Wi-Fi Goes to Town: Rapid Picocell Switching for Wireless Transit Networks

Every day, billions of commuters journey in and out of the world’s urban centers: many by train, light rail, or underground transport, others in vehicles that may soon become driverless in the coming decade. Today this commute is often wasted time, but we look forward to a nearby future with great demand for high-capacity wireless networks serving transportation corridors, allowing users to surf the web, complete video and audio calls or teleconferences, and stream video and music entertainment, all on the commute. This paper presents the design and implementation ofWi-Fi Goes to Town, the first Wi-Fi based roadside hotspot network designed to operate at vehicular speeds with meter-sized picocells. Wi-Fi Goes to Town APs make delivery decisions to the vehicular clients they serve at millisecond-level granularities, exploiting path diversity in roadside networks. In order to accomplish this, we introduce new buffer management algorithms that allow participating APs to manage each others’ queues, rapidly quenching each others’ transmissions and flushing each others’ queues. We furthermore integrate our fine-grained AP selection and queue management into 802.11’s frame aggregation and block acknowledgement functions, making the system effective at modern 802.11 bit rates that need frame aggregation to maintain high spectral efficiency. We have deployed eight Wi-Fi Goes to Town APs on the third floor of an office building overlooking a nearby road. APs communicate with the controller via Ethernet backhaul. Experiments compare Wi-Fi Goes to Town with a performance-tuned version of