The Study of Superframe Duration Scheduling with Coordinator Grouping for Zigbee Cluster-Tree WSNs

Aimed at a synchronized multi-hop cluster-tree network, which is quite suitable for QoS support in WSNs, this paper unveils the ambiguities regarding the use of the cluster-tree topology and proposes scheduling mechanisms approach based on super frame duration scheduling with coordinator grouping. In this approach, time is divided such that beacon frames and the super frame duration of a given coordinator are sent during the inactive period of its neighbor coordinators. The idea is that each coordinator selects the starting time Beacon_Tx_Offset to transmit its beacon frame. The starting time must be different from the starting times of its neighbor coordinators and their parents. This approach requires that a coordinator wakes up both in its active period and in its parent´s active period. The feasibility of the proposal is clearly demonstrated through an experimental test bed based on our own implementation of the IEEE 802.15.4/Zigbee protocols.