Measuring the Cost of Robotic Communication

Groups of robots are likely to accomplish certain tasks more quickly and robustly than single robots, [Jager and Nebel, 2001]. Many robotic domains such as robotic search and rescue, vacuuming, and waste cleanup are characterized by limited operating spaces where robots are likely to collide. In order to maintain group cohesion under such conditions, some type of information transfer is likely to be useful between members of the team. This is especially true as robotic domains are typically fraught with dynamics and uncertainty such as hardware failures, changing environmental conditions, and noisy sensors. Questions such as what to communicate and to whom have been the subject of recent study [Sen et al., 1994], [Jager and Nebel, 2001], [Tews, July 2001]. At times, forms of implicit coordination have been shown to allow agents better adaptability, robustness and scalability qualities [Sen et al., 1994]. In theory, the lack of communication allows such methods to be implemented on simpler robots. A second series of approaches attempt to improve group performance by having robots locally communicate information [Jager and Nebel, 2001]. A third type of approach involves the use of some type of central planner [Tews, July 2001]. We believe that each type of communication framework is best suited for different environmental conditions. A mechanism is needed to match the proper system to the given environment. This paper attempts to provide such a framework with its use of a coordination cost measure. We measure all coordination costs including the time and energy spent on coordination. We use this measure to evaluate the cost of communication. This result also allows us to create robots that alter their communication scheme when faced with dynamic domain conditions.