A location-based publish/subscribe framework for wireless sensors and mobile phones

Wireless sensor networks (WSNs) have been widely deployed for environmental monitoring and urban sensing applications. With the advancement of mobile phones, mobile users have increasing demands for sensing data relevant to their locations and activities. It is crucial to support reliable ubiquitous sensing for mobile users to retrieve sensing data of their interests anytime and anywhere. In this paper, we propose a novel location-based publish/subscribe framework for mobile users to subscribe for sensing data by simply specifying the event types and target locations of their interests. The framework is developed on a location-based Distributed Hash Table (DHT) overlay formed by a network of brokers. Event data can be subscribed by mobile users and then multicast to the subscribers through efficient location-based routing. To support client mobility, we further propose a reliable protocol to handle client registration, location look-up and client relocation. It can provide reliable data delivery without causing any data loss even when the users are disconnected or moved to a new place. Extensive simulation are conducted to evaluate the message delay, communication overheads, and the support of client mobility.