Mini-Slotted Alternating Priorities (MSAP) is a collision-free multiple access method with reservation technique
.MSAP can be considered as a polling operation with carrier sensing and distributed control. The time axis is divided into smallest time slots, minislots, whose size is equal to or smaller than the propagation delay
. In MSAP, connected stations are synchronized and start their transmission at the beginning of the minislot. Thereis alternating priority control
between stations, which provides equality for all stations. The protocol scheme of MSAP provides a reservation preamble that is considered by all stations. There are several MSAP variants of the collision-free access scheme. An improved variant is Basic Bit-Map (BBM).