RETRANSMISSION PROTOCOL FOR THE MESSAGE SERVICE OF A LAND MOBILE SATELLITE EXPERIMENT.

Abstract

The authors describe and analyze a retransmission protocol for the data message communications of MSAT-X, a proposed experimental land mobile satellite communication network. An adaptive mobile-access protocol (AMAP) has been developed for MSAT-X under error-free assumptions. In AMAP, the ALOHA multiple-access scheme is used 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** minus **3. Therefore, error-control schemes must be developed to ensure reliable transmission of data message from mobiles to the base station. The authors 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 is also applicable to the integrated voice and data services of MSAT-X. Various operational scenarios are investigated.