火星上的漫游者与轨道器通信：利用变化的拓扑结构
Rover-to-Orbiter Communication in Mars: Taking Advantage of the Varying Topology
摘要：
本文研究了火星表面漫游车与火星轨道卫星之间的通信问题。我们首先证明，在一个很好的程度上，漫游者到轨道器的通信问题，可以建模为一个$2 \times 2$ X通道的网络拓扑结构随时间变化的通信。对于发射机仅知道时变拓扑而不知道时变信道状态（即，无CSIT），我们提出了跨拓扑结构编码的编码策略，并开发了在拓扑结构变化的某些模式下被证明是紧的和自由度（DoF）的上界。此外，我们证明了所提出的计划近似实现遍历和网络的容量。使用建议的编码方案，我们数值评估遍历速率增益超过一个时分多址（TDMA）方案的瑞利和莱斯衰落信道。我们还数值证明，与实际的轨道参数，9.6%的自由度增益，以及超过11.6%的吞吐量增益可以实现的漫游者到轨道器的通信网络。
英文摘要：
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.
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