Improved access point selection

Abstract

This paper presents Virgil, an automatic access point discov- ery and selection system. Unlike existing systems that se- lect access points based entirely on received signal strength, Virgil scans for all available APs at a location, quickly as- sociates to each, and runs a battery of tests to estimate the quality of each AP's connection to the Internet. Virgil also probes for blocked or redirected ports, to guide AP selection in favor of preserving application services that are currently in use. Results of our evaluation across five neighborhoods in three cities show Virgil finds a usable connection from 22% to 100% more often than selecting based on signal strength alone. By caching AP test results, Virgil both improves per- formance and success rate. Our overhead is acceptable and is shown to be faster than manually selecting an AP with Windows XP.