Statistical observations of data transmission over land mobile satellite channels

It is shown how Rician fading limits the performance of the HDLC protocol. It is observed that for accurate reception, a packet must be transmitted entirely during an interfade interval. This means that packets ought to be sufficiently short so that most of them fall in the interfade time intervals. This leads to a high transmission efficiency. Consequently, the HDLC protocol is more efficient with shorter packets. However, a smaller packet size increases the overhead fraction of the packet and thereby reduces the effective throughput. In addition, the HDLC peak efficiency and optimum packet size increase with increasing fade margin and decrease with increasing vehicle velocity. Among other effects, the bit rate of the land-mobile satellite system channel is the most critical for optimum packet size and HDLC efficiency. Thus, a low bit rate implies long packet duration for a moderate packet size in bytes