A distributed access control method for wireless LANs in shadowing environments

In recent years, the trend to use wireless LANs to realize mobile or ad hoc network is expanding. Previous proposals for access control methods for wireless LANs included such methods as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and polling. However, both methods have problems of transfer efficiency and delay time. Research and development on new access control methods is required to implement high-performance wireless LANs. In this paper, we examine the development of a wireless version of the wired token passing LAN access control method as a new wireless LAN access control method and propose Dynamic Token Passing (DTP) as a wireless token passing LAN access control method that incorporates a token circulation method and a data relay scheme based on a reserved logical ring. The results show that compared to existing methods, such as the IEEE 802.11 protocol, the proposed method exhibits better performance in an environment suffering from transmission path failures caused by blocking objects. A discussion of the optimum configuration for the reserved logical rings shows that if A reserved logical rings are prepared and the optimum reserved logical ring is selected, then a network can continue operation under the condition of A-1 failures.