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

• Published in: IEEE transactions on communications Vol. 64; no. 2; pp. 572 - 585
• Main Authors: Songze Li, Kao, David T. H., Avestimehr, A. Salman
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-02-2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Channels; Coding; coding across topologies; Communication; Communication satellites; Earth; Encoding; Ergodic processes; Fading; Gain; Mars; Network topology; Networks; Receivers; rover-to-orbiter communication; Topology; Transmitters; varying topologies; X-channel; X-channel; coding across topologies; Mars; varying topologies; rover-to-orbiter communication
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2015.2506157

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 modeled as communication over a 2 × 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.