An Adaptive Beacon Scheduling Mechanism Using Power Control in Cluster-Tree WPANs

摘要

This paper presents an adaptive beacon scheduling mechanism using power control in cluster-tree network. We consider the emerging low-rate wireless personal area networks (LR-WPANs) technology as specified in the IEEE 802.15.4 standard that can support environmental monitoring applications. Node clustering is a useful topology management approach to reduce channel contention and improve the network lifetime in wireless sensor networks. A cluster-tree network conforming to the IEEE 802.15.4 standard is formed by several coordinators that periodically send beacon frames to the nodes of their cluster. However, if these periodic beacon frames are sent without any particular scheduling, they will collide with each other and those nodes that wait for them will lose synchronization with their coordinators. The purpose of this paper is to overcome this problem by proposing an adaptive beacon scheduling mechanism using power control, cluster grouping, and the group identifier (GID) in cluster-tree WPANs. This mechanism is designed such that all of the sensing devices send the measured received power level back to their cluster heads (CHs), thus enabling them to adjust their transmission power level after the construction of the topology. Following this, the PAN coordinator divides all of the CHs into several cluster groups (CGs) in order to transmit their beacon frames simultaneously without encountering any direct or indirect beacon frame collision problems. The PAN coordinator selects the group heads (GHs) and assigns the GID for each cluster group. In addition, the PAN coordinator controls the beacon transmission time of all of the CHs and GHs in the CGs using the GID information located in the beacon frame of the PAN coordinator in order to avoid beacon frame collisions. Accordingly, the overall lifetime of the network in cluster-tree WPANs is prolonged by solving the problem of beacon frame collisions. We evaluated the performance of our scheme through a mathematical analysis and a series of simulations using the Network Simulator 2 (NS-2).