[PAST EVENT] Yifan Zhang - Dissertation Defense - Computer Science

July 11, 2014
9:30am - 11:30am
McGlothlin-Street Hall, Room 002
251 Jamestown Rd
Williamsburg, VA 23185Map this location
Mobile applications are becoming an indispensable part of people's lives, as they allow access to a broad range of services when users are on the go. Improving efficiency of mobile applications is important to both users and mobile service providers. We present our efforts towards enabling efficient mobile applications in smartphones. Our goal is to improve efficiency of the underlying services, which provide essential functionality to mobile applications. In particular, we are interested in four major kinds of services in smartphones: network communication, power management, location reporting, and web content support.

For the network communication service, we focus on improving spectrum utilization efficiency for cognitive radio communications. We propose ETCH, a set of channel hopping based MAC layer protocols for communication rendezvous in cognitive radio communications. Compared to the existing solutions, ETCH fully utilizes spectrum diversity in communication rendezvous by allowing all the rendezvous channels to be utilized at the same time.

For the power management service, we are interested in saving energy in WiFi communications and providing an accurate CPU power modeling approach for multicore smartphones. For WiFi energy saving, we propose HoWiES, a system that saves WiFi energy in mobile devices by leveraging low-power ZigBee radio. For CPU power modeling for smartphones, we found that existing CPU power models are ill-suited for modern multicore smartphone CPUs. We present a new approach of CPU power modeling for smartphones. This approach takes CPU idle power states into consideration, and can significantly improve power estimation accuracy and stability for multicore smartphones.

For the location reporting service, we aim to design an efficient location proof solution for mobile location based applications. We propose VProof, a location proof scheme that allows users to construct location proofs by simply extracting certain contents from the packets received from the service provider. Our scheme is lightweight, since there is no communication required for a prover to obtain a location proof. Our scheme also well preserves users' privacy, as we do not put any information that can be related to a user's ID in a location proof.

For the web content service, we aim to provide a system-wide HTTP caching service for web content based mobile applications. We propose CacheKeeper, an OS web caching service that is transparent to mobile applications. CacheKeeper can not only effectively reduce overhead caused by poor web caching in mobile applications, but it also utilizes cross-app caching opportunities in smartphones. Furthermore, CacheKeeper is backward compatible, meaning that existing mobile applications can take advantage of CacheKeeper without any modifications.

Yifan Zhang was born in Liuzhou, a city in southern China known for its beautiful Karst scenery and the local industry. He studied Computer Science as his undergraduate major in Beihang University from 2000 to 2004. After graduation, he had worked at Huawei, a world-leading telecommunication company, as a software engineer for four years.

Yifan entered the Ph.D. program in the Computer Science Department at the College of William and Mary in Fall 2008, and was granted Ph.D. candidacy in Spring 2010. Since joining the program, he has worked with Dr. Qun Li in the fields of mobile computing and wireless communication. He is especially interested in the topics related to energy efficiency, performance, security and privacy in these fields.