Deployment of Asynchronous Robotic Sensors in Unknown Orthogonal Environments

We consider the problem of uniformly dispersing mobile robotic sensors in a simply connected orthogonal space of unknown shape. The mobile sensors are injected into the space from one or more entry points and rely only on sensed local information within a restricted radius. Unlike the existing solution, we allow the sensors to be asynchronous and show how, even in this case, the sensors can uniformly fill the unknown space, avoiding any collisions and without using any explicit communication, endowed with only O(1) bits of persistent memory and O(1) visibility radius. Our protocols are memoryand radiusoptimal; in fact, we show that filling is impossible without persistent memory (even if visibility is unlimited); and that it is impossible with less visibility than that used by our algorithms (even if memory is unbounded).