Rover-to-Orbiter Communication in Mars: Taking Advantage of the Varying Topology

TL;DR

This paper models rover-to-orbiter communication as a time-varying X-channel, proposing coding strategies that improve capacity and throughput, achieving notable gains over traditional schemes in Mars communication scenarios.

Contribution

It introduces novel coding strategies for time-varying topologies in rover-to-orbiter channels, providing tight bounds and capacity approximations without CSIT.

Findings

Achieves near-capacity sum-rate with proposed coding schemes.

Demonstrates 9.6% DoF gain in Mars communication scenarios.

Provides over 11.6% throughput improvement over TDMA.

Abstract

In this paper, we study the communication problem from rovers on Mars' surface to Mars-orbiting satellites. We first justify that, to a good extent, the rover-to-orbiter communication problem can be modelled as communication over a $2 \times 2$ X-channel with the network topology varying over time. For such a fading X-channel where transmitters are only aware of the time-varying topology but not the time-varying channel state (i.e., no CSIT), we propose coding strategies that code across topologies, and develop upper bounds on the sum degrees-of-freedom (DoF) that is shown to be tight under certain pattern of the topology variation. Furthermore we demonstrate that the proposed scheme approximately achieves the ergodic sum-capacity of the network. Using the proposed coding scheme, we numerically evaluate the ergodic rate gain over a time-division-multiple-access (TDMA) scheme for Rayleigh and Rice fading channels. We also numerically demonstrate that with practical orbital parameters, a 9.6% DoF gain, as well as more than 11.6% throughput gain can be achieved for a rover-to-orbiter communication network.