Performance of point-to-multipoint communication systems over nonstationary satellite-terrestrial links

The authors have been proposing a satellite point-to-multipoint communicati on hybrid ARQ protocol in a system in which the forward path is the satelli te link and the feedback path is the terrestrial computer network. This pap er evaluates the performance of the protocol by a simulation, for the case where the error rates of the receiving stations are not the same or the rou nd-trip delay times are not the same, as well as for the case where the ACK packet may be lost in the feedback path. When the packet is lost and the r eception ACK packet for a frame is not returned for a certain period, that frame must be retransmitted (timeout). This paper examines values adequate for the time-out based on the round-trip delay time. Lastly, the case where the state of the forward path is nonstationary is assumed, and a method is considered where the bit error rate is successively estimated in the recei ving station. It is shown that by introducing the adaptive multicopying fun ction for the protocol based on the estimated error rate, the average trans mission delay can be improved. (C) 2000 Scripta Technica.