Elsevier

Computer Networks

Volume 51, Issue 17, 5 December 2007, Pages 4849-4866
Computer Networks

Toward IP converged heterogeneous mobility: A network controlled approach

https://doi.org/10.1016/j.comnet.2007.07.010Get rights and content

Abstract

Envisioning a future where mobile terminals equipped with one or more network devices are able to roam across wireless or wired networks, in a diverse macro and micro wireless cells environment, requires the development of enhanced methods to control IP-based mobility. These methods should consider traditional terminal mobility (mainly due to user movement) as well as mobility across heterogeneous networks in the presence of semi-static users. For this to become reality, a cross layer interaction is required starting from a potentially large diversity of layer two access technologies up to the common IP layer, allowing the exchange of messages between terminals and network components. Furthermore, traditional host mobility driven concepts need to evolve, and include more stringent mobile operator requirements in context of fully driven network controlled mobility. This paper presents and evaluates a novel framework design, based on the IEEE 802.21 future standard, encompassing network driven as well as host driven mobility. This paper evaluates signalling aspects, algorithm design and performance issues.

Introduction

IP mobility has been widely explored in the research community. IETF2 protocols, such as [1], [2], [3], [4] and their extensions or optimizations [5], [6], are becoming mature and implementations are already available for deployment. This is being fostered by large scale ambitions for future generation networks, which will require synergy across multiple technology aspects [7]: liaisons between standardization bodies are happening with increasing frequency. As examples, 3GPP3 (defining architecture reference scenarios for next generation Mobile Operators networks), the WiMax forum4 (defining the WiMax mobile reference architecture) and the IEEE5 802.21 working group (defining standards for enhanced vertical handover strategies) are actively discussing liaisons with IETF to agree on a common set of requirements to ensure the compatibility between architectures and protocols for mobility [8], [9], [10]. In other words, while IETF mobility protocols use the IP layer as convergence layer, it still has to be practically proved (i) that these protocols suit physical architecture requirements and (ii) that these protocols can easily operate in heterogeneous wireless access networks.

Enhanced methods to control user mobility, across these multiple environments, are a requirement for an expected future in which terminals equipped with one or more network interfaces [8], [9] roam across networks, in a multi-diversity of macro and micro wireless cells, the so-called “4G networks” environment. These mobility methods should consider both traditional terminal mobility (mainly due to user movement), and mobility across heterogeneous networks [10] in novel scenarios, where network load balancing or user context preferences may require mobility triggers also in the network side. To combine these different triggers, there is a need of a cross layer approach, starting from a potentially large diversity of layer two access technologies up to the common IP layer, to exchange messages between terminals and network components. Traditional host mobility driven concepts need therefore to be combined with more stringent mobile operator requirements of network controlled mobility [11]. Thus, users on the move, while enjoying seamless services, can take advantage of optimal mobility choices, eventually mainly computed by network components.

Following this orientation, in the concept behind this paper we evolve standard mobility mechanisms by adding network intelligence able to (i) understand the diversity of layer two wireless cells, and (ii) converge new mobility services on top of an IP common layer. In this work, mobility is not regarded anymore as a pure reaction upon terminal movement, but rather as a potential service that future Mobile Operators might offer to customers in different forms and multiple degrees of complexity. Thus, terminal mobility can be either controlled by the network (upon network detection triggers coming from the terminal) or fully initiated from the network (supporting optimizations where required). We argue that 4G networks will require this combination as personalization in the user’s terminal and resource usage optimization by the network will have to be integrated at a consistent control plane. Also, the expected mobility dynamics, cell coverage, and multi-technology environment is different from the traditional scenario of current cellular networks, and thus the results of network initiated handover in these networks may not be directly applicable to 4G networks. To efficiently cope with these novel 4G mobility scenarios, in this paper we propose a flexible framework combining the global IP mobility management protocol (Mobile IPv6 [1]) and the future standard for enhanced vertical handover execution (IEEE 802.21 [12]), with embedded network controlled capabilities. The performance of our proposed framework is evaluated through simulation, considering WLAN and cellular systems, and we show that our mobility framework provides standards-based mobility support, with added flexibility while keeping insignificant signalling overhead.

Furthermore, it should be noted that having addressed the benefits of network controlled/initiated handovers and analyzed associated scenarios in [13], this paper proposes a framework to efficiently implement network controlled handover strategies. This study does not conclude that network controlled handovers outperform mobile terminal controlled handovers in all conditions, rather that when applied, this optimal implementation meets the requirements on seamless mobility (user experience) and operators’ policies.

The remainder of the paper is organized as follows. Section 2 presents a brief overview on (ours and others) work in the area. Section 3 introduces the network technologies basis for our framework, namely IEEE 802.21 and Mobile-IP. Section 4 describes our framework design and architectural choices. Sections 5 Simulation setup, 6 Results evaluation, respectively, present the simulation setup, including functional components’ design, and associated results. Section 7 derives considerations to be accounted for future 4G networks design, and Section 8 concludes the paper.

Section snippets

Related work

As explained in Section 1 several protocols have been standardized in IETF [1], [2], [3], [4] to support IP mobility. The research community has been quite active in the past years in understanding limitations and possibilities of these upcoming solutions [5], [6]. As an example [14] provides a complete solution to efficiently manage host mobility across WWAN and WLAN networks. This paper presents an optimized terminal architecture covering layer two issues (such as WLAN sensing and thresholds

Network technologies

The IEEE 802.21 [12], [18] (or Media Independent Handover (MIH)) technology is an enabler for the optimization of handovers between heterogeneous IEEE 802 systems as well as between 802 and cellular systems. The goal is to provide the means to facilitate and improve the intelligence behind handover procedures, allowing vendors and operators to develop their own strategy and handover policies. Furthermore, IEEE 802.21 is potentially usable in multiple mobility scenarios, both mobile and network

Framework design

As mentioned above, our framework exploits the R3 (IP based) interface in IEEE 802.21, between the MN and the PoS (central entity), integrating the control signalling with Mobile IP signalling for data plane update. For simplicity (and due to its current industry relevance) we will discuss our proposal only applied across WLAN and cellular technologies.

In our scenario, global coverage from cellular technologies is always available, and enhanced coverage is available in multiple WLAN hotspots, a

Simulation setup

In this section we present the simulation environment used to evaluate our framework, which also requires the detail of some of the entities involved in mobility management. Our study was conducted by simulating the movement of a MN attached to a 3G network and performing several handovers between 3G and WLAN hotspots, varying terminal speed and coverage threshold values.

The simulation scenario considers wide space with indoor characteristics (such as an airport) in which the user can move at

Results evaluation

We first present the Mobile Initiated and Network Controlled scenario where no admission control mechanism is applied. Fig. 5 depicts the percentage of failed handovers. Three speeds have been considered namely, 2, 5 and 10 m/s targeting indoor scenarios. From the graph we can see that by varying the threshold 3G  WLAN from −75 up to −65 dBm the percentage of failed handovers as defined above increases to almost 65% in case of 10 m/s. The curves follow a similar shape for 2 and 5 m/s. As can be

4G design considerations

The results presented in the previous section validate our framework design showing the feasibility of this new approach for mobility and handover management. Specifically the IEEE 802.21 signalling, while introducing minimized network overhead, leads to optimal network control of terminal mobility. The comparison of simulation results with and without network load knowledge shows a negligible impact on the chosen metrics. However, when considering future 4G networks and wide scale deployments

Conclusions

The paper presents a framework that integrates 802.21 and Mobile IP for heterogeneous networking. This framework is evaluated in the usual situation of mixed 3G and WLAN environments. Our results address handover management, heterogeneous networking and decisions making procedures implemented in the network diverging from more classic host-based solutions. The results show that the 802.21 usage does not impose meaningful network load, and that the network handover initiation features provide

Telemaco Melia received his Informatics Engineering degree in 2002 from the Polytechnic of Turin, Italy and his PhD in Mobile Communications from University of Goettingen in April 2007. Since June 2002 he is employed NEC Europe Ltd. in Heidelberg, Germany in the Mobile Internet Group. He worked on IPv6 based Mobile Communication within the EU IST Moby Dick Project. He is currently working on mobility architecture issues in the EU IST Daidalos project. His main research areas are IP mobility

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  • Telemaco Melia received his Informatics Engineering degree in 2002 from the Polytechnic of Turin, Italy and his PhD in Mobile Communications from University of Goettingen in April 2007. Since June 2002 he is employed NEC Europe Ltd. in Heidelberg, Germany in the Mobile Internet Group. He worked on IPv6 based Mobile Communication within the EU IST Moby Dick Project. He is currently working on mobility architecture issues in the EU IST Daidalos project. His main research areas are IP mobility support across heterogeneous networks and resource optimization control, closely following standardization bodies such as IEEE and IETF where he actively contributes. He is author of several publications in international conferences and he is currently employed as Senior Research Staff Member.

    Antonio de la Oliva received the Telecommunication Engineering degree from the Universidad Carlos III de Madrid, Madrid, Spain, in 2004. He is currently working towards the Ph.D. degree in the Telematics Department, Universidad Carlos III de Madrid, where he has been working as a Research and Teaching Assistant of Telematic Engineering since 2004. He is currently involved in several European projects such as EU IST Daidalos and EU IST OneLab.

    Albert Vidal is a researcher since May 2007 at the i2CAT Foundation in Barcelona. After receiving his Telecommunications Engineering degree from the Technical University of Catalonia (UPC) in Barcelona in 2005, he worked as a researcher at NEC Network Laboratories in Heidelberg, Germany, in several projects on the topics of mobility between heterogeneous wireless access networks and quality of service combined with power saving mechanisms for 3G/WLAN dual mode terminals. He is author of several technical papers and patent applications in these fields. From the standardization point of view, he currently participates in the IEEE standardization effort as a voting member and contributor to the 802.21 Working Group (Media Independent Handover), and previously he has also participated in the elaboration of certification programs at the Wi-Fi Alliance.

    Ignacio Soto received a Telecommunication Engineering degree in 1993, and a Ph.D. in Telecommunications in 2000, both from the University of Vigo, Spain. He was a research and teaching assistant in Telematics Engineering at University of Valladolid since 1993 to 1999. In 1999 he joined University Carlos III de Madrid, where he has been an associate professor since 2001. His research activities focus on mobility support in packet networks and heterogeneous wireless access networks. He has been involved in international and national research projects related with these topics, including the EU IST Moby Dick and the EU IST Daidalos projects. He has published several papers in technical books, magazines and conferences, lately in the areas of efficient handover support in IP networks with wireless access, network mobility support, and security in mobility solutions.

    Daniel Corujo received his Computer and Telematics Engineering degree in 2006 from the University of Aveiro, Portugal. He did his master at University of Aveiro on Heterogeneous Handover Environments. In September 2006 he joined the Heterogeneous Networking Group of Instituto de Telecomunicacoes, at the University of Aveiro, as a researcher. He worked on QoS, Mobility, IEEE802.21 and IEEE802.16 within the EU IST Daidalos Project. His main research areas are Mobility with QoS in Heterogeneous Networks.

    Rui L. Aguiar received a Ph.D. degree in electrical engineering in 2001 from the University of Aveiro, Portugal. He is currently a professor at the University of Aveiro and is also leading a research team at the Institute of Telecommunications, Aveiro, on next-generation network architectures and protocols. His current research interests are centered on the implementation of advanced wireless networks, systems, and circuits, with special emphasis on QoS and mobility aspects, areas where he has more than 200 published papers. He has been TPC-CoChair of ISCC’07 and ICNS’05, and General Chair of ICT’06, and a member of multiple scientific committees.

    This work was supported in part by IST FP6 Integrated Project DAIDALOS. DAIDALOS receives research funding from the European Community’s Sixth Framework Program. Nonetheless, the European Commission has no responsibility for the content of this paper.

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