TTDD: Two-tier data dissemination in large-scale wireless sensor networks

Sink mobility brings new challenges to data dissemination in large sensor networks. It suggests that information about each mobile sink's location be continuously propagated throughout the sensor field in order to keep all sensors informed of the direction of forwarding future data reports. Unfortunately, frequent location updates from multiple sinks can lead to both excessive drain of sensors' limited battery supply and increased collisions in wireless transmissions. In this paper, we describe TTDD, a Two-Tier Data Dissemination approach that provides scalable and efficient data delivery to multiple, mobile sinks. Each data source in TTDD proactively constructs a grid structure, which enables mobile sinks to continuously receive data on the move by flooding queries within a local cell only. TTDD's design exploits the fact that sensors are stationary and location-aware to construct and maintain the grid infrastructure with low overhead. We evaluate TTDD through both analysis and extensive simulations. Our results show that TTDD handles sink mobility effectively with performance comparable with that of stationary sinks.