Pharos: A Testbed for Mobile Cyber-Physical Systems TR-ARiSE-2011-001

As mobile cyber-physical systems (MCPS) begin to pervade our everyday environments, tools and techniques for robustly and reliably evaluating system solutions are an essential but as yet missing component for the development process. Our current methods and tools for validation and evaluation allow examination of components of the overall system in isolation; however our repertoire of tools lacks the ability to gain a complete system understanding of complex deployments with many unpredictable moving pieces. In this paper, we present the Pharos testbed, a networked system of autonomously mobile devices that can coordinate with each other and with networks of embedded sensors and actuators. Using Pharos, we identify and quantify many of the unique challenges associated with mobile cyber-physical systems. Through a series of experiments using the testbed, we demonstrate one of its most important aspects: push-button repeatability, or the ability to easily recreate the same experiment multiple times. Finally, we draw parallels between experiments in live mobile cyber-physical systems and simulation of them to demonstrate the complexities that are not fully captured in the latter and to posit mechanisms by which results of live experiments can be use to drive future mobile cyber-physical system simulations. These results, coupled with demonstrations of how the Pharos testbed can be used for a variety of experiments for mobile cyber-physical systems and how new experiments can be seamlessly executed on the testbed, demonstrate both the critical importance of real-world validation of mobile cyber-physical systems and the capabilities of Pharos in supporting such validation.