Link level ARQ for satellite-mobile communications over blockage channels with memory

We consider communication from a geosynchronous satellite to a mobile ground terminal that suffers from an intermittent channel due to blockages by objects in its environment. Since the blockage has memory and the duration is potentially long, a selective-repeat ARQ scheme is employed to mitigate packet losses. The paper studies the amount of memory required to store packets for retransmission and the amount of delay induced. The blockage channel with memory is modeled by a two-state Markov model. We also assume error-free acknowledgments with a certain delay and Bernoulli arrivals at the satellite of packets intended for a single mobile ground terminal. We derive closed-form expressions for the distributions and averages of both the queue length and the delay. Interpretations are given in terms of how they are affected by channel statistics and design parameters. Numerical examples are given to provide additional intuitions.