Graduate Thesis Or Dissertation
 

Quality of Experience Assurance Methods in Mobile Heterogeneous Wireless Communication Systems

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/m326m651p

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  • The proliferation of mobile users and internet content has advanced a plethora of research areas. Among these areas include mobile networks, transport layer protocols, and smart cities. Research shows that global mobile data traffic will increase sevenfold reaching 49 exabytes per month by 2021, most of which will be mobile video content, with a percentage projected to reach up to 78% by 2021. This resulted in efforts to integrate various wireless access technologies for improved performance, increased services and inter-connectivity of end users. The recent growth in data demand has prompted researchers to come up with new wireless techniques (e.g., MIMO, cooperative communication, femtocells, etc.) and develop new technologies (e.g., cognitive radio, LTE, etc.) to be able to meet this high demand. However, mobile user quality of experience (QoE) at the transport layer has largely been overlooked. As users become more mobile they are bound to encounter multiple wireless technologies and are thus equipped with multiple network interfaces. In addition, mobile users frequently experience handoffs when associating with wireless networks across a path. The contributions of this dissertation are threefold where our focus mainly encompasses timely delivery of internet content to mobile users through transport and physical layers and network infrastructure solutions. First, we investigate transport layer issues when mobile users encounter handoffs to and from fast and slow links. Specifically, cross-layer techniques are applied to the NewReno variant of the Transmission Control Protocol (TCP) to adapt to network conditions related to mobility. Our analysis shows that cross-layer modifications to TCP allows for less queuing delays, lower round-trip times, improved throughput and minimal packet jitter. Second, we investigate a promising transport protocol known as Multi-Path TCP (MPTCP) which allows for mobile devices to leverage a device's multiple network interfaces to maintain network connections even when endpoints of the connection change. This allows for connections to remain active during less than ideal scenarios when multiple Wi-Fi networks and cellular base stations are encountered across a mobile user's path. Default MPTCP congestion control protocols still experience service continuity issues when multiple networks are encountered across a path. A coupled, handoff-based cross-layer assisted, MPTCP congestion control algorithm and framework is proposed and designed to address these issues. Our system model monitors a device's received signal strength (RSS) in anticipation of a network handoff and congestion windows are proactively adjusted for a more seamless transition and experience for the end user. Lastly, the integration of the aforementioned wireless access technologies allows large geographic locations to be serviced providing millions of end users with continuous connectivity and optimal QoE. However, the world has seen unprecedented urban population growth over the years. By 2050, it is estimated that 70% of the world's population will be living in cities. Urban communication networks and content delivery networks have been introduced to leverage these technologies to better service cities and users alike. Content delivery networks are designed to improve overall network performance by bringing data closer to the geographical locations of users. However, traditional, regional content delivery nodes do not suffice for efficient and timely content delivery in large urban communication networks. We propose a fundamental shift to content-centric networks by consolidating these large urban communication networks with standalone edge cloud devices known as cloudlets and introducing geographically distributed content delivery cloudlets (CDC) which store popular Internet content. Advanced cooperative caching techniques are proposed, designed and employed at individual CDCs to push content closer to end users. Our proposed solutions are validated using, LinkNYC, a first-of-its-kind urban communications network aiming to replace all payphones in the five boroughs of New York City (NYC) with kiosk-like structures providing free super fast gigabit Wi-Fi to everyone. The amalgamation of urban population densities, multiple CDC placements and smarter caching techniques helps exploit the ultimate benefits of a content-centric urban communications network and dramatically improves overall network performance and responsiveness.
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  • 2017-11-06 to 2018-02-13

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