The task of designing algorithms for constantly changing networks is difficult. We focus on mobile ad-hoc networks, where mobile processors attempt to coordinate despite minimal infrastructure support. We develop new techniques to cope with this dynamic, heterogeneous, and chaotic environment. We mask the unpredictable behavior of mobile networks by defining and emulating a virtual infrastructure, consisting of timing-aware and location-aware machines at fixed locations, that mobile nodes can interact with. The static virtual infrastructure allows appplication developers to use simpler algorithms — including many previously developed for fixed networks. Virtual Stationary Automata programming layer. Our programming abstraction consists of a static infrastructure of fixed, timed virtual machines with an explicit notion of real time, called Virtual Stationary Automata (VSAs), distributed at known locations over the plane, and emulated by the real mobile nodes in the system. Each VSA represents a predetermined geographic area and has broadcast capabilities similar to those of the mobile nodes, allowing nearby VSAs and mobile nodes to communicate with one another. This programming layer provides mobile nodes with a virtual infrastructure with which to coordinate their actions. Many practical algorithms depend significantly on timing, and it is reasonable to assume that many mobile nodes have access to reasonably synchronized clocks. In the VSA programming layer, the virtual automata also have access to virtual clocks, guaranteed to not drift too far from real time. Our virtual infrastructure differs in key ways from others that have previously been proposed for mobile ad-hoc networks. The GeoQuorums algorithm [2] was the first to use virtual nodes; the virtual nodes in that work are atomic objects at fixed geographical locations. More general virtual mobile automata were suggested in [1]; our automata are more powerful than those in [1] in that ours include timing capabilities, which are important for many applications. Also, our automata are stationary, and are arranged in a connected pattern that is similar to a traditional wired ne-

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