A Retransmission Protocol for the Message Service of a Land Mobile Satellite Experiment

摘要

This paper describes and analyzes a retransmission protocol for the data message comunications of MSAT-X,a proposed experimental land mobile satellite communications network.An Adaptivc Mobile Access Protocol (AMAP) has been developed for MSAT-X under error-free assumptions.In AMAP,the ALOHA multiple access scheme is employed in the reservation channels,while the message channels are demand assigned.Preliminary propagation studies indicate that the bit error rate of satellite channels in a mobile environment can be as high as 10-3.Therefore,error-control schemes must be developed to ensure reliable transmissions of data messages from mobiles to the base station.In this paper we extend AMAP to include a retransmission scheme for single packet data messages.Since the number of channels available for reservation and data channels is fixed for a given voice call blocking probability and a fixed call arrival rate,the analysis presented in this paper is also applicable to the integrated voice and data services of MSAT-X.Various operational scenarios have been investigated.