Handover mechanisms in next generation heterogeneous wireless networks

University of Technology, Sydney. Faculty of Engineering.New access technologies such as IEEE 802.11 Wireless LAN are emerging as a new means of public wireless access. Working on public unlicensed bands, they are capable of providing high speed data services, but small radio coverage. The third generation cellular networks such as Universal Mobile Telecommunications System (UMTS) provide wide radio coverage, but have limited data rates. An integration of these heterogeneous wireless networks is expected to be an effective means of providing high speed data access in wide radio coverage in the Next Generation (NG) wireless networks. When a mobile user moves across these networks, it has to perform handover to maintain its services. During a handover, it is pivotal to guarantee both service continuity and service quality, which ensure that handover can be made seamlessly. To provide ubiquitous services, an extensive collaboration between network operators is anticipated to be an economic solution. Providing seamless handover and ubiquitous services in heterogeneous wireless networks presents many new research challenges. The objective of this thesis is to develop new handover management techniques for supporting seamless handover and facilitating ubiquitous services in heterogeneous wireless networks. More specifically, new techniques for dealing with the extensive collaboration of NG network operators, and new techniques that enable the interworking of heterogeneous wireless technologies. Regarding the extensive collaboration of network operators, a neighbour network trust information retrieval scheme is proposed for global roaming. With this scheme, an access network can obtain network trust information of its nearby access networks without relying on direct links with them. The retrieved trust information can be provided to an attached mobile user later to assist it with global roaming. Next, a handover decision algorithm that uses network trust information is presented. The proposed algorithm guarantees much more reliable handover in a multiple-operator environment. It is demonstrated how quality of service is maintained and overall network load is balanced using the proposed handover algorithm. The thesis moves further to a proxy based authentication localisation scheme that focuses on the handover across two networks without a trust relation. The proposed scheme provides a secure and effective method of localising authentication at a third-party entity during a handover. This avoids resorting to a mobile’s home network for identity verification in a handover, and thus, greatly reduces handover latency. In terms of the interworking of heterogeneous wireless technologies, the thesis presents a multi-interface mobile terminal model for media independent handover. The presented model addresses the challenge of working with heterogeneous wireless technologies from the perspective of a mobile terminal. Under the proposed multi-interface architecture, a mobile terminal can work with multiple network interfaces, and still uses common upper layer protocols such as Mobile IPv4. Being compatible with IEEE 802.21 framework, it uses a cross-layer design approach

A survey of performance enhancement of transmission control protocol (TCP) in wireless ad hoc networks

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Springer OpenTransmission control protocol (TCP), which provides reliable end-to-end data delivery, performs well in traditional wired network environments, while in wireless ad hoc networks, it does not perform well. Compared to wired networks, wireless ad hoc networks have some specific characteristics such as node mobility and a shared medium. Owing to these specific characteristics of wireless ad hoc networks, TCP faces particular problems with, for example, route failure, channel contention and high bit error rates. These factors are responsible for the performance degradation of TCP in wireless ad hoc networks. The research community has produced a wide range of proposals to improve the performance of TCP in wireless ad hoc networks. This article presents a survey of these proposals (approaches). A classification of TCP improvement proposals for wireless ad hoc networks is presented, which makes it easy to compare the proposals falling under the same category. Tables which summarize the approaches for quick overview are provided. Possible directions for further improvements in this area are suggested in the conclusions. The aim of the article is to enable the reader to quickly acquire an overview of the state of TCP in wireless ad hoc networks.This study is partly funded by Kohat University of Science & Technology (KUST), Pakistan, and the Higher Education Commission, Pakistan

Cross-layer design of multi-hop wireless networks

MULTI -hop wireless networks are usually defined as a collection of nodes equipped with radio transmitters, which not only have the capability to communicate each other in a multi-hop fashion, but also to route each others’ data packets. The distributed nature of such networks makes them suitable for a variety of applications where there are no assumed reliable central entities, or controllers, and may significantly improve the scalability issues of conventional single-hop wireless networks. This Ph.D. dissertation mainly investigates two aspects of the research issues related to the efficient multi-hop wireless networks design, namely: (a) network protocols and (b) network management, both in cross-layer design paradigms to ensure the notion of service quality, such as quality of service (QoS) in wireless mesh networks (WMNs) for backhaul applications and quality of information (QoI) in wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of this Ph.D. dissertation, different network settings are used as illustrative examples, however the proposed algorithms, methodologies, protocols, and models are not restricted in the considered networks, but rather have wide applicability. First, this dissertation proposes a cross-layer design framework integrating a distributed proportional-fair scheduler and a QoS routing algorithm, while using WMNs as an illustrative example. The proposed approach has significant performance gain compared with other network protocols. Second, this dissertation proposes a generic admission control methodology for any packet network, wired and wireless, by modeling the network as a black box, and using a generic mathematical 0. Abstract 3 function and Taylor expansion to capture the admission impact. Third, this dissertation further enhances the previous designs by proposing a negotiation process, to bridge the applications’ service quality demands and the resource management, while using WSNs as an illustrative example. This approach allows the negotiation among different service classes and WSN resource allocations to reach the optimal operational status. Finally, the guarantees of the service quality are extended to the environment of multiple, disconnected, mobile subnetworks, where the question of how to maintain communications using dynamically controlled, unmanned data ferries is investigated

Security and Privacy Issues in Wireless Mesh Networks: A Survey

This book chapter identifies various security threats in wireless mesh network (WMN). Keeping in mind the critical requirement of security and user privacy in WMNs, this chapter provides a comprehensive overview of various possible attacks on different layers of the communication protocol stack for WMNs and their corresponding defense mechanisms. First, it identifies the security vulnerabilities in the physical, link, network, transport, application layers. Furthermore, various possible attacks on the key management protocols, user authentication and access control protocols, and user privacy preservation protocols are presented. After enumerating various possible attacks, the chapter provides a detailed discussion on various existing security mechanisms and protocols to defend against and wherever possible prevent the possible attacks. Comparative analyses are also presented on the security schemes with regards to the cryptographic schemes used, key management strategies deployed, use of any trusted third party, computation and communication overhead involved etc. The chapter then presents a brief discussion on various trust management approaches for WMNs since trust and reputation-based schemes are increasingly becoming popular for enforcing security in wireless networks. A number of open problems in security and privacy issues for WMNs are subsequently discussed before the chapter is finally concluded.Comment: 62 pages, 12 figures, 6 tables. This chapter is an extension of the author's previous submission in arXiv submission: arXiv:1102.1226. There are some text overlaps with the previous submissio