
     At step 7, using the information regarding the ISW-enabled SGWs and TWAN that was provided in the request or retrieved from HSS, the 3GPP AAA Server  218  determines to allow the TWAN  212  to utilize its S1a-C connection  290  with the MME  234  for establishment of the PDN connection. 
     At step 8, the 3GPP AAA Server  218  generates and transmits the Diameter-EAP-Answer to the TWAP 264 over the STa interface  216  including an indication allowing for PDN connection establishment via the ISW-enabled MME  234 . 
     At step 9, the TWAP 264 generates and transmits an internal message to the Trusted WLAN Access Gateway (TWAG)  260  informing it to set up a GTP tunnel with an SGW  238  via the ISW-enabled MME  234 . 
     At step 10, the TWAG  260  sends a GTP-C Create Session Request message to the ISW-enabled MME  234  over the S1a-C interface  290 . The message may comprise, for example, information specifying APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc. 
     At step 11, the MME  234  transmits the Create Session Request message to the selected SGW  238  via the modified S11′ (“prime”) interface  274  which has been modified or extended to support the communications between MME  234  and SGW  238  as described herein. 
     At step 12, the SGW  238  uses the received information to select the PGW  222 . The SGW  238  transmits a GTP-C Create Session Request message to the selected PGW  222  over the S5 interface  240 . 
     At step 13, if dynamic policy and charging control (PCC) is implemented, the PGW  222  communicates the session establishment to the Policy and Charging Rules Function (PCRF)  294  in order to retrieve the QoS and charging rules. The PGW  222  enforces these rules as needed. If dynamic PCC is not implemented, such rules may be pre-configured in the PGW  222 . 
     At step 14, the PGW  222  uses the S6b interface to update the 3GPP AAA Server  218  with the associated PGW  222  connectivity information for the UE  262 . In addition, it also provides the associated SGW information. The 3GPP AAA Server  218  subsequently updates the Home Subscriber System (HSS)  270  with this information via the SWx interface  280 . 
     At step 15, the PGW  222  sends the GTP-C Create Session Response message to the SGW  238  over the S5 interface  240 . The response message comprises any information that is needed for further processing including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. The GTP tunnel between the PGW  222  and SGW  238  is thereby established. 
     At step 16, the SGW  238  transmits the GTP-C Create Session Response message to the MME  234  over the modified S11′ (“prime”) interface  274 . The message comprises any information needed for further processing including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. 
     At step 17, the MME  234  transmits the GTP-C Create Session Response message to the TWAG  260  over the S1a-C interface  290 . The message comprises any suitable information including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. 
     At step 18, the TWAG  238  generates and transmits an internal message to the TWAP 264 informing it that the S1a-U  292  bearer has been successfully established. 
     At step 19, the TWAP 264 communicates completion of the attach procedure to the UE  262  via the EAP Success indication in the EAPoL message over the SWw interface  2566 . 
     At step 20, the UE  262  may receive its IPv4 address from the TWAG  260  via DHCPv4. The TWAG  260  provides the UE  262  with its IP address as previously delivered in the GTP-C Create Session Response. Thereafter, the TWAG  260  routes packets between UE  262  and PGW  222  via SGW  238 . 
     Initial TWAN attach with multi-PDN connection capability via extended MME and combined SGW+TWAG 
     In the processing depicted in  FIGS.  4  and  5   , the TWAN was understood to provide “single-PDN” connectivity. According to another aspect of the disclosed embodiments, the systems for integrated system processing also accommodate TWANs that provide “multi-PDN” connections.  FIGS.  6 A-B  depict example processing related to a UE attaching to a PDN via a TWAN that supports multi-PDN connectivity. In the example processing of  FIGS.  6 A-B , it is presumed that the TWAG functionality has been located in the SGW as depicted in  FIG.  3   . 
     In connection with  FIGS.  6 A-B , the processing involves an initial attach, and subsequently initiating a PDN connection using the extended WLCP signaling between the UE  362  and the TWAN  312 . An ISW-enabled MME  334  and ISW-enabled SGW+TWAG  338  provide attachment to PDN gateway (PGW)  322  via TWAN  312 . During processing, the 3GPP AAA Server  318  provides the TWAN  312  with an indication that an ISW-enabled MME  334  may be used if available. 
     Referring to  FIG.  6 A , at step 0, as a preliminary matter, the transport network layer (TNL) connection is or previously has been established between TWAN  312  and MME  334  which may be performed using, for example, OAM. The 3GPP AAA Server  318  is configured with maintains information about the ISW-enabled MMEs  334 , ISW-enabled SGWs  338 , and ISW-enabled TWANs  312 . 
     Referring to  FIG.  6 A , at step 1, the UE  362  associates to a WiFi access point (AP) that is part of an operator&#39;s Trusted WLAN Access Network (TWAN)  312 . The association occurs via standard IEEE 802.11 procedures via the SWw interface  356 . The UE  362  may discover and attempt association with this WiFi AP based on pre-configured information, ANDSF policies, ANQP signaling, etc. In the scenario where the UE  362  has an existing PDN connection via LTE access, the requested results in multiple access PDN connectivity “MAPCON,” i.e., simultaneous use of cellular and WiFi access for PDN connectivity. 
     At step 2, the EAP authentication is performed. The processing is substantially the same as described above in connection with steps 2-8 of  FIG.  4 A  with the exception that in the scenario associated with  FIG.  6 A , the EAP Payload may contain an indication of the UE&#39;s “multi-PDN” TWAN capability as per the SaMOG phase-2 solution described in 3GPP TR 23.852 v 12.0.0. 
     At step 3, and after the UE  362  has attached to the TWAN  312 , the UE  362  requests a PDN Connection from the WLAN AN  310  via the SaMOG phase-2 “WLAN Control Protocol” (WLCP). In the example processing depicted in  FIG.  6 A , the UE  362  requests connection to a PDN to which the UE  362  is not currently connected. 
     At step 4, the WLAN AN  310  generates and transmits a GTP-C Create Session Request message to the selected MME  334  over S1a-C interface  390 . 
     At step 5, the MME  334  transmits a GTP-C Create Session Request message to the SGW over the S11′ (“prime”) interface  374 . The message may comprise any suitable information that is need for further processing. In an example embodiment, the message may comprise, for example, an APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc. 
     At step 6, the SGW  338  transmits the GTP-C Create Session Request message to the selected PGW  322  over the S5 interface  340 . 
     At step 7, if dynamic policy and charging control (PCC) is implemented, the PGW  322  communicates the session establishment to the Policy and Charging Rules Function (PCRF)  394  in order to retrieve the QoS and charging rules. The PGW  322  enforces these rules as needed. If dynamic PCC is not implemented, such rules may be pre-configured in the PGW  322 . 
     At step 8 depicted on  FIGS.  6 A-B , the PGW  322  uses the S6b interface  396  to update the 3GPP AAA Server  318  with the associated PGW connectivity information for the UE  362 . In addition, it provides the associated SGW information. The 3GPP AAA Server  318  subsequently updates the Home Subscriber System (HSS)  370  with this information via the SWx interface  380 . 
     At step 9 of  FIG.  6 B , the PGW  322  generates and transmits a GTP-C Create Session Response message to the SGW  338  over the S5 interface  340 . The response message comprises any suitable information that is needed for further processing, including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. The GTP tunnel between the PGW  322  and SGW  338  is thereby established. 
     At step 10, the SGW  338  transmits the GTP-C Create Session Response message to the MME  334  over the modified S11′ (“prime”) interface  374 . 
     At step 11, the MME  334  transmits the GTP-C Create Session Response message to the WLAN AN  310  over the S1a-C interface  390 . The message comprises any suitable information including, for example, GTP tunnel information, bearer parameters, and the allocated UE IP address. 
     At step 12, the WLAN AN  310  communicates the successful PDN Connection establishment to the UE  362  via the WLCP protocol over the SWw interface  356 . 
     At step 13, if the UE  362  did not receive its IPv4 address in the previous step, it may receive the IPv4 address from the WLAN AN  310  via DHCPv4. The TWAG  338  can now route packets between the UE  362  and PGW  322  via the combine SGW+TWAG  338 . 
     Initial TWAN attach with multi-PDN connection capability via extended MME and standalone SGW 
     In the example embodiment of  FIG.  2   , the TWAG  260  is located in the TWAN  212  rather than in the SGW as in  FIG.  3   .  FIGS.  7 A-B  depict a flow diagram depicting example processing associated with a UE attaching to a PDN via a TWAN in a system such as depicted in  FIG.  2    wherein the TWAN has multi-PDN connectivity. More particularly,  FIGS.  7 A-B  depict processing in an example system embodiment wherein the TWAN  212  supports a multi-PDN connection and wherein the TWAG functionality is located in the TWAN  212 . 
     It will be appreciated that this scenario consists of two separate procedures: one for the initial attach using EAP extensions, and one for subsequent PDN connection(s) using the extended WLCP signaling between the UE and TWAN. In this particular example, it is understood that the TWAN consists of a WLAN AN, TWAP and TWAG. 
     Referring to  FIG.  7 A , at step 0, as a preliminary matter, the transport network layer (TNL) connection is or previously has been established between TWAN  212  and MME  234 . The 3GPP AAA Server  218  is configured with and maintains information about the ISW-enabled MMEs  234 , ISW-enabled SGWs  238 , and ISW-enabled TWANs  212 . 
     Referring to  FIG.  7 A , at step 1, the UE  262  associates with a WiFi access point (AP) that is part of an operator&#39;s Trusted WLAN Access Network (TWAN)  212 . The association occurs via standard IEEE 802.11 procedures via the SWw interface  256 . The UE  262  may discover and attempt association with this WiFi AP based on pre-configured information, ANDSF policies, ANQP signaling, etc. In the scenario where the UE  262  has an existing PDN connection via LTE access, the requested results in multiple access PDN connectivity “MAPCON,” i.e., simultaneous use of cellular and WiFi access for PDN connectivity. 
     At step 2, the EAP authentication is performed. The processing is substantially the same as described above in connection with steps 2-8 of  FIG.  5 A  with the exception that in the scenario associated with  FIG.  7 A , the EAP Payload may contain an indication of the UE&#39;s “multi-PDN” TWAN capability as per the SaMOG phase-2 solution described in 3GPP TR 23.852 v 12.0.0. 
     At step 3, the UE  262  requests a PDN Connection via the SaMOG phase-2 “WLAN Control Protocol” (WLCP). For this example scenario, it is understood that the UE  262  requests connection to a PDN to which it is not currently connected. 
     At step 4, the WLAN AN  210  function in the TWAN  212  forwards the PDN Connection Request to the TWAG  260 . 
     At step 5, the TWAG  260  sends a GTP-C Create Session Request message to the selected MME  234  over the S1a-C interface  290 . 
     At step 6, the MME  260  transmits a GTP-C Create Session Request message to the SGW  238  over the S11′ (“prime”) interface  274 . The message comprises any suitable information needed for further processing including, for example, an APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc. 
     At step 7, the SGW  238  transmits a GTP-C Create Session Request message to the selected PGW  222  over the S5 interface  240 . 
     At step 8, if dynamic policy and charging control (PCC) is implemented, the PGW  222  communicates the session establishment to the Policy and Charging Rules Function (PCRF)  294  in order to retrieve the QoS and charging rules. The PGW  222  enforces these rules as needed. If dynamic PCC is not implemented, such rules may be pre-configured in the PGW  222 . 
     At step 9 of  FIG.  7 A , the PGW  222  uses the S6b interface  396  to update the 3GPP AAA Server  218  with the associated PGW connectivity information for the UE  262 . In addition, it also provides the associated SGW information. The 3GPP AAA Server  218  subsequently updates the Home Subscriber System (HSS)  270  with this information via the SWx interface  280 . 
     At step 10 shown on  FIG.  7 B , the PGW  222  generates and transmits the GTP-C Create Session Response message to the SGW over the S5 interface including GTP tunnel information, bearer parameters, and the allocated UE IP address. The GTP tunnel between the PGW  222  and SGW  238  is thereby established. 
     At step 11, the SGW  238  transmits the GTP-C Create Session Response message to the MME  234  over the S11′ (“prime”) interface  274 . 
     At step 12, the MME  234  transmits the GTP-C Create Session Response message to the TWAG  260  over the S1a-C interface  290 . The message includes GTP tunnel information, bearer parameters, and the allocated UE IP address. 
     At step 13, the TWAG  260  generates and transmits an internal message to the WLAN AN  210  informing it that the S1a-U  292  bearer has been successfully established. 
     At step 14, the WLAN AN  210  communicates the successful PDN Connection establishment to the UE  262  via the WLCP protocol over the SWw interface  256 . 
     At step 15, if the UE  262  did not receive its IPv4 address in the previous step, it may receive the IPv4 address from the TWAG  260  via DHCPv4. The TWAG  260  can now route packets between the UE  262  and PGW  222  via the SGW  238 . 
     Intra-MME/Intra-SGW Handover from LTE to TWAN 
     The processing described above in connection with  FIGS.  4 - 7    relates to various scenarios whereby a UE attaches to a PDN via a TWAN. In the instance where a UE has attached to a PDN, it may be useful to hand over a connection to the PDN to another of the wireless access networks, i.e. WiFi and cellular LTE. For example, where a UE has an established connection to a PDN via cellular LTE, the UE may wish to hand over the communication to the PDN to a WLAN connection that the UE has with the PDN. Alternatively, where a UE is connected to a PDN through both a WLAN and cellular connection, the UE may wish to hand over the communication received on the WLAN to the cellular connection. 
       FIGS.  8 A-C  depict example processing associated with handing over a communication path from an existing LTE connection to a WLAN connection. The UE attaches via TWAN to establish a connection to a PDN to which it was already connected via LTE. 
     In the example scenario of  FIGS.  8 A-C , the source (H)eNB LTE access network and target TWAN are both controlled by the same ISW-enabled MME  234  and served by the same standalone ISW-enabled SGW  238 . Once the TWAN connection is established, the UE  264  releases the associated LTE connection thereby completing a handover from LTE to TWAN. 
     In the example processing depicted in  FIGS.  8 A-C , the TWAN is understood to have a multi-PDN connection. It will be appreciated that similar processing may be performed in connection with a TWAN that provides single-PDN connectivity. 
     Referring to  FIG.  8 A , at step 0, as a preliminary matter, the transport network layer (TNL) connection is or previously has been established between TWAN  212  and MME  234  which may be performed using, for example, OAM. The 3GPP AAA Server  218  is configured with and maintains information about the ISW-enabled MMEs  234 , ISW-enabled SGWs  238 , and ISW-enabled TWANs  212 . 
     At step 1, the UE  262  uses its established connection via an (H)eNB LTE access network  295  to a PDN through the PGW  222  via an ISW-enabled SGW  238 . In an example scenario, the connection may consist of a concatenation of the following: an LTE radio bearer over the Uu interface  297  between the UE  262  and (H)eNB  295 ; a GTP tunnel over the  51  interface  298  between the (H)eNB  295  and SGW  238 ; and a GTP tunnel over the S5 interface  240  between the SGW  238  and PGW  222 . 
     At step 2, the UE  262  discovers a WiFi AP belonging to the operator&#39;s TWAN  212  and determines to hand over an existing PDN connection from the (H)eNB  295  to the TWAN  212 . The UE  262  may discover and attempt association with this WiFi AP based on pre-configured information, ANDSF policies, ANQP signaling, etc. 
     At step 3, the UE  262  associates to the WiFi access point (AP). Association occurs via standard IEEE 802.11 procedures via the SWw interface. 
     At step 4 of  FIG.  8 A , EAP authentication is performed similar to steps 2-8 described above in connection with  FIG.  5    with the exception that in the processing of  FIG.  8   , the EAP Payload may contain an indication of the UE&#39;s “multi-PDN” support per the SaMOG phase-2 solution described in 3GPP TR 23.852 v 12.0.0. 
     At step 5 shown on  FIG.  8 B , the UE  262  requests a PDN Connection via the SaMOG phase-2 WLAN Control Protocol (WLCP). The request comprises any information needed for further processing including, for example, the APN for the current PDN connection existing over LTE. 
     At step 6, the WLAN AN  210  function in the TWAN  212  forwards the PDN Connection Request to the TWAG  260 . 
     At step 7, the TWAG  260  generates and transmits a GTP-C Create Session Request message to the ISW-enabled MME  234  over the S1a-C interface  290 . The message comprises any information that is need for further processing including, for example, an APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc.), along with the “handover” indication. 
     At step 8, the MME  234  transmits a GTP-C Create Session Request message to the SGW over the modified S11′ (“prime”) interface. The message comprises any suitable information needed for further processing including, for example, an APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc.), along with the “handover” indication. 
     At step 9, the SGW  238  transmits a Create Session Request with “Handover” Indication for the existing APN to the PGW  222 . The example processing of  FIG.  8    involves intra-SGW handover over an existing PDN connection. Accordingly, the same PGW  222  is used for both the LTE and WLAN connections. Therefore, when the PGW  222  sees the Create Session Request message with the “Handover” indication, the PGW  222  uses the existing GTP tunnel rather than create a new one with the SGW  238 . The main effect of this message is to allow the PGW  222  to notify the PCRF  294  of the change in access such that the appropriate policy and charging takes place. 
     At step 10, if dynamic policy and charging control (PCC) is implemented, the PGW  222  communicates the session establishment to the Policy and Charging Rules Function (PCRF)  294  in order to retrieve the QoS and charging rules. Since the “Handover” Indication is included, the PGW  222  executes a PCEF-initiated IP-CAN Session Modification Procedure with the PCRF  294  to obtain the policy and charging rules to be enforced. The PGW  222  enforces these rules as needed. If dynamic PCC is not implemented, such rules may be pre-configured in the PGW  222 . 
     At step 11, the PGW  222  uses the S6b interface  296  to update the 3GPP AAA Server  218  with the associated PGW  222  connectivity information for the UE  262 . In addition, the PGW  222  provides the associated SGW information. The 3GPP AAA Server  218  subsequently updates the Home Subscriber System (HSS)  270  with this information via the SWx interface  280 . 
     At step 12, the PGW  222  generates and transmits a GTP-C Create Session Response message to the SGW  238  over the S5 interface  240  including GTP tunnel information, bearer parameters, and the allocated UE IP address. The message further comprises the previously allocated IP address for the UE. The GTP tunnel between the PGW  222  and SGW  238  is thereby established. 
     At step 13, the SGW  238  transmits the GTP-C Create Session Response message to the MME  234  over the S11′ interface  274 . The message comprises any suitable information needed for further processing including, for example, GTP tunnel information, bearer parameters, and the previously allocated IP address for the UE. 
     At step 14 of  FIG.  8 B , the MME  234  transmits the GTP-C Create Session Response message to the TWAG  260  over the S1a-C interface  290 . The message comprises any suitable information needed for further processing including, for example, GTP tunnel information, bearer parameters, and the previously allocated IP address for the UE. 
     At step 15 shown on  FIG.  8 C , the TWAG  260  function in the TWAN  212  transmits the PDN Connection Response to the WLAN AN  210 . 
     At step 16, the WLAN AN  210  communicates the successful PDN Connection establishment to the UE  262  via the WLCP protocol over the SWw interface  256 . 
     At step 17, the TWAG  260  is able to route packets between the UE  262  and PGW  222  via the SGW  238 . 
     At step 18, the UE  262  initiates release of the 3GPP EPS bearer. In other words, the UE  262  drops use of the LTE connection. 
     At step 19, the UE  262  and SGW  238  transmit and receive associated PDN packets exclusively via the TWAG  260 . 
     Intra-MME/Intra-SGW Multi-connection Attach via TWAN 
     According to another aspect of the disclosed systems and methods, a UE may maintain multiple connections to a PDN. For example, a UE may maintain a first connection to the PDN via WiFi (i.e., TWAN) and a second connection to the same PDN via an LTE access network. Multi-connection attachments may be implemented in embodiments of the disclosed systems incorporating “single-PDN” and “multi-PDN” TWAN connections and wherein the architectures include a local TWAG or a remote SGW+TWAG combination.  FIGS.  9 A-C  depict example processing performed in connection with establishing a multi-connection. It is understood that the processing is performed in an architecture featuring a multi-PDN TWAN connection and a local TWAG. It will be appreciated that the concepts described in connection with  FIGS.  9 A-C  may be applied to other scenarios such as, for example, where the TWAN is a single-PDN TWAN and/or the TWAG is combined in an SGW. 
     In a multi-connection attachment scenario, an ISW-enabled MME  234  and ISW-enabled SGW  238  are already serving the UE  262  via an LTE connection to a particular PDN. Once the TWAN connection is established to the same PDN, the UE  262  maintains both connections and assigns transmission of specific uplink IP traffic flows to either the TWAN or LTE access depending on locally stored policies, signal conditions, etc. Although the access can change on a packet-by-packet basis, it is expected that a specific access will typically be used for a stable period of time as long as conditions allow. The SGW  238  keeps track of the access for received uplink IP packets and may transmit the associated downlink packets (e.g., based on corresponding 5-tuple) via the same access. Alternatively, the SGW  238  may send downlink packets over either access based on its own criteria, e.g., for load balancing, etc. 
     Referring to  FIG.  9 A , at step 0, as a preliminary matter the transport network layer (TNL) connection has been established between TWAN  212  and MME  234  which may be performed using, for example, OAM. The 3GPP AAA Server  218  maintains information about the ISW-enabled MMEs  234 , ISW-enabled SGWs  238 , and ISW-enabled TWANs  212 . 
     At step 1, the UE  262  uses its established connection via an (H)eNB LTE access network  295  to a PDN through the PGW  222  via an ISW enabled MME  234  and an ISW-enabled SGW  238 . In an example scenario, the connection may consist of a concatenation of the following: an LTE radio bearer over the Uu interface  297  between the UE  262  and (H)eNB  295 ; a GTP tunnel over the  51  interface  298  between the (H)eNB  295  and SGW  238 ; and a GTP tunnel over the S5 interface  240  between the SGW  238  and PGW  222 . 
     At step 2, the UE  262  discovers a WiFi AP belonging to the operator&#39;s TWAN  212  and determines to establish a multi-access connection to the existing PDN. The UE  262  may discover and attempt association with this WiFi AP based on pre-configured information, ANDSF policies, ANQP signaling, etc. The UE  262  may determine to initiate the multi-access PDN connection based on local policies and conditions (e.g., signal strength, perceived congestion, battery power, etc.). 
     At step 3, the UE  262  associates to a WiFi access point (AP) that is part of the operator&#39;s Trusted WLAN Access Network (TWAN)  212 . In an example embodiment, association may occur via standard IEEE 802.11 procedures via the SWw interface  256 . 
     At step 4, which is shown on  FIG.  9 B , EAP authentication is performed similar to steps 2-8 described above in connection with  FIG.  5    with the exception that in the processing of  FIG.  9   , the EAP Payload may contain an indication of the UE&#39;s “multi-PDN” support per the SaMOG phase-2 solution described in 3GPP TR 23.852 v 12.0.0. 
     At step 5, the UE  262  requests a PDN Connection via the SaMOG phase-2 WLAN Control Protocol (WLCP). The request comprises any information that is needed for further processing including, for example, the APN for the same PDN accessed via the existing LTE connection. The request may further comprise a “Multi-connection” indicator which allows the network to assign the same IP address for the UE access to the PDN through the TWAN as is being used for access through the LTE access network  295 . 
     At step 6, the WLAN AN  210  function in the TWAN  212  forwards the PDN Connection Request to the TWAG  260 . 
     At step 7, the TWAG  260  generates and transmits a GTP-C Create Session Request message to the ISW-enabled MME  234  over the S1a-C interface  290 . The message comprises any information that is need in further processing including, for example, a multi-connection indication, an APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc. 
     At step 8, the MME  234  transmits a GTP-C Create Session Request message to the SGW  238  over the S11′ (“prime”) interface  274 . The message comprises any information that is need in further processing including, for example, a multi-connection indication, an APN, IMSI, RAT type (e.g., ISW-WLAN), BSSID, SSID, etc. 
     At step 9, the SGW  238  transmits a Create Session Request with “Multi-connection” indication for the existing APN to the PGW  222 . The example processing of  FIG.  9    involves intra-SGW multi-connection attachment over an existing PDN connection. Accordingly, the same PGW  222  is used for both the LTE and WLAN connections. Therefore, when the PGW  222  identifies the Create Session Request message with the “Multi-connection” indication, the PGW  222  uses the existing SGW GTP tunnel rather than create a new one with the SGW  238 . One effect of this message is to allow the PGW  222  to notify the PCRF  294  of the additional TWAN  212  access such that the appropriate policy and charging takes place. 
     At step 10, if dynamic policy and charging control (PCC) is implemented, the PGW  222  indicates the TWAN session establishment to the Policy and Charging Rules Function (PCRF)  294  in order to retrieve the QoS and charging rules. Since the “Multi-connection” indication is included, the PGW  222  executes a PCEF-initiated IP-CAN Session Modification Procedure with the PCRF  294  to obtain the policy and charging rules to be enforced. The PGW  222  enforces these rules as needed. If dynamic PCC is not implemented, such rules may be pre-configured in the PGW  222 . 
     At step 11, the PGW  222  uses the S6b interface  296  to update the 3GPP AAA Server  218  with the associated PGW connectivity information for the UE  262 . In addition, the PGW  222  provides the associated SGW address and multi-connection information. The 3GPP AAA Server  218  subsequently updates the Home Subscriber System (HSS)  270  with this information via the SWx interface  280 . 
     At step 12, the PGW  222  generates and transmits a GTP-C Create Session Response message to the SGW  238  over the S5 interface  240  including GTP tunnel information, bearer parameters, and the allocated UE IP address. This message further comprises the previously allocated IP address for the UE. 
     At step 13, the SGW  238  transmits the GTP-C Create Session Response message to the MME over the S11′ interface  274 . The message comprises any suitable information needed for further processing including, for example, GTP tunnel information, bearer parameters, and the previously allocated IP address for the UE. 
     At step 14, the MME  234  transmits the GTP-C Create Session Response message to the TWAG  260  over the S1a-C interface  290 . The message comprises any suitable information including, for example, GTP tunnel information, bearer parameters, and the previously allocated IP address for the UE 
     At step 15, which is shown on  FIG.  9 C , the TWAG  260  in the TWAN  212  forwards the PDN Connection Response to the WLAN AN  210 . 
     At step 16, the WLAN AN  210  communicates the successful PDN Connection establishment to the UE  262  via the WLCP protocol over the SWw interface  256 . 
     At step 17, the TWAG  260  is able to route packets between the UE  262  and PGW  222  via the SGW  238 . 
     At step 18, the UE  262  may route packets via ISW-SGW  238  to the PDN over either TWAN  212  or the (H)eNB LTE access network  295 . Likewise, the SGW  238  may route packets to the UE  262  over either TWAN  212  or the (H)eNB LTE access network  295 . 
     LTE (H)eNB Connections via ISW-enabled MME and SGW 
     The above discussions in connection with  FIGS.  4 - 9    have focused primarily on connections to a PDN that have been initiated via a TWAN. The disclosed systems and methods apply as well, however, to connections initiated via an LTE access network. 
     Initial Attach via LTE (H)eNB 
     In the disclosed systems and methods, an initial attach via an LTE (H)eNB network is performed substantially as defined in existing 3GPP standards. An initial attach via (H)eNB utilizes the standard MME  234  and SGW  238  baseline EPC architecture and protocols. However, in the disclosed systems and methods for integrated small cell and WiFi access, one deviation from existing processing is the ability of the MME  234  to assign an ISW-enabled SGW  238  for initial LTE access. The MME  234  is made aware of this information as part of the extended information provided by the HSS  270  via the S6a interface. 
     Intra-SGW Handover from TWAN to LTE 
     A process for intra-SGW handover from an LTE connection to TWAN connection is described above in connection with  FIG.  8   . The disclosed systems and methods are likewise adapted to support handovers from a TWAN connection to an LTE connection.  FIGS.  10 A-B  depict example processing performed in connection with a handover procedure from a TWAN connection to an LTE connection. 
     With respect to intra-system LTE handover, existing 3GPP standards support two forms of intra-system handover: S1-based handover; and X2-based handover. In case different SGWs are serving the source and target eNBs, the required SGW “relocation” procedure is also specified. All intra-LTE handovers are network-initiated, usually based on UE measurements reported to the network. 
     With respect to inter-system LTE handover, per existing 3GPP standards, all inter-system handovers are initiated by the UE. Handovers are likewise initiated by the UE in connection with the systems and methods for inter system integration disclosed herein. However, pursuant to the presently disclosed systems and methods, and in contrast with the existing methodologies, inter-system LTE/WiFi handovers employ an S1a interface defined between the MME and WLAN. 
       FIGS.  10 A-B  depict example processing performed in connection with a handover procedure from a TWAN connection to an LTE connection. Handover processing may be implemented in embodiments of the disclosed systems incorporating “single-PDN” and “multi-PDN” TWAN connections and wherein the architectures include a local TWAG or a remote SGW+TWAG combination. For the purposes of the process depicted in  FIGS.  10 A-B , it is understood that the processing is performed in an architecture featuring a multi-PDN TWAN connection and a local TWAG. It will be appreciated, however, that the concepts described in connection with  FIGS.  10 A-B  may be applied to other scenarios such as, for example, where the TWAN is a single-PDN TWAN and/or the TWAG is combined in an SGW. 
     Both intra-SGW and inter-SGW handover are supported by the disclosed system embodiments. However, the processing associated with intra-SGW handover provides the benefit of being handled locally. 
     In connection with  FIGS.  10 A-B , an inter-system handover using an intra-MME/intra-SGW procedure is described. It is understood for this particular scenario that a PDN connection already exists via the concatenation of a WLAN link between UE and TWAN, a GTP tunnel between TWAN and SGW, and another GTP tunnel between the SGW and PGW. The scenario could be extended to include the handover of one or more dedicated bearers using the concatenation of additional GTP tunnels. 
     Referring to  FIG.  10 A , at step 1, the UE employs a TWAN  212  to connect to the PGW  222  via an ISW-SGW  238  as described above in connection with  FIGS.  5 A- 5 B . The connection consists of a concatenation of the following: a WLAN link over the SWw interface  256  between the UE  262  and TWAN  212 ; a GTP tunnel over the S1a-U interface  292  between the TWAN  212  and SGW  238 ; and a GTP tunnel over the S5 interface  240  between the SGW  238  and PGW  222 . 
     At step 2, the UE  262  determines to transfer its current sessions (i.e., handover) from the TWAN  212  to the (H)eNB network  295 . In an example scenario, the UE  262  may use ANDSF policies to determine the course of action. 
     At step 3, the UE  262  generates and transmits an Attach Request comprising an Attach Type and APN through the LTE (H)eNB network  295  to the MME  234 . The message is routed by the (H)eNB  295  to the MME  234 . In the scenario wherein the handover were an inter-system handover, the UE  262  would include the “Handover” indication. For inter-system “Handover”, the UE would also include any one of the APNs corresponding to the PDN connections in the TWAN. 
     At step 4, the MME  234  contacts the HSS  270  and authenticates the UE  262 . 
     At step 5, after successful authentication, the MME  262  performs a location update procedure and subscriber data retrieval from the HSS  270 . If the Request Type was “Handover”, the PGW address conveyed to the MME  234  is stored in the MME&#39;s PDN subscription context. The MME  234  receives information for the UE&#39;s TWAN PDN connection via the Subscriber Data obtained from the HSS  270 . The HSS  270  may include information identifying the MME  234  and SGW  238  as “ISW-enabled.” According to an aspect of the disclosed system embodiments, the HSS  270  may comprise information regarding the SGW  238  that the UE  262  is connected to via the TWAN  212 . 
     At step 6, the MME  234  selects an APN, SGW, and PGW. In case the (H)eNB network  295  can be served by the same SGW as the TWAN (i.e., it is an ISW-enabled SGW), the MME  234  generates and transmits a Create Session Request (including IMSI, MME Context ID, PGW address, APN, and “Handover” indication) message to the selected SGW  238 . 
     At step 7, which is shown on  FIG.  10 B , the SGW  238  transmits a Create Session Request (“Handover” Indication) message to the PGW  222 . In the scenario wherein an intra-SGW handover of an existing PDN connection is being performed, the same PGW  222  is used. When the PGW  222  identifies the Create Session Request message with the inter-system “Handover” indication and the same APN as per the existing session with the TWAN  212 , the PGW  222  uses the existing GTP tunnel rather than create a new one with the SGW  238 . One effect of this message is to notify the PCRF  294  of the change in access such that the appropriate policy and charging takes place. 
     At step 8, since the “Handover” indication is included, the PGW  222  executes a PCEF-initiated IP-CAN Session Modification Procedure with the PCRF  294  to obtain the policy and charging rules to be enforced. 
     At step 9, the PGW  222  responds with a Create Session Response message to the SGW  238 . In case of inter-system “Handover,” this message includes the IP address or prefix that was assigned to the UE  262  for TWAN access. It also contains the charging ID that was assigned for the PDN connection through the TWAN  212 . 
     At step 10, the SGW  238  returns a Create Session Response message to the MME  234 . The message comprises the IP address of the UE  262 . 
     At step 11, the MME  234  initiates access bearer establishment between the (H)eNB LTE access network  295  and SGW  238 , and Radio Bearer establishment between the UE  262  and the (H)eNB LTE access network  295 . 
     At step 12, the MME  234  sends a Modify Bearer Request (eNB address, eNB TEID, inter-system “Handover” indication) to the SGW  238  in order to complete the GTP tunnel to the (H)eNB LTE access network  295 . The existing GTP tunnel between SGW  238  and PGW  222  is not affected. 
     At step 13, the SGW acknowledges by sending a Modify Bearer Response (with EPS Bearer Identity) message to the MME  234 . 
     At step 14, the UE  262  sends and receives data via the (H)eNB LTE access network  295 . 
     At step 15, the MME  234  initiates TWAN resource allocation deactivation by sending the Delete Bearer Request to the TWAN  212  over the S1a-C interface  290 . 
     At step 16, the TWAG  260  utilizes the WLCP: PDN Connection Release message to release the UE-TWAN connection. 
     At step 17, the UE acknowledges the release via the WLCP: PDN Disconnection Response message to the TWAN  212  and releases the WLAN connection. 
     At step 18, the TWAN  212  indicates release of the TWAN connection by sending the Delete Bearer Response to the MME  234  via the S1a-C interface  290 . 
     Intra-SGW Multi-connection Attach via LTE 
     In connection with  FIG.  9    above, a process is described for establishing a multi-connection attachment between a UE and PDN wherein a connection via a TWAN is added to an existing LTE connection. The disclosed systems and methods are similarly adapted to support forming multi-channel connections by adding an LTE channel to a previously existing TWAN connection.  FIGS.  11 A-B  depict example processing performed in connection with establishing a multi-channel connection by adding an LTE channel to a previously existing TWAN connection. 
     In the embodiment depicted in connection with  FIGS.  11 A-B , based on information provided by the HSS, the MME assigns an ISW-enabled SGW as an intermediate gateway for the LTE PDN connection, possibly with HSS-based policies for handling specific IP data flows over the LTE access. Furthermore, it is understood that the ISW-enabled SGW is already serving the UE via a TWAN connection to the same PDN. Once the LTE connection is established, the UE maintains both connections and assigns transmission of specific uplink IP traffic flows to either the TWAN or LTE access depending on locally stored policies, signal conditions, etc. Although the access can change on a packet-by-packet basis, it is expected that a specific access will typically be used for a stable period of time as long as conditions allow. Based on policy provided by the MME, the SGW keeps track of the access for received uplink IP packets and transmits the associated downlink packets (e.g., based on corresponding 5-tuple) via the same access. Alternatively, the SGW may send downlink packets over either access based on its own criteria, e.g., for load balancing, etc. 
     Referring to  FIG.  11 A  and step 1, the UE  262  uses a TWAN  212  to connect to the PGW  222  via an ISW-SGW  238 . The connection consists of a concatenation of: a WLAN link over the SWw interface  256  between the UE  262  and TWAN  212 ; and a GTP tunnel over the S1a-U  292  interface between the TWAN  212  and SGW  238 ; and a GTP tunnel over the S5 interface  240  between the SGW  238  and PGW  222 . 
     At step 2, the UE  262  discovers an (H)eNB LTE access network  295  and determines to establish a multi-access connection to an existing PDN. In an example scenario, the UE  262  may use ANDSF policies to determine the course of action. 
     At step 3, the UE  262  generates and transmits an Attach Request to the MME  234  including Attach Type and APN. The message is routed by (H)eNB network  295  to MME  234 . In the case of multi-access connectivity to an existing PDN, the message includes an indication for “Multi-connection” Attach. For “multi-connection” attach, the UE  262  includes any one of the APNs corresponding to the PDN connections in the TWAN. 
     At step 4, the MME  234  contacts the HSS  270  and authenticates the UE  262 . 
     At step 5, after successful authentication, the MME  234  performs a location update procedure and subscriber data retrieval from the HSS  270 . If the Request Type was “Multi-connection,” the PGW address conveyed to the MME  234  is stored in the MME&#39;s PDN subscription context. The MME  234  receives information for the UE&#39;s TWAN PDN connection via the Subscriber Data obtained from the HSS  270 . According to an aspect of the disclosed embodiment, the HSS  270  also includes new information regarding the SGW  238  that the UE  262  is connected to via the TWAN  212 . 
     At step 6, the MME  234  selects an APN, SGW, and PGW. In case the (H)eNB network  295  can be served by the same SGW  238  as the TWAN  212  (i.e., it is an ISW-enabled SGW), the MME  234  transmits a Create Session Request (including IMSI, MME Context ID, PGW address, APN, “Multi-connection” indication, access routing policy) message to the selected SGW  238 . 
     At step 7, which is depicted on  FIG.  11 B , the SGW  238  transmits a Create Session Request (“Multi-connection” Indication) message to the PGW  222 . In the scenario involving an intra-SGW multi-access connection to an existing PDN, the same PGW is used. Therefore, when the PGW  222  identifies the Create Session Request message with the “Multi-connection” indication and the same APN as per the existing session with the TWAN  212 , the PGW  222  uses the existing GTP tunnel rather than create a new one with the SGW  238 . One effect of this message is to notify the PCRF  294  of the change in access such that the appropriate policy and charging takes place. 
     At step 8, since the “Multi-connection” indication is included, the PGW  222  executes a PCEF-initiated IP-CAN Session Modification Procedure with the PCRF  294  to obtain the policy and charging rules to be enforced. 
     At step 9, the PGW  222  responds with a Create Session Response message to the SGW  238 . Where the message involves “Multi-connection,” the message includes the IP address or prefix that was assigned to the UE for TWAN access. It also contains the charging ID that was assigned for the PDN connection through the TWAN. 
     At step 10, the SGW  238  returns a Create Session Response message to the MME. The message includes the IP address of the UE  262 . 
     At step 11, the MME  234  initiates access bearers establishment between the (H)eNB network  295  and SGW  238 , and Radio Bearer establishment between the UE  262  and the (H)eNB network  295 . 
     At step 12, the MME  234  transmits a Modify Bearer Request (eNB address, eNB TEID, “Multi-connection” indication) to the SGW  238  in order to add the GTP tunnel from the (H)eNB network  295 . The existing GTP tunnel between SGW  238  and PGW  222  is not affected. 
     At step 13, the SGW acknowledges by sending a Modify Bearer Response (with EPS Bearer Identity) message to the MME  234 . 
     At step 14, the UE  262  sends and receives data at this point via the (H)eNB network  295  or TWAN  212 . The SGW may route packets to the US  262  over either TWAN  21  or the (H)eNB LTE access network  295 . 
     Example Computing Environment 
       FIG.  12 A  is a system diagram of an example wireless communications device  30 , such as, for example, a UE. As shown in  FIG.  12 A , the device  30  may include a processor  32 , a transceiver  34 , a transmit/receive element  36 , a speaker/microphone  38 , a keypad  40 , a display/touchpad/indicator(s)  42 , non-removable memory  44 , removable memory  46 , a power source  48 , a global positioning system (GPS) chipset  50 , and other peripherals  52 . In an example embodiment, display/touchpad/indicator(s)  42  may comprise one or more indicators that operate as part of a user interface. It will be appreciated that the device  30  may include any sub-combination of the foregoing elements while remaining consistent with an embodiment. The device  30  of  FIG.  12 A  may be a device that uses the serving gateway extensions for inter-system mobility systems and methods as discussed above. 
     The processor  32  may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, one or more Application Specific Integrated Circuits (ASICs), one or more Field Programmable Gate Array (FPGAs) circuits, any other type and number of integrated circuits (ICs), a state machine, and the like. The processor  32  may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the device  30  to operate in a wireless environment. The processor  32  may be coupled to the transceiver  34 , which may be coupled to the transmit/receive element  36 . While  FIG.  12 A  depicts the processor  32  and the transceiver  34  as separate components, it will be appreciated that the processor  32  and the transceiver  34  may be integrated together in an electronic package or chip. The processor  32  may perform application-layer programs (e.g., browsers) and/or radio access-layer (RAN) programs and/or communications. The processor  32  may perform security operations such as authentication, security key agreement, and/or cryptographic operations, such as at the access-layer and/or application layer for example. 
     The transmit/receive element  36  may be configured to transmit signals to, and/or receive signals from, an eNode-B, Home eNode-B, WiFi access point, etc. For example, in an embodiment, the transmit/receive element  36  may be an antenna configured to transmit and/or receive RF signals. The transmit/receive element  36  may support various networks and air interfaces, such as WLAN, WPAN, cellular, and the like. In an embodiment, the transmit/receive element  36  may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element  36  may be configured to transmit and receive both RF and light signals. It will be appreciated that the transmit/receive element  36  may be configured to transmit and/or receive any combination of wireless or wired signals. 
     In addition, although the transmit/receive element  36  is depicted in  FIG.  12 A  as a single element, the device  30  may include any number of transmit/receive elements  36 . More specifically, the device  30  may employ MIMO technology. Thus, in an embodiment, the device  30  may include two or more transmit/receive elements  36  (e.g., multiple antennas) for transmitting and receiving wireless signals. 
     The transceiver  34  may be configured to modulate the signals that are to be transmitted by the transmit/receive element  36  and to demodulate the signals that are received by the transmit/receive element  36 . As noted above, the device  30  may have multi-mode capabilities. Thus, the transceiver  34  may include multiple transceivers for enabling the device  30  to communicate via multiple RATs, such as UTRA and IEEE 802.11, for example. 
     The processor  32  may access information from, and store data in, any type of suitable memory, such as the non-removable memory  44  and/or the removable memory  46 . The non-removable memory  44  may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory  46  may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor  32  may access information from, and store data in, memory that is not physically located on the device  30 , such as on a server or a home computer. 
     The processor  30  may receive power from the power source  48 , and may be configured to distribute and/or control the power to the other components in the device  30 . The power source  48  may be any suitable device for powering the device  30 . For example, the power source  48  may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like. 
     The processor  32  may also be coupled to the GPS chipset  50 , which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the device  30 . It will be appreciated that the device  30  may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment. 
     The processor  32  may further be coupled to other peripherals  52 , which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals  52  may include an accelerometer, an e-compass, a satellite transceiver, a sensor, a digital camera (for photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like. 
       FIG.  12 B  depicts a block diagram of an exemplary computing system  90  that may be used to implement the systems and methods described herein. For example, the computing system  1000  may be used to implement devices that operate as, for example, MME, SGW, WLAN, TWAP, and PGW such as referenced herein. Computing system  90  may comprise a computer or server and may be controlled primarily by computer readable instructions, which may be in the form of software, wherever, or by whatever means such software is stored or accessed. Such computer readable instructions may be executed within central processing unit (CPU)  91  to cause computing system  90  to do work. In many known workstations, servers, and personal computers, central processing unit  91  is implemented by a single-chip CPU called a microprocessor. In other machines, the central processing unit  91  may comprise multiple processors. Coprocessor  81  is an optional processor, distinct from main CPU  91  that performs additional functions or assists CPU  91 . CPU  91  and/or coprocessor  81  may receive, generate, and process data related to the disclosed serving gateway extensions for inter-system mobility systems and methods. 
     In operation, CPU  91  fetches, decodes, and executes instructions, and transfers information to and from other resources via the computer&#39;s main data-transfer path, system bus  80 . Such a system bus connects the components in computing system  90  and defines the medium for data exchange. System bus  80  typically includes data lines for sending data, address lines for sending addresses, and control lines for sending interrupts and for operating the system bus. An example of such a system bus  80  is the PCI (Peripheral Component Interconnect) bus. 
     Memory devices coupled to system bus  80  include random access memory (RAM)  82  and read only memory (ROM)  93 . Such memories include circuitry that allows information to be stored and retrieved. ROMs  93  generally contain stored data that cannot easily be modified. Data stored in RAM  82  may be read or changed by CPU  91  or other hardware devices. Access to RAM  82  and/or ROM  93  may be controlled by memory controller  92 . Memory controller  92  may provide an address translation function that translates virtual addresses into physical addresses as instructions are executed. Memory controller  92  may also provide a memory protection function that isolates processes within the system and isolates system processes from user processes. Thus, a program running in a first mode can access only memory mapped by its own process virtual address space; it cannot access memory within another process&#39;s virtual address space unless memory sharing between the processes has been set up. 
     In addition, computing system  90  may contain peripherals controller  83  responsible for communicating instructions from CPU  91  to peripherals, such as printer  94 , keyboard  84 , mouse  95 , and disk drive  85 . 
     Display  86 , which is controlled by display controller  96 , is used to display visual output generated by computing system  90 . Such visual output may include text, graphics, animated graphics, and video. Display  86  may be implemented with a CRT-based video display, an LCD-based flat-panel display, gas plasma-based flat-panel display, or a touch-panel. Display controller  96  includes electronic components required to generate a video signal that is sent to display  86 . 
     Further, computing system  90  may contain network adaptor  97  that may be used to connect computing system  90  to an external communications network, such as PDNs. In an embodiment, network adaptor  97  may receive and transmit data related to the disclosed serving gateway extensions for inter-system mobility systems and methods. 
     Accordingly, applicants have disclosed example systems and methods for inter-system mobility in integrated LTE and WiFi systems. A control plane interface, referred to as the S1a-C interface, is defined between a trusted WLAN access network (TWAN) and a mobility management entity (MME) comprised in an LTE wireless access network. A user plane interface, referred to as the S1a-U interface, is defined between the TWAN and a server gateway (SGW) in the LTE wireless access network. The MME operates as a common control plane entity for both LTE and TWAN access, while the SGW operates as a user plane gateway for both LTE and TWAN. The integrated MME and SGW allow for user equipment (UE) to access the capabilities of a packet data network (PDN) through either the LTE access network or TWAN. Moreover, an existing communication connection between a UE and a PDN may be handed over from one of the LTE access network or TWAN to the other. Still further, the MME and SGW provide for simultaneously maintain two communication paths, one via the LTE access network and one via the TWAN, between a UE and a packet network. 
     The disclosed systems and methods may result in various benefits. For example, communication performance is improved by enabling execution of inter-system mobility procedures close to the edge of the network. Communication latency is reduced by minimizing the need for signaling procedures deep in the core network, i.e., toward the PGW. This can be especially beneficial when an MNO deploys both small cell and WiFi access in a common geographic area. Scalability is also improved by reducing the PGW processing burden, e.g., by distributing some inter-system mobility functions to the MME and SGW. 
     The ability to establish concurrent connections, one via LTE and one via WiFi improves mobility robustness and reduces handover ping-ponging. An alternate path to the PDN can be made available as needed without incurring handover setup delays. This improves the user experience by reducing session interruptions when the primary data path is degraded, which can be a common occurrence given the limited coverage of small cell and WiFi access points. 
     It will be appreciated that while illustrative embodiments have been disclosed, the scope of potential embodiments is not limited to those explicitly set out. For example, while the system has been described with primary reference to “Trusted” WLAN Access Networks (TWAN), the envisioned embodiments extend as well to embodiments that employ “Untrusted” WLANs. Moreover, it will be appreciated that the disclosed embodiments may encompass single-PDN TWANs as well as multi-PDN TWANs. Still further, the envisioned embodiments include all configurations and placements of TWAG functionality. 
     It should be understood that the various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination of both. Thus, the methods and apparatus of the subject matter described herein, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the subject matter described herein. In the case where program code is stored on media, it may be the case that the program code in question is stored on one or more media that collectively perform the actions in question, which is to say that the one or more media taken together contain code to perform the actions, but that—in the case where there is more than one single medium—there is no requirement that any particular part of the code be stored on any particular medium. In the case of program code execution on programmable computers, the computing device generally includes a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. One or more programs that may implement or utilize the processes described in connection with the subject matter described herein, e.g., through the use of an API, reusable controls, or the like. Such programs are preferably implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations. 
     Although example embodiments may refer to utilizing aspects of the subject matter described herein in the context of one or more stand-alone computer systems or devices, the subject matter described herein is not so limited, but rather may be implemented in connection with any computing environment, such as a network or distributed computing environment. Still further, aspects of the subject matter described herein may be implemented in or across a plurality of processing chips or devices, and storage may similarly be affected across a plurality of devices. Such devices might include personal computers, network servers, handheld devices, supercomputers, or computers integrated into other systems such as automobiles and airplanes. 
     The following is a list of acronyms relating to service level technologies that may appear in the above description.
     AAA Authentication, Authorization, and Accounting   ANDSF Access Network Discovery and Selection Function   ANQP Access Network Query Protocol   AP Access Point   APN Access Point Name   CAPWAP Control And Provisioning of Wireless Access Points   DHCP Dynamic Host Configuration Protocol   EAP Extensible Authentication Protocol   EAP-AKA EAP Authentication and Key Agreement   EAP-AKA′ EAP AKA “prime”   EAPoL EAP over LAN   EPC Evolved Packet Core   GPRS General Packet Radio Service   GTP GPRS Tunneling Protocol   HSS Home Subscription System   IETF Internet Engineering Task Force   IMSI International Mobile Subscriber Identity   IP Internet Protocol   ISW Integrated Small-cell and WiFi   ISWN Integrated Small-cell and WiFi Networks   LTE Long Term Evolution   MAC Medium Access Control   MAPCON Multi Access PDN Connectivity   MCN Mobile Core Network   MME Mobility Management Entity   MNO Mobile Network Operator   NAS Non Access Stratum   NSWO Non Seamless WLAN Offload   OAM Operations, Administration, and Maintenance   PCRF Policy and Charging Rules Function   PDN Packet Data Network   PGW PDN Gateway   PMIP Proxy Mobile IP   QoE Quality of Experience   QoS Quality of Service   RAT Radio Access Technology   RRC Radio Resource Control   SaMOG S2a Mobility Over GTP   SCTP Stream Control Transport Protocol   SGW Serving Gateway   TEID Tunneling Endpoint Identifier   TWAG Trusted WLAN Access Gateway   TWAN Trusted WLAN Access Network   TWAP Trusted WLAN AAA Proxy   UDP User Datagram Protocol   UE User Equipment   WFA WiFi Alliance   WiFi Wireless Fidelity   WLAN Wireless Local Area Network   WLC Wireless LAN Controller   WLCP Wireless LAN Control Protocol   

     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.