Message waiting time performance for meteor-burst communication systems

The author investigates the performance of the meteor burst channel in terms of the waiting time required to transmit reliably a message of length N bits. Two modulation techniques are considered. The first is the traditional fixed-rate modulation scheme where the modem operates at a constant bit rate whenever the channel is available for message traffic. The second is an adaptive modulation method where the channel symbol rate varies continuously to match the time-varying signal-to-noise ratio at the receiver. New closed-form expressions for waiting time and optimal bit rate are derived for the fixed-rate modem. Bounds on mean waiting time are derived for the adaptive-symbol-rate modem. It is shown that, for fixed-rate modems operating at the optimal bit rate and for adaptive modems operating at a minimum bit rate equal to this rate, the improvement in mean waiting time can never exceed 2