A time division beacon scheduling mechanism for IEEE 802.15.4/Zigbee cluster-tree wireless sensor networks

摘要

While the IEEE 802.15.4/Zigbee protocol stack is beingconsidered as a promising technology for low-cost low-powerWireless Sensor Networks (WSNs), several issues in the standardspecifications are still open. One of those ambiguous issues is howto build a synchronized multi-hop cluster-tree network, which isquite suitable for ensuring QoS support in WSNs. In fact, thecurrent IEEE 802.15.4/Zigbee specifications restrict thesynchronization in the beacon-enabled mode (by the generation ofperiodic beacon frames) to star-based networks, while it supportsmulti-hop networking using the peer-to-peer mesh topology, butwith no synchronization. Even though both specifications mentionthe possible use of cluster-tree topologies, which combine multihopand synchronization features, the description on how toeffectively construct such a network topology is missing. Thispaper tackles this problem, unveils the ambiguities regarding theuse of the cluster-tree topology and proposes a synchronizationmechanism based on Time Division Beacon Scheduling toconstruct cluster-tree WSNs. We also propose a methodology foran efficient duty cycle management in each router (cluster-head) ofa cluster-tree WSN that ensures the fairest use of bandwidthresources. The feasibility of the proposal is clearly demonstratedthrough an experimental test bed based on our own implementationof the IEEE 802.15.4/Zigbee protocol.