Collision-free beacon scheduling mechanisms for IEEE 802.15.4/Zigbee cluster-tree wireless sensor networks

摘要

The recently standardized IEEE 802.15.4/Zigbeeprotocol stack offers great potentials for ubiquitous and pervasivecomputing, namely for Wireless Sensor Networks (WSNs).However, there are still some open and ambiguous issues that turnits practical use a challenging task. One of those issues is how tobuild a synchronized multi-hop cluster-tree network, which isquite suitable for QoS support in WSNs. In fact, the current IEEE802.15.4/Zigbee specifications restrict the synchronization in thebeacon-enabled mode (by the generation of periodic beaconframes) to star-based networks, while it supports multi-hopnetworking using the peer-to-peer mesh topology, but with nosynchronization. Even though both specifications mention thepossible use of cluster-tree topologies, which combine multi-hopand synchronization features, the description on how to effectivelyconstruct such a network topology is missing. This paper tacklesthis problem, unveils the ambiguities regarding the use of thecluster-tree topology and proposes two collision-free beaconframe scheduling schemes. We strongly believe that the resultsprovided in this paper trigger a significant step towards thepractical and efficient use of IEEE 802.15.4/Zigbee cluster-treenetworks.