Interference-free scheduling with bounded delay in cluster-tree wireless sensor networks

Abstract

Convergecast is a typical form of data collection in wireless sensor networks (WSNs), wherein nodes sample data from the environment and send them to a common destination. In order to prolong the network lifetime, a duty-cycle mechanism is usually coupled with a routing tree structure, in which nodes are organized in clusters. Each cluster aggregates data and sends them towards the root of the tree. However, clusters can interfere each other if their active time is not properly chosen. Furthermore, scheduling can lead to a long data delivery delay when a duty-cycle mechanism is used. In this article, we introduce a receiver-oriented scheduling algorithm for cluster-tree WSNs which provides a bounded latency for convergecast data collection. In contrast with most of the existing works in the literature, where two nodes are assumed to interfere if they are at most 2 hops away, we address the more general and realistic case where interfering nodes can be up to t hops away from each other, where te2. We first show that the minimum-latency convergecast problem is NP-hard for cluster-based WSNs with arbitrary topologies. We then focus on tree-based WSNs and derive bounds on the latency for convergecast data collection. We also propose a heuristic to obtain a t-interference-free scheduling in O(nt) time, where n is the number of clusters in the WSN. We finally validate our findings by simulation on both synthetic topologies and routing trees obtained from WSN deployments.