Eliminating the high stand-by energy consumption of ad-hoc Wi-Fi

Ad-hoc Wi-Fi is well known in disaster communications systems, because of its ability to form infrastructure-free peer-to-peer networks. However, ad-hoc Wi-Fi has a major disadvantage due to the lack of coordinating infrastructure: Its energy consumption is very high, reducing battery life to as little as 1.5 hours. Thus, while it would be highly desirable for mobile phones to use ad-hoc Wi-Fi communications in disasters and remote areas, this is not practical in most instances. In this paper, we draw on innovations in passive radio sensing, and combine these with a simple Contiki-inspired protocol that can be used with existing Wi-Fi hardware to allow use of ad-hoc Wi-Fi with zero energy consumption when idle, and yet allow communications to be established in milliseconds. Feasibility is demonstrated through proof-of-concept hardware, demonstrating that it is possible to provide devices with ad-hoc Wi-Fi communications capabilities with zero impact on stand-by energy consumption. This simple innovation reactivates the possibility of true peer-to-peer high-bandwidth, low-latency direct phone-to-phone communications, without any supporting equipment, such as a Serval Mesh Extender, increasing the opportunities for resilient and decentralized mobile communications during a disaster.