Design of Hybrid Mobile Communication Networks for Planetary Exploration

The mobile exploration system project (MEX) at NASA Ames Research Center has been conducting studies into hybrid communication networks for future planetary missions. These networks consist of space-based communication assets connected to ground-based Internets and planetary surface-based mobile wireless networks. These hybrid mobile networks have been deployed in rugged field locations in the American desert and the Canadian arctic for support of science and simulation activities on at least six occasions. This work has been conducted over the past five years resulting in evolving architectural complexity, improved component characteristics and better analysis and test methods. A rich set of data and techniques have resulted from the development and field testing of the communication network during field expeditions such as the Haughton Mars project and NASA mobile agents project. This paper defines design, analysis and test methods for hybrid mobile communication networks, identifying the key issues and constraints that affect performance in both the radio frequency (RF) and network engineering disciplines. Previous work by the MEX team has addressed the architecture and detailed analysis of wireless networks including the results of field tests. We continue the analysis using a new 802.11b backbone utilizing two repeaters that significantly increase range and coverage but greatly increase latency, which reduces overall network throughput. The addition of a satellite link can result in significant additional throughput loss due to light-speed delays in the space segment interacting with variable latencies in the multi-hop wireless network. The paper analyzes and presents RF domain field test results combined with network performance metrics which describe a comprehensive approach for designing and optimizing future hybrid mobile networks.