In the last years, wireless sensor networks (WSNs) are acquiring more importance as a promising technology based on tiny devices called sensor nodes or motes able to monitor a wide range of physical phenomenon through sensors. Numerous branches of science are being benefited. The intrinsic ubiquity of sensor nodes and the absence of network infrastructure make possible their deployment in hostile or, up to now, unknown environments which have been typically unaccessible for humans such as volcanos or glaciers, providing precise and up-to-date data. As potential applications continue arising, both new technical and conceptual challenges appear. The severe hardware restrictions of sensor nodes in relation to computation, communication and specifically, energy, have posed new and exciting requirements. In particular, research is moving towards heterogeneous networks that will contain different devices running custom WSN operating systems. Operating systems specifically designed for sensor nodes are intended to efficiently manage the hardware resources and facilitate the programming. Nevertheless, they often lack the generality and the high-level abstractions expected at this abstraction layer. Consequently, they do not completely hide either the underlying platform or its execution model, making the applications programming close to operating system and thus reducing the portability. This thesis focuses on the portability of applications in heterogeneous wireless sensor networks. To contribute to this important challenge the thesis proposes a generic software architecture based on sensor node, which supports the process of applications development by homogenizing and facilitating the access to different WSN operating systems. Specifically, the next main objectives have been established. * Designing and implementing a generic sensor node-centric architecture distinguishing clearly the different abstraction levels in a sensor node. The architecture should be flexible enough in order to incorporate high-level abstractions which facilitate the the programming. * As part of the architecture, constructing an intermediate layer between applications and sensor node operating system. This layer is intended to abstract away the operating system by demultiplexing a set of homogeneous services and mapping them into operating system-specific requests. To achieve this, programming language extensions have to be also specified on top of the architecture, in order to write portable applications. In this way, platform-specific code can be generated from these high-level applications for di erent sensor node platforms. In this way, architecture deals with the problem of heterogeneity and portability. * Evaluating the feasibility of incorporating the abstractions above mentioned within the development process in terms of portability, efficiency and productivity. In this environment the footprint is a specially critical issue, due to the hardware limitations. In fact, an excessive overhead of applications size could make prohibitive the proposed solution. The thesis presents a generic software architecture for portable applications in heterogeneous wireless sensor networks. The proposed solution and its evaluation is described in this document. Theoretical and practical contributions of this thesis and the main future research directions are also presented.-------------------------------------------------------------------------------------------------------------------------
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