Abstract-We propose a novel framework for location detection with sensor networks, based on the theory of identifying codes. The key idea of this approach is to allow sensor coverage areas to overlap so that each resolvable position is covered by a unique set of sensors. In this setting, determining a sensor-placement with a minimum number of sensors is equivalent to constructing an optimal identifying code, an NPcomplete problem in general. We thus propose and analyze new polynomial-time algorithms for generating irreducible (but not necessarily optimal) codes for arbitrary topologies. Our algorithms incorporate robustness properties that are critically needed in harsh environments. We further introduce distributed versions of these algorithms, allowing sensors to self-organize and determine a (robust) identifying code without any central coordination. Through analysis and simulation, we show that our algorithms produce nearly optimal solutions for a wide range of parameters. In addition, we demonstrate a tradeoff between system robustness and the number of active sensors (which is related to the expected lifetime of the system). Finally, we present experimental results, obtained on a small testbed, that demonstrate the feasibility of our approach.

Abstract-We propose a new framework for providing robust location detection in emergency response systems, based on the theory of identifying codes. The key idea of this approach is to allow sensor coverage areas to overlap in such a way that each resolvable position is covered by a unique set of sensors. In this setting, determining a sensor-placement with a minimum number of sensors is equivalent to constructing an optimal identifying code, an NP-complete problem in general. We thus propose and analyze a new polynomial-time algorithm for generating irreducible codes for arbitrary topologies. We also generalize the concept of identifying codes to incorporate robustness properties that are critically needed in emergency networks and provide a polynomial-time algorithm to compute irreducible robust identifying codes. Through analysis and simulation, we show that our approach typically requires significantly fewer sensors than existing proximity-based schemes. Alternatively, for a fixed number of sensors, our scheme can provide robustness in the face of sensor failures or physical damage to the system.

Abstract. We present the design, implementation and evaluation of a location detection system built over a Radio Frequency network based on the IEEE 802.11 standard. Our system employs beacons to broadcast identifying packets from strategic positions within a building infrastructure in such a way that each resolvable position is covered by a unique collection of beacons; a user of such a system can thus determine his location by means of the beacon packets received. The locations from which beacons broadcast is determined from a formalization of the problem based on identifying codes over arbitrary graphs. We present experimental evidence that our location detecting system is practical and useful, and that it can achieve good accuracy even with a very small number of beacons.

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