PhD, University of Cincinnati, 2008, Engineering : Computer Science and Engineering

Wireless Ad Hoc Networks have emerged as an advanced networking paradigm based on collaborative efforts among multiple self-organized wireless communication devices. Without the requirement of a fixed infrastructure support, wireless ad hoc networks can be quickly deployed anywhere at any time when needed. The decentralized nature, minimal configuration and quick deployment of wireless ad hoc networks make them suitable for various applications, from disaster rescue, target tracking to military conflicts. Wireless ad hoc networks can be further categorized into mobile ad hoc networks (MANETs), wireless sensor networks (WSNs), and wireless mesh networks (WMNs) depending on their applications.Security is a big challenge in wireless ad hoc networks due to the lack of any infrastructure support, dynamic network topology, shared radio medium, and resource-constrained wireless users. Most existing security mechanisms applied for the Internet or traditional wireless networks are neither applicable nor suitable for wireless ad hoc network environments. In MANETs, routing security is an extremely important issue, as the majority of the standard routing protocols assume non-hostile environments. Once deployed in a hostile environment and working in an unattended mode, existing routing protocols are vulnerable to various attacks. To address these concerns, we propose an anonymous secure routing protocol for MANETs in this dissertation, which can be incorporated with existing routing protocols and achieve enhanced routing security with minimum additional overheads. In WSNs, key distribution and management is the core issue of any security approaches. Due to extremely resource-constrained sensor nodes and lack of any infrastructure support, traditional public-key based key distribution and management mechanisms are commonly considered as too expensive to be employed in WSNs. In this dissertation, we propose two efficient pairwise key pre-distribution and management mechanisms f (open full item for complete abstract)

Committee: Dharma Agrawal (Committee Chair); Jerome Paul (Committee Member); Wen-Ben Jone (Committee Member); Chia-Yung Han (Committee Member); Ernest Hall (Committee Member) Subjects: Communication; Computer Science

PhD, University of Cincinnati, 2007, Engineering : Computer Science and Engineering

Recent years have witnessed an extensive proliferation of wireless technology in every domain of day-to-day life. Examples include mobile phones, broadband communication, wireless LAN, wireless enabled PDAs, cordless phones, garage-door openers and the list continues. Advancements in radio technology, antenna technology, low power computational digital signal processing (DSP) and micro-electro-mechanical systems (MEMS) are instrumental in reducing the size and cost of wireless devices. A wireless network consists of wireless devices forming an infrastructure-based or a peer-to-peer network. A network can be a single-hop or multihop network. Single-hop networks are already in existence and have been substantially investigated. This dissertation thus focuses on multihop wrireless networks, where the intermediate wireless devices also act as routers. Depending on their functionality, multihop wireless networks can be categorized into ad hoc, mesh and sensor networks. A mobile ad hoc network (MANET) aims at provding a mobile network with connectivity similar to a wired network without the need for any infrastructure support. A wireless mesh network (WMN) typically extends the infrastructure based single hop wireless network and has become a new paradigm for providing last mile broadband access. A wireless sensor network (WSN) is similar to an ad hoc network, providing a cheap alternative to monitoring applications. Each of these multihop wireless networks has their own set of challenges with respect to operation and implementation. The first part of this dissertation focuses on developing on-demand medium access control (MAC) protocols for multiple beam smart antennas (MBSAs) in ad hoc and mesh environments. MBSA has the unique capability of simultaneously initiating packet transmissions or receptions in multiple beams. Thus, compared to traditional omnidirectional antennas, MBSA can better utilize the spatial bandwidth, thereby increasing the capacity of wireless netwo (open full item for complete abstract)

Committee: Dr. Dharma Agrawal (Advisor) Subjects: Computer Science

PhD, University of Cincinnati, 2004, Engineering : Electrical Engineering

Wireless ad hoc networks have emerged as a new information-transmission paradigm based on collaborative efforts of multiple self-organized mobile nodes. Without the support from any fixed infrastructure, this type of network provides an extremely flexible method for establishing communications in situations where geographical or terrestrial constraints demand totally distributed network system. While the inherent characteristics of an ad hoc network make it useful for many applications, they also bring in a lot of research challenges. One of the important issues is the security, since conventional security approaches adopted for traditional networks are not directly applicable to ad hoc networks. Secure ad hoc network is critical to the development of any real application of wireless ad hoc networks. In this dissertation, we attempt to develop an integrated and distributed security scheme with resource-awareness to enhance the security of ad hoc networks. Our scheme can be logically divided into two parts. An efficient intrusion prevention mechanism is developed to prevent the various attacks from external intruders, and an intrusion detection mechanism is used to provide a second line of defense for the misbehaviors of internal intruders. In the intrusion prevention mechanism, the identity-based cryptography, bivariate polynomial-based pairwise key and one way hash chain techniques are used to provide various security goals, such as availability, integrity, confidentiality, authentication and non-repudiation. Considering the self-organizing property of ad hoc networks, the intrusion detection is implemented in a distributed fashion, in which the behavior of each node is monitored and analyzed using a cooperative functions involved in the network. The intrusion detection scheme can detect both the internal and external attacks, but it pays more attention on the attacks that cannot handled by the intrusion prevention approach, and the result of intrusion detection wo (open full item for complete abstract)

Committee: Dr. Dharma Agrawal (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2005, Computer and Information Science

Ad Hoc wireless networks have been gaining importance in the communication world for the past decade. Wireless network extends the access to the network by removing the restriction of physical wires. Ad hoc network further improves the network coverage and availability to places without infrastructure support. Clock synchronization and dominating set are two of the fundamental issues in the wireless ad hoc networks. They are important for the correctness and/or performance of many protocols and applications. We focus on IEEE 802.11 wireless ad hoc networks in this dissertation due to the wide deployments of 802.11 networks. The theories and practices are definitely extensible to other types of ad hoc networks. IEEE 802.11 wireless network depends heavily on the distribution of timing information to all the stations in the network. Clock synchronization is important for frequency hopping, power saving and wireless medium reservation. We review the Timing Synchronization Function (TSF) of Ad Hoc mode defined in the 802.11 standard. It is well-known that the 802.11 TSF is not scalable. We carefully analyze the root causes of the scalability problem and design new schemes to overcome the problem. Our new schemes show great improvement over the 802.11 TSF and other solutions in the fields. Our solutions have nice characteristics: scalable, accurate, bounded and adaptive to station mobility. We are able to control the maximum clock differences under 25 micro seconds and 50 micro seconds in single hop and multihop networks respectively. The performance improvement is at least 200% or more compared with the current solutions. Dominating set has been widely used in multihop ad hoc networks (MANET) by numerous routing, broadcast and collision avoidance protocols. The problem to construct a minimum sized dominating set is known to be NP-hard. We propose a protocol that is simple, distributed, inexpensive, and adaptive to station mobility. We show that our protocol can construc (open full item for complete abstract)

Committee: Ten-Hwang Lai (Advisor) Subjects: Computer Science

MS, University of Cincinnati, 2011, Engineering and Applied Science: Computer Science

There are many ways to geographically determine the boundary of an event based on its location and its nature through Satellite imaging and other learning mechanisms. In these methods, the availability of resources to perform the detection, their capabilities, actual time available to determine the event and its accessibility are constraints. At times, the satellite images may not be sufficient to get complete information about an event. Here we consider a particular case where the aim is to detect the actual boundary of an event based on its estimated boundary with the above constraints. A typical situation would be to determine the actual boundary of fire given the smoke area, or to estimate the concentration of chemical content, ideally any situation where sensors need to be used in an unmanned situation. We use a deploying agent to drop the sensors and there is a Base Station (BS) to which the event details are communicated by connectivity through localization with neighboring sensors. The research targets dynamic deployment of sensors with coverage and connectivity handled simultaneously as the information can reach the base station only if the sensors are able to connect to it. This is critical for real time applications. So we use an intelligent distribution scheme to test the behavior of different kinds of deployments using random, Gaussian, controlled random and combinational methods to deploy sensors. The set of parameters which are constraints are the communication radius of the base station, sensors & the event, the proximity of the event from the base station and location determination of the event based on the current state of the system. We use a weighted approach with more sensors around the event border and lesser inside to be able to detect the event and yet preserve the sensors as they might be lost due to fire or damage depending on the event. Additionally partial event boundary detection is used as experiment results show that we can reduce the (open full item for complete abstract)

Committee: Dharma Agrawal DSc (Committee Chair); Raj Bhatnagar PhD (Committee Member); George Purdy PhD (Committee Member) Subjects: Computer Science

MS, University of Cincinnati, 2004, Engineering : Computer Science

Routing protocols in wireless ad hoc network are highly insecure and prone to various attacks owing to its inherent characteristics of open medium, dynamically changing topologies and distributed cooperation between the member nodes. Having a secure routing protocol in wireless ad hoc networks appears to be a problem that is not trivial to solve. We propose a scheme to enhance the fault-tolerance of cluster head's functionality in CBRP. CBRP with a single cluster head is single point of failure and unsuitable especially for functionalities like key distribution. By distributing the cluster head service to a group of cluster heads called Council nodes and utilizing the (k, n) secret sharing scheme, we can increase the fault tolerance of network manifolds against security attacks. Simulation results obtained demonstrates that our proposed algorithm enables simultaneous formation the Council based clusters, thereby making the scheme time efficient and comparable to CBRP. Results also show that since large size clusters are formed in Council based clusters, it is feasible to apply (k, n) secret sharing concepts. The scheme is more suitable for low mobility networks due to the less signaling overhead involved in during cluster reformations.

Committee: Dr. Dharma Agrawal (Advisor) Subjects: Computer Science

MS, University of Cincinnati, 2003, Engineering : Computer Science

Majority of applications on the Internet today use TCP for reliable communication. TCP has been designed for and fine tuned to wired environments, but recent studies have shown that its performance suffers in wireless network environments, particularly in ad hoc networks because of the presence of multiple wireless hops. Routing has been the most focused area of research in recent years in wireless ad hoc networking area. Many on-demand routing protocols have been proposed to improve robustness in the face of link and route failures and facilitate packet transmission. Using multiple paths to route packets is one of them. We examine the performance of the TCP protocol with multiple paths in mobile ad hoc networks (MANETs). We set up multiple routes between the TCP source and destination either manually or using an on-demand multipath routing protocol, and forward packets on both paths to reduce the load on one single path. Ordinarily one would expect the multiple paths to reduce conflict between TCP data and acknowledgement packets thus giving better overall performance. Our results do incidate that TCP performance with multipath routing shows some improvement for long routes; however, shorter routes may experience slight degradation in performance as compared to single path routing. This observation remains true even when contention-based scheduling is used to schedule packets on different paths, or the multiple routes are chosen such that they have a minimum radio interference among themselves. We conclude that the TCP could gain only limited benefits with multipath routing.

Committee: Dr. Samir R. Das (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2005, Computer and Information Science

Communication networks can be either infrastructure-based or infrastructure-less. Information dissemination and routing are two important research areas in networking, as the first is one of the ultimate goals forconstructing a network and the second provides the underlying support for disseminating information among nodes within the network. This dissertation presents three major research results, with the first falling into the category of information dissemination on the Internet, specifically, server replica placement, and the second and the third into the category of information dissemination and routing in wireless ad hoc networks, respectively. The World Wide Web is a popular mechanism that creates a client-server information sharing model to facilitate information dissemination across the Internet. With the explosive growth of the WWW, popular Web sites experience increasingly heavy workloads and a large percentage of Internet traffic. To alleviate the workload and the network traffic, these sites usually place a set of servers geographically distributed across the Internet and replicate their contents to the selected replicas. The server replica placement scheme addresses the problem of properly placing a set of replicas among sets of candidate sites to optimize system performance gain. More specifically, using an optimum replica placement algorithm, we study the relationship between the replica size and the optimized performance gain through a trace-driven simulation. We also perform a parametric study to find out the effect of client demand patterns on the optimized performance gain growth. The field of wireless ad hoc networks has become a prosperous research field in recent years thanks to the rapid development and popularity of various mobile devices. The lack of infrastructure allows a fast and inexpensive deployment of wireless ad hoc networks and, thus, makes them suitable for surveillance applications. However, the ad hoc networks' flexibility and (open full item for complete abstract)

Committee: Ming T. Mike Liu (Advisor) Subjects: Computer Science