Three Signaling Systems for Double Access to an Active Satellite

An active satellite is modeled as a repeater with a summer at its input and with a constant power output. The effectiveness of the following digital communication strategies for a constant bandwidth are compared in terms of Rcopmof the resulting channel: 1) "time pulsing," 2) "frequency division," and 3) "CW signaling,\´\´ where both transmitters simultaneously use the entire bandwidth while transmitting not necessarily synchronized or equal power signals, which are chosen from the same -ary alphabet and have identical duration. Rcompformulas are obtained, and parametric families of their curves are given. Among others, the following conclusions may be drawn: 1) For sufficiently high signal-to-noise ratios, CW signaling is best, the potential improvement increasing with increasing alphabet size. 2) Noncoincidence of time intervals of the two transmitters improves the performance of CW signaling.