and f.arrichiello@unicas.it Fig. 1. Setup for testing and benchmarking the NAMOS system. of anchored buoys (the static nodes), and a robotic boat (the mobile robot) capable of measuring temperature and chlorophyll concentrations. Thus, the testbed is a collection of static nodes as well as mobile/actuated nodes. A key research goal of the NAMOS project is determining how to coordinate the mobile robots and the static nodes such that the error associated with the estimation of a scalar field is

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... inimized subject to the constraint that the energy available to the mobile robot is bounded. Specifically, if each static node makes a measurement, and the total energy available to the network is known, what path should the mobile robot take to minimize the integrated mean square error (MSE) associated with the reconstruction of the entire field? Typically, it had been assumed that the energy consumed by communication and sensing was negligible compared to the energy consumed by moving the mobile robot [6]. Another common assumption was that the mobile robot could communicate essentially errorfree with all the static nodes and acquire sensor readings from them. In the currently implemented NAMOS system, communication is over a multi-hop wireless ad-hoc network described in [4] . This network employs 802.11 and thus communicates over-the-air. With the inclusion of underwater acoustic communication, we will have a proxy for a truly underwater mobile robot such as a glider or small submarine. In this new context, the cost of communications and the variability of the communication channel cannot be ignored. Thus, in addition to examining mobile node location as a function of estimation accuracy, we shall also consider the rDoCkI L9 Floating dock water USC/NAMOS Boat Acoustic 1I"ansducer GPS Receiver U. Mitra and S.