Mobility management is one of the most challenging research issues for vehicular networks to support a variety of intelligent transportation system (ITS) applications. The traditional mobility management schemes for Internet and mobile ad hoc network (MANET) cannot meet the requirements of vehicular networks, and the performance degrades severely due to the unique characteristics of vehicular networks (e.g., high mobility). Therefore, mobility management solutions developed specifically for vehicular networks would be required. This paper presents a comprehensive survey on mobility management for vehicular networks. First, the requirements of mobility management for vehicular networks are identified. Then, classified based on two communication scenarios in vehicular networks, namely, vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, the existing mobility management schemes are reviewed. The differences between host-based and network-based mobility management are discussed. To this end, several open research issues in mobility management for vehicular networks are outlined. Copyright © 2009 John Wiley & Sons, Ltd.

Mobility and handoff management in vehicular networks: a survey

While host mobility support for individual mobile hosts (MHs) has been widely investigated and developed over the past years, there has been relatively less attention to NEtwork MObility (NEMO). Since NEMO Basic Support (NEMO-BS) was developed, it has been the central pillar in Intelligent Transport Systems (ITS) communication architectures for maintaining the vehicle's Internet connectivity. As the vehicle moves around, it attaches to a new access network and is required to register a new address obtained from the new access network to a home agent (HA). This location update of NEMO-BS often results in unacceptable long handover latency and increased traffic load to the vehicle. To address these issues, in this paper, we introduce new NEMO support protocols, which rely on mobility service provisioning entities introduced in Proxy Mobile IPv6 (PMIPv6), as possible mobility support protocols for ITS. As a base protocol, we present PMIPv6-based NEMO (P-NEMO) to maintain the vehicle's Internet connectivity while moving and without participating in the location update management. In P-NEMO, the mobility management for the vehicle is supported by mobility service provisioning entities residing in a given PMIPv6 domain. To further improve handover performance, fast P-NEMO (FP-NEMO) has been developed as an extension protocol. FP-NEMO utilizes wireless L2 events to anticipate the vehicle's handovers. The mobility service provisioning entities prepare the vehicle's handover prior to the attachment of the vehicle to the new access network. Detailed handover procedures for P-NEMO and FP-NEMO are provided, and handover timing diagrams are presented to evaluate the performance of the proposed protocols. P-NEMO and FP-NEMO are compared with NEMO-BS in terms of traffic cost and handover latency.

Performance Analysis of PMIPv6-Based NEtwork MObility for Intelligent Transportation Systems

Wireless technology is a revolutionary advancement providing users with ubiquitous data and telephony access anywhere and anytime with no physical (PHY) connection. The currently deployed wireless networks like Wi-Fi, Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications Systems (UMTS), and Long Term Evolution (LTE) systems have different characteristics that make them complementary in terms of performance, coverage, and cost. This network variety presents an opportunity to provide better services to end users, given the advances in mobile terminals (MTs). To reach this goal, an appropriate automatic network selection (ANS) mechanism, which is able to always select the best access network, is needed. This consists of constantly monitoring any type of available access network, i.e., automatically selecting and switching to the best one, as the network that maximizes the users quality of experience, taking into account their preferences and the terminal and network conditions. ANS is a multidimensional decision-making problem that can be solved by finding an appropriate complex tradeoff between possibly conflicting criteria. In this paper, we propose an analytical model to capture the preferences of end users. Based on this model, we design an ANS mechanism that takes into account all aspects of the tradeoff between the quality of the connections, the preferences of the end users, and the cost. To highlight the benefits of our approach from the perspectives of both end users and network operators, we have implemented and tested the solution in a multitechnology simulator. Results show that the proposed solution outperforms mainstream approaches.

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Multicriteria Optimization of Access Selection to Improve the Quality of Experience in Heterogeneous Wireless Access Networks

Vertical handover decision making is one of the key problems in heterogeneous networks environment. In IEEE 802.21 standard, a Media Independent Handover (MIH) framework is proposed to improve user experience of mobile devices by facilitating handover in heterogeneous networks with measurements and triggers from link layers. However, vertical handover decision making can benefit from the information more than link layers. In this paper, an Enhanced Media Independent Handover (EMIH) framework is proposed by integrating more information from application layers, user context and network context. Given such information, there is also another important problem on how to select a favorite network. Two quite important problems from realistic scenario are as follows: (1) how to make use of partial knowledge due to incomplete value measurement on decision factors; (2) how to deal with robustness problem due to inaccurate measurement on decision factors. In order to tackle these problems, two novel Weighted Markov Chain (WMC) approaches based on rank aggregation are proposed in this paper, in which a favorite network is selected as the top one of rank aggregation result fused from multiple ranking lists based on decision factors. Moreover, an entropy weighting method, combined with WMC approach, is studied. The simulations demonstrate the effectiveness of these proposed approaches.

Handover Management in Enhanced MIH Framework for Heterogeneous Wireless Networks Environment

The requirement for in-vehicle passengers to access Internet multimedia services has risen recently. As a consequence, Vehicle Ad hoc NETwork (VANET) has gained much attention, and is regarded as a promising solution for providing in-vehicle Internet service through inter-vehicle and infrastructure communication. A new developed wireless network technique, termed WiMAX Mobile Multihop Relay (MMR), provides a good communication framework for a VANET formed from vehicles on high-speed freeways. Applying MMR WiMAX allows some public transportation vehicles to act as relay vehicles (RVs) to provide Internet access to passenger vehicles. However, the standard handover procedure of mobile or MMR WiMAX suffers long delay due to the lack of information about the next RV. This study presents a cross-layer fast handover scheme, called vehicular fast handover scheme (VFHS), where the physical layer information is shared with the MAC layer, to reduce the handover delay. The key idea of VFHS is to utilize oncoming side vehicles (OSVs) to accumulate physical and MAC layers information of passing through RVs and broadcast the information to vehicles that are temporarily disconnected, referred to as disconnected vehicles (DVs). A DV can thus perform a rapid handover when it enters the transmission range of one of approaching RVs. The effectiveness of VFHS is verified using ns2 simulations. Simulation results indicate that VFHS significantly decreases handover latency and packet loss. Copyright © 2009 John Wiley & Sons, Ltd.

Cross-layer design vehicle-aided handover scheme in VANETs

In this paper, we optimize the handover procedure in the fast handover for mobile IPv6 (FMIPv6) protocol by using the IEEE 802.21 media independent handover (MIH) services. FMIPv6 is used to enhance the performance of handovers in mobile IPv6 and its basic extension for network mobility (NEMO), i.e., the fundamental mobility management protocols used in vehicular networks. With the aid of the lower three layers' information of the mobile node/router (MN/MR) and the neighboring access networks, we tackle the radio access discovery and candidate access router (AR) discovery issues of FMIPv6. We introduce an "information element container" to store static and dynamic layer 2 (L2) and layer 3 (L3) information of neighboring access networks and propose to use a special cache maintained by the MN/MR to reduce the anticipation time in FMIPv6, thus increasing the probability of the predictive mode of FMIPv6 operation. Furthermore, we propose a cross-layer mechanism for making intelligent handover decisions in FMIPv6. The lower layer information of the available links obtained by MIH services and the higher layer information such as quality-of-service (QoS) parameter requirements of the applications are used by a policy engine to make intelligent handover decision. We will show through analysis and simulations of the signaling procedure that the overall expected handover (both L2 and L3) latency in FMIPv6 can be significantly reduced in the proposed mechanism.

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Q.B. Mussabbir

Papers

Optimized FMIPv6 Using IEEE 802.21 MIH Services in Vehicular Networks