Sergio Servetto Cornell University
the most pressing need after a major urban disaster---earthquakes, fires, (accidental or induced) infrastructure collapse---is for information needed to deal with the situation. Such information includes, for example, the presence of toxic chemicals, the location and condition of survivors trapped by debris, or stress forces acting on an unstable damaged structure that may lead to further collapse. A similar need takes place when the goal is to prevent such disasters: in this case information needed includes, for example, time evolution of the concentration per unit-area of pollutant/toxic agents, of the temperatures in a forest, or of damage to the ozone layer.
In all the examples in which we envision the use of sensors to measure and then act upon the state of some physical process, there are two well defined stages. In an initial stage there is a distributed signal acquisition problem, in which each sensor gets to observe a spatially localized function of the process. Each one of these sensors will have autonomous computation, communication, and power generation capabilities. In a second stage, after processing the raw sensor measurements, some representation of all the data collected needs to be relayed to a collection point, where this data is to be analyzed and acted upon. (These actions could consist of, for example, direct rescue efforts to appropriate places, evacuate unstable structures, direct fire fighters to appropriate forest locations at the onset of a fire, etc.) These collection points can take the form of fixed and mobile receivers placed outside of the sensor coverage (and thus out of the way of potential harm). Collection points may be permanently dedicated facilities, as with monitoring points for the critical infrastructure. They may also be mobile, as with aircraft overflying the site of a disaster. This research program focuses on the engineering and, primarily, on the information-theoretic issues of the *sensor reachback* problem, i.e., the problem of establishing reliable communication between the sensor array and the collection point.
