FreeBee: Cross-technology Communication via Free Side-channel
This paper presents FreeBee, which enables direct unicast as well as cross-technology/channel broadcast among three popular wireless technologies: WiFi, ZigBee, and Bluetooth. Our design aims to shed the light on the opportunities that cross-technology communication has to offer including, but not limited to, cross-technology interference mitigation and context-aware smart operation. The key concept of FreeBee is to modulate symbol messages by shifting the timing of periodic beacon frames already mandatory for wireless stan-dards without incurring extra traffic. Such a generic cross-technology design consumes zero additional bandwidth, al-lowing continuous broadcast to safely reach mobile and/or duty-cycled devices. A new interval multiplexing technique is proposed to enable concurrent broadcasts from multiple senders or boost the transmission rate of a single sender. Theoretical and experimental exploration reveals that Free-Bee offers a reliable symbol delivery under a second and supports mobility of 30mph and low duty-cycle operations of under 5%.