AD LOC: Location-based Infrastructure-free Annotation

We introduce AD LOC, a system for mobile users to collaboratively tie persistent virtual notes to physical locations without the need for any servers embedded in the environment or accessed via the Internet. Instead, all notes are proactively cached solely on the mobile devices of passing participants and served up to others in the vicinity via ad hoc wireless protocols like WiFi. By making use of any of the increasingly ubiquitous positioning technologies, such as GPS, devices attempt to ensure notes remain cached at the physical locations they were published. Through simulation we demonstrate AD LOC’s behaviour under different scenarios and caching strategies. Our results show that despite the unpredictable and inconstant storage medium, surprisingly few participants are required for remarkably robust note persistence. Furthermore, the number of transmissions between devices needed to realise the caching strategies is relatively low and increases linearly with the number of participants.