Network lifetime equalization in interconnected 802.15.4 clusters

Abstract

We consider the problem of maintaining the prescribed event sensing reliability in a network formed by two 802.15.4 sensor clusters (child and parent). In order to maximize cluster lifetime, both clusters have redundant sensors which are periodically sent to sleep through distributed activity management. The clusters are connected through a bridge which also takes on the role of the coordinator in one of the clusters. In order to maximize the network lifetime, the lifetime of both clusters should be nearly the same, but the increased contention caused by the bridge reduces the lifetime of the parent cluster. We model this problem analytically and derive the probability distribution of the network lifetime. We also derive the expression for node count in the parent cluster that compensates for the interaction with the bridge. The use of this technique ensures that both clusters have nearly the same lifetime, with all the nodes dying within a short time period centered around the mean lifetime.