Slot Length and Line-of-Sight Protection

The reasoning which led to the particular slot structure defined for the collision avoidance system specified by the Air Transportation Association Collision Avoidance System Technical Working Group is discussed. The objectives were to choose a slot length that would 1) minimize the probability of interference, 2) maximize the capacity of the information channel (as measured by the number of messages received in a unit of time). Interference can be manifested by the garbling of either the collision avoidance message or the synchronization signals.