The last hop of global notification delivery to mobile users: accommodating volume limits and device constraints

Events injected by publishers into a publish/subscribe system may reach users through a variety of devices: a stationary desktop, a laptop, or a mobile phone. We argue that the "last hop" - from the network to the output device & has unique properties, owing to the mobile nature of these devices, and as such demands special consideration. In particular, the user\´s preferences and location may limit what should be forwarded to the device. Furthermore, technological constraints, such as network bandwidth availability and battery power, suggest that the decision when to forward messages is also important for maximizing the quality of service. We describe a new publish/subscribe system with volume-limiting mechanisms and explain how the user\´s preferences, context, and device constraints can be accommodated in such a system. Notably, based on results of simulations, we propose a simple algorithm for low-cost "prefetching" of notifications to mobile devices in cases when network bandwidth is insufficient.