Enabling ad-hoc-style communication in public WLAN hot-spots

Opportunistic networking between mobile devices relies on the capabilities of those devices to establish ad-hoc communication among each other. While the two dominant wireless interface technologies, IEEE 802.11 wireless LAN and Bluetooth, offer such capabilities in theory, limitations of the protocol specification, chipsets, and operating systems in mobile devices render those features largely unusable in practice. Researchers have recognized these shortcomings and devised mechanisms in which mobile devices act as WLAN access points to simulate WLAN infrastructure-based operation. In this paper, we complement these approaches by instrumenting commercial WLAN APs that do not employ L2 security to serve as link layer packet relays without requiring the mobile nodes to authenticate with the WLAN hot-spot. We present different mechanisms for peer discovery, evaluate their feasibility for a set of commercial hot-spots, and discuss operational considerations for fair use of commercial access points.