Browsing by Author "Wenye Wang, Committee Chair"

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    Design and Analysis of Authentication Mechanisms in Single- and Multi-Hop Wireless Networks
    (2005-08-12) Liang, Wei; Wenye Wang, Committee Chair; Michael Devetsikiotis, Committee Member; Khaled A. Harfoush, Committee Member; Arne A. Nilsson, Committee Member
    The increasing demand for ubiquitous Internet services imposes more security threats to communications due to open mediums in wireless networks. Thus, security mechanisms are proposed to protect communications, while putting more overheads on the transmission. As one of most widely used security mechanisms, authentication is used to identify mobile nodes (MNs), prevent unauthorized usage, and negotiate credentials with heavy overhead. Nevertheless, authentication mechanisms also induce heavy burdens, such as encryption/decryption load and long delay, in wireless networks. Although some solutions are proposed to reduce the burdens caused by the authentication, there have been little quantitative analysis, flexible protocol design, and optimized architecture implementation on the authentication that are adaptive to the quality of service (QoS) up to date. In this thesis, we propose in-depth design and analysis of the authentication protocol and architecture to improve the authentication efficiency, such as delay and call dropping probability, in single- and multi-hop wireless networks. In the single-hop wireless networks, we first analyze the impact of authentication on the security and QoS quantitatively. Then, we present enhanced protocols for net-to-net and mobile-to-net authentication on hierarchical authentication architecture (HAA), which is the most widely used in wireless networks. The enhanced protocols are designed with the dynamic security associations (SAs) based on different functions of metrics to reduce the authentication delay and cost. Moreover, considering that HAA is not sufficient to network manageability and security, we further propose a new architecture with two control schemes for net-to-net and mobile-to-net authentication. The architecture is composed of licensed authentication centers and intelligent control schemes based on a utility function. The design of this architecture is effective to reducing the authentication latency, improving network scalability, and enhancing the network security in terms of reducing the number of SAs when inter-domain roaming happens. In the multi-hop wireless networks, we propose reliable clustering algorithms to improve the service availability, which can cooperate with the proposed authentication protocols between clusters. In this design, the energy consumption and mobility of nodes are evaluated quantitatively, and the proposed authentication protocols are entangled with the construction of hierarchical clusters dynamically, which is not only able to handle the failure of nodes efficiently, but also able to guarantee the security even from the start of constructing network architectures when mobile nodes frequently join and leave the multi-hop wireless networks. As shown in the numerical and simulation results, by improving the authentication efficiency, such as delay and call dropping probability, in single- and multi-hop wireless networks significantly, our research demonstrates an in-depth impact of authentication on security and QoS in wireless networks, and builds a solid ground for future improvement of authentication protocols and architectures.
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    Design, Modeling, and Analysis of User Mobility and its Impact on Multi-hop Wireless Networks
    (2009-08-05) Zhao, Ming; Arne A. Nilsson, Committee Member; Wenye Wang, Committee Chair; Khaled Harfoush, Committee Member; Michael Devetsikiotis, Committee Member
    Due to the readily deploy-able and self-organizing nature of mobile ad hoc networks (MANETs), various demanding applications are expected to be widely performed in military, civilian,law enforcement, and disaster recovery environments etc. Since MANETs do not rely on fixed wireless infrastructures, the constrained power consumption of wireless devices limits the communication zone between mobile nodes, so that the communication between nodes has to via a multi-hop fashion. The fundamental issue in MAENTs is that performance degrades dramatically as the increase of path failures. A path failure occurs when the inter-media nodes along the path become unavailable due to the node mobility. Hence, node mobility is a dominating factor to MANET performance and in turn, the most fundamental problem in mobility related MANET studies. The study of node mobility in MAENTs has drawn great attentions in the past decade, nevertheless the in-depth interpretation of mobility patterns and their effects upon system results still remains elusive. Therefore, understanding the impacts and implications of node mobility is essential to the system design, topology control, and routing optimization in MANETs. In this doctoral study, we first propose a novel mobility model named Semi-Markov Smooth (SMS) model, after finding that existing random mobility models can lead to biased or even misleading results for MANETs performance evaluation and analysis. We showed that the proposed SMS model not only captures the transient user mobility according to the physical law of a smooth movement, but also achieves the necessary stationary properties including stable average speed and uniform node distribution. We find that MANET link performance is influenced by the joint effects of radio channel environments and node mobility. Hence by applying the results from our first work, we continue to investigate the link properties upon these two joint effects in the second work. We showed that radio channel characteristics predominate the link performance for slower mobile nodes, while node mobility dominates the link performance for faster mobile nodes. In addition, the link lifetime distribution can be effectively approximated by the exponential distribution with parameter V/R, characterized by the ratio of average node speed to the transmission range. As wireless devices are generally attached to humans, in the third work, we studied human mobility impact on the properties of contact-based metrics, especially the inter-meeting time (MANETs). By investigating the empirical human mobility traces, we demonstrated that both pause time and trip displacement of human mobility exhibit a cutoff-power distribution. Then, we showed that the human diffusive rate r characterizes the joint temporal-spatial effect of human mobility regarding pause time and trip displacement on inter-meeting time. Especially, when the power law head characterizes the distribution of human mobility, we showed that the human diffusive capability (rate) r is, r = 2α/β, where α and β are the power law coefficients for the pause time and trip displacement and 0 < α < 1 and 0 < β < 2. Upon simulation demonstration, we find that the human diffusive rate r directly captures the cutoff power law property of inter-meeting time. Especially, the higher the diffusive rate r is, the shorter the power law head is, while the longer the exponential tail becomes in the distribution of inter-meeting time. In the fourth work, we studied the inherent properties of group mobility in MANETs. Specifically, we analyzed the correlation between group members by taking human social correlation, similarity of the nodes’ movements and proximity of nodes’ geographical location into consideration. We observed that human groups in MANETs exhibit the group evolution process regarding the variation of group size (the total number of group members) with time. Hence, based on the group correlation metric, we further studied several metrics for characterizing the stability of group structures and investigated the condition of node switch between neighboring groups. Finally, by applying the studied metrics, we propose a novel birth-to-death group mobility to describe the group evolution behaviors in MAENTs. Electrical and Computer Engineering
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    Effects of Medium Access Control on the Capacity of Mobile Ad Hoc Networks
    (2005-11-14) Xia, Heng; Huaiyu Dai, Committee Member; Wenye Wang, Committee Chair; Arne A. Nilsson, Committee Member
    As various wireless networks evolves into the next generation to provide better services, a key technology, mobile ad hoc networks (MANETs), has emerged recently. The dynamic topology, multi-hop transmission, and the nature of wireless channels create many challenging research topics in the area of MANETs. Recently, there has been work on determining the capacity of MANETs. The effects of some factors, such as node mobility, number of nodes, and transmission range, on the capacity of MANETs have been considered. In this work, we define and investigate the capacity of MANETs, considering the effects of medium access control (MAC). Since all the nodes in MANETs use a single or multiple channels to communicate, MAC plays an important role in coordinating channel access among nodes so that information gets through from one node to another. The MAC affects the capacity of MANETs in two aspects: collisions and spatial reuse. Three basic mechanisms are adopted to eliminate the incidence of collisions and maximize spatial reuse, i.e., carrier sense, handshake, and back-off. We define and use persistent probability, sensing range and back-off time to represent the effect of these mechanisms. The characteristics of MAC are thoroughly examined and an analytical solution for capacity evaluation is proposed. Numerical results are presented to demonstrate the effects of MAC, including carrier sense, handshake and back-off mechanism on the capacity of MANETs in terms of persistent probability, sensing range, and back-off time.
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    Energy-Efficient and Reliable Data Transfer in Wireless Sensor Networks
    (2008-12-02) Tezcan, Nurcan; Wenye Wang, Committee Chair; Injong Rhee, Committee Member; Ioannis Viniotis, Committee Member; Arne A Nilsson, Committee Member
    Wireless Sensor Networks (WSNs) have emerged as a new information-gathering paradigm based on the collaborative efforts of large number of sensors. Sensor nodes are low-cost, low-power devices that are equipped with acoustic, seismic, infrared, video, or audio sensors. WSNs come in a wide variety forms covering different geographical areas of interest to collect and transmit real-time data to a gateway node. The existing and potential applications of WSNs span a wide range, including real-time target tracking, homeland security, battlefield surveillance, and biological or chemical attack detection. Many of these WSN applications requires energy-efficient and reliable communication services to report of conditions within a region where the environmental conditions changes due to an observed event. Although WSNs provide redundant detection and reporting, this does not guarantee end-to-end reliability. For real-time applications such as monitoring where decision, control and update processes are based on the received data, reliable packet delivery is an important issue. An elegant reliability solution should benefit by constructing an energy-efficient topology, in order to be effective within this resource-constraint networking domain. Moreover, solutions should be flexible enough to support wide range of applications where WSNs are lack of centralized coordination and have different types of sensors such as audio, video sensors which bring unique characteristics and challenges coupled with the limitations of wireless environments. In this thesis, the problem of energy-efficient reliable data transport is addressed targeting wide range of WSN domains that matches the unique characteristics of sensor networks. The proposed protocols fit into different class of wireless sensor networks supporting both centralized and distributed solutions. We first present the design of an asymmetric and reliable transport (ART) mechanism, and evaluated the scheme by simulating and implementing it using realistic scenarios based on a reference home WSN application. Next, an energy efficient two-tier self-scheduling (TTS) paradigm is proposed. Specifically, TTS enables sensor nodes to construct a scalable topology under stringent energy, coverage and reliability constraints. Sensor nodes aim to preserve sensing coverage, while scheduling themselves into sleep in phases for energy conservation. By incorporating ART reliability mechanism, we show that high precision event detection at the collector node can be achieved with guaranteed event and query delivery performance. TTS has been studied to fit both centralized and distributed WSN domains. In distributed version, sensors are self- organized targeting to generate the scalable topology by self-discovery and self-calculation of their sensing coverage. In addition, self-organization is extended for wireless multimedia sensor networks having directional sensing views. A distributed scheme is designed and simulated for multimedia sensor nodes to compute their directional coverage, through which orientations are calculated for efficient self-organization. Finally, a case study of questioning and improving the reliability of home WSNs is presented and performance of ART in home wireless sensor networks are investigated. The results are promising and provide a basis for future investigations of home WSN applications that requires reliable communication services.
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    Performance Evaluation and Protection Management for Wireless Networks
    (2009-08-07) Agarwal, Avesh Kumar; Arne Nilsson, Committee Member; Carla D Savage, Committee Member; Wenye Wang, Committee Chair; David Thuente, Committee Member; Mihail Sichitiu, Committee Member
    Wireless networks are more vulnerable to attacks compared with wired networks due to their open and shared medium. A number of security mechanisms are available for providing different levels of protection, but with a side effect that is performance degradation. Given a wide range of real-time and non real-time applications, there is a critical demand for providing better performance in wireless networks. Motivated by this demand and the limitations of current research, we devote this dissertation to performance evaluation, and protection management in wireless networks. In this dissertation, we first study the performance impact of security mechanisms at different networking layers in wireless LANs, on a testbed with IP mobility support. One of the important observations is that statically configured security mechanisms may not be used to achieve a satisfactory performance. Motivated by the results of our first study, we propose a Self-TunEd Performance and Protection (STEP2) management framework, which is a generalized architecture for balancing the protection strength and performance for wireless clients based on network and user requirements. By implementing STEP2 in a wireless LAN testbed, we demonstrate the benefits of STEP2 such as significant reduction in delay and packet losses in various scenarios. With the growing deployment of multi-hop networks, we next extend our research to wireless mesh networks. Specifically, we investigate the performance impact of attacks in wireless mesh networks (WMNs). We study path-based denial of service (DoS) attacks as they are easy to carry out and can cause significant performance degradation. The measurements obtained in a wireless mesh testbed demonstrate the interaction between a set of factors, such as link qualities, physical diversity, packet size and rate, and the intensity of path-based DoS attacks. We believe that the comprehensive results in this dissertation will shed new lights on the performance analysis of secure wireless networks.