Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Enabling real-time communications in resource-constrained networks(Montana State University - Bozeman, College of Engineering, 2023) Mekiker, Batuhan; Co-chairs, Graduate Committee: Clemente Izurieta and Mike WittieThe Internet of Things (IoT) applications require flexible and high-performance data channels, but many IoT networks can only support single-use case applications, which limits their performance and flexibility for real-time and streaming applications. LoRa offers a flexible physical network layer but lacks the resource management needed in its link layer protocols to support real-time flows. My initial contribution, the Beartooth Relay Protocol (BRP), expands the performance envelope of LoRa, making it suitable for a wide range of IoT applications, including those requiring real-time and streaming capabilities, and aims to address the problem. However, the resource-limited nature of LoRa does not allow BRP to scale to multi-hop mesh network deployments while maintaining real-time streams. To address the limitations of BRP in supporting mesh network deployments and real-time streams beyond two hops, we focus on developing the second-generation Beartooth Radios, MKII, and the first-generation Beartooth Gateways. We utilize Commercially-available Of the Shelf Components (COTS) in the radios to provide a cost-effective, power-efficient, and compact solution for establishing real-time situational awareness. The self-healing mesh network provided with MKII and Gateways also enhances the reliability of the overall network, ensuring connectivity even in case of node failures. By incorporating military information brokers, such as the Tactical Assault Kit (TAK), the Beartooth Gateway establishes a hybrid network between Beartooth radios, gateways, and other TAK-capable devices, ensuring compatibility with existing IP networks. Building upon the premise that voice communications are an integral part of real-time SA, the last part of my research focuses on assessing audio quality and efficacy of audio codecs within bandwidth-constrained networks. Delving into voice communications in resource-constrained networks, my research contrasts the performance of Text-to-Speech (TTS) models with traditional audio codecs. I demonstrate that TTS models outperform audio codec compressed voice samples in quality while also effectively managing scarce resources and available capacity more efficiently. By combining flexible link layer protocol elements in BRP, Beartooth MKII radios, Gateways, and insights on integrating TTS systems for voice communication, my research demonstrates a versatile and flexible solution that provides real-time application streams and critical situational awareness capabilities in bandwidth-constrained networks and mission-critical applications.Item Towards responsive user services in edge computing(Montana State University - Bozeman, College of Engineering, 2023) Rahman, Saidur; Co-chairs, Graduate Committee: Mike Wittie and Sean Yaw; This is a manuscript style paper that includes co-authored chapters.Mobile applications can improve battery and application performance by offloading heavy processing tasks to more powerful compute servers. Cloud servers are located far from mobile devices that may not meet the responsiveness requirements of those applications. Edge servers deployed at the edge of the network to provide the compute resources to achieve low latency. So the combination of 5G and edge computing has the potential to offer low latency user services that can make the mobile applications responsive. 5G provides fast communication between users and servers, however, additional communication delays can occur because of increasing number of roundtrip communication to locate the servers using domain name system (DNS). So, I propose a caching mechanism to reduce the DNS roundtrip delay. Furthermore, the edge server and cellular tower use the same compute resources, which are limited. It is not clear how to place the tasks on the limited edge resources and how to handle the resource sharing when Radio Access Network (RAN) process needs more computation resources to handle network traffic fluctuations. So, I present several techniques to implement task checkpointing, task checkpointing overhead prediction, and task migration to provide low latency and responsive services to mobile applications. I also show how the proposed techniques can manage the shared resources between mobile network and edge servers, utilize the available edge resource effectively and increase users' quality of experience.Item Development of a cognitive array system(Montana State University - Bozeman, College of Engineering, 2010) Weber, Raymond Joseph; Chairperson, Graduate Committee: Richard Wolff; Yikun Huang (co-chair)This thesis proposes a design for a cognitive array system for next generation wireless communication systems, combining the techniques of cognitive radios and adaptive array systems. This novel array system allows for the possibility of greater spectral usage and reuse, and improved communication ranges. In this thesis, numerous algorithms were studied to map an RF environment in both spatial and spectral domains that would be useful in this system. Towards this goal, direction of arrival estimation, frequency sensing and spectral hole finding algorithms were studied, in addition to a joint frequency and direction of arrival estimation algorithm. Beamforming was also studied as a means of improving signal quality and increasing range. Once the direction to a target was found, localization and tracking were studied to further refine the target's position and change in position over time. After the algorithms were studied in simulation to determine their properties, hardware calibration was performed followed by laboratory tests of the methods with a uniform circular array testbed at Montana State University to verify the expected performances.Item Design and evaluation of test bed software for a smart antenna system supporting wireless communication in rural area(Montana State University - Bozeman, College of Engineering, 2008) Panique, Michael David; Chairperson, Graduate Committee: Richard Wolff; Yikun Huang (co-chair)This paper explores the design and development of a test bed to analyze feasibility of utilizing adaptive smart antennas in conjunction with high bandwidth WiMAX radio systems to achieve improved performance for mobile nodes and to suppress potential interference from unwanted signals. Although the new WiMAX standard offers the potential for using smart, adaptive antennas, this functionality has not been implemented. This design serves as a common platform for testing adaptive array algorithms including direction of arrival (DOA) estimation, beamforming, and adaptive tracking, as well as complete wireless communication with a WiMAX radio. Heavy emphasis will be placed on ease of implementation in a multi-channel / multi-user environment. Detailed here, is the design and development of an 8-channel adaptive smart antenna test bed for WiMAX radio systems. The test bed consists of an 8-element circular antenna array, a PC running a software interface, and RF receiver and transmission boards which enable DOA estimation and beamforming to take place. We have developed a LabVIEW interface for a PC controlled smart antenna test bed supporting two mobile targets. The main system has three components, DOA estimation and signal validation, beamforming (null steering or multi-beam), and target tracking. The interface is implemented in a modular fashion so that a maximum amount of flexibility is available to test bed users. The test bed was used in conjunction with MATLAB simulations to analyze DOA estimation, beamforming, and nullsteering algorithms necessary to realize a smart antenna system capable of handling multiple users and suppressing nearby strong interference. The results of tests run using the test bed showed that communication delay and hardware limitations on the RF transmission board were a limiting factor in the performance of the smart antenna system.Item Automated radio network design using ant colony optimization(Montana State University - Bozeman, College of Engineering, 2008) Sharkey, Jeffrey Allen; Chairperson, Graduate Committee: John PaxtonRadio networks can provide reliable communication for rural intelligent transportation systems (ITS). Engineers manually design these radio networks by selecting tower locations and equipment while meeting a series of constraints such as coverage, bandwidth, maximum delay, and redundancy, all while minimizing network cost. As network size and constraints grow, the design process can quickly become overwhelming. In this thesis we model the network design problem (NDP) as a generalized Steiner tree-star (GSTS) problem. Any solution to the minimum Steiner tree (MST) problem on a constructed GSTS graph will directly identify the tower locations and equipment needed to build the network at an optimal cost. The direct MST solution can only satisfy coverage constraints. Because the MST problem is known to be NP-hard, our research applies ant colony optimization (ACO) to find near-optimal MST solutions. Using ACO also allows us to meet bandwidth, maximum delay, and redundancy constraints. We verify that our approach finds near-optimal designs by comparing it against a 2-approximation algorithm in several different scenarios.Item Improved control system for process, voltage, and temperature compensation of CMOS active inductors(Montana State University - Bozeman, College of Engineering, 2011) Hollender, Reinhold Frederick William, III; Chairperson, Graduate Committee: James P. BeckerWireless communications play an increasingly large role in today's society. Today, many wireless functions are necessarily integrated into chips and other small packages to support miniaturized wireless devices such as cell phones, laptops, netbooks, etc. These Radio Frequency Integrated Circuits (RFICs) often require inductances to perform their function. Most RFICs utilize spiral inductors. Spiral inductors have their properties defined by their physical dimensions, often taking up large areas of IC real estate. There has been research into replacing these spiral inductors with active elements to reduce their size. However, these active inductors are based on parasitic elements that can vary significantly over temperature, supply voltage, and processing variations of the wafers themselves. This professional paper documents an improved control scheme to maintain correct active inductor behavior over process, voltage, and temperature variations in applications where the active inductor is used in a Wilkinson power divider.Item Performance evaluation of routing protocols for QOS support in rural mobile ad hoc networks(Montana State University - Bozeman, College of Engineering, 2008) Bohannan, Chad Brian; Chairperson, Graduate Committee: Jian TangWe evaluate several routing protocols, and show that the use of bandwidth and delay estimation can provide throughput and delay guarantees in Mobile Ad Hoc Networks (MANETs). This thesis describes modifications to the Dynamic Source Routing (DSR) protocol to implement the Quality Aware Source Routing (QASR) network routing protocol operating on an 802.11e link layer. QASR network nodes exchange node location and flow reservation data periodically to provide information necessary to model and estimate both the available bandwidth and the end-to-end delay of available routes during route discovery. Bandwidth reservation is used to provide end-to-end Quality of Service, while also utilizing the differentiated Quality of Service provided by the 802.11e link layer. We show that QASR performs significantly better in several performance metrics over the DSR and the Ad-Hoc On-Demand Distance Vector (AODV) protocols, and performs more consistently in all quality metrics when traffic demand exceeds network capacity.Item Wireless communication for sparse and rural areas(Montana State University - Bozeman, College of Engineering, 2007) Zhang, Mingliu; Chairperson, Graduate Committee: Richard WolffWireless technology experienced a fast development in the past few decades. However, research and investment in wireless communication so far has been focused mainly on high-density domains or fully connected networks. The technologies/solutions developed for above domains do not readily apply to rural and sparse domains. The users in rural and sparse areas are still served predominantly by either low-speed dialup access or have no data service available at all. This research work explores the largely overlooked rural and sparse domains, where distance, rough terrain and low node density are the key parameters driving system design and performance, from the perspectives of fixed wireless applications to mobile wireless applications. For fixed wireless applications, a baseline wireless network structure for rural and sparse areas is defined and the potential for improved high-speed fixed communication services in rural and remote areas is examined. The potential of using multi-hop network topologies in very sparse areas is explored. The cost benefits of several other emerging technologies and approaches are also investigated with the objective of finding cost-effective and affordable high-speed broadband communications solutions for rural and remote areas.Item Topology control and interference aware resource allocation algorithms using directional antenna for QoS (802.16e) performance in multi-hop wireless networks(Montana State University - Bozeman, College of Engineering, 2010) Annavarapu, Vishwanath; Chairperson, Graduate Committee: Jian TangIn recent years, there has been a lot of research work being done on the wireless networking using Directional antennas. But not many approached the issue together with resource allocation and channel assignment in multi-channel multi-radio networks, especially in multi-hop WiMAX (802.16e) networks. This work also explores the implementation of Directional antenna for communication in mobile scenario where the nodes move either in specified trajectory or randomly. The overall goal of this research is to work towards improving the wireless communication and proposing solutions for some existing issues. The methods of topology control algorithms for maximizing the minimum link capacity and then a different approach to balance the network load should be one of the few pieces of work in this regard. Implementation of these proposed methods have improved the network performance in aspects like throughput, delay, network capacity, interference, traffic congestion and network balance. The major issues that determine the performance of wireless networks include traffic congestion, interference, signal quality, Quality of Service (QoS), mobility issues like handover. These issues for a multi-hop WiMAX scenario that would possibly emerge in future were studied and solution were suggested and tested. Large numbers of WiMAX scenarios of different sizes with different type of applications, models, devices, resources and methodologies have been simulated and various aspects like mobility, QoS, interference control, traffic congestion and network balance have been studied. During the course of research, various wireless communication issues have been addressed by providing feasible to optimal solutions; new designs and methodologies for the WiMAX models is being incorporated to induce useful functionalities; communication models, antennas and other devices and technically enhanced. Also, the QoS in WiMAX networks hasn't been studied much; our research work includes simulation and detailed analysis of various service classes in different conditions and scenarios for WiMAX multi-hop networks.Item Resource allocation algorithm using directional antennas in WiMAX(Montana State University - Bozeman, College of Engineering, 2009) Gurdasani, Neeraj; Chairperson, Graduate Committee: Brendan MumeyThis paper discusses different algorithms to create directional antenna patterns in OPNET Modeler. We describe algorithms to create conical and pencil beam antenna patterns. We also present a version of this algorithm that creates antenna patterns whose gain follows a cosine squared curve. We have also implemented tracking in OPNET to utilize these directional antenna patterns. These algorithms can be used to create antenna patterns for any wireless technology in OPNET such as WiFi and WiMAX. This paper also discusses an integer linear programming (ILP) formulation for a resource allocation problem. This is a centralized optimization algorithm where the base station decides which subscriber station will be assigned to which relay station in the network such that the throughput of the entire network is maximized. We present some simulation results showing 10Mbps improved throughput using directional antennas with the assignment strategy. This is a centralized algorithm and can be used in any technology that has a centralized resource allocation scheme such as WiMAX.