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Scott, Kevon KOcclusion-Aware Sensing and Coverage in Unmanned Aerial Vehicle (UAV) Networks
MS, University of Cincinnati, 2016, Engineering and Applied Science: Computer Engineering
The use of small and miniature Unmanned Aerial Vehicles (UAVs) for remote sensing and surveillance applications has become increasingly popular in the last two decades. Networks of UAVs, capable of providing flexible aerial views over large areas, are playing important roles in today's distributed sensing systems. Since camera sensors are sensitive to occlusions, it is more challenging to deploy UAVs for sensing in geometrically complex environments, such as dense urban areas and mountainous terrains. The intermittent connectivity in a sparse UAV network also makes it challenging to efficiently gather sensed multimedia data. This thesis is composed of two pieces of work. In the first piece of work, a new occlusion-aware UAV coverage technique with the objective of sensing a target area with satisfactory spatial resolution subject to the energy constraints of UAVs is proposed. An occlusion-aware waypoint generation algorithm is first designed to find the best set of waypoints for taking pictures in a target area. The selected waypoints are then assigned to multiple UAVs by solving a vehicle routing problem (VRP), which is formulated to minimize the maximum energy for the UAVs to travel through the waypoints. A genetic algorithm is designed to solve the VRP problem. Evaluation results show that the proposed coverage technique can reduce energy consumption while achieving better coverage than traditional coverage path planning techniques for UAVs. In the second piece of work, a communication scheme is designed to deliver the images sensed by a set of mobile survey UAVs to a static base station through the assistance of a relay UAV. Given the planned routes of the survey UAVs, a set of relay waypoints are found for the relay UAV to meet the survey UAVs and receive the sensed images. An Online Message Relaying technique (OMR) is proposed to schedule the relay UAV to collect images. Without any global collaboration between the relay UAV and the survey UAVs, OMR utilizes a markov decision process (MDP) that determines the best schedules for the relay UAV such that the image acquisition rate could be maximized. Evaluation results show that the proposed relaying technique outperforms traditional relaying techniques, such as the traveling salesman problem (TSP) and the random walk, in terms of end-to-end delay and frame delivery ratio.

Committee:

Rui Dai, Ph.D. (Committee Chair); Dharma Agrawal, D.Sc. (Committee Member); Carla Purdy, Ph.D. (Committee Member)

Subjects:

Computer Engineering

Keywords:

Unmanned Aerial Vehicle;UAV;Occlusion;FANET;Flying Ad-Hoc Networks;Remote Sensing

Kumar, VijayDead Reckoning Location Service For Mobile Ad Hoc Networks
MS, University of Cincinnati, 2002, Engineering : Computer Engineering
A mobile ad hoc network consists of wireless hosts that may often move. Routing in such a network is a challenging task. Location based routing protocols utilize location information of the nodes (obtained using the global positioning system or some other means) to route packets. Some of these protocols assume a location service exists, which provides location information on all the nodes in the network. In this research work a predictive model-based scheme, called dead reckoning location service, is developed for mobile ad hoc networks. It disseminates both location and movement models of mobile nodes in the network so that every node is able to predict or track the movement of every other node with a very low overhead. The basic technique is optimized to use “distance effect”, where distant nodes maintain less accurate tracking information to save overheads, by using a layering and buffering approach. The dead reckoning location service (DRLS) mechanism is evaluated against three known location dissemination service protocols: Simple, DREAM and GRSS. The evaluation is done with geographic routing as an application. It is observed that dead reckoning significantly outperforms the other protocols in terms of packet delivery fraction. It also maintains low control overhead. Its packet delivery performance is only marginally impacted by increasing speed or noise in the mobility model, thataffects its predictive ability. DRLS based routing also performs better than Ad hoc On Demand Distance Vector (AODV) routing protocol in delivering data packets to the destinations, particularly for large networks. Using efficient broadcasting schemes will improve DRLS even further.

Committee:

Dr. Samir R. Das (Advisor); Dr. Raj Bhatnagar (Other); Dr. James Caffery, Jr. (Other)

Subjects:

Computer Science

Keywords:

mobile ad hoc networks; location services; geographic routing protocols; location protocols; performance evaluation

Kumar, KavithaIntrusion Detection in Mobile Adhoc Networks
Master of Science in Engineering, University of Toledo, 2009, Electrical Engineering

Mobile ad hoc networks (MANETs) are autonomous, infrastructure-less networks in which mobile nodes organize themselves in a network without the help of any predefined infrastructure. Securing MANETs is an important part of deploying and utilizing them, since they are often used in critical applications where data and communications integrity in important. Existing solutions for wireless networks can be used to obtain a certain level of such security. However, these solutions may not always be sufficient for MANETs, since their characteristics create vulnerabilities that cannot be addressed by these solutions. To obtain an acceptable level of security in such a context, traditional security solutions should be coupled with an intrusion detection mechanism.

We propose using a quantitative method to detect intrusion in MANETS with mobile nodes. Our method is a behavioral anomaly based system, which makes it dynamic, scalable, configurable and robust. We verify our method using simulations where mobile nodes follow linear movement patterns. The simulations are run with mobile nodes and employing Ad-hoc on-demand Distance Vector (AODV) routing. It is observed that the malicious node detection rate is very good, and the false positive detection rate is low.

Committee:

Mansoor Alam, Dr (Committee Chair); Daniel Solarek (Committee Member); Henry Ledgard, Dr (Committee Member)

Subjects:

Computer Science; Electrical Engineering

Keywords:

Mobile Ad hoc networks;MANETs with mobile nodes;Intrusion Detection in MANETs;Intrusion Detection in MANETs with mobile nodes

LENAGALA, ROSHAN M.S.STUDY OF STARVATION ISSUES IN THE IEEE 802.11e MAC LAYER PROTOCOL
MS, University of Cincinnati, 2006, Engineering : Computer Science and Engineering
The proliferation of multimedia applications requiring strict QoS requirements have tested the performance of the widely used IEEE 802.11 MAC layer protocol for its ability to provide proper service differentiation and QoS. The IEEE 802.11e MAC layer protocol was put forward as an improvement to the IEEE 802.11 MAC layer protocol, focusing on service differentiation and QoS. The nature of IEEE 802.11e is such that in the presence of intensified high priority network traffic, the low priority traffic starves. In this thesis work possible causes for starvation of low priority traffic and the use of dynamic MAC layer parameters in removing starvation of low priority traffic and at the same time providing proper service differentiation and QoS for higher priority traffic in par with IEEE 802.11e EDCF are presented. Two novel schemes are presented which use dynamic MAC parameters. The proposed schemes change the inter frame spacing and contention window parameters based on the calculated collision probability and the fraction of transmission opportunities taken by each traffic class. The proposed schemes are evaluated under static (single hop and multi-hop) and mobile network (multi-hop) conditions. The issues that arise in a multi-hop network and the impact of mobility on the proposed schemes are discussed.

Committee:

Dr. Qing-An Zeng (Advisor)

Subjects:

Computer Science

Keywords:

starvation prevention; IEEE 802.11e EDCF; IEEE 802.11 DCF; Ad hoc networks

Joshi, VineetCaching-based Multipath Routing in Mobile Ad Hoc Networks
MS, University of Cincinnati, 2009, Engineering : Computer Science
Mobile ad hoc networks represent a new approach towards computer networking which does not depend on an infrastructure for its operation. This flexibility gives rise to new applications of networks which were not possible with the networks that critically depend on an infrastructure for their operation. However this absence of infrastructure also gives rise to a host of problems with the network operation. Routing data from a source to destination is one such problem. Mobility of the nodes causes frequent topological changes and further complicates the problem. Many protocols have been proposed to help route data in mobile ad hoc networks. A sub class of these protocols makes use of a set of multipath routes to transmit data from the source to the destination. During the course of our research we discovered inefficiencies associated with these routing protocols. We have proposed the reuse of cached routes as a technique to reduce these inefficiencies and improve the performance of mobile ad hoc network along various performance parameters. We have proposed a new multipath routing protocol called CMR that makes use of the technique of reusing cached routes in determining new routes. Through extensive simulation experiments we have been able to analyze the performance of new protocol and demonstrate its advantages.

Committee:

Qing-An Zeng, PhD (Committee Chair); Raj Bhatnagar, PhD (Committee Member); Fred Annexstein, PhD (Committee Member)

Subjects:

Computer Science

Keywords:

Mobile Ad Hoc Networks; Multipath Routing

Mostafa, Ahmad APacket Delivery Delay and Throughput Optimization for Vehicular Networks
PhD, University of Cincinnati, 2013, Engineering and Applied Science: Computer Science and Engineering
Vehicular networking is a new emerging wireless technology that supports the communication amongst vehicles and enables vehicles to connect with the Internet. This networking technology provides vehicles with endless possibility of applications, including safety, convenience, and entertainment applications. Examples for these applications are safety messaging, real-time traffic, route updates, and general purpose Internet access. The goal of vehicular networks is to provide an efficient, safe, and convenient environment for the vehicles. In vehicular networking technology, vehicles connect either through other vehicles in an ad-hoc multi-hop fashion or through road side units (infrastructure) which connects them to the Internet. Each approach has its own advantages and disadvantages. However, one of the main objectives of vehicular networking is to achieve a minimal delay for message delivery, and encourage a continuous connectivity for vehicles. This dissertation introduces a novel hybrid communication paradigm for achieving seamless connectivity in Vehicular Ad-hoc NETworks (VANET), wherein the connectivity is often affected by changes in the dynamic topology, vehicles' speed, as well as traffic density. Our proposed technique ---named QoS-oriented Hybrid Vehicular Communications Protocol (QoSHVCP)--- exploits both existing network infrastructure through a Vehicle-to-Infrastructure (V2I) protocol, as well as a traditional Vehicle-to-Vehicle (V2V), that satisfies Quality-of-Service requirements. We analyze time delay as a performance metric, and determine delay propagation rates when vehicles are transmitting high priority messages via QoSHVCP. Focusing on V2V communication, we propose a novel reliable and low-collision packet-forwarding scheme, based on a probabilistic rebroadcasting. Our proposed scheme, called Collision-Aware REliable FORwarding (CAREFOR), works in a distributed fashion where each vehicle receiving a packet, rebroadcasts it based on a predefined probability. The success of rebroadcast is determined based on allowing the message to travel the furthest possible distance with the least amount of packet rebroadcast collision. Moreover, we present a QoS-Aware node Selection Algorithm (QASA) for VANET routing protocols. Our algorithm is focused on selecting the vehicle to communicate with, and is achieved by exploiting the bridging approach for message forwarding i.e., vehicles on the east (west) select from west (east). The QoS metrics that are being optimized are the throughput in the network, as well as end-to-end delay for packets. Finally, we exploit the use of autonomous vehicles in order to optimize the end-to-end packet delivery delay. Our protocol introduces a dynamic metric that depends on the vehicular density on the highway in order to control the inter-vehicle distance. Our results show a great promise for their future use in vehicular technology.

Committee:

Dharma Agrawal, D.Sc. (Committee Chair); Raj Bhatnagar, Ph.D. (Committee Member); Yizong Cheng, Ph.D. (Committee Member); John Franco, Ph.D. (Committee Member); Chia Han, Ph.D. (Committee Member); Yiming Hu, Ph.D. (Committee Member)

Subjects:

Computer Science

Keywords:

Vehicular Networks;Ad Hoc Networks;QoS;Autonomous Vehicles;

TALWAR, SUMEETPERFORMANCE EVALUATION OF MULTIPATH ROUTING WITH MULTICHANNEL AD HOC NETWORKS
MS, University of Cincinnati, 2003, Engineering : Computer Engineering
A mobile ad hoc network is a collection of autonomous nodes connected to each other in a peer-to-peer fashion on a wireless medium. Such networks are used in emerging applications which require co-operative mobile data exchange in areas where there is little or no infrastructure available or where providing such infrastructure is not cost effective. Efficient dynamic routing is a major research challenge in such a network. Multipath routing provides a strong potential for efficient routing by maintaining multiple routes. This provides some form of fault-tolerance, as alternate paths can be used when one breaks. Also, data packets can be forwarded via multiple paths concurrently thus exploiting a larger network capacity. However, CSMA (carrier-sense multiple access) being a dominant form of channel access protocol in mobile ad hoc network, multipath forwarding is often unable to exploit its full potential. This is because multiple paths may form in each others’ radio neighborhood limiting spatial diversity. Data transmission in one path causes sufficient interference in another such that only one path can be used at a time. This phenomenon has been known as “route coupling.” We investigate the use of multichannel CSMA-based medium access protocols to reduce the impact of such route coupling. We use two such multichannel protocols to demonstrate that a significant throughput improvement is possible at high offered loads relative to the single channel CSMA for multipath data forwarding scenarios. One of the protocols chooses the channel based on interference power measurement at the sender. The other chooses a unique channel for each path. Our study shows that the multichannel protocols are able to limit the impact of interference between neighboring transmissions effectively.

Committee:

Dr. Samir R. Das (Advisor)

Subjects:

Computer Science

Keywords:

AD HOC networks; multichannel MAC; multipath; IEEE 802.11; route coupling

Alhashim, Najeeb S.Performance of Disparate-Bandwidth DS-SS Systems in Spectral Overlay Ad Hoc Networks
Master of Science (MS), Ohio University, 2009, Electrical Engineering (Engineering and Technology)
In this thesis we investigate the performance of direct sequence spread spectrum(DS-SS) overlay ad hoc networks by performing computer simulations and numerical evaluations based upon mathematical analysis. Two such DS-SS systems, with different bandwidths, are studied. We investigate performance statistics for a terrestrial network model in a limited two-dimensional area, in which user (node) locations are random, and statistics are gathered over numerous realizations of these random node locations. For all users in both systems we collect statistics on performance in terms of signal-to-noiseplus-interference ratio (SNIR) and bit error probabilities, to illustrate aggregate behavior attainable in such systems. We first illustrate our technique for a specified reference system with a given set of parameters, then we vary several of these parameters to assess the effects on performance. Parameters we vary include transmit power, data rates,processing gain, path loss exponent and shadowing standard deviation. We demonstrate that overlay of different-bandwidth DS-SS systems in an ad hoc network can be practical by specifying appropriate system design parameters.

Committee:

David W. Matolak, PhD (Advisor); Jeffrey Dill, PhD (Committee Member); Trent Skidmore, PhD (Committee Member); Sergio Lopez, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

DS-SS Overlay; CDMA; Ad Hoc Networks

KADAMBARI, SIREESHAUSING TRACKING AND BUFFERING TO IMPROVE DELIVERY PERFORMANCE IN AD HOC NETWORKS
MS, University of Cincinnati, 2003, Engineering : Computer Engineering
An ad hoc network is a collection of wireless mobile hosts dynamically forming a network without the use of any existing stationary network infrastructure. If two nodes in an ad hoc network are not in each other's communication range, data packets must be routed by intermediate nodes. Routing in an ad hoc networks is a significant challenge because of the difficulty in maintaining a successful communication path between a source-destination pair in spite of changing topology. This is complicated by the fact that most wireless networks have low bandwidth, thus routing and data forwarding must be done prudently so as not to overwhelm a low capacity network. A significant amount of work has been done in designing efficient routing protocols for mobile ad hoc networks and many routing protocols have been developed. The focus of the community, however, has been on best effort traffic where packets must be routed as quickly as possible with minimum possible delay. However, it turns out that routing performance in terms of bandwidth usage and throughput may improve if packets are allowed to wait in buffers at the source or at intermediate nodes and are delivered to destinations with a minimum number of hop-wise transmissions at opportune moments. This obviously reduces bandwidth usage as a small number of transmissions are needed to deliver a packet. It also indirectly improves throughput as packet losses become less likely as packets are buffered when routes are unavailable and also packets are exposed less to wireless channel errors. However, the buffering increases end-to-end packet delay; so such an approach is applicable only to delay-tolerant applications. Also, care must be taken to prevent starvation where packets wait indefinitely in the buffers. In this thesis, we design and develop two location-based routing protocols "Geographic Forwarding with Buffering" and "Topology Based Forwarding with Buffering" based on the above idea that encourages buffering to gain better bandwidth usage and lower packet loss. The protocols use intelligent location tracking. Tracking is provided by a dead reckoning-based location service developed earlier. Packets are buffered when the destination is far and forwarded when it comes near. Packets are also buffered when congestion develops or when no route is available. The protocols are implemented in the network simulator Glomosim and their performance is evaluated against two standard routing protocols: one location based - GPSR and the other non-location based - AODV. The evaluations show that our protocols offer much better packet delivery ratios, often close to 100 % as well as a significant reduction in average hop-wise transmissions per packet, while the end-to-end delay degrades only slightly.

Committee:

Dr. Samir R. Das (Advisor)

Keywords:

Ad Hoc Networks; routing protocols; wireless networks; bandwidth; location tracking

GUPTA, RAHULExperimental Study of Wireless Ad Hoc Networks
MS, University of Cincinnati, 2003, Engineering : Computer Science
An ad hoc network is a collection of wireless hosts that spontaneously forms a network without the use of any existing network infrastructure or centralized administration. Due to the limited transmission range of wireless network interfaces, multiple network "hops" may be needed for one node to exchange data with another node across the network. Thus, individual nodes must also act as routers. The routing problem gets complex if the nodes are mobile. Dynamic routing in the face of topological changes is an important problem in such mobile ad hoc networks. Such networks find tremendous applications in any type of mobile collaborative applications, where the network must be set up on the fly. Examples include emergency response, law enforcement,explorations, conferencing and military. Not all ad hoc networks are mobile. A network of embedded sensors collaborating to perform a high level sensing task is one such example. Since sensor nodes are powered by battery and sensor networks must be operational in an unattended fashion for a long time,solving problems with low communication overhead is critical. This means communication must be primarily local. The overall goal of this thesis is to perform experimental study on real ad hoc network testbeds. Two types of network testbeds have been used – (i) a mobile ad hoc network using NovaRoam wireless IP routers,and (ii) a sensor network using the Berkeley MICA mote platform. Our focus is experimental protocol design and evaluation on these testbeds. In the NovaRoam-based mobile ad hoc network testbed, we have implemented a version of the well-known AODV (Ad hoc On Demand Distance Vector) routing protocol. It has been implemented as a part of the usual TCP/IP protocol stack. This thesis presents the design decisions for this implementation, as well as performance evaluation of dynamic multihop routing using UDP and TCP on this testbed. As demonstrated in current literature, the performance degrades with larger number of hops in the network and with high offered load. To exercise the sensor network testbed, we have focused on a collaborative monitoring problem. We have developed a simple algorithm that detects and tracks a moving target, and alerts sensor nodes along the projected path of the target. The algorithm involves only simple computation and localizes communication only to the nodes in the vicinity of the target and its projected course. The algorithm has been evaluated on the Berkeley MICA mote testbed using a light source as the moving target. The performance results are presented emphasizing the accuracy of the technique, along with a discussion about our experience in using such a platform for target tracking experiments.

Committee:

Dr. Samir R. Das (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc Networks; Routing; Ad Hoc Testbed; sensor network; sensor testbed

Agarwal, Aarti SubhashUse of Query Control and Location for Routing in Mobile Ad Hoc Networks
MS, University of Cincinnati, 2002, Engineering : Computer Science
A mobile ad hoc network is a collection of wireless mobile nodes dynamically forming a network without the use of any existing network infrastructure or centralized administration. As the nodes are mobile, the network topology is dynamic leading to frequent unpredictable connectivity changes. It is critical to route packets to destinations effectively without generating excessive overhead. This presents a challenging issue for protocol design since the protocol must adapt to frequently changing network topologies in a way that is transparent to the end user. A class of routing protocols called on-demand protocols has received a lot of interest because of their low routing overhead. In this thesis, we study techniques that can reduce this routing overhead even further. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Network-wide floods incur substantial overhead. Techniques have been proposed to contain the flood in a limited region where a route to the destination is highly likely to be found. Techniques have also been proposed to reduce redundant broadcasts. We propose various mechanisms to improve on these existing techniques. We propose adaptive mechanisms that utilize prior routing histories, mobility pattern and network load to choose the area in which the query flood should be contained. In addition, we propose a technique that utilizes the neighborhood information to reduce or eliminate redundant broadcasts. We evaluate their performances in isolation and in tandem. In the next part of the thesis, we turn our attention to use of location information for routing. In has been shown in prior work that availability of location information can substantially reduce routing overheads. However, equipping all mobile nodes with GPS or other positioning system is not a cost effective proposition. We develop and evaluate a localization technique that can localize mobile nodes even when only a fraction of nodes in the network has direct access to location information. The rest of the nodes localize themselves by hearing radio beacons emitted from the nodes that have access to direct location information. We evaluate the localization accuracy using our technique via simulations. We show that the accuracy is better than the radio range even when only about 10% of the network nodes have direct access to location information. To be useful for routing, each node in the network must learn the location of every other node. However, disseminating this information sufficiently frequently can incur large overhead. To counter this, we develop a mobility prediction and location tracking model based on the dead-reckoning navigation technique. Here, both current location and movement model of mobile nodes are disseminated via flooding. Every other node is now able to track the movement with some accuracy until the movement model changes bstantially. We use this technique along with a geographic routing protocol to solve the unicast routing problem in ad hoc networks. Simulation studies show that it performs better than well-known on-demand routing protocols.

Committee:

Dr. Samir Das (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc Networks; Routing; Dead Reckoning Model; Location based routing

Zhang, QianComparing Duplexing, Multiplexing, and Multiple Access Techniques in Ad Hoc Networks
Doctor of Philosophy (PhD), Ohio University, 2013, Electrical Engineering (Engineering and Technology)
Wireless ad-hoc networks have seen much attention in recent years, and are still a topic of much interest, especially as a result of an increasing need for ubiquitous connectivity. Ad-hoc networks have applications in tactical military systems as well as in commercial systems because of the numerous benefits they offer. There are still a number of open research questions regarding these networks, and this dissertation work addresses the question of which duplexing, multiplexing, and multiple access (D/M/MA) techniques are preferable in ad hoc networks. These techniques have substantial impact on network performance, yet surprisingly this particular topic has seen little attention. Moreover, most of the existing literature is focused on higher layers such as medium access control (MAC) and network layers, while our work concentrates on the physical (PHY) layer, which plays an important and fundamental role in network design. In this dissertation, we investigate D/M/MA techniques in ad-hoc networks and more generally, how to allocate time/frequency resources to achieve better network performance. We provide a comparison of time, frequency, and time-frequency schemes in terms of a number of features, including duty cycles, required data rate per transmission, required transmit power per link, throughput, relative range and capacity. To keep the analyses tractable, topologies we study are full mesh networks, relay networks, and several special cases of ad-hoc networks. The main results show that for a peak power constraint, in terms of data rate, range, or capacity, continuous single-carrier waveforms are superior to bursted multi-carrier waveforms, and these schemes are attained with appropriate application of “hybrid” time-frequency division. Latency and throughput simulation results are provided for mesh networks, and analytical signal-to-noise-plus-interference ratio, multi-hop gain and simulation results for relay networks are also presented, to support our theoretically-based claims and aid in the network design.

Committee:

Jeffrey Dill (Committee Chair); David Matolak (Advisor); Chris Bartone (Committee Member); Bryan Riley (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Wireless ad hoc networks; multi-hop relay; mesh networks; resource allocation; multiple access

GOYAL, DEVENDRADELAYING OR AVOIDING PARTITIONING IN MOBILE AD HOC NETWORKS USING NETWORK SURVIVABILITY CONCEPTS
MS, University of Cincinnati, 2002, Engineering : Computer Science
Mobile ad hoc networks (MANET) consist of a collection of wireless mobile nodes, often with unpredictable mobility patterns, dynamically forming a network without using any existing network infrastructure or central control. Due to these mobility patterns, nodes in the network can be separated into partitions and reconnected a number of times. Whenever a larger partition divides into two smaller ones, there is a critical link that fails and thus divides the partition into two separate partitions. In graph theory, the two nodes forming this critical link are referred to as separation nodes while the graphs are referred to as mono-connected graphs and have been thoroughly studied in literature under network survivability concepts. In this work, we propose an approach that utilizes these concepts to detect the critical links whose failure will give rise to partitions in the network. Once the critical link has been detected, we propose three ways to delay or avoid its failure: change the trajectory of one or both nodes forming the link to reinforce it; bring in another node to reinforce the link; and the combination (hybrid) of these two. It is assumed that the nodes know their locations and periodically update their neighbors with their current location. We implement these techniques in the network simulator ns-2 and show that the approach can signicantly improve the network performance and reduce the degree of partitioning.

Committee:

Dr. James Caffery, Jr. (Advisor)

Subjects:

Computer Science

Keywords:

AD HOC Networks; partitioning; DFS

Joshi, AvinashLoad Balancing, Queueing and Scheduling Mechanisms in Mobile Ad Hoc Networks
MS, University of Cincinnati, 2001, Engineering : Computer Science and Engineering
An ad hoc network is a collection of mobile nodes with wireless links that dynamically form a network without the use of any existing network infrastructure or centralized administration. Due to the limited range of the wireless links, multiple network “hops” may be needed for one node to exchange data with another across the network. In recent years, a variety of new routing protocols targeted specifically at this environment has been developed. It is our thesis that capacity of wireless networks being limited, routing performance is heavily influenced by congestion, load imbalance, scheduling priorities and wireless link quality. Our work focuses on developing techniques to address these issues. The overall goal is improved overall routing performance. The following techniques have been studied in connection with on-demand routing protocols, specifically AODV (ad hoc on-demand distance vector routing). Typically, routing protocols discover shortest path route based on number of hops. This routing philosophy can lead to bottlenecks as some links tend to be used by many routes. We present techniques which try to balance the load and avoid such bottlenecks. We use a new routing cost metric which is a function of the current load on each node on a route. The idea of the cost metric is to be able to route around the nodes that are congested for which alternate routes are available. In addition, rerouting is done proactively when any node on an active route starts getting congested. We also investigate efficient queueing paradigms to be used at the radio interfaces for nodes in wireless ad hoc networks. Low bandwidth of wireless links makes queueing paradigms critical for the performance of the network routing protocol. We investigate various packet drop and priority scheduling policies. We demonstrate that effective queueing paradigms can improve routing performance. Unlike wired networks, packets transmitted on wireless channels are often subject to burst errors which cause back to back packet losses. Most link layer protocols recover from packet losses by retransmission. When the wireless channel is in a burst error state, retransmission attempts typically fail, thereby causing poor utilization of the wireless channel. We investigate a channel state dependent scheduling policy where packets are scheduled at the radio interface based on the link quality. Packets seeing a better link quality get higher priority. Conversely, packets seeing weak links are buffered to be transmitted later. We show this technique improves overall channel utilization which in turns improves routing performance.

Committee:

Dr. Samir Das (Advisor)

Subjects:

Computer Science

Keywords:

Mobile Ad Hoc Networks; dropping policies; scheduling policies

Li, YingjieInformation dissemination and routing in communication networks
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 convenience do come at a price. The infamous characteristics of these networks, such as unstable wireless media, dynamic network topology due to link disruptions and node mobility, and power constrained wireless devices, require protocols designed for these networks to be fully distributed, energy efficient, fault (disruption) tolerant, and scalable. Following these design rules, we propose Scalable Data Storage and Retrieval Service (SDSR), to enhance data dissemination for large-scale wireless ad hoc networks, and Disruption Tolerant Geographic Routing protocol (DTGR) to enhance the performance of geographic routing schemes in the presence of frequently occurring disruptions for wireless ad hoc networks.

Committee:

Ming T. Mike Liu (Advisor)

Subjects:

Computer Science

Keywords:

Wireless Ad Hoc Networks; Communication Network; Routing algorithm; information Dissemination

Gupta, NishantResource Management in Ad Hoc Networks
MS, University of Cincinnati, 2001, Engineering : Computer Science
An ad hoc network is a collection of wireless mobile nodes dynamically forming a network without the use of any existing network infrastructure orcentralized administration. Dynamic routing protocols have been developed that allow such nodes to communicate using multi-hop routes, but existing protocols typically provide only best-effort service. In particular, they do not directly provide any way to control the resource usage in the network. This thesis focuses on the management of two such resources, viz., battery power and the bandwidth available to the nodes. Both are premium resources in a wireless network with mobile nodes. We develop our techniques as extensions of “on-demand” routing protocols because of their superior performance as reported in current literature. These are routing protocols that compute routes on an “as needed” basis. All protocols and techniques developed in this thesis are evaluated using extensive simulations using a multi-layer network simulator. To manage battery power, we develop a technique to make on-demand routing protocols energy-aware. The goal is to increase the operational lifetime of the network where mobile nodes are operating on battery power alone, and batteries cannot be recharged or replaced. The idea here is to balance the residual energy levels of the batteries in the mobile nodes by dynamically shifting routing loads from nodes with low battery levels to those with higher battery levels. The technique also switches off network interfaces strategically to conserve energy. Simulations show significant improvement of the energy budget of the network as a whole resulting in increased operational lifetime. The most improvement is noticed for high loads and modest mobilities. To understand the question of bandwidth usage better, we develop empirical techniques to determine network capacity and utilization when the network is running commonly used routing and medium access protocols. While the technique is general, we specifically apply it to determine the network capacity and utilization for on-demand routing protocols and “virtual carrier sensing”- based medium access protocols. Simulation analysis with this technique reveals several interesting results. Specifically, it shows that a significant portion of the network capacity remain unutilized regardless of traffic and mobility conditions. Also, the network capacity increases with mobility, but the routing protocol is unable to take any advantage of this additional capacity. While these results have an important bearing on their own, they also help us forming realistic expectations from any bandwidth management techniques that could be developed for ad hoc networks. As a final contribution, we develop a quality-of-service (QoS) extension of on-demand routing protocols that attempts to provide bandwidth guarantees to sessions that request it. The guarantee is achieved via bandwidth reservation along the route of the session and taking admission control decisions at the source. Sessions are not admitted if the requested bandwidth guarantees cannot be provided. Simulation results demonstrate that QoS guarantees are indeed provided for most sessions that are admitted; while without this QoS extension the routing protocol admits all sessions, but fails to provide QoS guarantees to most of them. A set of validation experiments provide a background sanity check; that the QoS extension protocol actually admits sessions that could be admitted.

Committee:

Dr. Samir Das (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc Networks; QoS; Energy; Capacity; Simulation

GUPTA, RAHULA TCP ANALYSIS: IMPACT OF RECEIVER PERCEIVED INFORMATION ON THE PERFORMANCE OF TCP OVER Ad Hoc NETWORKS
MS, University of Cincinnati, 2002, Engineering : Computer Science
An Ad hoc network is a completely wireless network with a dynamic nature of topology, which rapidly changes with time. Due to the node movement there are sudden losses of packets and delays. Transport protocols like TCP have been designed for reliable fixed networks. TCP misapprehend these packet losses as congestion in the network and call upon congestion control, which leads to avoidable retransmissions and loss in overall performance. In this work we propose a receiver information based approach, so that source can distinguish between route failure and network congestion. Simulation results show that the use of this feedback approach provides a significant improvement in performance. TCP does not differentiate between congestion and packet loss due to transmission errors or route failures, because it is designed for use over fixed low-error networks like the internet. In internet route failures and disruptions are very sporadic since network is fixed, therefore, packet losses, which is detected by TCP as a timeout, can be interpreted as a symptom of congestion in the network. A lot of research has been done on reliable transport protocols for cellular wireless networks. All the mechanisms proposed heavily depend on the presence of wired base station network, and hence cannot be directly applied to ad-hoc networks. In this work we study TCP performance over ad hoc networks and propose receiver information based feed back scheme, to control the TCP window at the sender side. TCP performance is tested in ad hoc network routed with DSR routing protocol, with two versions of TCP, TCP-new Reno, and TCP-feecon (proposed). With this study, we see number of unique characteristic of ad hoc networks for TCP, such as increasing ratio of out-of-order packet delivery, multiple competing connections contending for the bandwidth-constrained wireless channel and induce network congestion, mobility-induced disconnection, and reconnection. We propose an adaptive feed back technique which uses receiver information to command and control the sender side TCP window. Our implementation complexity is on the receiver side and is stable.

Committee:

Dr. Dharma P Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc Networks

Sardana, DivyaControl-channel Reuse-based Multi-channel MAC Protocol for Ad Hoc Networks
MS, University of Cincinnati, 2009, Engineering : Computer Science
Ad hoc networks have become a popular type of wireless network in the present world. In order to match with the increasing demand of ad hoc networks, a lot of research is being done towards solving the issues related to the design of ad hoc networks. The design of a Medium Access Control (MAC) protocol for ad hoc networks is one such issue. Traditional MAC protocols involve the use of a single channel as the wireless medium. However, throughput of a single channel MAC degrades as the node traffic in the system increases. One of the interesting approaches towards alleviating this problem is the use of more than one channel as the underlying medium. The use of multiple channels allows more than one communication to take place simultaneously thereby improving the throughput of the system. Multiple channels have been mostly used in the literature by assigning one of the channels as the control channel used only for control packet transfer and the rest of the channels as data channels used for Data packet transfer. Using such an approach towards designing a multi-channel MAC protocol leads to a poor utilization of the available bandwidth. In this thesis, we propose a multi-channel MAC protocol called as Control-channel Reuse based Multi-channel MAC (CRM-MAC) which aims at improving the overall bandwidth utilization. We illustrate the efficacy of our protocol through elaborate simulations.

Committee:

Qing-An Zeng, PhD (Committee Chair); Fred Annexstein, PhD (Committee Member); Raj Bhatnagar, PhD (Committee Member)

Subjects:

Computer Science

Keywords:

multi-channel MAC; mobile ad hoc networks; IEEE 802.11

Wang, QiheScheduling and Simulation of Large Scale Wireless Personal Area Networks
PhD, University of Cincinnati, 2006, Engineering : Computer Science and Engineering

As the earliest standard for Wireless Personal Area Networks (WPAN), Bluetooth has been widely used in cell phone, headset, car, GPS, etc. As a frequency hopping based system, however, constructing a large scale network using Bluetooth technology presents a real challenge. This dissertation explores this problem and presents several feasible solutions.

Firstly, bridge devices, which connect multiple piconets into a connected scatternet by participating in a time division multiplex basis in adjacent piconets, need to be carefully coordinated to enable smooth operations of the scatternet; secondly, the lengthy device discovery and link setup phases make scatternets impossible to maintain, without disruptive interruptions to normal data communications. To address the bridge coordination problem efficiently and effectively, this dissertation proposes a novel distributed dichotomized bridge scheduling algorithm, coupled with an adaptive Rendezvous Window based polling scheme. A new method for device discovery is also introduced to address the scatternet formation and maintenance problems.

The proposed algorithms have been tested on our own Bluetooth simulator (UCBT) which models the lower part of Bluetooth stack in detail and provides several example large scale scatternet configurations for executing our proposed scheduling algorithms. Extensive simulations have been conducted, and the performance results illustrate that large scale scatternets can operate efficiently.

This dissertation also looks at applying scatternets to sensor networks by constructing a 480 nodes scatternet in our simulator. The simulation results illustrate that Bluetooth scatternet can be a good choice for low duty cycle sensor networks.

The scheduling technique developed in Bluetooth scatternet can be applied to newly introduced IEEE 802.15.4 based Zigbee network as well. This is a new standard introduced to save consumed energy by defining a beacon controlled low duty cycle. Beacon collision problem presents a real challenge in any large sensor network setting. By applying scatternet technique, each adjacent cell may operate in a different channel to avoid timing critical beacon collision. Inter-cell communication can be achieved by having bridge type devices participating in multiple channels in a time division multiplex basis. Initial simulation results show our technique to be very promising.

Committee:

Dr. Dharma Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

Ad-Hoc Networks, Beacon Scheduling, Bluetooth, Low Duty; Cycle, Polling Scheme, Power Management, Rendezvous Point, Scatternet; Formation, Scheduling, Sensor Networks, Simulation, Zigbee.

Jiang, HongboINFORMATION SEARCH AND EXTRACTION IN WIRELESS AD HOC NETWORKS
Doctor of Philosophy, Case Western Reserve University, 2008, Computing and Information Science

Wireless ad hoc networks consist of a set of autonomous nodes which spontaneously create impromptu communication links, and then collectively perform a task with little help from centralized servers or established infrastructure. Because of the stringent constraints on system resources, as well as highly dynamic and even lossy wireless communication environments, wireless ad hoc networks face challenges for providing information search and extraction with good scalability and efficiency. Scalability and efficiency are assessed mainly with respect to the metric of network communication cost. This thesis explores these issues through the development of novel approaches in two types of emerging wireless networks: mobile ad hoc networks and sensor networks.

We study the information search problem and use wireless mobile ad hoc networks as an example. We propose adaptive strategies that combine both proactive advertising by the servers and on-demand discovery by the mobile hosts. These adaptive strategies determine the relative rate of proactive advertising and on-demand discovery according to system characteristics such as host mobility level and offered load.

We study the information extraction problem and use wireless sensor networks as an example. First, a scalable and robust data aggregation algorithm for information extraction is proposed to obtain the overall data distribution. This data aggregation algorithm exploits the mixture model and the expectation maximization algorithm for parameter estimation. Second, we present energy-aware prediction models, analyze the performance tradeoff between reducing communication cost and limiting prediction cost, and design algorithms to exploit the benefit of energy-aware prediction.

Throughout our study, our efforts focused on dealing with various challenges introduced by the dynamic network environments and stringent resource constraints. This thesis shows that with our efforts the communication cost can be significantly reduced. For example, the adaptive strategies reduce traffic cost by several times compared to the previous proactive strategies and reactive strategies. The proposed framework using data aggregation and prediction reduces communication cost by up to one order of magnitude compared to centralized solutions without aggregation.

Committee:

Shudong Jin (Committee Chair); Meral Ozsoyoglu (Committee Member); Michael Robinovich (Committee Member); Wei Lin (Committee Member)

Subjects:

Computer Science

Keywords:

Wireless ad hoc networks; information search; information extraction

JAIN, NITINMULTICHANNEL CSMA PROTOCOLS FOR AD HOC NETWORKS
MS, University of Cincinnati, 2001, Engineering : Computer Science and Engineering
An ad hoc network is a collection of wireless mobile nodes dynamically forming a network without the use of any existing stationary network infrastructure. The network can be multi-hop and mobile; there is no central controller and packet transmissions are typically unsynchronized. The efficiency of the medium access control (MAC) protocol to coordinate the access to the shared radio medium is critical. Carrier sense multiple access (CSMA) protocols are typically used. However, their efficiency is limited when the load and the level of contention is high. This thesis proposes use of multichannel CSMA protocols to reduce contention on the wireless medium. Though the aggregate capacity with a multichannel scheme is the same as a single channel, contention per channel is now lower and thus channel access is more efficient. We show that only a handful of channels provide optimum performance as with too many channels per-channel bandwidth is too low that affects performance adversely. Since the number of channels are much lower than the number of nodes, effective channel selection schemes are needed. We propose a receiver-based channel selection (RBCS) scheme that selects channel based on interference levels on different channels at the receiver. We implement this technique as an extension of IEEE standard 802.11 MAC protocol (which is a single channel protocol) on a network simulator. We show that it provides superior delay performance at high loads compared to single channel, as well as other, previously studied, channel selection schemes, such as selcting a random free channel or selecting channel based on sender-side signal power. As a final contribution, we study the effect of multichannel CSMA protocols for multipath routing on ad hoc networks. With use of single channel CSMA, ''route coupling'' can exist for multipath routes. This means that routes can form in radio neighborhood, and their transmissions can interfere with each other, preventing multiple routes to be used concurrently. Thus, the load balancing advantages of multiple paths are lost. We show that the use of multichannel CSMA protocols as above can remarkably improve the effectiveness of the multipath routing by providing more diversity.

Committee:

Dr. Samir R. Das (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc Networks; medium access control; multichannel MAC; wireless networks; channel selection techniques

ANAND, KUMARA SCALABLE EXPLICIT MULTICAST PROTOCOL FOR MOBILE AD HOC NETWORKS
MS, University of Cincinnati, 2004, Engineering : Computer Engineering
Multicast applications are becoming increasingly important in Mobile Ad hoc Networks (MANETs) due to proliferation in group oriented computing. Due to dynamic topology of MANETs, stateless multicast protocols are finding increased acceptance since they do not require maintenance of state information at intermediate nodes. Recently, several multicast schemes have been proposed which scale better with the number of multicast sessions than traditional multicast strategies. These schemes are also known as Explicit Multicast (Xcast; explicit list of destinations in the packet header) or Small Group Multicast (SGM). In this Thesis work, we propose a new scheme for small group multicast in MANETs named Extended Explicit Multicast (E2M), which is implemented on top of Xcast and introduces mechanisms to make it scalable with number of group members for a given multicast session. Unlike other schemes, E2M does not make any assumptions related to network topology or node location. It is based on the novel concept of dynamic selection of Xcast Forwarders (XFs) between a source and its potential destinations. The XF selection is based on group membership and the processing overhead involved in supporting the Xcast protocol at a given node. If the number of members in a given session is small, E2M behaves just like the basic Xcast scheme with no intermediate XFs. As group membership increases, nodes may dynamically decide to become an XF. This scheme, which can work with few E2M aware nodes in the network, provides the transparency of stateless multicast, reduces header processing overhead, minimizes Xcast control traffic and makes Xcast scalable with the number of group members.

Committee:

Dr. Dharma Agrawal (Advisor)

Keywords:

Multicast; Explicit Multicast; Wireless Ad Hoc Networks; Small Group Multicast

Gossain, HrishikeshPower Control and Spatial Reusability in Mobile Ad Hoc Networks
PhD, University of Cincinnati, 2005, Engineering : Computer Science
In this dissertation, we focus on the issue of power control and spatial reusability in Mobile Ad Hoc Networks (MANETs). We introduce a novel Spatial Reuse MAC (SRM) protocol based on IEEE 802.11 which accomplishes spatial reuse by employing a combination of power control and a distributed transmission sneaking mechanism. Our MAC scheme provides an improved power efficiency and enhanced throughput as compared to existing schemes. We also focus on the spatial reusability by using directional antennas. Existing MAC protocols which have been designed under the omnidirectional antenna assumptions are inadequate to fully exploit the benefits of directional antennas. Hence, the design of an efficient MAC protocol for directional antennas is an important issue and needs further investigation. We introduce a new MAC protocol for Directional Antennas (MDA) which exploits the benefits offered by such an environment. Through simulation work we show that MDA outperforms all exiting directional MAC protocols. We have also addressed directional routing issues in MANETs and propose an on-demand Directional Routing Protocol (DRP) which assumes a cross layer interaction between the routing and the MAC layers. The main features of DRP include an efficient route discovery mechanism, establishment and maintenance of directional routing and directional neighbor tables and a novel directional route recovery mechanism. A detailed study of issues related to routing in directional antenna systems is done and the behavior of different IEEE 802.11 system parameters in a multihop directional environment is also provided undertaken.

Committee:

Dr. Dharma Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

IEEE 802.11; MAC; Power Control; Spatial Reuse; Routing; Ad Hoc Networks; MANETs; Wireless

POOSARLA, RAJANI DEVIAUTHENTICATED ROUTE FORMATION AND EFFICIENT KEY MANAGEMENT SCHEMES FOR SECURING Ad Hoc NETWORKS
MS, University of Cincinnati, 2003, Engineering : Computer Science
Ad hoc networks provide a new approach for wireless communication. These networks have no pre-deployed infrastructure available for achieving end-to-end routing of packets in the network. Nodes communicate with each other without the intervention of centralized access points or base stations, so each node acts both as a router and as a host. Securing routing in ad hoc networks creates difficulties not present in traditional network: neither centrally administrated secure routers nor strict policy exists in an ad hoc network; the nodes in the networks can be highly mobile, thus rapidly changing the network topology and the presence or absence of links. So the routing in ad hoc networks is especially hard to accomplish securely, robustly and efficiently. Security primitives such as authentication, non-repudiation, data integrity and confidentiality, which would otherwise be provided by a central server, must be enabled by one or more network nodes. In this thesis, we focus on two issues of security, routing security and key management. We have discussed various threats to routing protocols in ad hoc networks and proposed methods to enhance the security of these protocols. We have put forth a new authentication scheme for on-demand routing protocols, specifically Dynamic Source Routing (DSR), by using public key cryptography in order to prevent the attacks against routing. The use of public key infrastructure in ad hoc networks raises the issue of key management. Certification of public keys of the nodes belonging to an ad hoc network is a non-trivial problem. Existing techniques for certifying keys are not well suited for ad hoc networks due to their sensitivity to single point of failure. We have defined a new key management paradigm, which can effectively deal with the challenges inherent in ad hoc networks and combat the attacks on the key management system itself. The proposed solution is then integrated into an existing hierarchical routing protocol.

Committee:

Dr. Dharma Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc networks; security; authentication; key management

Shukla, ManishTCP Performance With Multipath Routing in Wireless Ad Hoc Networks
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)

Keywords:

TCP over wireless; TCP over AD HOC Networks; multipath routing; TCP performance with multipath; multipath in wireless network

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