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

Master of Science, The Ohio State University, 2019, Statistics

The adjustment of students to a school environment is fundamentally linked to the friendship networks they form with their peers. Consequently, the complete picture of a student' adjustment can only be obtained by taking into account both their friendship network and their reported perceptions of the school environment. However, there is a lack of flexible statistical models and methods that can jointly analyze a social network with an item-response data matrix. In this paper, we propose an extended latent space model for heterogeneous (multimodal) networks (LSMH) and its extension LSMH-I, which combine the framework of latent space modeling in network analysis with item response theory in psychometrics. Using LSMH, we summarize the information from the social network and the item responses in a person-item joint latent space. We use a Variational Bayesian Expectation-Maximization estimation algorithm to estimate the item and person locations in the joint latent space. This methodology allows effective integration, informative visualization and prediction of social networks and item responses. We apply the proposed methodology to data collected from 16 third-grade classrooms comprised of 451 third-grade students' self-reported friendships and school liking, which were collected as part of the Early Learning Ohio project. Through the person-item joint latent space, we are able identify students with potential adjustment difficulties and found consistent connection between students' friendship networks and their well-being. We believe that using LSMH, researchers will be able to easily identify students in need of intervention and revolutionize the the understanding of social behaviors.

Committee: Subhadeep Paul (Advisor); Paul De Boeck (Committee Member); Jessica Logan (Committee Member); Peter Craigmile (Committee Member) Subjects: Statistics

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 (open full item for complete abstract)

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

MS, University of Cincinnati, 2006, Engineering : Computer Engineering

A majority of group communication applications in cellular-based heterogeneous wireless setups entail secure data exchange. The problem can be effectively tackled if the underlying cellular infrastructure is used to provide an authentication backbone to the security associations. We propose a novel distributed ID based key exchange mechanism using shared polynomials in which the shares are generated by the communicating groups. Our idea employs a mechanism where the Base Stations (BSs) carry out an initial key generation by a polynomial in a distributed manner and then pass on the key material to the Mobile Stations (MSs). The multi-interface MSs can now securely communicate over interfaces other than cellular. The scheme incorporates symmetric polynomials, which are chosen by the BS acting as polynomial distributors. Simulations done to measure performance have shown encouraging results.

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

MS, University of Cincinnati, 2005, Engineering : Computer Engineering

This thesis describes the concept of sensor networks which has been made viable by the convergence of MEMS system technology and efficient routing protocols. Sensor nodes possess finite, non-renewable energy that they expend in sensing a multitude of modalities including temperature, moisture, pressure, light and infrared radiation. A radio-interconnected collection of such sensors forms a sensor network and the information collected from the network is transmitted for analysis at a distant location termed as the sink. The main purpose of a sensor network is to gather information about the various parameters of the area in which it is deployed and to transmit this information to the sink for appropriate utilization. A wireless sensor node is capable of only a limited amount of communication and processing. Therefore, unlike traditional networks, where the objective is to maximize channel throughput, the chief consideration in a sensor network is to extend the system lifetime as well as system robustness. Wireless ad hoc and sensor networks are comprised of energy–constrained nodes. This limitation has led to the dire need for energy-aware protocols to produce an efficient network. Heterogeneity is introduced in a wireless sensor network by having a large number of low power sensor nodes and a small number of more powerful nodes to serve as cluster heads. We propose a self-tuning scheme that improves the lifetime of a heterogeneous wireless sensor network by appropriately scheduling the transmission rate of individual sensor nodes in the network. We consider a distance based sleep scheduling problem for equal energy consumption rates in low power sensor nodes and evaluate the optimal settings required in a heterogeneous sensor network. We evaluate the efficiency of our proposed algorithm based on an analytical model and perform simulations to verify the adequacy of our scheme in terms of important network parameters and compare with existing heterogeneous sensor netw (open full item for complete abstract)

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

MS, University of Cincinnati, 2000, Engineering : Computer Engineering

This thesis proposes a CASE tool ACASE which is an integration of different techniques for the formal modeling and simulation of Active Networks. Active networks, proposed by DARPA, have revolutionized the traditional view of networks from a passive carrier of data into a more of a computational engine. Usage of formal methods for the specification and verification of such systems offers a high level of modular abstraction and early design error detection. Simulations also aid in the examination of complicated network scenarios and help shape a better understanding on systems that would, otherwise, prove very difficult to analyze. However the implementation of formal methods is hard even for experienced users especially in complex applications, thus, trends in rendering formal methods more transparent are presently emerging. This thesis offers a solution by offering a new and extensive tool that combines the ActiveSPEC formal specification framework and the ANSE simulation engine. ACASE isa high-level graphical user interface for the development (services, policies and protocols) and simulation of active networks.

Committee: Dr. Perry Alexander (Advisor) Subjects:

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

PhD, University of Cincinnati, 2008, Engineering : Electrical Engineering

Wireless and mobile networks (WMNs) are witnessing a great success inrecent years. Although there are different types of WMNs (e.g., cellular networks, WLANs, etc.) that can provide different types of services (e.g., different bandwidth and coverage), any single type of existing WMN is not able to provide all types of services such as high bandwidth with wide cov- erage. In order to provide more comprehensive services, a concept of integrated heterogeneous wireless and mobile network (IHWMN) is introduced by combing different types of WMNs. Additionally, with the advance of software defined radio (SDR) technologies, it is possible to integrate multiple WMN interfaces into a single mobile terminal and let the terminal be able to access multiple WMNs. It is obvious that the introduction of IHWMN as well as multi-interface terminal brings more flexible and plentiful access options for mobile users. However, it faces great challenges, such as the architecture of network integration, network selection strategies, handoff scheme, resource allocation, etc. Although IHWMN is a very promising candidate for the future WMNs, a lot of problems have to be solved before launching to the commercial market. In this research thesis, we briefly review the existing work for IHWMN. Then, traffic and system models are proposed for IHWMNs. Based on the proposed models, we tackle the network selection problem in IHWMNs, which is required to determine which network should be accessed. A cost-function-based network selection (CFNS) strategy is proposed based on system's perspective, which also takes into account of the user's needs. Theoretical model is used to evaluate the system performance of the proposed CFNS strategy and simulations are also conducted to verify our analysis. Then, we propose preemption-based resource management schemes to support real-time and non-real-time traffic in IHWMNs. The proposed resource management schemes take advantage of heterogeneities of multiple traffi (open full item for complete abstract)

Committee: Qing-An Zeng (Committee Chair); Kenneth Berman (Committee Member); Raj K. Bhatnagar (Committee Member); Wen-Ben Jone (Committee Member); Heng Wei (Committee Member) Subjects: Computer Science

MS, University of Cincinnati, 2007, Engineering : Electrical Engineering

Self-organization is emerging as an important method for engineering large-scale complex systems such as sensor networks, robot swarms, multi-agent systems, self- reconfiguring robots and smart structures. It provides an inherently scalable, flexible and robust way to obtain effective functionality without the need for global communication or control. However, most theoretical work on structural self-organization has focused on abstract models such as cellular automata, percolation, sandpiles, etc. In contrast, systems for engineering applications must accomplish goal-directed tasks, and their self-organization rules must be based on domain-specific considerations such as bandwidth, capacity, cost, energy resources, etc. Ultimately, such self-organization procedures must be judged by system performance — an issue seldom considered in abstract models. In this thesis, we consider a relatively simple but important class of systems — geometric networks — and present a set of self-organization rules that try to optimize a specific, application-relevant performance criterion. We show empirically that the resulting networks are indeed close to optimal, that their performance derives from the specific structuring of their heterogeneity rather than from simple generic attributes, and that they represent atypical samples in the overall configuration space. The study has also produced an interesting conclusion about homogeneous networks, showing that, with randomly deployed nodes, networks that seek homogeneous out-degree have an advantage over networks that simply use the same connection radius for all nodes — though both are worse than heterogeneous configurations.The simulation results show that highly optimized network configurations are as robust as non-optimized ones with respect to random node failure, but are much more susceptible to targeted attacks that preferentially remove nodes with the highest connectivity. This confirms the “robust-yet-fragile” property postulat (open full item for complete abstract)

Committee: Dr. Ali Minai (Advisor) Subjects:

MS, University of Cincinnati, 2006, Engineering : Electrical Engineering

Wireless sensor networks with randomly deployed nodes are becoming increasingly viable for several applications. The nodes in these networks communicate wirelessly. Most models for wireless sensor networks have used homogeneous nodes with the same communication range. These networks have symmetric connectivity, which makes them easier to analyze using percolation models. It is well-known that heterogeneous networks, where each node can customize its transmission radius, potentially provide many advantages. However, devising algorithms for such reconfiguration has proved to be difficult. Scalability requires that any configuration process be completely distributed, which presents the classic problem confronting all self-organized systems: How to obtain global optimality from local adaptation. We present a heuristic for the self-organization of heterogeneous networks with the explicit goal of producing robust networks that minimize energy consumption. The results show that the heuristic networks are both effective and efficient than the homogeneous networks in all the measures considered.

Committee: Dr. Ali Minai (Advisor) Subjects: Computer Science

Master of Science (MS), Ohio University, 1996, Industrial and Manufacturing Systems Engineering (Engineering)

Combining genetic algorithms and artificial neural networks to select heterogeneous dispatching rules for a job shop system

Committee: Luis Rabelo (Advisor) Subjects: Engineering, Industrial

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-qual (open full item for complete abstract)

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