UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Optimization of Signal Routing in Disruption-Tolerant Networks(2021) Singam, Caitlyn; Ephremides, Anthony; Systems Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Communication networks are prone to disruption due to inherent uncertainties such as environmental conditions, system outages, and other factors. However, current state-of-the-art communication protocols are not yet optimized for communication in highly disruption-prone environments, such as deep space, where the risk of such uncertainties is not negligible. This work involves the development of a novel protocol for disruption-tolerant communication across space-based networks that avoids idealized assumptions and is consistent with system limitations. The proposed solution is grounded in an approach to information as a time-based commodity, and on reframing the problem of efficient signal routing as a problem of value optimization. The efficacy of the novel protocol was evaluated via a custom Monte Carlo simulation against other state-of-the-art protocols in terms of maintaining both data integrity and transmission speed, and was found to provide a consistent advantage across both metrics of interest.Item PERFORMANCE EVALUATION OF DISRUPTION TOLERANT NETWORKS WITH IMMUNITY MECHANISM AND CODING TECHNIQUE(2015) Lee, Jin Na; La, Richard J; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We examine the performance of a Disruption Tolerant Networks (DTNs) with an epidemic routing (ER) scheme with the coding technique and/or immunity mechanism under the various network environments. We are interested in the scenarios of opportunistic dissemination of large files. First, we study how the different implementations of the ER scheme perform in diverse network settings. We compare the performance of ER with its summary vector implemented as both a list and as a Bloom filter. Second, we examine how network coding affects the performance of the ER scheme. To this end, we investigate the performance of encoding-based routing (EBR), a variant of the ER scheme which uses random linear coding at source nodes. EBR is expected to mitigate what is commonly known as the coupon collector’s problem, which arises when a large file is chopped into small fragments and then the fragments are disseminated throughout the network. We compare this to the case where intermediate non-source nodes are allowed to create new linear combinations from the ones it already holds. Lastly, we evaluate the benefits of two different types of immunity mechanisms – one based on file ID and the other based on bundle ID – with not only the ER scheme but also two different EBR schemes in various network scenarios and settings. We also investigate the performance gain from compressing the immunity list. By presenting and analyzing extensive simulation results, we provide information that could provide a guideline for employing each of the aforementioned techniques in routing schemes of interest in various network settings.Item Using Commercial Ray Tracing Software to Drive an Attenuator-Based Mobile WIreless Testbed(2012) Taylor, Keith Richard; Jaja, Joseph; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We propose and build a prototype architecture for a laboratory-based mobile wireless testbed that uses highly detailed, site-specific channel models to dynamically configure a many-to-many analog channel emulator. Unlike similar systems that have used abstract channel models with few details from the physical environment, we take advantage of commercial ray tracing software and high-performance hardware to make realistic signal power and characteristics predictions in a highly detailed environment. The ray tracing results are used to program a many-to-many analog channel emulator. Using this system, we can conveniently, repeatedly, and realistically subject real wireless nodes to the effects of mobility. We use our prototype system and a detailed CAD model of the University of Maryland campus to compare field test measurements to measurements made from the same devices in the same physical scenario in the testbed. This thesis presents the design, implementation, and validation phases of the proposed mobile wireless testbed.Item Properties of a DTN Packet Forwarding Scheme Inspired By Themodynamics(2010) Mathew, Bipin; La, Richard J.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this thesis, we develop a discrete time model of a recently proposed algorithm, inspired by thermodynamics, for message routing in Disruption Tolerant Networks (DTNs). We model the evolution of the temperature at the nodes as a stochastic switched linear system and show that the temperatures converge in distribution to a unique stationary distribution that is independent of initial conditions. The proof of this result borrows tools from Iterated Random Maps (IRMs) and Queuing theory. Lastly, we simulate the proposed algorithm, using a variety of mobility models, in order to observe the performance of the algorithm under various conditions.