Rover-to-orbiter communication in Mars: Taking advantage of the varying topology

In this paper, we study the problem of communication from rovers on Mars' surface to Mars-orbiting satellites (orbiters). We first justify that, to a good extent, the problem can be modelled as communication over a 2×2 Gaussian Xchannel with varying topologies. We then study the capacity of such a channel under the assumption that no channel state information is provided to the transmitters (i.e., no CSIT) other than the network topology. By proposing a strategy that takes advantage of coding across topologies and developing novel upper bounds, we characterize the sum degree-of-freedom (DoF) and the ergodic sum capacity to within a constant gap for the 2×2 X-channel with varying topologies. In addition, we demonstrate the performance gain of the proposed scheme over the baseline time-division-multiple-access (TDMA) scheme currently in use.