Cluster communication synchronization in delay-sensitive wireless sensor networks

Clustering has been widely used in wireless sensor networks to increase scalability, improve energy efficiency and provide QoS guarantees. In such networks, frequent interactions between the intra-cluster communication and the inter-cluster communication are inevitable, which may severely downgrade the communication efficiency and hence the network performance if not handled properly. This is especially problematic in delay-sensitive data gathering applications. Thus, proper synchronization among these two types of communications is required. In this paper, we propose two approaches to schedule the communications in clustered wireless sensor networks aiming at delay-sensitive applications. In the first approach, an efficient cycle-based synchronous scheduling is proposed to achieve low average packet delay and high throughput by optimizing the cycle length and transmission order. In the second approach, a novel clustering structure is introduced to eliminate the necessity of communication synchronization so that packets are transmitted with no synchronization delay, yielding very low end-to-end packet delay. Our extensive experimental results demonstrate the superior performance of both approaches. The distinct behavior of two scheduling approaches enables them to support a wide range of data gathering applications with different performance requirements in clustered wireless sensor networks.