Q-NIGHT: adding QoS to data centric storage in non-uniform sensor networks

Storage of sensed data in wireless sensor networks is essential when the sink node is unavailable due to fail- ure and/or disconnections, but it can also provide efficient access to sensed data to multiple sink nodes. Recent ap- proaches to data storage rely on Geographic Hash Tables for efficient data storage and retrieval. These approaches however do not support different QoS levels for different classes of data as the programmer has no control on the level of redundancy of data. They result in a great unbal- ance in the storage usage in each sensor, even when sen- sors are uniformly distributed. This may cause serious data losses, waste energy and shorten the overall lifetime of the sensornet. In this paper, we propose a novel protocol, Q- NiGHT, which (1) provides a direct control on the level of QoS in the data dependability, and (2) uses a strategy sim- ilar to the rejection method to build a hash function which scatters data approximately with the same distribution of sensors. The benefits of Q-NiGHT are assessed through a detailed simulation experiment, also discussed in the paper. Results show its good performance on different sensors dis- tributions on terms of both protocol costs and load balance between sensors.