Browsing by Subject "Measurements"
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Item A Comprehensive Examination of Emerging 5G Services: Challenges and Opportunities(2021-09) Narayanan, Arvind2019 marks the year when 5G services were rolled out commercially to consumers. 5G is expected to support sub-millisecond latency as well as ultra-high throughput of 20~Gbps that is a 100x improvement compared to its predecessor 4G/LTE. However, there exists a vacuum in understanding how 5G as a technology performs in-the-wild and whether it can fulfill its promises. Even after two years of being deployed commercially, the impact of 5G services on network performance or power consumption is not well understood. It is also unclear how applications and services today practically benefit from 5G technology. In an attempt to fill these voids, this dissertation is dedicated to examine the commercial 5G landscape ``from'' and ``across'' several key dimensions -- network performance, radio power characteristics, and quality-of-experience implications for mobile applications -- to provide key insights for interested stakeholders, and propose intelligent mechanisms for application developers to better leverage 5G technology that can aid in building future 5G-aware apps and services. To that end, using tools such as 5G Tracker developed in-house, we conducted a detailed measurement study to provide a first impression of the network performance characteristics of 5G services (including that of the much anticipated mmWave) and helped establish an important baseline for studying the evolution of 5G's performance. Subsequently, we expanded its scope and conducted the first comprehensive measurement study to investigate power consumption of 5G radio on commodity smartphones. Overall, our findings reveal key characteristics of commercial 5G services in terms of throughput, latency, performance bottlenecks, coverage, radio state transitions and radio power consumption under diverse scenarios, application performance (web-browsing, file-download, video streaming) with detailed comparisons to 4G/LTE networks. Furthermore, we also quantitatively reveal critical trade-offs (e.g. ultra-high vs. stable network performance, performance vs. energy) that get amplified with 5G and how challenges lie for upper layers (transport and up) to effectively utilize 5G. Leveraging the insights obtained from our measurement studies, we statistically reveal that, unlike in 4G/LTE, location alone is not sufficient for mapping 5G (especially mmWave) performance. We further proposed Lumos5G, a data-driven machine learning based framework for mmWave 5G throughput prediction that utilizes and fuses a variety of contextual features that can be collected on the smartphone, including its location, mobility information, geometric relationship with the 5G base station, and cellular connectivity information for predicting 5G throughput. We discuss how approaches like these provide opportunities as well as challenges in building future 5G-aware apps. In summary, this thesis contributes to better understanding the emerging commercial 5G landscape in the U.S. by systematically designing measurement methodologies and timely conducting experiments and analysis. With the rate at which 5G advancements and adoption are taking place, clearly 5G is on its evolutionary path for the next few years. The insights and challenges highlighted by our research will hold a mirror up to the implications of this new emerging technology. Artifacts of our research have been made available in the form of: datasets (5Gophers v1.0, Lumos5G v1.0, SIGCOMM21-5G v1.0), a smartphone-based measurement tool (5G Tracker) and a 5G mapping platform (5Gophers.umn.edu) for visualizing 5G coverage.Item How Choices Between Flexibility And Persistence During Idea Search Processes Contribute To Creativity(2022-09) Wu, YihanCreative problem solving is a dynamic process during which individuals need to constantly navigate toward their goal through an ill-defined solution path. Theoretical and empirical endeavors suggest that individuals need both flexible and persistent approaches to succeed in creative tasks, yet little work has given attention to how to measure flexibility and persistence during the ideational search process. Three studies were devoted to this question.(a) The first study presents new process-based measures of flexibility and persistence and validates how well they can predict creative performance in several typical laboratory-based creativity tasks and in an ecologically valid complex design task. (b) The second study introduces an instructional intervention to examine the effects on creative performance when participants are given external prompts to shift more frequently or to dwell longer. The findings suggest that – after controlling for pre-existing dispositional differences in divergent-thinking ability across conditions – participants who had the autonomy to choose when to shift (flexible approach) or to dwell (persistent approach) performed better, or similarly to, participants who were externally prompted to shift more frequently or to dwell longer. (c) Building on the emerging literature on the context adaptivity account of metacontrol biases towards either flexibility or persistence, Study 3 tested how varying task contexts shape an individual's tendencies toward flexibility versus persistence. It revealed both interindividual metacontrol biases and intraindividual variation in response to changing task-related constraints. Together, this work enriches our understanding of how an individual's choices between flexibility and persistence during the creative problem-solving process, and their subsequent performance, are guided both by individual differences and environmental factors such as task contexts and task goals.