Study of Beaconing in Multihop Wireless PAN with Distributed Control

摘要

Distributed Media Access Control (MAC) architecture has many merits to make it a favorable candidate for high data rate Wireless Personal Area Networks (WPANs) with PHY layer based on UWB technology. This paper focuses on the WiMedia MAC which is the first distributed MAC for WPANs, approved as a standard. In such a MAC, all devices transmit their beacons to provide timing reference and to broadcast control and reservation information, that is, to maintain device synchronization. We investigate problems related to beacon collisions which occur when multiple devices join a piconet almost at the same time. To join a piconet or to resolve a collision, a device chooses a slot for its beacon randomly within some window. We show that improper slot choice scheme leads to repeated collisions, increasing the time overhead to achieve device synchronization. It also leads devices into trouble in joining and collision resolution and even into deadlocks, when devices have no chance to escape repeated collisions. We develop an analytical model to evaluate performance of various slot choice schemes for multi-hop WPANs. The model is employed to compare efficiency of these choice schemes and to optimize their parameters to achieve the best performance.