A hybrid medium access control protocol for wireless LANs

The author describes a medium access control protocol for efficient use of the radio channel in a cell. Channel time is structured as a sequence of frames of equal duration. The MAC protocol is a hybrid of centrally scheduled, contention-free data transfer (reservation-based) and decentralized, contention-based (slotted-ALOHA) protocols. The protocol relies on the use of broadcast messages from a central controller that demarcates contention-free intervals and the contention-based intervals in a frame. An adaptively movable boundary separates the contention-free and contention-based portions in each frame. This provides for flexibility of bandwidth allocation to meet a variety of asynchronous and isochronous services that are anticipated in future wireless LAN applications