SEAMLESS SERVICE PROVISION FOR MULTI HETEROGENEOUS ACCESS

Transcription

1 SEAMLESS C ONTENT DELIVERY IN THE FUTURE MOBILE I NTERNET SEAMLESS SERVICE PROVISION FOR MULTI HETEROGENEOUS ACCESS LAMBROS SARAKIS AND GEORGE KORMENTZAS, NCSR DEMOKRITOS FRANCISCO MOYA GUIRAO, EUROPEAN COMMISSION AN2 LMAP The authors review emerging protocols and architectures aiming to support inter-system handovers between next-generation wireless systems and present an optimized handover framework built around the functionality introduced by the IEEE standard. F ABSTRACT The key enabling function for seamless mobility and service continuity among a variety of wireless access technologies is the handover. Handovers within the same radio system are addressed by the standardization bodies involved in the development of the corresponding technologies (e.g., 3GPP, 3GPP2, IEEE, DVB), while handovers between heterogeneous systems are managed by protocols developed by the IETF. However, the interoperability between radio access systems that is required to realize the vision of Beyond 3G calls for coordinated actions and integrated solutions combining individual strengths. This article reviews emerging protocols and architectures aiming to support intersystem handovers between nextgeneration wireless systems and presents an optimized handover framework built around the functionality introduced by the IEEE standard. Mapping of this framework to the entities of the 3GPP evolved system architecture is discussed and handover procedures involving key entities of this architecture are presented. INTRODUCTION In any IP multimedia subsystem (IMS), pre-ims, or combined network, handover is the key enabling operation for seamless service provision and content delivery in a variety of mobile/wireless (and wireline) access technologies. Handovers within the same radio system are addressed by the standardization bodies involved in the development of the corresponding technologies, such as the Third Generation Partnership Project (3GPP), 3GPP2, IEEE, and Digital Video Broadcasting (DVB). On the other hand, handovers between heterogeneous systems are managed by protocols developed by the Internet Engineering Task Force (IETF), such as Mobile IP (MIP) [1, 2] and Session Initiation Protocol (SIP). However, the interoperability between radio access technologies that is required to realize the vision of Beyond 3G calls for coordinated actions and integrated solutions combining individual strengths. In this regard, 3GPP leverages on mobility management protocols from IETF for its evolved network architecture [3, 4], which aims to deliver a packet-optimized system that supports multiple radio access technologies and mobility between them, higher data rates, lower latency, improved system capacity and coverage, and reduced operating costs. The 3GPP evolved system architecture paradigm shows that IETF mobility protocols, like MIP and its variants, are identified as key components for mobility between existing and emerging heterogeneous networks; however, these protocols lack features enabling seamless handovers (i.e., handovers that do not result in noticeable service disruption), which are crucial for the performance of real-time applications. With respect to this, the IEEE standard [5, 6] provides standardized mechanisms for closer to seamless handovers among 3GPP, 3GPP2, and several IEEE 802- based networks. In a similar direction, that of enabling radio resource usage optimization in future composite wireless networks, the IEEE standard [7] addresses the architectural building blocks residing at the terminal and network sides that provide for efficient decisions for dynamic network reconfigurability. In the context of the standard, the handover function can be regarded as a reconfigurability enabler for networks involving radio access technologies with fixed spectrum allocation; other enablers include dynamic spectrum assignment and dynamic spectrum access. To achieve its objectives, the standard specifies entities for context information collection, decision making on the basis of context, operator policies and regulatory constraints, and reconfiguration control. This article reviews emerging protocols and architectures that aim to efficiently support handovers between heterogeneous next-generation wireless systems. Relevant efforts of the IETF, IEEE, and 3GPP are presented, and an optimized handover framework, built around the functionality introduced by IEEE , is /09/$ IEEE

2 LMAP LMAP GMAP SR AN1 SR AN2 SR CN LMAP The basic scheme for terminal mobility management in IP networks is the MIP. This works by allocating two addresses to a Mobile Terminal (): a long-term global address (home address) and a short-term local address (Care of Address [CoA]). : First hop router LMAP: Local mobility anchor point : Access network gateway GMAP: Global mobility anchor point : : AN: CN: SR: Point of attachment Mobile terminal Access network Correspondent node Standard router Figure 1. Key mobility-enabling entities in IP networks. discussed. As far as mobility management is concerned, emphasis is placed on MIP-based network-layer protocols, since these correspond to complete solutions for mobility management (i.e., handover and location management) and session continuity. (On the contrary, transportlayer approaches like mobile Stream Control Transmission Protocol [msctp] do not support location management, and application-layer solutions like SIP cannot avoid session reestablishment.) The handover framework, which also leverages entities specified in IEEE , is mapped to the 3GPP evolved network architecture, and signaling for handover initiation, preparation, and execution is discussed. The rest of this article is organized as follows. First, network-layer mobility management protocols are briefly described and compared according to their ability to support seamless mobility and service provision. Then a framework for optimized handover operations is presented, and its components are mapped to entities of the 3GPP evolved system architecture. Based on the functionality of the key building blocks of this architecture, handover procedures are described for an example case of handover from 3GPP to a WiMAX access network. The last section summarizes the work presented herein. OVERVIEW OF NETWORK-LAYER MOBILITY SOLUTIONS The basic scheme for terminal mobility management in IP networks is MIP. This works by allocating two addresses to a mobile terminal (): a long-term global address (home address) and a short-term local address (care of address [CoA]). The home address belongs to the s home domain, while the CoA, used by the mobile when it is away from the home network, belongs to the visiting network. The home address is used as the endpoint identifier for the transport layer, while the CoA is used as the location identifier. With respect to Fig. 1, Mobile IPv4 (MIPv4) [1] requires mobility-related functionality in the, the global mobility anchor point (GMAP) (corresponding to the MIP home agent [HA] in the home network), and, optionally, in the firsthop router (), which undertakes the role of the MIP Foreign Agent (FA). The CoA can be determined either by FA advertisements (in which case it is called FA-CoA) or external mechanisms such as Dynamic Host Configuration Protocol (DHCP). In the latter case (collocated CoA), no FA is needed. A node (correspondent node [CN]) that communicates with the sends packets to the by using always the s home address as the destination address. When the is away from the home network, these packets are received by the HA and then tunneled to either the FA or the itself (changes of the CoA are reported to the HA through location update signaling). In the reverse direction, the sends the packets to the FA, which in turn routes them to CN. In case of collocated CoA, the packets are directly sent by the to the CN. This type of routing, called triangular routing, can be very inefficient when the and the CN are topologically close and the HA is located away from them. 33

3 The basic MIP schemes introduce handover delay due to procedures like movement detection, new CoA configuration and location update. This delay is often unacceptable for real-time applications. Compared to MIPv4, MIPv6 [2] has several advantages that aim to optimize the communication between the CN and. In MIPv6 FAs are not needed, route optimization (including elimination of triangular routing) is supported as part of the basic functionality (as opposed to MIPv4 where this facility is provided as an enhancement to the basic scheme), and there is inherent support for the coexistence of route optimization and routers performing ingress filtering (i.e., routers that refrain from forwarding packets whose IP address does not belong to the domain). However, the direct communication between the CN and the (route optimization) requires that the CN be able to support mobility-aware operations and, furthermore, makes the protocol vulnerable to simultaneous movements (i.e., when both nodes are mobile and move at the same time). The basic MIP schemes introduce handover delay due to procedures like movement detection, new CoA configuration, and location update. This delay is often unacceptable for real-time applications. Two protocols (in principle, optimizations of MIPv6) have been proposed to reduce the handover delay of MIPv6: Fast MIPv6 (FMIPv6) [8] and Hierarchical MIPv6 (HMIPv6) [9]. FMIPv6 works by allowing the to retrieve information about the next subnet prior to handover and start using the next link before location update with the CN is concluded. Handover preparation signaling is established between the and the previous, as well as between the previous and next s. The signaling between s is used to transfer the mobile s context (in mobility management terminology, the term context is used to describe information regarding access control, quality of service [QoS] profile, and header compression), expedite IP configuration in the new subnet (e.g., by checking the validity of the prospective CoA), and set up tunnels to forward packets to/from the before route update is completed. Compared to MIPv6, the scheme adds complexity to the and s but has the potential to deliver a closer to seamless experience. HMIPv6, on the other hand, allows for localized mobility management (i.e., management of topologically small movements within an access network) by introducing a new functional entity called the local mobility anchor point (LMAP). The LMAP, which can be located at any level in a hierarchical network of routers, aims to play the role of the MIPv6 HA in a local domain. Acting as a local HA, the LMAP binds the s on-link CoA (i.e., address belonging to the ) with an address on the LMAP s subnet (called a regional CoA). On-link CoA reconfiguration takes place when the moves to a new subnet; however, its regional CoA does not change, provided that the remains in the same local mobility domain. In order to leverage on MIPv6 for global mobility support, the registers its regional CoA with the global HA and the CN. The protocol calls on routers to advertise support for HMIPv6 functionality and allows s to maintain multiple bindings with distinct LMAPs located at different levels of network hierarchy (e.g., the s and access network gateways [s] in Fig. 1 can also be LMAPs). All protocols described thus far are hostbased in the sense that the s need to implement mobility-related functionality to perform handover and location management signaling when they move between network subnets. Recently, the IETF specified a network-based localized mobility management protocol that allows s to move between subnets within the same access network without requiring changes in their IPv6 protocol stack. This protocol, called Proxy MIPv6 (PMIP) [10], requires mobility support functionality in s and LMAPs (mobile access gateways [MAGs] and local mobility anchors [LMAs], respectively, in PMIP terminology). The former perform mobility management on behalf of the mobile, while the latter act as localized HAs. The main role of the is to provide, in cooperation with the LMAP, router advertisements that make the believe it is still connected to the home network, within which it can keep the same address. The detects the movement of the and initiates the signaling with the LMAP to update the route to/from the s home address. Parts of this signaling include the retrieval of the s policy profile that describes the mobility services that can be offered. The previous discussion shows that the current trend in network-layer mobility management protocol design is to enhance the level of coordination between distinct network entities. However, efficient handover management calls not only for that but also for close interaction of functions inside the entities themselves. This interaction is essential to reduce the delays associated with handover operation. These delays are made up of latencies introduced by functions at both link and network layers. Link-layer latencies are due to factors like late detection of link state changes, and lengthy scanning and authentication/association procedures. On the other hand, network-layer bottleneck factors include late detection of the loss of IP connectivity (late movement detection), a lengthy IP layer parameter configuration process (address, default router, Domain Name System [DNS], etc.), and time-consuming address registration updates. The latencies introduced by functions at these layers are, from the application point of view, cumulative since networklayer configuration presupposes that the link-layer connection to the target network is established and ready for use. In turn, this means that despite any optimizations in the networklayer procedures, seamless handovers cannot be experienced unless the link-layer handover procedures are also optimized, and smooth cooperation between link- and network-layer functions is established. This cooperation will allow linklayer events to trigger functions at the network layer. With respect to that, exploitation of linklayer events has been deemed particularly important for detecting network attachment and expediting IP reconfiguration, as well as enhancing the performance of mobility management protocols. 34

4 Terminal information DB Network information DB Mobility (handover) policies THM NHM Context information SIP VHC-t CIC-t Transport provider: L3 and above transport CIC-n msctp MIP MIH_SAP MIH_LINK_SAP GPP Mobile terminal DVB Transport provider: L2 transport - unidirectional from to for DVB MIH users MIH_SAP MIH_LINK_SAP 802 and possibly DVB PoS in Proxy MIP MIH_SAP VHC-n PoS in non- core/access network node MIH_SAP PoS node with IS in home, visited, or virtual operator core newtork Figure 2. IEEE based vertical handover framework. A FRAMEWORK FOR OPTIMIZED HANDOVER OPERATIONS The lack of standardized mechanisms and services facilitating handovers between heterogeneous networks has been addressed by IEEE This standard provides an optimized handover framework that leverages generic linklayer intelligence independent of the specifics of mobile nodes or radio access networks (RANs) [5]. In this regard, the mobility management protocol stack of the network elements engaged in handover signaling is readdressed, and a logical entity is introduced between the link (L2) and upper layers (L3 and above). This entity, called the MIH function (), provides three kinds of services event, command, and information services to MIH users (i.e., modules, functions, and protocols that make use of the MIH services). The primitives that are used to provide these services are grouped in a media-independent service access point (SAP) MIH_SAP. Communication between the and the link layers, on the other hand, takes place through primitives that are defined in the media-dependent MIH_LINK_SAP and mapped to technology-specific primitives. The exploits triggers from the link layer to facilitate handover initiation (network discovery, network selection, handover negotiation) and handover preparation (L2 and L3 connectivity, resource reservation). The study has particularly focused on handovers between Ethernet (IEEE 802.3), Wi-Fi (IEEE ), WiMAX (IEEE ), 3GPP, and 3GPP2 access networks. However, there has been recent interest from the broadcasting world in incorporating broadcast services into a common service platform to address future market scenarios. This introduces additional requirements for an optimized handover framework, which have to do with the way the interacts with the DVB technology and addresses unidirectional DVB links possibly complemented by separate reverse (interactive) channels provided by a foreign technology (e.g., 3GPP). A vertical handover framework built around the concept of IEEE and complemented by modules inspired by IEEE for context information collection and efficient handover decision making and control is depicted in Fig. 2. According to this figure, an is capable of operating 3GPP, DVB, and IEEE and interfaces, and utilizes the services provided by the for enhanced mobility. Mobility management at the terminal side may be provided by protocols at the network (e.g., MIP), transport (e.g., msctp), or application layer (e.g., SIP), which can be examples of MIH users. The vertical handover controller at the terminal side (VHC-t) applies the terminal handover manager s (THM s) decisions and orchestrates 35

5 ANDSF: MIIS: EPC: 3GPP Access network discovery and selection function MIH information server Evolved packet core THM MIP, SIP G RAN 3G RAN Untrusted AN Trusted AN /PoS /PoS /PoS /PoS /PoS 3GPP evolved RAN (LTE) SGSN MAG A1/MIH PoS/MIPv4 FA (P)MIP (P)MIP MAG A2/MIH PoS/MIPv4 FA GPP EPC (MIP/PMIP-based mobility) Serving gateway (PMIP MAG) PDN gateway (MIP HA/ PMIP LMA) epdg (PMIP MAG) MIIS/ ANDSF NHM IMS service control (SIP-based) IEEE MIH information server, 3GPP ANDSF & IEEE based handover policy decision point Figure 3. Example mapping of optimized handover framework entities to 3GPP evolved system architecture. the execution of the mobility management protocols. This controller is a potential MIH user, as it can use MIH signaling for handover initiation and preparation. The context information collector at the terminal, CIC-t, can also leverage MIH signaling for gathering context information, which is subsequently stored in a data base (DB) inside the terminal (terminal information DB [TIDB]). (However, this does not mean that the CIC-t cannot utilize other supplementary means for retrieving context information.) The THM sends terminal context information to the network handover manager (NHM) and receives mobility (handover) policies. Although the format of the policies is not addressed by the IEEE , the standard does provide the necessary facilities for transferring this information from NHM to THM. Transfer of MIH messages between an and the network node that serves it (MIH point of service [PoS]) can happen over either L2 or L3 and above layers. L2 transport can be used when the PoS is collocated with the network-side endpoint of a L2 link (i.e., the point of attachment []). MIH data transport over L2 has been specified for IEEE 802.3, , and access technologies, while for the DVB case it is an open issue as the relevant standardization is at an early stage. An can reside at different nodes inside a network; at a, at a non- in the access/core network, or far deeper inside the home, visited, or virtual mobile operator core network. With respect to these alternatives, Fig. 2 shows a possible placement for key MIH users including the Proxy MIP network-based mobility management protocol (other mobility management protocols like MIP can also be supported), the vertical handover controller at the network (VHC-n), the context information collector at the network (CIC-n), and the NHM. (Additional MIH users may include entities for resource reservation and pre-authentication [6].) The VHC-n receives handover decisions from the NHM and coordinates the execution of Proxy MIP, while the CIC-n retrieves (through MIH signaling and possibly other means) global network/terminal context data and stores it at a network information DB (NIDB). The role of the MIH information server (MIIS), which is the entity that provides IEEE information services, can be undertaken by the NHM; however, the latter has additional functionality for handover policy derivation and policy efficiency evaluation. THE OPTIMIZED HANDOVER FRAMEWORK IN THE CONTEXT OF THE 3GPP EVOLVED SYSTEM ARCHITECTURE The 3GPP is already addressing the system architecture evolution (SAE) (along with the evolution of the access network, Long Term 36

6 Evolution [LTE]) to make it able to support, among others, a variety of different access systems (existing and future ones), and access selection based on combinations of operator policies, user preferences, and access network conditions. The new system architecture, which is closer to the direction of all-ip networks and leverages on mobility protocols developed by IETF, aims to support access to the 3GPP network through multiple non-3gpp access networks, including WiFi and WiMAX. A possible realization of future interoperable networks based on the current 3GPP evolved system architecture is illustrated in Fig. 3. The depicted heterogeneous network comprise untrusted Wi-Fi, trusted WiMAX, and GPRS/US/LTE access segments. Mobility management and IEEE based handoverenabling functions have been indicatively mapped to and key network nodes [3, 11], and are complemented by facilities for distributed handover decision-making supported by the NHM and THM. Entities responsible for functions like context information collection and vertical handover control are not shown in the figure; they can be placed in the and suitable PoSs in the access and/or core network. Network-based localized mobility is based on PMIP, while MIP-based solutions are utilized to support mobility across administrative domains. The evolved packet core (EPC) includes two main gateways. The serving gateway is involved in mobility between 3GPP systems (2G/3G/LTE), while the packet data network (PDN) gateway addresses mobility between 3GPP and non- 3GPP systems. Another gateway, the evolved packet data gateway (epdg), is used to address connections that originate from untrusted non- 3GPP networks (e.g., Wi-Fi). With respect to the provision of network context information and operators policies, which can be leveraged by s to discover available access networks and make efficient handover decisions, Fig. 3 depicts three facilities that can be used: the MIIS, the NHM, and the 3GPP access network discovery and selection function (ANDSF) [3]. The ANDSF is conceptually similar to MIIS; it provides terminals with network information and the operator s intersystem mobility policies, constraints, rules, and preferences. In this way, s are able to detect available access networks quickly and make decisions on the most appropriate network for service continuation. HANDOVER PROCEDURES FOR SEAMLESS SERVICE PROVISION The potential of IEEE , IEEE , and 3GPP ANDSF to support efficient handover operations for next-generation composite radio networks built around the 3GPP EPC is better illustrated through an example case of handover from 3GPP to WiMAX (the networks are interconnected as in Fig. 3). (The presented handover procedures and signaling are quite generic, and thus can also be applied to handovers between other access technologies.) The mobility management facility is provided by MIPv4 with THM/TIDB Identification of handover target CIC-t context information retrieval including access network discovery Context update Transfer of context Transfer of network context Transfer of radio resource selection policies Figure 4. Handover initiation based on IEEE the FA-CoA; however, the choice of mobility management protocol is highlighted only at the handover execution phase. Figure 4 illustrates how IEEE can be exploited for handover initiation. According to the standard, the CIC-t collects terminal context information, including information on available networks in its vicinity. This context can be subsequently stored in an internal repository integrated into the THM (TIDB). In a similar fashion, the CIC-n collects both static and dynamic network context information, which can be stored at a repository integrated into the NHM (NIDB). Based on context exchange between the network and the terminal, the NHM generates radio resource selection policies and constraints, and sends them to the THM. These policies and constraints may trigger a handover; in such a case, the final decision on the handover target, which has to be consistent with the network policies and constraints, is made by the THM (network-terminal distributed handover decision making). In contrast to IEEE , which only specifies the architectural building blocks that are needed for radio resource usage optimization, IEEE defines specific services and primitives for access network discovery and terminal measurement collection. Such primitives and their use are illustrated in Fig. 5. In this figure the THM, acting as an MIH user, asks for information about the status of an active link by sending an MIH_Link_Get_Parameters request () message to the local. The latter responds to this request with an MIH_Link_Get_Parameters response (.res) message. (Apart from the sequence of messages depicted in Fig. 5, there are further interactions CIC-n Network context information retrieval Network Context update NHM/NIDB Generation of radio resource selection policies 37

7 Serving PoS Candidate PoS Core network PoS THM/TIDB RM RM NHM/MIIS NHM/ANDSF.res MIH_Link_Get_Parameters MIH_Link_Parameters_Report.ind Network context information and mobility policies or MIH_Link_Going_Down.ind.ind Transfer of access network information and policies.ind MIH_Get_Information.res or MIH_Push_Information Access network info request Access network info response MIH_Link_Actions (LINK_SCAN) Identification of potential handover targets.ind.res MIH_MN_HO_Candidate_query.ind MIH_N2N_HO_query_resources.res MIH_MN_HO_Candidate_query Identification of handover target Figure 5. Handover initiation using IEEE IS and 3GPP ANDSF. between the and the link layer of the access technologies; the primitives involved in these interactions are media-dependent and are not discussed in this article.) Additional enablers for retrieval of terminal context information are the MIH_Link_Parameters_Report and MIH_Link_Going_Down indications (.ind) that are sent by the in an asynchronous manner when preconfigured QoS parameter thresholds (set by an MIH user) have been crossed or loss of connection is imminent, respectively. Apart from information obtained locally, the terminal can retrieve (basically static) network context information (and handover policies) from an MIIS (which is assumed to be incorporated in the NHM in Fig. 5) by using the MIH_Get_Information message (the requested information is delivered through a sequence of request, indication, response, and confirm [] primitives). Alternatively, information from the MIIS can be provided in a periodic push fashion through the MIH_Push_Information message. Similar to MIIS, access network information and the operator s mobility policies can be provided to the terminal by the ANDSF. (Figure 5 illustrates the message exchange in the request/reply information provision model.) Based on the received information from the MIIS or the entity that hosts the ANDSF, the terminal performs scanning on the candidate networks in order to retrieve dynamic information about current link conditions (scanning is performed through the MIH_Link_Actions command with the appropriate action parameter). The scanning results can be used for the identification of a potential handover target. The next step in handover initiation is the resource availability check on the candidate network (WiMAX in this example). This check is supported by the MIH_MN_HO_Candidate_query and MIH_N2N_HO_query_resources messages that are exchanged between an appropriate MIH user at the terminal (this can be the 38

8 3GPP serving PoS WiMAX PoS PDN gateway CN UP entity VHC-t MIPv4 VHC-n RM MIPv4 FA MIPv4 HA UP entity MIH_MN_HO_Commit MIH_N2N_HO_Commit MIH_Link_Actions (LINK_POWER_UP) MIH_Link_Up.ind MIPv4 execution FA solicitation FA advertisement Registration Registration reply Registration Registration reply Traffic flow Figure 6. Handover preparation and MIPv4 execution. THM) and an appropriate MIH user at the serving/3gpp PoS (this can be a resource manager [RM]), as well as between MIH users at the serving and candidate PoSs (e.g., RMs). The handover preparation and handover execution phases (Fig. 6) involve resource reservation and connection establishment to the target network, as well as data forwarding and binding updates. In mobile-initiated handovers, resource reservation is done through exchange of MIH_MN_HO_Commit (used to denote that the terminal is committed to perform a handover) and MIH_N2N_HO_Commit (used to trigger resource reservation) commands (for simplicity, the primitives of these commands are not shown in Fig. 6). These commands are exchanged between an appropriate MIH user at the mobile terminal (e.g., the VHC-t) and MIH users at the network (e.g., VHC-n, RMs). Link layer connection establishment is triggered by the MIH_Link_Actions command and communicated through the MIH_Link_Up event. For the MIPv4-based mobility addressed in this example, the handover execution could involve triggering MIPv4 operation by the VHCt MIH user. (It should be noted that this approach offers better coordination of the execution of the MIP; however, the trigger can also come from the itself, provided that the MIP acts as an MIH user and has subscribed to appropriate events.) After the exchange of FA solicitation, FA advertisement, MIPv4 registration, and registration reply messages between the mobile terminal and the FA located at the (this signaling triggers also exchange of registration request and reply messages between the FA and the HA located at the PDN gateway), a tunnel (depicted with a tick arrow in Fig. 6) is established to carry data between the and the PDN gateway. SUMMARY This article presents an optimized handover framework that aims to provide seamless service provision and content delivery to mobile users in a Beyond 3G heterogeneous networking environment. The framework is based on the emerging IEEE standard and is complemented by IETF protocols for mobility management and facilities derived from IEEE for context information collection, vertical handover control, and efficient mobility decision making. An indicative application of this framework to the 3GPP evolved system architecture is presented and example handover procedures involving handover initiation, preparation, and execution are discussed. ACKNOWLEDGMENTS The work was undertaken in the context of the project INFSO-ICT HURRICANE (Handovers for Ubiquitous and Optimal Broadband Connectivity among Cooperative Networking Environments), which has received research funding from the European 7th Framework Programme. 39

9 REFERENCES [1] C. Perkins, Ed., IP Mobility Support for IPv4, IETF RFC 3344, Aug [2] D. Johnson, C. Perkins, and J. Arkko, Mobility Support in IPv6, IETF RFC 3775, June [3] 3GPP TS V8.6.0, Architecture Enhancements for Non-3GPP Accesses (Release 8), June [4] 3GPP TR V8.0.0, 3GPP System Architecture Evolution: Report on Technical Options and Conclusions (Release 8), Sept [5] IEEE , IEEE Standard for Local and Metropolitan Area Networks Media Independent Handover Services, Jan [6] K. Taniuchi et al., IEEE : Media Independent Handover: Features, Applicability, and Realization, IEEE Commun. Mag., Jan [7] IEEE , IEEE Standard for Architectural Building Blocks Enabling Network-Device Distributed Decision Making for Optimized Radio Resource Usage in Heterogeneous Wireless Access Networks, Feb [8] R. Koodli, Ed., Mobile IPv6 Fast Handovers, IETF RFC 5268, June [9] H. Soliman et al., Hierarchical Mobile IPv6 (HMIPv6) Mobility Management, IETF RFC 5380, Oct [10] S. Gundavelli, Ed., Proxy Mobile IPv6, IETF RFC 5213, Aug [11] G. Lampropoulos, A. Salkintzis, and N. Passas, Media- Independent Handover for Seamless Service Provision in Heterogeneous Networks, IEEE Commun. Mag., Jan BIOGRAPHIES LAMBROS SARAKIS has been with the Institute of Informatics & Telecommunications of the National Center for Scientific Research Demokritos since 2004, currently as Associate Researcher. He received his Diploma in electrical engineering & computer science from the National Technical University of Athens (NTUA), Greece, in 1996, his M.Sc. in Communications & signal processing from Imperial College in 1997, and Ph.D. in Computer Science from NTUA in His research interests include performance evaluation of heterogeneous wireless networks, traffic modeling and analysis, QoS support in packet-switched networks, and hardware/software co-design for embedded systems. GEORGE KORMENTZAS is a research associate with the Institute of Informatics and Telecommunications of the National Center for Scientific Research Demokritos and an assistant professor in the University of the Aegean, Department of Information and Communication Systems Engineering. He received his Diploma in electrical and computer engineering and Ph.D. in computer science, both from NTUA, in 1995 and 2000, respectively. He is a member of esteemed professional societies, and an active reviewer and guest editor for several journals and conferences. Currently, he is the project manager of the FP7-ICT-STREP HURRICANE project and chair of one of the working groups of the emobility Technology Platform. FRANCISCO MOYA GUIRAO (Francisco.Guirao@ec.europa.eu) is a scientific officer in the Information and Communication Technologies (ICT) Priority at the European Commission (DG Information Society), part of the 7th Framework Programme for Research. He graduated as a Telecommunication Engineer from the Universidad Politécnica de Madrid (UPM). He specializes in the domain of future networks. He joined the European Commission in May He started his work in TV operation with Spanish TV (TVE). Then he moved to research and technological development programs in the area of advanced networks and services for integrated broadband communications, in particular in image processing and TV broadcasting. 40