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

Abstract

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 × 2 Xchannel 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-offreedom (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 sumcapacity of the network. Using the proposed coding scheme, we numerically evaluate the ergodic rate gain over a time-divisionmultiple-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.

Degrees of Freedom of the Bursty MIMO X Channel Without Feedback

“…Since (27) is symmetric to (26), in light of (4) We show {ℎ( 1 | 1 , 1 )} = ⟨ , − , ⟩ (a.s.) here, using the simple fact above. Other terms in Section VI and other places can be proved along similar lines.…”

“…Note also that [25] and [26] study the capacity (DoF) of the fading interference networks with time-varying topology, which can be viewed as fading and bursty channels. Clearly, our work is most closely related to [4], [8] and [26].…”

“…Clearly, our work is most closely related to [4], [8] and [26]. We introduce burstiness to the MIMO X channel and evaluate its impacts on the INBF schemes propounded in [4].…”

“…Our work differs from [8] in that we consider MIMO X channel with arbitrarily correlated symmetric burstiness. Lastly, compare to [26], which considers the fading SISO X channel with perfect burstiness knowledge at the transmitters but without CSIT, we investigate another extreme -the non-fading MIMO X channel without burstiness knowledge at the transmitters but with perfect CSIT.…”

Degrees of Freedom of the Bursty MIMO X Channel with Instantaneous Topological Information

“…This motivates a sequence of works to further explore the benefits of delayed CSIT, including [8]- [10] for the IC and XC. Moreover, for networks with time-varying topology, communication rate gains have been reported even with only topological information at the transmitters [11], [12]. The highlight of the achievability schemes in these works is coding over multiple channel uses or topologies.…”