MASCARA, a MAC Protocol for Wireless ATM

The Medium Access Control (MAC) protocol of a Wireless ATM (WATM) system is a critical component as it lies between the traditional ATM layer and the RF-based physical layer whose characteristics are far from those of fibberor copper-based conventional ATM media. The constraints imposed on the MAC protocol of a WATM system lead to consider the design of a Half Duplex (HDX), point-to-multipoint, error prone communication channel while regular ATM Quality of Service (QoS) must be enforced. To take into account the former constraints, a novel MAC protocol has been designed by the Magic WAND project. It is a TDMA-based access scheme which combines both reservation and contention methods. This paper gives an overview of this protocol by describing its time frame structure and mode of operation, by introducing how ATM traffic is scheduled and by presenting the Data Link Control (DLC) and MAC Control means used to guarantee efficient and proper operations.