Conservation of Communications Bandwidth for Traffic Control

This paper analyzes the quantity of information present in a group of aircraft moving at known average velocities within a definite geographical sector. Computations of time required between determination of the position of each aircraft is computed on the basis of the residuals of an infinite time series representation of aircraft position. The positionl information quantities and the time intervals required between samples are utilized to compute the time rate of flow of information, and this, in turn, used to compute the bandwidth of the physical data transmission equipment required to obtain this information at a central point. A dead reckoning device is added in each aircraft so that it may ascertain its position for longer sampling intervals. The velocity information utilized by the dead reckoning system is assumed to be transmitted to the ground where it is stored for tracking, which is a process of dead reckoning on the ground. The bandwidth of the system is then recomputed and it is shown that the use of relatively inexpensive dead reckoning equipment capable of measuring velocities to within 10 percent of the actual value is capable of further reducing the system bandwidth by a factor of 10. Curves are shown illustrating bandwidth requirements near 3 kc for 200 aircraft in a 256 mile radius without the use of inexpensive dead reckoning. By the use of dead reckoning either 200 aircraft may be handled at 300 cps or 2000 aircraft at 3 kc.