Research Projects

An Object Positioning System using Smartphones

Can a distant object be localized by looking at it through a smartphone? Consider and example use case, while driving on a highway entering New York, we want to look at one of the skyscrapers through the smartphone camera, and compute its GPS location. With the growing number of sensors on smartphones, combined with advances in computer vision, we harness new opportunities through a system called Object Positioning System (OPS) that achieves reasonable in localizing objects that we can see in the distance.

Paper to appear in ACM MobiSys 2012.

Monitoring the Health of Home Wireless Networks

Deploying home access points (AP) is hard. Untrained users typically purchase, install, and configure a home AP with very little awareness of wireless signal coverage and complex interference conditions. We envision a future of autonomous wireless network management that uses the Internet as an enabling technology. By leveraging a P2P architecture over wired Internet connections, nearby APs can coordinate to manage their shared wireless spectrum, especially in the face of network-crippling faults. As a specific instance of this architecture, we build RxIP, a network diagnostic and recovery tool, initially targeted towards hidden terminal mitigation.

Paper to appear in IEEE INFOCOM 2012

Network Support for Energy Management on WiFi Smartphones

WiFi continues to be a prime source of energy consumption in mobile devices. WiFi network congestion (contention) among different network access points (APs) can dramatically increase a client's energy consumption. We design a system that achieves energy efficiency by evading inter-AP network contention. Our prototype provides immediate, no-change compatibility with all WiFi devices, yielding up to 2x battery life improvement under real-world traffic loads for the latest Android-based smartphones.

Paper in ACM MobiSys 2011

Interactive Multiplayer Mobile Gaming over Cellular 3G

Supporting interactive multiplayer games on mobile phones over cellular networks is difficult. It will soon become essential, following the explosion of mostly single-player or turn-based games. Highly variable cellular link performance yields frequent failed games or unacceptably-slow network connections among players. We have built a scalable service for matchmaking in mobile games -- assigning players to games so that end-to-end latency requirements are met -- by learning the properties of each cellular link.

Paper in ACM MobiSys 2011

Strong Location Privacy for Mobile Social Services

Conventional mobile social services rely on two classes of trusted relationships: participants trust a centralized server to manage their location information and trust between users is based on existing social relationships. These assumptions are not secure or general enough, especially given demonstrated and repeated failure of service providers to protect privacy-sensitive location data. We design a “missed-connections” mobile service which does not rely upon the central server to preserve data confidentiality.

Paper in ACM CCS 2009, Slides (PPT), Slides (PDF)

Transmission Reordering in Wireless Networks

Modern wireless interfaces support a physical layer capability called Message in Message (MIM). Briefly, MIM allows a receiver to disengage from an ongoing reception, and engage onto a stronger incoming signal. Links that otherwise conflict (strongly interfere) with each other can be made concurrent with MIM, by initiating transmissions in a specific order. We design, build, and test an enhanced network system to exploit the opportunity in MIM-aware reordering, yielding dramatic throughput improvements.

Paper in ACM MobiCom 2009, Slides (Flash), Slides (PDF)