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CAVALCANTI, DAVE ALBERTO TAVARESINTEGRATED ARCHITECTURE AND ROUTING PROTOCOLS FOR HETEROGENEOUS WIRELESS NETWORKS
PhD, University of Cincinnati, 2006, Engineering : Computer Science and Engineering
One of the main challenges in next generation wireless networks is to integrate heterogeneous wireless technologies to provide seamless connectivity, with guaranteed Quality of Service (QoS), to mobile users “anytime, anywhere and with any device”. In this dissertation, we investigate the problem of integrating cellular networks and Wireless Local Area Networks (WLANs) with the multi-hop communication paradigm used in Mobile Ad hoc Networks (MANETs) to exploit all the connectivity alternatives available to different types of Mobile Stations (MSs). We propose an integrated architecture based on three basic functionalities, namely, topology discovery, gateway discovery, and link quality estimation. We combine these three functionalities into an integrated routing mechanism that exploits all connectivity alternatives available in a generic heterogeneous scenario. Then, we provide a simulation-based analysis of our architecture and integrated routing mechanism in different heterogeneous networking scenarios. Our results show improvements in network’s capacity and coverage achieved by our architecture as compared to isolated networks. The results also highlight the importance of the link quality estimation in providing QoS to users, as well as indicate that multi-hop links can be exploited in a controlled network configuration, but the QoS in multi-hop routes cannot be always guaranteed. Furthermore, we address the problem of selecting the best connectivity opportunity for a given service type based on the applications’ QoS requirements, as well as on the network condition and user mobility profile. We propose the Connectivity opportunity Selection Algorithm (CSA) that allows MSs to select the connectivity opportunity most appropriate for a given type of service and mobility profile. Furthermore, we describe how our proposed selection algorithm can be introduced into the IEEE 802.21 standard for Media Independent Handover services.

Committee:

Dr. Dharma Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

Heterogeneous Wireless Networks.; Routing Protocols for Heterogeneous Wireless Networks; Multi-hop communications in integrated wireless networks; network selection; always best connectivity

Haldar, Kuheli LEfficient Quality of Service Provision Techniques in Next Generation Wireless Networks
PhD, University of Cincinnati, 2014, Engineering and Applied Science: Computer Science and Engineering
Recent evolution of communication networks comprises of different segments and technologies, where each segment maybe implemented using different QoS. Further, the proposed all-IP core infrastructure of the future networks will offer varying QoS level multimedia services to the users. However, IP being a best effort service, seamless provision of end-to-end QoS guarantees is extremely important. In today's world, devices with multiple networking capabilities is quite common. The traditional approach in networking includes grouping identical traffic and allocating them to the network that has the maximum available data rate. This creates unbalanced traffic load in the network, leading to poor utilization of the associated resources. This problem can be greatly alleviated if the traffic can be allocated intelligently to the networks. For fair traffic distribution, we modeled the AP of each network as a single queuing server. Then, suitable equations and algorithms are designed to divide the incoming traffic flow into multiple subflows and allocated to the APs based on their available data rates. Network Selection in a Heterogeneous Cognitive Radio Wireless Network is a challenging task, since the users need to select the appropriate channels of the network in addition to the network itself. The varying levels of interference experienced by the secondary user (SUs) is due to the presence of primary user (PU)s in the adjacent channels. Hence, SUs transmitting highly sensitive data must find a channel that is interference free. In this dissertation, we develop a novel network and channel selection scheme that categorizes both the user applications and the network channels depending on their sensitivity level for interference and select them using a bipartite graph matching algorithm. The effectiveness of Cognitive Radios is based on opportunistic access of the licensed channels by SUs while protecting the PU transmission. But channel sensing incurs cost in terms of time overhead and energy consumption. However, infrequent sensing also results in loss of transmission opportunity for the SUs. Hence, an interesting and challenging question arise: when should the SU sense the channel, sleep or transmit, to minimize the total cost? In this dissertation, we developed a novel scheme for deriving the optimal inter-sensing duration in a Cognitive Radio network, on the requirement of protecting the PUs' communications while minimizing the cost for the SUs. The scheme has been presented for both non-erroneous and erroneous channel sensing conditions. Handling the "mobile data tsunami" in the future and providing indoor coverage is a significant challenge for the operators. The answer is LTE femtocells. However, limited spectrum availability in the cellular networks causes severe interference in the neighboring femtocell users that are transmitting in the same radio band. In densely deployed environments, interference problems in co-channel femtocells causes significant degradation in performance. In this dissertation, we proposed a CASFR scheme, that assigns distinct set of PRBs to each interfering femtocells in the downlink. In the uplink we proposed a PSE algorithm to further reduce any interference that may remain after performing CASFR. Finally, the topics for future work have been clearly identified.

Committee:

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

Subjects:

Computer Science

Keywords:

Heterogeneous Wireless Networks;Next Generation Wireless Networks;Cognitive Radio;Inter-cellular Interference;Femtocells;4G

Wang, XiaoyuanNetwork Selection and Rate Allocation in Heterogeneous Wireless Networks and Systems
MS, University of Cincinnati, 2009, Engineering : Computer Science

Heterogeneous wireless network (HWN) technology has emerged in the next generation mobile networks, which enables mobile client (MC) to simultaneously communicate with multiple heterogeneous access networks for better quality of services (QoS) and lower service cost. By the context of conventional network protocols, separately and independently operating network interfaces cannot fully utilize the potential of a HWN.

In this thesis, we model and analyze a HWN and system. The issues are identified as the multi-MAC management between MCs and access networks, and the multi-network (multi-NET) management between application servers and access networks. We propose a multi-MAC management scheme over multiple heterogeneous interface MACs to optimize multi-application performance with network selection and rate allocation for uplink traffic. We also propose a multi-NET management scheme for multi-user performance optimization in the downlink traffic, which is network-centric and distributes traffic into multiple access networks by supporting the inter-networking operations. Besides necessary optimization algorithms, procedures to implement our schemes are also provided.

Committee:

Dharma Agrawal, DSc (Committee Chair); Wen-Ben Jone, PhD (Committee Member); Chia-Yung Han, PhD (Committee Member)

Subjects:

Computer Science

Keywords:

Heterogeneous Wireless Networks;Network Selection;Optimization;Rate Allocation

Champion, Adam C.Unobtrusive, Pervasive, and Cost-Effective Communications with Mobile Devices
Doctor of Philosophy, The Ohio State University, 2017, Computer Science and Engineering
Mobile devices such as smartphones are ubiquitous in society. According to Cisco Systems, there were eight billion mobile devices worldwide in 2016, which surpassed the human population. Mobile devices and wireless network infrastructure form an "electronic world" of signals that is part of daily life. However, navigating this world with users' devices is challenging. The volume of signals may confuse users, wireless communications often require manual connection establishment, and latency may be large (such as Bluetooth device discovery). Pervasive mobile device communications offer large-scale measurement opportunities when many devices connect to wireless networks. For example, base stations to which devices connect can indicate human mobility patterns. But existing work only studies coarse-grained cellular call records and datasets used in wireless local area network (WLAN) studies typically consist of laptops. Besides, existing vehicular communications technologies tend to be expensive and available for new vehicles only. This dissertation studies three topics that arise in the electronic world: unobtrusive communication among mobile devices without manual connection establishment; pervasive mobile device communications measurement; and cost-effective vehicular communication among mobile devices. First, we design Enclave that enables unobtrusive communication among mobile devices without network connections or configurations. Unobtrusive communication is efficient wireless communication that does not require user interruption such as manual device connection or network configuration. Enclave consists of a delegate mobile device (such as an unused phone) that interposes between a user's "master" device (such as her smartphone) and the electronic world. Enclave communicates between the master and delegate devices using wireless name communication and picture communication. Second, we study a new dataset with over 41 million anonymized (dis)association logs with WLAN access points (APs) at The Ohio State University (via the osuwireless network) over 139 days from January to May 2015. The dataset includes more than 5,000 university students with their birthdays, genders, and majors, which are made available after anonymization. Using mobility entropy as our metric, we find that entropy increases with age (for 19-21-year-olds), students' entropic rates of change vary with majors, and all students' long-term entropy follows a bimodal distribution that has not been previously reported. We design a mobile application that localizes users indoors for 73 campus buildings using WLAN site survey information. In general, our app achieves room-level accuracy. Finally, we propose SquawkComm for cost-effective vehicular communication using mobile devices and FM signals. SquawkComm encodes data as audio, which is sent via inexpensive FM transmitters that plug into vehicles' cigarette lighters and received via vehicle stereos. SquawkComm uses a new physical-layer coding scheme and link-layer mechanisms for channel access. Our experimental evaluation illustrates the promise of our work in the electronic world. We conclude with directions for future work.

Committee:

Dong Xuan, Ph.D. (Advisor); Feng Qin, Ph.D. (Committee Member); Ten-Hwang Lai, Ph.D. (Committee Member)

Subjects:

Computer Science

Keywords:

Mobile device; smartphone; Bluetooth; Wi-Fi; FM; student; wireless networks; measurement; mobility entropy; vehicular communication

Ouyang, WenzhuoScheduling in Wireless Networks with Limited and Imperfect Channel Knowledge
Doctor of Philosophy, The Ohio State University, 2014, Electrical and Computer Engineering
In a wireless network, the efficiency of scheduling algorithms over time-varying channels depends heavily on the accuracy of the Channel State Information (CSI), which is usually quite “costly” in terms of consuming network resources. In the meanwhile, communication channels in wireless systems typically fluctuate in a temporally-correlated manner. We hence consider scheduling in wireless networks with limited and imperfect channel state knowledge, where the scheduler can exploit the temporal-correlation inherent in channels with memory for better channel state knowledge. We consider the channel state acquisition mechanism with ARQ-styled feedback, whereby the channel states are revealed at the end of only scheduled users' transmissions. In the presence of temporally-correlated channel evolution, the desired scheduler must optimally balance the `exploitation-exploration trade-off’, whereby it schedules transmissions both to exploit those channels with up-to-date CSI and to explore the current state of those with outdated CSI. We model the scheduling problems as Partially Observable Markov Decision Processes (POMDPs). POMDPs are known to be difficult to solve. We are able to analyze the problems in the framework of Restless Multi-armed Bandit Processes and utilize the Whittle’s indexability analysis. Based on our analysis, we propose low-complexity scheduling algorithms that have optimality performance in different wireless networks. Our work reveals that, under limited and imperfect channel state information, exploiting channel memory and ARQ-styled feedback for scheduling can result in significant system-level performance gains and that the proposed polynomial-complexity algorithms have provably optimal performances in various settings.

Committee:

Ness Shroff (Advisor); Atilla Eryilmaz (Advisor); Hesham El Gamal (Committee Member)

Subjects:

Computer Science; Electrical Engineering; Engineering; Operations Research

Keywords:

wireless networks, scheduling, network control algorithm, time-correlated wireless channel, channel memory, imperfect channel state information, queueing networks, ARQ feedback, Partially Observable Markov Decision Process

Hirve, Sachin C.Multihop Transmission Opportunistic Protocol on Software Radio
Master of Science in Electrical Engineering, Cleveland State University, 2009, Fenn College of Engineering

The need of high speed communication motivates us to use high bit rate communication to transmit more information in as little time as possible. However, MAC layer protocol overheads dominate the transmission capability particularly at high rates and hinder high speed transmission. Opportunistic transmission has been proposed to help to overcome this disadvantage by transmitting packets back-to-back without inter-packet delays. Though this approach alleviates the problem in single-hop wireless LAN scenario, it doesn't help in multi-hop networks. This thesis presents an approach for multi-hop wireless networks, which is named as Multi-hop Transmission OPportunity (MTOP). It achieves better performance by ensuring better end-to-end packet transmission by allowing back-to-back packet transmission over multiple hops rather than that by one node.

Recent developments in wireless communication research have fueled verification of new approaches on real-life systems rather than simulation. In this thesis, the MTOP approach has been implemented and verified on a widely known software radio platform i.e. USRP hardware and GNU Radio open source software framework. Software radio has emerged as one of the potential platforms for future wireless applications. The wide spread acceptance of software radio is due to the flexibility achieved by porting complex hardware functions to software. This not only speeds up the development, but also creates the multi-standard support for wireless applications. The results show that MTOP improves network performance in a multi-rate ad-hoc network as compared to the contemporary approaches.

Committee:

Chansu Yu, Ph.D. (Advisor); Wenbing Zhao, Ph.D. (Committee Member); Vijay Konangi, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Multihop wireless networks; USRP; Software Radio; GNU Radio

Vora, Adnan ZoebEfficient Location Verification, Neighbor Discovery and Routing in Ad Hoc Wireless Networks
PHD, Kent State University, 2009, College of Arts and Sciences / Department of Computer Science

Wireless networks as a class presents challenges that traditional wired networks do not have to overcome. Often, new algorithms have to be devised to solve fundamental networking problems like security and routing because traditional algorithms fare poorly within the constraints of wireless networks.

A sub-class of wireless networks, ad hoc wireless networks are networks that do not depend on a fixed infrastructure for their operation. Wireless nodes in such networks communicate directly with each other, often relying on other wireless nodes to relay messages. Basic networking functions like security and routing must be performed by the wireless nodes themselves, in addition to data generation and consumption.

In this dissertation, we exploit the unique properties of ad hoc wireless networks, such as broadcast communication and relation between physical location and network topology, to formulate algorithms that solve three basic networking problems – Location Verification, Neighbor Discovery and Geometric Routing – in ad hoc wireless networks.

Our location verification algorithm allows a wireless node to verify the location claims of another wireless node. The algorithm can withstand byzantine or malicious nodes trying to fake its location using a variety of means including directional antennae and collusion with other nodes. Moreover, it does so without using any special hardware or complex cryptographic algorithms. We further extend our algorithm to include various realistic scenarios and discuss how this algorithm can be used to implement a complete system.

The neighbor discovery algorithms is designed to withstand the Sybil attack which is considered intractable. Our algorithm exploits the network topology and broadcast communication model and uses appropriate external devices, or Universe Detectors, to solve this problem. We explore the bounds of finding a solution to this problem and prove that the external devices used, are the weakest possible devices that can be employed.

Finally, we present a geometric routing technique – VOID – that can improve on the performance of traditional geometric routing algorithms by expanding the scope of their applicability, whilst guaranteeing message delivery.

Committee:

Mikhail Nesterenko, PhD (Committee Chair); Hassan Peyravi, PhD (Committee Member); Paul Farrell, PhD (Committee Member); Volodymyr Andriyevskyy, PhD (Committee Member); Gerassimos Petratos, PhD (Committee Member)

Subjects:

Computer Science

Keywords:

Ad Hoc Wireless Networks; Location Verification; Neighbor Discovery; Sybil Attack; Geometric Routing

Li, RuoguPrinciples and Methods of Adaptive Network Algorithm Design under Various Quality-of-Service Requirements
Doctor of Philosophy, The Ohio State University, 2012, Electrical and Computer Engineering

Motivated by the increasing deployment of the real-time applications over various networks, we are interested in the design and analysis of new adaptive algorithms to satisfy their quality-of-service (QoS) requirements that are beyond the widely studied throughput performance. For example, most real-world applications are sensitive to the mean end-to-end delay they experience, interactive applications often have a stringent delay constraint, the VoIP applications need a certain fraction of their packets to be delivered successfully before a fixed deadline, and online video streaming applications may require a fixed bandwidth and regulated service rate.

However, unlike the more extensively studied throughput performance that is determined by the first-order statistics, such QoS requirements often relate to the higher-order statistics of the arrival and service processes in the network. Hence, they are highly challenging to characterize and analyze directly, and new approaches must be developed in the design of provably good algorithms in satisfying the aforementioned QoS requirements. In this dissertation, we address this deficiency by systematically exploring the principles and methods of adaptive network algorithm design to manage variety of challenging QoS requirements, including the traffic heterogeneity, delay, reliability, and service regularity, with theoretical guarantees.

Since the above QoS metrics are typically challenging to analyze, we utilize different frameworks and methods to overcome different types of QoS requirements. For example, in designing the adaptive network algorithm under real vs. non-real-time traffic heterogeneity, we utilize an optimization-based formulation, leading to a novel two-leveled prioritization queueing architecture that achieves the optimal load-balancing and utility maximization solution. In the direction of achieving low mean delay performance, we reveal and exploit a unique characteristic of a well-known dual solution of the joint congestion control and routing problem to develop an efficient adaptive routing scheme that avoids unnecessary loops and hence provides significant improvement in the mean delay performance.

While these design methods are based on appropriately formulated optimization frameworks, other QoS metrics necessitate the use of stochastic control methodologies, requiring the introduction and control of new dynamic variables into the system. For example, we add deficit counters for the deadline-constrained flows with delivery ratio requirements, whose value measures how this requirement is violated over time. In the challenging scenario of deadline-constrained multi-hop flows, we develop a novel queueing architecture in addition to deficit counters that are used by our adaptive algorithms to automatically adapt the service discipline to their deadline and reliability requirements. In the case of serving such deadline-constrained flows with channel coding capabilities over fading channels, an untraditional finite-horizon dynamic-programming approach is employed to solve the optimization problem. In the formulation and analysis of the service regularity performance, the novel parameter of time-since-last-service is introduced, which enables us to study the second moment behavior of the inter-service time by analyzing the mean of this new quantity.

Our investigations in these QoS metrics yield different adaptive algorithms with provable QoS performance. These results show the powerfulness and significance of the method of exploiting new elements in the system when designing adaptive algorithms to satisfy QoS requirements.

Committee:

Atilla Eryilmaz (Advisor); Ness Shroff (Committee Member); Eylem Ekici (Committee Member)

Subjects:

Electrical Engineering

Keywords:

scheduling; quality of service; network control algorithm design; cross layer design; mean delay; end-to-end delay constraint; service regularity; wireless networks

Bansal, TarunNetwork-Centric Mechanisms for Performance Improvement in Dense Wireless Networks
Doctor of Philosophy, The Ohio State University, 2014, Computer Science and Engineering
In recent years, the number of wireless devices and the amount of data generated by these devices has seen an exponential growth. However, the number of channels available for data transmission has not increased significantly leading to the problem of spectrum crunch. Our measurements show that the existing wireless deployments employ high density of wireless devices (access points, smartphones etc.). However, to prevent interference, the current wireless algorithms prohibit these neighboring wireless devices to operate simultaneously. The main focus of this thesis is on improving the network experience on the mobile devices by leveraging the high density of wireless devices. This thesis proposes four different solutions that are suited for different wireless topologies: Symphony, RobinHood, Mozart and R2D2. Symphony and RobinHood are best suited for Enterprise wireless networks where multiple access points are connected to each other and are willing to cooperate. Both Symphony and RobinHood use novel cooperative decoding techniques to enable multiple neighboring access points to simultaneously receive different packets on the same channel. Symphony is suitable for wireless networks that span large geographical areas while RobinHood is suitable for smaller deployments. Symphony and RobinHood leverage the high density of access points in WiFi networks that otherwise remain unused in traditional wireless solutions. Mozart is suitable for WiFi networks where neighboring access points belong to different entities that may not be willing to cooperate. Mozart takes an unconventional approach of letting all transmitters collide at the access point and then lets the access point decode the collided packets in the fewest number of slots. Finally, R2D2 is designed for cellular networks and it enables neighboring devices to efficiently communicate with each other while reducing the dependence on the cellular base stations. R2D2 leverages the temporal spatial asymmetry in the traffic patterns to efficiently allocate resources across cellular base stations as well as to efficiently schedule links at each of the base stations. The thesis discusses all the solutions in detail, along with the techniques to address the challenges involved in their practical implementation.

Committee:

Prasun Sinha (Advisor)

Subjects:

Computer Science

Keywords:

Wireless Networks; Symphony; Mozart; RobinHood; Performance

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

Zheng, ZizhanSparse Deployment of Large Scale Wireless Networks for Mobile Targets
Doctor of Philosophy, The Ohio State University, 2010, Computer Science and Engineering

Deploying wireless networks at large scale is challenging. Despite various effort made in the design of coverage schemes and deployment algorithms with static targets in mind, how to deploy a wireless network to achieve a desired quality of service for mobile targets moving in a large region without incurring prohibitive cost largely remains open. To address this issue, this dissertation proposes Sparse Coverage, a deployment scheme that provides guaranteed service to mobile targets while trading off service quality with cost in a deterministic way.

The first part of this dissertation discusses two sparse coverage models for deploying WiFi access points (APs) along a city-wide road network to provide data service to mobile vehicles. The first model, called Alpha Coverage, ensures that a vehicle moving through a path of length α is guaranteed to have a contact with some AP. This is the first partial coverage model (in contrast to the more expensive full coverage model) that provides a performance guarantee to disconnection-tolerant mobile users. We show that under this general definition, even to verify whether a given deployment provides Alpha Coverage is co-NPC. Thus, we propose two practical metrics as approximations, and design efficient approximation algorithms for each of them. The concept of Alpha Coverage is then extended by taking connectivity into account. To characterize the performance of a roadside WiFi network more accurately, we propose the second sparse coverage model, called Contact Opportunity, which measures the fraction of distance or time that a mobile user is in contact with some AP. We present an efficient deployment method that maximizes the worst-case contact opportunity under a budget constraint by exploiting submodular optimization techniques. We further extend this notion to the more intuitive metric -- average throughput -- by taking various uncertainties involved in the system into account.

The second part of this dissertation studies sparse deployment techniques for placing sensor nodes in a large 2-d region for tracking movements. We propose a sparse coverage model called Trap Coverage, which provides a bound on the largest gap that a mobile target, e.g., an intruder or a dynamic event, is missed by any sensor node. In contrast to the current probabilistic partial coverage models, this is the first 2-d coverage model that can trade off the quality of tracking with network lifetime in a deterministic way. For an arbitrarily deployed sensor network, we propose efficient algorithms for determining the level of Trap Coverage even if the sensing regions have non-convex or uncertain boundaries. We then discuss a roadmap assisted geographic routing protocol to support efficient pairwise routing in large sensor networks with holes, which embodies a novel hole approximation technique and makes desired tradeoff between route-stretch and control overhead.

Committee:

Prasun Sinha (Advisor); Ness Shroff (Committee Member); Yusu Wang (Committee Member)

Subjects:

Computer Science

Keywords:

Wireless networks; sensor networks; coverage; sparse coverage; approximation algorithms

Oliveira, Talmai B.Dealing with Uncertainty and Conflicting Information in Heterogeneous Wireless Networks
PhD, University of Cincinnati, 2012, Engineering and Applied Science: Computer Science and Engineering

Inspired by challenges of multi-constraint path selection and the need for providing a desired QoS, this dissertation focuses on devising an efficient network selection algorithm that satisfies multiple user constraints with uncertainty in a heterogeneous wireless network (HWN), while under imprecise and dynamic network conditions. We start by determining the impact of the partial network knowledge on the optimal solution. We introduce a Dynamic Programming (DP) solution approach to the routing problem using a well established routing metric. We then compare the impact of using a more realistic scenario with stochastic metrics and formulate an approximate optimal strategy for routing between mobile devices (MD). A fuzzy logic model is then proposed which aims at translating the uncertainty of the network conditions to accurate values. We perform a thorough analysis of the metric values offered by various wireless technologies, and derive crisp values for imprecise network parameters. A sensitivity analysis is performed that reflects the performance and relative importance of the metrics on each network. These results are shown to impact user’s decision in handing data over to an appropriate interface.

While earlier works focused on multi-constrained routing or handover decision in a HWN, we consider dynamically changing network conditions. This is expected in a realistic deployment where a user is uncertain about what exactly is required under a given circumstance, indicates their preference in vague terms, and expects multiple deployments, with scenarios that are prone to failures, reliability strategies are considered in order to try to determine when to stop retransmitting a message in order to ensure proper delivery while still being energy efficient. A simple effective link-attribute estimator is presented that is capable of identifying the quality of communication between neighboring mobile devices while maintaining scalability. By relying on this link-quality estimator, a maximum number of attempts is computed which (probabilistically) ensures delivery while maintaining an energy-efficient network. Simulations show that our estimator maintains acceptable message delivery ratio while increasing the overall energy efficiency.

Finally, a study is made regarding dealing with conflicting information, and how devices can cope with data that may overlap or even conflict with each other through a localized protocol. Specifically, this dissertation looks at the impact of transient and permanent failures on the accuracy of decision making. The behavior of a wireless network is analyzed with respect to the detection of an event by increasing the number of failures. We compare four different schemes: simple majority between neighboring MDs, a more adaptive reputation-based protocol, fuzzy logic to quantify the MDs’ uncertainty and a combination of fuzzy logic and the Transferable Belief Model (TBM) framework. Through simulations, we show that our proposed TBM-based solution has the lowest number of incorrect decisions, even when used in deciding and detecting anomalies under an extremely large percentage of faulty MDs.

Committee:

Dharma Agrawal, DSc (Committee Chair); Kenneth Berman, PhD (Committee Member); Raj Bhatnagar, PhD (Committee Member); Chia Han, PhD (Committee Member); Mara Helmuth, DMA (Committee Member)

Subjects:

Computer Science

Keywords:

uncertainty; conflicting information; heterogeneous wireless networks; multiple user constraints; partial knowledge; reliability

Hosny, Sameh Shawky IbrahimMOBILITY AND CONTENT TRADING IN DEVICE-TO-DEVICE CACHING NETWORKS
Doctor of Philosophy, The Ohio State University, 2016, Electrical and Computer Engineering
The mismatch between user demand and service supply creates a congestion in mobile wireless networks. The literature has a strong evidence that user behavior is highly predictable. Service Providers (SPs) can track, learn and predict user demand and mobility patterns. Taking advantage of user demand predictability allows SPs to smooth out the network load. Caching some of the data items in the off-peak times shifts some of the network load and reduces the incurred service cost. Moreover, the Device-to-Device (D2D) communication allows users to share their proactive downloads with other users in their neighborhood. Therefore, users find their request either in their local cache or with other users around them. Nevertheless, harnessing the information about user mobility enhances SP's caching decisions and reduces the incurred service cost. The information about users trajectories allows the SP to predict their presence in some popular locations, which experience high demand levels. Finding an optimal caching strategy alleviates the network congestion in these locations and improves the network performance. This dissertation introduces a study to extend the capabilities of D2D caching networks and investigates how to enhance its performance. The research consists of three main directions: (1) exploiting user behavior predictability to smooth out the network load, (2) leveraging the relations between users to introduce a content trading marketplace, and (3) leveraging the information about user mobility to enhance the caching strategy. We start by investigating how to exploit the user behavior predictability to cache some data contents during off-peak times for a future possible request during peak times. This part of the research creates a benchmark that allows us to evaluate the performance of the proposed models. We compare the gains achieved by this proactive caching scheme with the flat pricing scenario. The gains achieved later, by content trading and mobility-aware D2D caching networks, are compared with the gains of this proactive caching scheme. Further, we highlight how to leverage the relations between users demand to introduce another benefit of the cached data items. Predicting users requests for peak times, correlated with the SP smart pricing, guides them to proactively cache some data contents during off-peak times. Moreover, users are equipped with D2D communication and SP helps them by announcing some anonymous information about users demand. This motivates the SP to hold a marketplace where users can trade their proactive downloads. Remarkably, we show that an appropriate manipulation of this marketplace allows the SP to maximize its profit, while users minimize their payments, and an equilibrium can be attained. Our research plan extends to shed light on the impact of user mobility on the caching decision. We consider both centralized and decentralized caching schemes. Users carry cached data while they are moving and share it at the popular locations using the D2D communication. Most of the users demand are served through the D2D communication which alleviates the network congestion in these locations. This model allows users to minimize their payment while the SP minimizes the incurred service cost and hence achieves a higher profit.

Committee:

Hesham ElGamal (Advisor); Atilla Eryilmaz (Advisor); Yuejie Chi (Committee Member); Jian Tan (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Proactive Caching, Mobility, Content Trading, Game Theory, Optimization Theory, Wireless Networks

Ji, BoDesign of Efficient Resource Allocation Algorithms for Wireless Networks: High Throughput, Small Delay, and Low Complexity
Doctor of Philosophy, The Ohio State University, 2012, Electrical and Computer Engineering

Designing efficient resource allocation mechanisms is both a vital and challenging problem in wireless networks. In this thesis, we focus on developing resource allocation and control algorithms for wireless networks that are aimed towards jointly optimizing over three critical dimensions of network performance: throughput, delay, and complexity.

We first focus on multihop wireless networks under general interference constraints, and aim to designing efficient scheduling algorithms that jointly optimize the network performance over different dimensions among the aforementioned three dimensions. We develop frameworks that enable us to design throughput-optimal scheduling algorithms that can reduce delays and/or incur a lower complexity in the following sense: smaller amount of required information, simpler data structure, and lower communication overhead.

We then turn to a simpler setting of single-hop multi-channel systems. A practically important example of such multi-channel systems is the downlink of a single cell in 4G OFDM-based cellular networks (e.g., LTE and WiMax). Our goal is to design efficient scheduling algorithms that achieve provably high performance in terms of both throughput and delay, at a low computational complexity. To that end, we first develop new easy-to-verify sufficient conditions for rate-function delay optimality in the many-channel many-user asymptotic regime (i.e., maximizing the decay-rate of the probability that the largest packet waiting time in the system exceeds a certain fixed threshold, as system size becomes large), and for throughput optimality in non-asymptotic settings. These sufficient conditions have been designed such that an intelligent combination of algorithms that satisfy both of the sufficient conditions allows us to develop low-complexity hybrid algorithms that are both throughput-optimal and rate-function delay-optimal. Further, we propose simpler greedy policies that are throughput-optimal and rate-function near-optimal, at an even lower complexity.

Finally, we investigate the scheduling problem in multihop wireless networks with flow-level dynamics. We explore potential inefficiency and instability of the celebrated back-pressure algorithms in the presence of flow-level dynamics, and provide interesting examples that are useful for obtaining insights into developing a unified throughput-optimal solution.

Our results in this thesis shed light on how to design resource allocation and control algorithms that can simultaneously attain both high throughput and small delay in practical systems with low-complexity operations. On the other hand, our studies also reveal that when flow-level dynamics is taken into account, even optimizing a single metric of throughput becomes much more challenging, not to mention achieving high network performance over all the three dimensions.

Committee:

Ness Shroff (Advisor); Ness Shroff (Committee Chair); Atilla Eryilmaz (Committee Member); Can Koksal (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Scheduling; Wireless Networks; High Throughput; Small Delay; Low Complexity; Fluid Limits; Large-Deviations Theory

Bhargava, SonaliGeneric and Scalable Security Schemes for Ad Hoc Networks
MS, University of Cincinnati, 2002, Engineering : Computer Science

An Ad Hoc network is a collection of wireless, mobile nodes that dynamically form a network without the use of centralized, fixed network infrastructure. Inherent characteristics of an Ad Hoc network such as dynamic topology and limited physical security poses severe security challenges to the network. Hence, these networks demand much stronger security mechanisms than the traditional, wired and static networks. Well established contemporary routing protocols seem to adapt to the dynamic conditions as well. However, they provide either no security mechanisms at all, or have only partial solutions for protecting the dynamic routing framework.

It is hard to achieve security and robustness in the routing protocols at the same time in such networks. Several issues have to be understood and addressed before devising a security mechanism. Moreover, challenges involved in addressing attacks differ from one protocol to the other. This thesis targets at securing reactive routing protocol AODV. The routing protocol is vulnerable to two kinds of attack: External and Internal attack. We have discussed some existing external attacks and possible malicious behavior from compromised nodes. To mitigate the attacks, we propose a dual level security model. On the first level, we have External Attack Detection Model(EADM), that secures the network with authentication and confidentiality that rely on mutual trust between nodes. And on the second level, Intrusion Detection Model (IDM) identifies the misbehaving nodes using the knowledge base and Response Model (RM) isolates these nodes from the network.

Committee:

Dr. Dharma P. Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

Ad Hoc Networks; security; AODV; IP sec; wireless networks

Felemban, EmadProtocols for Mission-Critical Wireless Sensor Networks
Doctor of Philosophy, The Ohio State University, 2009, Electrical and Computer Engineering
Wireless Sensor Networks can be used in Mission-Criticalapplications where the success of the mission depends on stringent QoS requirements. In this dissertation, two innovative cross-layer delivery protocols targeted for mission-critical networks are proposed. Multi-path Multi-SPEED (MMSPEED) protocol provides service differentiation and probabilistic QoS guarantees in two QoS domains. By allowing higher layers to select the most appropriate level of service, MMSPEED allocates network resources to packets and provide probabilistic guarantee to deliver packets within the applications's QoS requirements. The second protocol is called Sectored-Antenna MAC (SAMAC) protocol which is an integrated set of cross-layer communication protocols that exploits the potential benefits of sectored-antennas. In addition, we propose two analytical models for IEEE 802.11 DCF mechanism that accurately predict the performance of the DCF mechanism with a wide range of system parameters. Simplified versions of these models are used to optimize the performance of MMSPEED by selecting the optimal protocol parameters and to predict the E2E delay performance of SAMAC protocol.

Committee:

Ekici Eylem, PhD (Advisor); Füsun Ozgüner, PhD (Committee Member); Atilla Eryilmaz, PhD (Committee Member)

Subjects:

Computer Science; Electrical Engineering

Keywords:

Sensor Network,; mission-critical; Sectored-Antennas; Quality of Service; Wireless 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

SINGH, DAMANJITCROSS LAYER TECHNIQUES TO ENHANCE LINK PERFORMANCE IN WIRELESS NETWORKS
MS, University of Cincinnati, 2007, Engineering : Electrical Engineering
In this thesis, we improve the link performance by employing cross-layer techniques in two totally different wireless environments: a) IEEE 802.11 wireless networks and b) ultra-wideband wireless ad hoc networks. The cross-layer information exchange between the MAC and the PHY layer is used to maximize the link throughput. In the first part, we achieve the throughput gain by solving the problem of rate adaptation in IEEE 802.11 networks using the proposed Stochastic Automata Rate Adaptation (SARA) algorithm. SARA is inspired from Stochastic Learning Automata (SLA), a machine learning technique for adaptation in random environments and is fully compatible with IEEE 802.11 MAC. Next, we focus on improving the link performance in ultra-wideband wireless networks by exposing the MAC layer to the presence of multiple orthogonal pulse shapes at the physical layer. These pulse shapes have been recently proposed for ultra-wideband systems and have been used to improve the system performance at the physical layer. However, at the MAC layer, very few designs based on utilizing these pulse shapes have been proposed. In this thesis, we first propose an alternative way to use these pulse shapes at the physical layer to achieve high data rates. Next, we show that these pulse shapes can increase both the rate and the reliability of packet transmission at the MAC layer. To achieve better reliability, we introduce and develop the idea of ‘pulse shape redundancy’. Two throughput optimization techniques based on these ideas and findings are then analytically developed. After this, we propose a new MAC protocol, namely Redundancy-Enabled MAC (REMAC), which is capable of employing either of the two proposed schemes. Finally, we illustrate the performance gain achieved by REMAC and the role of redundancy through extensive simulation results and discussions.

Committee:

Dr. Dharma Agrawal (Advisor)

Keywords:

Wireless Networks; Ultra-wideband networks; Cross layer techniques; link adaptation

SUBRAMANIAN, VINODSOCRATES: Self-Organized Corridor Routing and Adaptive Transmission in Extended Sensor Networks
MS, University of Cincinnati, 2003, Engineering : Electrical Engineering
Large-scale sensor networks (LSSN's) are formed when very large numbers of miniaturized sensor nodes with wireless communication capability are deployed randomly over an extended region, e.g., scattered from the air or embedded in material. Systems such as smart matter, smart paint and smart dust imply the existence of LSSN's, but they can also be used in applications involving large geographical regions such as environmental monitoring or disaster relief. Our contention is that, given their scale and random structure, LSSN's should be treated as complex systems rather than as standard wireless networks. Approaches from wireless networks typically have difficulty scaling up to large numbers of nodes, especially when the nodes have limited capabilities and are deployed over a region much larger than their communication range. We explore how a system comprising of very large number of randomly distributed sensor nodes can organize itself to communicate information. To keep the system realistic, we assume that nodes in our system are unreliable, have limited energy resources and have minimal on-board computational capabilities. Our focus is on the efficient routing of messages in such a system, specifically on the network algorithms aspect, rather than on issues such as hardware, signal processing and communication. The goal is to develop a system that scales effectively and is robust to node failures. The approach we propose is to limit the usage of bandwidth and energy while tapping the inherent parallelism of simple flooding to achieve robustness. Simulation results show significant improvement in performance compared to simple flooding algorithms.

Committee:

Dr. Ali A. Minai (Advisor)

Keywords:

sensor networks; wireless networks; complex systems; adaptation; large scale networks

Sakai, KazuyaSecurity and Privacy in Large-Scale RFID Systems
Doctor of Philosophy, The Ohio State University, 2013, Computer Science and Engineering
Radio Frequency Identification (RFID) is an electronic tagging technology that allows objects to be automatically identified at a distance without a direct line-of-sight using an electromagnetic challenge-and-response exchange of data. An RFID system consists of RF readers and RF tags. RF tags are attached to objects, and used as a unique identifier of the objects. RFID technologies enable a number of business and personal applications, and smooth the way for physical transactions in the real world, such as supply chain management, transportation payment, animal identification, warehouse operations, and more. Though bringing great productivity gains, RFID systems may cause new security and privacy threats to individuals or organizations, which have become a major obstacle for their wide adaptions. Therefore, it is important to address the security and privacy issues in RFID systems. In this dissertation, we investigate security and privacy issues for large-scale RFID systems. Since any object is uniquely identifiable with an RF tag, the tag's ID must be protected from adversaries during data communications in keeping with the authenticity of tags. Hence, we first propose private authentication protocols that RF readers to singulate individual tags without disclosing tags' content to adversaries. To design a secure access protocol, two different approaches are taken, encryption-based and non-encryption-based. In the encryption-based approach, we propose a structured key management with low cost cryptographic operations based on a skip list. This can be applied to a large-scale RFID systems. On the other hand, shared key exchanges are not feasible in some contexts. Hence, we develop a distributed RFID architecture for secure data communications without shared secret. With a novel encoding scheme and jamming technique, the distributed RFID authentication scheme protects tags from various types of adversaries. With a private authentication protocol, readers can securely validate tags' authenticity. After reading a tag, an RFID system updates object's status or generates data. Thus, any piece of data in the back-end server is associated with a particular tag. For a high quality RFID-based data service, the authenticity of data is of concern. Therefore, we study the verifiable RFID systems, where a set of data related to a tag can be verified in the sense that the data is associated with the tag and any element of the data cannot be modified without being detected. To realize such a verifiable RFID system, we build a new RFID architecture that integrates multiple RFID systems into single exa-scale RFID system, then formulate data verification problem, and then propose data verification protocols. The proposed solutions are mathematically analyzed, and computer simulations are conducted to measure all aspects of the RFID systems, including the degree of security and the cost of control overhead. Furthermore, we implement a prototype of a verifiable RFID system. The performance evaluations show that the proposed protocols achieve their design goals. We believe this research serves the foundation for the next generation of RFID systems.

Committee:

Ten H. Lai (Advisor); Dong Xuan (Committee Member); Feng Qin (Committee Member)

Subjects:

Computer Science

Keywords:

security, privacy, RFID, Radio Frequency Identification, mobile computing, wireless networks

Bapat, Sandip ShriramOn reliable and scalable management of wireless sensor networks
Doctor of Philosophy, The Ohio State University, 2006, Computer and Information Science
Wireless sensor networks have shown great potential as the technology that will change the way we interact with the physical world around us and have forced researchers to reconsider the way they think about distributed systems. However, these networks have to deal with a great deal of uncertainty arising out of the unique differences in their computational model such as unreliable communication, severely resource constrained devices and vulnerability to different types of faults. To meet these challenges, we must first understand the different reliability issues related to wireless sensor networks and then design appropriate mechanisms to deal with them. We believe network management to be a key enabler for such networks to deal with these challenges. In this dissertation, we first present a comprehensive study of different types of node and network faults that occur in wireless sensor networks and propose a fault model for these networks. Based on this fault model, we identify key elements of a network management architecture for wireless sensor networks. We then present MASE, a Management Architecture for SEnsor networks, that addresses management issues at all levels in a sensor network: at individual nodes, in the network, and also at the base station. We emphasize self-stabilizing designs for MASE components to deal with anticipated and unanticipated faults. We present key network management services such as the Stabilizing Reconfiguration service, the Chowkidar health monitoring service and the Reporter termination detection service that we have designed and implemented as part of MASE. We also present our network-based experiment orchestration framework which closes the loop in sensor network management by automating common execution and experimentation patterns. The different architectural components presented in this dissertation have been validated not only through experiments, but also in field deployments for managing large scale sensor network systems such as “A Line In The Sand” and “ExScal”. Implementations for existing services and tools developed as part of the MASE architecture, for mote, Stargate and server platforms, are also publicly available in the form of a MASE toolkit.

Committee:

Anish Arora (Advisor)

Subjects:

Computer Science

Keywords:

Wireless sensor networks; Wireless networks; Network management; Stabilization; Fault tolerance