Bosheng Zhou

An energy-aware virtual backbone tree for wireless sensor networks

Provision of an efficient communication infrastructure is a critical task for wireless sensor networks, and Virtual backbones have been proposed as an efficient mechanism for providing this. In this paper, we propose an energy-aware virtual backbone tree (EVBT) for general-purpose communications in wireless sensor networks. The EVBT has some salient features: the overhead for constructing an EVBT is very low; the delivery of data along the tree depletes minimum energy from the network; and the tree nodes are those with high energy levels. In addition to these, the proposed algorithm is adaptive in nature - it automatically adapts to the addition and removal of the sensor nodes. The use of multiple EVBTs improves the robustness of the communications infrastructure. Simulation results are presented that demonstrate the efficiency of the proposed algorithm.

A Random Packet Destruction DoS Attack for Wireless Networks

Denial of service (DoS) attacks, and jamming in particular, present a significant threat to wireless networks because they are easy to mount and difficult to detect and prevent. We present and analyze a special type of DoS attack, called random packet destruction (RPD) that works by transmitting short periods of noise signals. The RPD DoS attack can effectively shut down a wireless network. Since the attacker does not need to pretend to be a legal user participating in the network, current anti-attack measures such as encryption, authentication and authorization cannot prevent these types of attacks. RPD DoS attacks are pervasive in nature and can potentially be launched against any wireless networks that are detectable. An attacker can launch RPD attacks against wireless networks used for mission critical systems to inflict serious damages on lives or properties. The paper presents for the first time, both theoretical analysis and performance simulations of WLANs when operating under RPD DoS attacks for a range of types of network traffic.

The non-responsive receiver problem in mobile ad-hoc networks

IEEE 802.11 MAC based Mobile Ad-hoc Networks (MANETs) are known to experience serious unfairness problems particularly for TCP connections. The unfairness is caused by a number of factors and to date, no solution has completely addressed all the factors, so that the unfairness is never completely solved. The work presented here identifies the common factors that lead to the unfairness, and from a consideration of these, a novel solution based on carrier sensing is developed, that can completely solve the serious unfairness problem in MANETs. Simulation results are presented which show the effectiveness of our solution.

A New Trust Management Framework for Detecting Malicious and Selfish Behaviour for Mobile Ad Hoc Networks

With the development of wireless network applications, wireless networks need more interactions between many entities, and a rapidly increasing requirement for designing secure applications among these entities is trust management. Therefore, a lot of attacks against distributed environment are aimed at the trust management. This article presents a new trust management framework (TMF) for Mobile Ad hoc Networks. The proposed framework calculates a nodes trust value based on observations from neighbour nodes by using Grey theory and Fuzzy sets. The TMF chooses multiple rather than a single parameter to obtain trust values. Simulations conducted in a Mobile Ad hoc Network (MANET, 802.11-based) with Random Waypoint Mobility Mode show what the proposed framework can do is not only detecting abnormal trust behaviour, but also discovering which parameter for forming trust values of a mobile node is abnormal, that means it can identify the possible attack strategy in both static and mobile environment. The TMF has shown good performance in calculating trust values of mobile wireless nodes under normal and abnormal (attack) conditions, and hence can be considered as an effective trust framework for MANETs.

Performance Analysis of Fault-Tolerant Offloading Systems for Pervasive Services in Mobile Wireless Environments

Offloading (also known cyber-foraging) is an approach to leverage the severity of resource constrained nature of mobile devices (such as PDAs) by migrating part of the computation of applications to some nearby resource-rich surrogates (e.g., desktop PCs). It is an essential mechanism for the execution of pervasive applications. However, the mobile nature of mobile devices and the unstable connectivity of wireless links all render a less predictability of the performance of a pervasive application running under the control of offloading systems. This paper proposes an analytical model to express the performance of fault- tolerant offloading systems in mobile wireless environments. We model the failure recovery time and total execution time of pervasive applications that run under the control of the fault- tolerant offloading systems. The model is analyzed numerically and primarily evaluated based on a real application.

A cross-layer architecture for DiffServ in mobile ad-hoc networks

The delivery of service differentiation in mobile ad hoc networks presents a number of technical challenges because of the inherent constraints due to the dynamic nature of these environments, such as limited bandwidth and energy capacity. This paper proposes a cross-layer architecture for implementing DiffServ (CLAD) in IEEE 802.11 based mobile ad hoc networks. This provides differentiated services to four types of applications: conversation, streaming, interactive, and best-effort, by defining per hop behaviours (PHBs). Novel features of CLAD include a least busy routing protocol (LBRP) which is designed to discover the least busy routes and evenly distribute the network load; a hybrid signalling system which is used to dynamically monitor route states and to regulate adaptive real time applications; and an adaptive rate controller which controls traffic rate. Preliminary simulation results demonstrate that CLAD can provide efficient service differentiation in MANETs.

A QoS-based Rate Adaptation Strategy for IEEE a/b/gPHY Schemes using IEEE 802.11e in Ad-hoc Networks

A dynamic rate selection technique is presented as a way to enhance the performance of ad-hoc networks. In particular, for IEEE 802.11-based networks using rate adaptation, the PHY scheme can vary and each IEEE 802.11 standard has different channel coding and modulations. The work proposes that the transmission rate should be chosen in an adaptive manner since the wireless channel condition varies over time due to such factors as channel characteristics, the PHY scheme selected, time-varying interference, and the priority of services (QoS demands) from MAC/PHY layers. Excessive high speed transmission can result in increased frame error rate (FER) over the link resulting in reduced throughput. This paper considers a new approach to alleviating FER by dynamically adjusting the transmission rate according to the quality of service (QoS) requirements from applications. Results are presented that show how this scheme achieves much higher throughput and lower end-to-end delay compared to the current IEEE 802.11 a/b/g ad-hoc networks. The results also show that the stability of the system is improved when operating under the QoS mechanisms supported in IEEE 802.11e MAC protocol

Modeling energy consumption in error-prone IEEE 802.11-based wireless ad-hoc networks

In the IEEE 802.11 MAC layer protocol, there are different trade-off points between the number of nodes competing for the medium and the network capacity provided to them. There is also a trade-off between the wireless channel condition during the transmission period and the energy consumption of the nodes. Current approaches at modeling energy consumption in 802.11-based networks do not consider the influence of the channel condition on all types of frames (control and data) in the WLAN. Nor do they consider the effect on the different MAC and PHY schemes that can occur in 802.11 networks. In this paper, we investigate energy consumption corresponding to the number of competing nodes in IEEE 802.11s MAC and PHY layers in error-prone wireless channel conditions, and present a new energy consumption model. Analysis of the power consumed by each type of MAC and PHY over different bit error rates shows that the parameters in these layers play a critical role in determining the overall energy consumption of the ad-hoc network. The goal of this research is not only to compare the energy consumption using exact formulae in saturated IEEE 802.11-based DCF networks under varying numbers of competing nodes, but also, as the results show, to demonstrate that channel errors have a significant impact on the energy consumption.

Wireless Security Issues in Pervasive Computing

Pervasive computing is a rapidly developing area of Information and Communications Technology (ICT). It refers to the increasing integration of ICT into people’s lives and environments, made possible by the convergence of advanced electronic - and particularly, wireless - technologies and the Internet. Wireless technologies are expected to connect various devices in many potential applications, from health and home care to environmental monitoring and intelligent transport systems. While wireless technologies play a critical role in pervasive computing, their security is a main concern. This paper elaborates a number of security issues for wirelessly connected devices, in particular using Wi-Fi, one of the most popular wireless technologies in pervasive computing. A solution to defeat wireless ARP spoofing is also proposed.

Novel Wireless Mesh Networking Architectures for Future Smart Homes

Future smart homes will create comfortable living environments which are embedded with a wide range of intelligent functionalities including home computing, entertainment, health care, and security. These place stringent requirements on the home networking architecture. In this paper, we propose a novel concept of Virtual Wireless Wire (Viwiwire), which is a set of consecutive high bandwidth wireless links over which concurrent transmission and reception can operate without interference. Based on this concept, a number of specific mesh networking architectures are proposed for future smart home networking. These include: wireless busline mesh, wireless ring mesh, and general multi-path mesh. The paper presents analyses that demonstrate the high performance of the proposed networking architectures.