A Network-Based Architecture for Seamless Mobility ... - IEEE Xplore

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Charles Kalmanek, John Murray, and Chris Rice, AT&T Labs Research. Bob Gessel and ... there is growing interest in seamless mobility — applications and ...
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SCALING THE MOBILE INTERNET

A Network-Based Architecture for Seamless Mobility Services Charles Kalmanek, John Murray, and Chris Rice, AT&T Labs Research Bob Gessel and Ravindra Kabre, Ericsson Andre Moskal, NewStep

ABSTRACT Given the tremendous growth in mobile voice and data usage and the emergence of new multifunction, multiradio handheld devices, there is an emerging interest in seamless mobility — applications and services that provide service portability and application persistence across multiple network connections. Seamless mobility ultimately allows users to transparently access all of their data and services in a consistent method. This article describes an implementation of a networkbased architecture for seamless mobility services that supports the full range of applications — voice, data, video, and messaging — using bimode devices that interface to both Global System for Mobile Communications (GSM) and Wireless Fidelity (Wi-Fi) networks. This solution provides advanced functionality to existing cellular devices, while providing a solid migration path to full IP-based multimedia services. The solution relies on network-based interfaces and systems, providing a multinetwork-capable, scalable solution with a unified service experience for the user from a single device.

INTRODUCTION AND MOTIVATION Given the tremendous growth in mobile voice, data, and messaging usage and the emergence of new multifunction, multiradio portable devices, there is growing interest in seamless mobility — applications and services that provide service portability and application persistence across multiple network connections. Seamless mobility implies that the infrastructure transparently manages connectivity so that the user is “always best connected.” However, this problem is complex in practice and the user’s definition of “best connected” depends on cost, performance, location, or other factors. Services such as cellular voice are based on complex legacy infrastructure, and existing wireless local area networks (WLANs) have many deficiencies, such as quality of service (QoS) and an array of methods for access control. Nonetheless, several key technical and social drivers are contributing to the interest in seamless mobility. Device convergence, the consolidation of multiple functions into small, portable

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devices with integrated cellular and Wi-Fi based [1] WLAN interfaces, is a trend that is of interest to users in both business and consumer environments. Other drivers are improvement in productivity, cellular cost management, and improved service coverage. An increasingly mobile workforce and the blurring of boundaries between the traditional workplace, the home workplace, and the mobile workplace are requiring subscribers to access all of their voice, data and messaging services, independent of their location or the particular access network they are using. This article describes work initiated by AT&T Labs Research, and brought together in a research collaboration with six other companies, to create an end-to-end architecture for providing seamless voice, data, and messaging services across disparate access networks that would address the needs of global enterprises. The goals of the architecture are: • Support services on existing devices, as well as next-generation, multifunction, multiradio devices. • Align the work with the emerging Internet Protocol Multimedia Subsystem (IMS) standards [2], allowing the solution to leverage industry investment in IMS. • Define a unified interface to the cellular network that provides a scalable, standardsbased solution for seamless mobility. This interface should enable new services such as location-based services to also be supported within the same framework. • Use network intelligence and create standardized clients to take advantage of the architecture. • Provide operations, administration, maintenance, and provisioning (OAM&P) systems to support solution deployment. AT&T Labs Research started this work by creating the initial architecture; the focus was to create a proof-of-concept implementation by leveraging the strengths of the participating companies. The implementation is now being used to quantify various aspects of performance, cost, and complexity of next-generation IP-based converged networks. Seamless mobility is especially well suited to services delivered over Internet Protocol (IP)

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There are a number of different approaches being taken in the industry to provide seamless mobility services. We have grouped these solutions into three broad categories: enterprise or PBXbased solutions; cellular-network based solutions; and IP-network based solutions.

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networks, but the project is challenging because it rides on top of several complex building blocks, as shown in Fig. 1, each of which must be integrated into a holistic solution. A key decision was to leverage an IMS-based infrastructure as the common service delivery platform to handle all call control and new service delivery. This approach makes sense because innovation in multimedia services is occurring in areas of VoIP applications based on IETF Session Initiation Protocol (SIP) [3] applications; hence, a solution that invests in these areas rather than legacy technology is important. Interworking with the cellular network uses existing Signaling System #7 (SS7) interfaces [4, 5] and is configured so that all calls to and from cellular devices are routed to the IMS infrastructure for call control. Multiradio devices, a well-managed wireless LAN infrastructure, and OAM&P support for all aspects of the network and service infrastructure are all essential elements. Seamless mobility sits as a middleware layer on top of these building blocks, with application services such as IP Centrex (Central Exchange), IP-PBX (Private Branch Exchange), and so forth riding on top of the seamless mobility layer. As a service provider, AT&T wants to ensure all services can be supported by seamless mobility, not just voice. For example, in the 2.5G cellular and Wi-Fi cases, the cellular services of short message service (SMS), multimedia messaging service (MMS), push-to-talk service, and so on must be available via the same device user interface on either network.

ARCHITECTURAL ALTERNATIVES There are a number of different approaches being taken in the industry to provide seamless mobility services. We have grouped these solutions into three broad categories. Those solutions include enterprise or PBX-based solutions; cellular-network based solutions, such as Unlicensed Mobile Access (UMA); and IP-network based solutions, such as the architecture proposed in this article. We summarize the advantages and disadvantages of each of these solutions. PBX-based seamless mobility solutions are starting to become available today. These approaches utilize several techniques, such as virtual numbers (a solution for incoming calls that allows callers to reach a subscriber using find-me follow-me techniques), various two-stage dialing approaches, or software loaded on handsets to control their operation. For example, when originating a call, a proprietary (IP-PBXspecific) handset on the cellular network may utilize two-stage dialing to place a call to the PBX, where features are provided and the call is completed. The handset is an extension on the IP-PBX within the corporate Wi-Fi network, allowing the user to roam the building or campus with full IP-PBX services. The advantage of the solution is that it leverages existing infrastructure on the IP-PBX. The dial plan and feature set are familiar to enterprise users. However, IP-PBX solutions may not address the full range of seamless mobility requirements and face challenges in scaled deployments. Chal-

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lenges remain with handsets, device management, cellular interconnectivity costs, and interoperability requirements and testing for the variety of systems in the enterprises. Finally, this solution does not extend easily outside of the individual enterprise domain (e.g., to the home, wireless hotspots, etc.). Unlicensed Mobile Access (UMA) is a cellular network-based solution. UMA delivers GSM and GPRS mobile services [6] over unlicensed spectrum technologies like Wi-Fi essentially by encapsulating GSM signaling in IP, and routing it to a gateway in the cellular network. UMA enables subscribers to roam, and supports handover between cellular networks and public/private Wi-Fi networks using bimode handsets. One of the advantages of UMA is that subscribers receive the same user experience for both their cellular and Wi-Fi mobile voice services as they transition between networks, but limited to the cellular experience. Another advantage for UMA is its standardization, which could help to promote widespread adoption and interoperability. The limitations are that many enterprise customers prefer enhanced features such as corporate dialing plans, coverage plans, voicemail, and other features. Additionally, UMAbased solutions may not integrate easily with other IP services or advancements in VoIP. UMA can be viewed as near-term opportunity for cellular operators to bring WiFi-based access solutions to market. Another cellular-based solution emulates a traditional GSM Visitor Location Register (VLR) [6] for Wi-Fi-based VoIP calls. The objective is to enable roaming between Wi-Fi and cellular networks. GSM-MAP or ANSI-41 protocols are used for performing handovers similar to traditional cellular handover between cellular network switches (known as Mobile Switching Centers or MSCs). This approach requires updating of the neighbor list in the Radio Network Controller or Base Station Controller to include the new IP VLR for Wi-Fi roaming. A VoIP gateway emulates a serving MSC to register the IP interface of the phone and perform handoffs from/to the Wi-Fi access domain using standard VLR techniques. The issue with this approach is the complexity of supporting both VoIP and VLR implementations, while providing only a minimal set of feature enhancements beyond the expanded connectivity, because all services are still provided by the existing MSC infrastructure.

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Longer term, cellular providers are planning to migrate to a 3G air interface capable of endto-end voice over IP (VoIP) with services enabled on the next-generation service platform defined by the Third-Generation Partnership Project (3GPP) [7], referred to as the IP Multimedia Subsystem (IMS). This platform will support all users and bring a new generation of services in the future.

ARCHITECTURAL GOALS The 3GPP IP Multimedia Subsystem provided inspiration for the solution presented in this article; we extended the IMS framework by using Intelligent Networking and SIP-based call-control concepts to seamlessly provide IMS services independent of access type. Our goal was to maintain and strengthen the advantages of the above solutions, while removing the disadvantages. The ultimate goal of the architecture is to provide a consistent user experience for all services, independent of how the user connects to the network. The user should benefit from seamless mobility in their enterprise, on the cellular network, at home, in a hotspot, and even when visiting other enterprise networks as a guest. Seamless mobility is often described in terms of the voice user experience, but actually should cover a complete solution across voice, data, video, and messaging services. There are challenges and high user expectations for each of the different services. For voice, the challenge is to provide call continuity across multiple networks which utilize different technologies and support the continued migration from legacy to IP-based communica-

tions. The principal issue is seamless movement of the voice stream between different call legs, but it is also important to centrally manage number treatment, call routing, and feature delivery for originating and terminating calls. Centralizing the handling of these functions in the network simplifies provisioning and improves service scaling. For data, session continuity is important so that users can continue to be productive as they move between networks. This becomes more important as usage models move from portable laptops to always connected multifunction mobile devices. One of the challenges is to seamlessly maintain VPN tunnels, which are required for security by business users as they move between the different access technologies and locations. The final area is messaging, which needs to extend the current cellular messaging services of SMS and MMS over IP interfaces so that users can continue to access services while on IP interfaces such as Wi-Fi. In addition, users are expecting consistency in services for SMS/MMS, instant messaging, and email on the same device. Though some of the issues for messaging are common with data sessions, it is important that the applications, devices, and services work to provide the transparency that users expect. The 3GPP TR 23.204 [8] standard addresses the delivery/origination of SMS/MMS in the IMS domain. Our architecture and proof-of-concept implementation were designed to address the user requirements presented above. In addition, there were several technical objectives. The first was to anchor data sessions, call control (including control of multiple calls legs), service provisioning, and billing in a single network domain, based on

Though some of the issues for messaging are common with data sessions, it is important that the applications, devices, and services work to provide the transparency that users expect. The 3GPP TR 23.204 standard addresses the delivery/origination of SMS/MMS in the IMS domain.

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sd Call flow SSP

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■ Figure 3. Call/session flow overview. an IMS core, independent of the access technology that is being used. This requirement includes the ability to provide an IMS subscription and anchor point for existing 2G/2.5G cellular handsets. A second goal was to provide a seamless experience for bimode devices where call continuity and services are maintained during handoffs between cellular and Wi-Fi networks in real-time. A third goal was to leverage investments in IP applications and infrastructure by reusing them in the cellular, Wi-Fi, and wired IP network domains. Even though our work started almost in parallel with the 3GPP Voice Call Continuity (VCC) standardization process, our approach was a clear choice to maximize flexibility and minimize impact on existing networks [9]. Our solution was developed to address these basic principles: • The solution should work everywhere where existing cellular voice and/or Wi-Fi service are available. • Call control for all calls to/from a “converged subscriber” is “anchored” in the IMS domain. • Call routing between the cellular and IMS networks is done using standard Intelligent Network (IN) triggering based on CAMEL [10] or equivalent Code-Division Multiple Access (CDMA) [11] standards. • Ingress and egress of cellular calls to/from the IMS Seamless Mobility network over ISUP trunks managed by signaling and media gateways compatible with IMS standards. • Applications and services are supported via IN service control points (SCPs) accessed using PARLAY open services access (OSA) interfaces [12] or via SIP application servers supporting the IMS service control (ISC) interface [2].

INTELLIGENT NETWORK-BASED SEAMLESS MOBILITY ACCESS ARCHITECTURE This section presents the IN Seamless Mobility Access (IN-SMA) architecture in detail. Some

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familiarity with the IP Multimedia Subsystem (IMS) is assumed. IN-SMA utilizes an IMSbased call control infrastructure, similar to 3GPP. The IN-SMA solution, shown in Fig. 2, is based on an IMS infrastructure. The IMS core provides SIP session control to calls originated and terminated to the bimode subscribers. A Mobility Management Application on the Mobility Server provides the mobile call handoff service with automatic restore-back to cellular in case of WiFi service interruption. Since we expect that both cellular networks and Wi-Fi networks will have issues of spotty coverage, the IN-SMA manages multiple call legs in a mobility layer that operates in an application server above the IMS core. The mobility server keeps track of call state and acts as a SIP “back-to-back user agent,” allowing both legs of the call (handset to network and network to calling party) to be held in place independently. The mobility layer is obviously essential to seamless mobility, but also supports an enhanced user experience through features such as call recovery of network-dropped calls. Since the approach is network based, the infrastructure can be leveraged across many customers. This approach allows service providers to offer advanced features to devices connected to existing access networks, including new features on existing cellular handsets.

INTELLIGENT NETWORK TRIGGERS AND APPLICATIONS One of the requirements to provide next-generation services to cellular users in the Seamless Mobility architecture is to enable IN triggers for Seamless Mobility subscribers utilizing cellular access. The originating and terminating IN triggers provide information to the cellular MSC on how to route Seamless Mobility calls to/from the IMS network. For originating cellular calls, an IN trigger is associated with the user’s subscription in the home location register/home subscriber server (HLR/HSS) [2, 11]. A trigger is activated whenever a subscriber makes a call. The trigger causes the MSC to send a request to a system signaling point (SSP) or a signaling control point (SCP), where an IN-based mobility application responds with routing information that will be used by the MSC to properly route the call towards the IMS network. The MSC routes the call over an ISUP trunk to the proper media gateway (MGW) and media gateway controller (MGC), which interface to the IMS network. Depending on the relationship between the cellular operator and the owner of the Seamless Mobility IMS network, it is important to note that deploying the MGC/MGW nodes near the MSCs in the cellular operator’s network can significantly reduce service costs, for example, by allowing the Seamless Mobility provider to cost effectively transport cellular traffic across a global IP/MPLS core network. The example in Fig. 3 uses the GSM CAMEL protocol; similar examples exist for CDMA-based wireless networks.

IMS CORE The IP Multimedia Subsystem (IMS) is an internationally recognized standard, first specified in 3GPP/3GPP2 and embraced by ETSI/TISPAN,

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■ Figure 4. A closer look at IMS core elements. ATIS, and the ITU. The IMS standards not only define a new call control and services architecture, they also specify interoperability and roaming, and provide bearer control, charging, and security. Additionally, they are integrated well with voice and data network standards, while adopting many of the key characteristics of the IP domain. This makes IMS a key enabler for fixed-mobile convergence applications. The Seamless Mobility architecture (Fig. 2) uses an IMS core, including serving call/session control function (S-CSCF), proxy CSCF (PCSCF), interrogating CSCF (I-CSCF), and HSS for subscriber data. For interworking between networks, border gateway/control functions (BGCFs) [2] and PSTN interworking gateways are used. ENUM [13] servers map between the telephone numbers and the IP address of an associated VoIP endpoint or gateway. Other IMS-compatible elements are needed to complete the common infrastructure and border elements, including session border controllers for network-to-network and access-to-network interfaces, media gateway, and controllers for interfacing cellular and PSTN networks. The MGC inter-works between the SS7 ISUP and SIP protocols. The media resource function (MRF) provides common media services, including announcements, multiparty bridges, messaging, and other media oriented functions. Figure 4 shows a logical representation of the IMS Core elements and their relationship to one another. The IMS core provides SIP-based session control to calls originated and terminated to Seamless Mobility subscribers, who may be using legacy cellular or PSTN phones, bimode devices, or VoIP phones. The subscribers are provisioned in the HSS. The S-CSCF applies the filter criteria to determine whether to forward SIP requests to the Mobility Management Application and/or the IP Centrex Application Server in a preconfigured sequence. These initial filter criteria are stored in the HSS as part of the user profile and are downloaded when receiving an initial request

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today. to the S-CSCF upon user registration, or terminating initial request for an unregistered user. After downloading the user profile from the HSS, the S-CSCF assesses the filter criteria and invokes the appropriate application in the prescribed order for each subscriber call scenario.

IMS APPLICATIONS One of the primary motivations for deploying an IMS infrastructure is to be able to leverage new services across a service provider’s entire customer base. The first IMS services such as pushto-talk over cellular (PoC) and wireline broadband VoIP/IP-Centrex standard services are being deployed today. The IMS architecture can also be used to enhance mobile circuitswitched telephony, by delivering advanced services to legacy 2G/2.5G cellular devices. The section addresses how the IN-SMA architecture can transparently deliver new VoIP services to Seamless Mobility subscribers independent of access type. Application Servers — To demonstrate the Seamless Mobility application architecture, we have integrated two application servers. The first is the Mobility Server, which manages the call control and interworking between cellular and Wi-Fi networks. The second is an existing VoIP application server providing IP-Centrex and residential VoIP services that was integrated into the proof-of-concept platform to demonstrate that rich VoIP services can be extended to access types such as traditional cellular access. Since VoIP applications are relatively new to the market, many application server vendors are able to adapt their existing SIP interfaces to the 3GPP standard ISC interface. By adapting to the ISC interface, these applications can then be reused across access types within the IMS domain. Once the application servers are running on the ISC interface, subscriptions can be created in IMS that trigger the application based on the traffic type and characteristics of the device and

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access method. The extension of traditional VoIP-based services, such as IP-Centrex, to legacy 2G mobile devices in the cellular domain is a powerful demonstration of our architecture.

ble, scalable solution for seamless mobility. It leverages established and scalable cellular interfaces such as MAP and CAMEL for GSM and provides a single consistent interface to the cellular operator for all seamless mobility users, independent of the business grouping or service set to be provided to the user.

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Mobility Application Server — The IN-SMA architecture uses the Mobility Server to provide call continuity between circuit-switched and packet-switched domains. The Mobility Server is SIP-based and can be used in deployments that are not IMS-based; however, its primary benefits are achieved in conjunction with an IMS infrastructure. In this case, the Mobility Server acts as an application server interfacing to the S-CSCF through the IP multimedia service control (ISC) interface. The Mobility Server acts as a SIP application server, providing interworking functions for specific services between the Public Switched Telephone Network (PSTN)/Public Land Mobile Radio Network (PLMN) and the VoIP network. The interworking functions between the networks include call routing, joining, reconfiguring, notifying a network event to the terminal, and gathering user input/state. The Mobility Server tracks the state of each access network, and whether or not the client or network is requesting a handoff between access networks. As a traditional SIP application server, the Mobility Server can also provide enhanced services to enable connectivity and service enhancement with respect to ongoing calls. To achieve the required call control and signaling anchoring in the packet-switched domain, the Mobility Server correlates and extends the IN interface from the circuit-switched domain. The IN interface is based on the Customized Application for Mobile Network Enhanced Logic (CAMEL) [10] or CDMA-based Wireless Intelligent Network standards [11]. (Refer to Fig. 2 for interaction of the Mobility Server and the IMS core with the signaling and access networks.) For data mobility, the solution leverages mobile IP to provide IP session continuity and a smart client to manage device network registration. The IN-SMA approach offers a number of benefits listed below that can be viewed as advantageous over other SMA approaches discussed previously: • Voice call continuity between GSM/UMTS and IMS is provided even when the user is roaming to a foreign network (subject to the foreign network supporting the IN triggering mechanism). • Correlation of charging is provided for the GSM/UMTS and for the IMS parts of the session when service continuity between the domains is performed. • The network selects the service domain associated with a particular call based on operator policy. This allows introduction of additional application servers within the IMS domain to cooperate with the Mobility Server through the ISC interface providing enhanced consumer or enterprise services as part of the service logic execution chain. • Voice call continuity is provided with minimal service disruption (200–300 ms) that is hardly perceived by the end user. This is achieved by having the device maintain a

simultaneous connection via the circuitswitched and packet-switched radio access interfaces during the handoff [9].

CONCLUSIONS AND FUTURE WORK The IN-SMA architecture provides a flexible, scalable solution for seamless mobility. It leverages established and scalable cellular interfaces such as MAP and CAMEL for GSM and provides a single consistent interface to the cellular operator for all seamless mobility users, independent of the business grouping or service set to be provided to the user. The solution is flexible enough to bring all users to the same service platform; for example, both IP-Centrex or IPPBX solutions can be supported with simplified number planning because call routing only needs to be provisioned and managed in one centralized system. By leveraging the intelligence in the network, the system manages the connectivity to the end user and the terminating connection as separate call legs. This allows the system to control each connection, hold the terminating connection open during periods of movement between the networks, temporarily open multiple paths to the user, and even recover any one leg of the communication path if it is temporarily lost. With seamless mobility built as a service layer within IMS, all new services built and deployed on IMS can inherit seamless mobility. New IP services can be delivered to existing 2G cellular devices by connecting the cellular network to the IP infrastructure though a VoIP gateway; the advantage of this approach is that it positions the solution to work with IP-based networks like Wi-Fi and potentially WiMAX and 3G networks, as they are deployed. It is believed by the authors that the approach discussed in this article provides the greatest flexibility, performance, scalability, and consistency, while providing end users with the best experience and functionality, compared with other solutions. Detailed descriptions of the call flows to support Seamless Mobility and system-level descriptions of key interfaces and the functional elements have been developed in this work, although only a subset have been described in this article due to space limitations. While the architecture was created to support SIP-based handoff of calls between existing cellular networks and Wi-Fi networks, it is readily extensible to cover other options, such as UMA-based, CDMA-based, future networks (e.g., WiMAX), and other legacy networks, including plain old telephone service (POTS). Future work will include definition of standard client needs on the devices to support such services, integration of the system with backoffice functions, description of the call details and billing needs, account management between different personas that the user may have (office use, home use, shared use, etc.), integration of enterprise-based (e.g., PBX) and network-based features, and further definition of services available from such a system. We will also be addressing extensions of this concept to include mechanisms for dynamic anchoring of calls using GPRS and other data bearer connectivity for foreign networks that do not support IN.

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REFERENCES [1] Wi-Fi Alliance, http://www.wi-fi.org [2] G. Camarillo and M. A. Garcia-Martin, The 3G IP Multimedia Subsystem — Merging the Internet and the Cellular Worlds, Hoboken, NJ: Wiley, 2004 [3] J. Rosenberg et al., SIP: “Session Initiation Protocol,” IETF RFC 3261, June 2002, work in progress. [4] L. Dryburgh and J. Hewitt, Signaling System No. 7 (SS7/C7): Protocol, Architecture, and Services, Cisco Press, 2004 [5] ETSI Tech. Spec. 100 974 V7.10.0, “Digital Cellular Telecommunications Systems (Phase 2+), Mobile Application Part (MAP),” Rel. 1998, Jan. 2002. [6] M. Rahnema, “Overview of the GSM System and Protocol Architecture,” IEEE Commun. Mag., Apr. 1993. [7] 3GPP, http://www.3gpp.org [8] 3GPP TS 23.204 Tech. Spec., “Group Services and System Aspects; Support of SMS and MMS over Generic 3GPP IP Access; Stage 2,” Rel. 7. [9] 3GPP TR 23.806 Tech. Spec., “Group Services and System Aspects; Voice Call Continuity between CS and IMS Study,” Rel. 7. [10] ETSI Tech. Spec. 03.78 v. 2, “CAMEL (Customized Applications for Mobile Networks Enhanced Logic),” Rel. 98. [11] J. S. Blogh and L. Hanzo, Third-Generation Systems and Intelligent Wireless Networking: Smart Antennas and Adaptive Modulation, Hoboken, NJ: Wiley, 2002. [12] 3GPP Tech. Spec. 29.198 Series, “Open Service Access (OSA) Application Programming Interface Specifications.” [13] P. Faltstrom and M. Mealling, “The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application (ENUM),” IETF RFC 3761, Apr. 2004.

BIOGRAPHIES CHARLES R. KALMANEK received his undergraduate degree from Cornell University, and M.S. degrees in electrical engineering and computer science from Columbia University and New York University, respectively. He is vice president of Internet and Network Systems Research at AT&T Labs, where he is responsible for AT&T’s Research program in IP network and performance management; leadership and incubation of new networking technologies including wireless and optical technologies; and innovation in IP-based services. He joined AT&T Bell Laboratories in 1980, and has conducted research on packet-based access and backbone networks for more than 25 years. He has extensive experience in network architecture, protocols, and distributed systems, and has worked on ATM switch and host interface design, congestion control, routing, voice over IP and multimedia streaming, access network architectures, wireless networks, and management of large-scale IP networks. His current work includes advanced transport and IP network architectures, IP traffic monitoring and analysis, network survivability tools, wireless access technologies, and network-based applications such as content distribution networks and storage networking. In the late 1980s, he was a principal investigator in a project that developed an access and home networking architecture for handling voice and data. This work demonstrated a packet-based home network called INCON, and extensions to traditional Digital Loop Carrier access that made use of unused time slots for a packet access channel. In the early 1990s, he was a project leader in the XUNET project, which designed and deployed an experimental ATM network connecting research labs at several universities, government labs, and AT&T. He pioneered work on broadband access over CATV networks, including work on QoS, policy control, and SIP-signaling for VoIP and multimedia services. He has worked on a number of IP routing related projects and 3G wireless standards in 3GPP. CHRISTOPHER W. RICE ([email protected]) graduated summa cum laude from Virginia Tech with B.S.E.E. and M.S.E.E. degrees, and received his M.B.A. from the University of Central Florida. From 1995 to 1998 he performed post-graduate work with WINLAB at Rutgers University and received a Graduate Certificate in Wireless Information Networks. He is a director at AT&T Labs Research, where he is responsible for advanced broadband transmission research. His areas of work include broadband architectures, wireless access and distribution networks, wireless security, and advanced communication’s technologies. In 1995 he joined then AT&T Bell Laboratories to focus on wireless and

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broadband communication systems. He worked on satellite communication systems and broadband data communication systems, and led development efforts for a digital radio-based picocellular base station, which provided inbuilding, mobile voice communication on standard cellular phones. In 1988 he worked for Q-bit Corporation, a small startup company focused on defense subsystems and cellular radio technologies. There, as engineering manager, he was responsible for all research and product development activity, and led the engineering and production effort that shifted the company’s product focus from defense-related subsystems to wireless base station products. In 1984 he started his professional career at Harris Corporation in the Government Communication Systems Division where he worked on satellite communication systems, RF and microwave assemblies, and monolithic microwave integrated circuits. JOHN F. MURRAY received his B.S.E.E.T. from the College of New Jersey and his Master’s from Stevens Institute of Technology. He is a technical consultant at AT&T Labs Research working on access systems and services. He has been with AT&T for more than 10 years and has more than 23 years in the industry. His previous employment included RCA Astro, where he was involved in ground systems, and Boonton Electronics, where he helped create several new RF power measurement instruments. Cellular-related work within AT&T has included efforts on in-building cellular solutions, bimodal systems utilizing 802.11 alternate wireless networks, seamless mobility, and IMS systems. Other areas of activity have included work on cable systems for voice and data, home networking, small business networking, and VoIP solutions. He was part of the team that launched the AT&T CallVantage®.

While the architecture was created to support SIP-based handoff of calls between existing cellular networks and Wi-Fi networks, it is readily extensible to cover other options, such as UMA-based, CDMA-based, future networks (e.g., WiMAX), and other legacy networks, including plain old telephone service (POTS).

B O B G E S S E L [M] has a B.S.E.E. degree from Southern Methodist University (SMU). He is currently working at Ericsson as a solutions architect, responsible for solution architecture design, systems integration, and strategic solution evolution for fixed mobile convergence strategic initiatives. He is a communications industry veteran of 19+ years. In 2001 he founded MobileStream Wireless, Inc. which later became SceneScape, Inc., to capitalize on the converging growth markets of short-range wireless data, multimedia, and on-site mobile applications and content delivery. MobileStream’s SceneStream system focused on “extreme wireless entertainment,” an exciting new wireless multimedia solution for the sports and entertainment market, as well as localized hot spot interactive content. Prior to 2001 he also spent 12 years with Ericsson as business innovation manager and research, operations manager for mobile enterprise software development, in addition to being principal engineer where he was inventor of the GSM-based VoIP product line known as “GSM on the Net.” He also created a testing technology group to build advanced software simulation technologies that received worldwide recognition, receiving Ericsson’s Best Improvement Project of the Year award in 1998. He also spent a combined six years in various software engineering positions with Siemens and Northern Telecom. He has been issued four patents and has two patents pending. He is SMU Engineering Alumni Co-Chairman, an SMU Computer Science Advisory Board Member, and a member of the UT-Arlington CSE Industrial Advisory Board. A NDRE M OSKAL was graduated in computer control engineering technology from Confederation College. He is CTO of NewStep Networks, responsible for the product strategy and technology roadmap addressing fixed-mobile convergence. Prior to his role at NewStep, he served as CTO of Blueslice Networks, where he worked on the IMS subscriber profile management solution. In addition, he held technical and leadership roles with SS8 Networks, Mitel, Gandalf, and Nortel that provided him with more than 20 years of experience developing innovative voice and data networking products. R AVINDRA K ABRE received a Bachelor’s in electronics engineering from the Indian Institute of Technology, Kharagpur, and an M.B.A. from the University of Texas at Dallas. He is a solutions architect in the Convergence Group at Ericsson Inc. He has more than 15 years of experience in the telecommunication industry in wireless, wireline, and VoIP technologies. Previous employment included Lucent Technologies, Motorola Inc., and Singapore Telecom in different roles in systems analysis, product development, and technical presales for the Asia-Pacific region.

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