RDAG: A structure-free real-time data aggregation protocol for wireless sensor networks

Data aggregation is an effective technique which is introduced to save energy by reducing packet transmissions in WSNs. However, it extends the delay at the intermediate nodes, so it can complicate the handling of delay-constrained data in event-critical applications. Besides, the structure-based aggregation as the dominant data gathering approach in WSNs suffers from high maintenance overhead in dynamic scenarios for event-based applications. In this paper, to make aggregation more efficient, we design a novel structure-free Real-time Data Aggregation protocol, RDAG, using a Real-time Data-aware Routing policy and a Judiciously Waiting policy for spatial and temporal convergence of packets. Extensive simulations in NS-2 verify the superiority of RDAG in WSNs.