Papers by Andreas Savvides
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Mobile Networks and Applications, 2003
The recent advances in MEMS, embedded systems and wireless communication technologies are making ... more The recent advances in MEMS, embedded systems and wireless communication technologies are making the realization and deployment of networked wireless microsensors a tangible task. In this paper we study node localization, a component technology that would enhance the effectiveness and capabilities of this new class of networks. The n-hop multilateration primitive presented here, enables ad-hoc deployed sensor nodes to accurately estimate their locations by using known beacon locations that are several hops away and distance measurements to neighboring nodes. To prevent error accumulation in the network, node locations are computed by setting up and solving a global non-linear optimization problem. The solution is presented in two computation models, centralized and a fully distributed approximation of the centralized model. Our simulation results show that using the fully distributed model, resource constrained sensor nodes can collectively solve a large non-linear optimization problem that none of the nodes can solve individually. This approach results in significant savings in computation and communication, that allows fine-grained localization to run on a low cost sensor node we have developed.
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IEEE Transactions on Mobile Computing, 2005
Ad hoc localization of wireless sensor nodes is a fundamental problem in wireless sensor network... more Ad hoc localization of wireless sensor nodes is a fundamental problem in wireless sensor networks. Despite the recent proposals for the development of ad hoc localization algorithms, the fundamental behavior in systems using measurements has not been characterized. In this ...
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The wide availability of radio signal strength attenuation information on wireless radios has rec... more The wide availability of radio signal strength attenuation information on wireless radios has received considerable attention as a convenient means of deriving positioning information. Although some schemes have been shown to work in some scenarios, many agree that the robustness of such schemes can be easily compromised when low power IEEE 802.15.4 radios are used. Leveraging a recently installed sensor network testbed, we provide a detailed characterization of signal strength properties and link asymmetries for the CC2420 IEEE 802.15.4 compliant radio using a monopole antenna. To quantify the several factors of signal unpredictability due to the hardware, we have collected several thousands of measurements to study the antenna orientation and calibration effects. Our results show that the often overlooked antenna orientation effects are the dominant factor of the signal strength sensitivity, especially in the case of 3-D network deployments. This suggests that the antenna effects need to be carefully considered in signal strength schemes.
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IEEE Transactions on Mobile Computing, 2003
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We describe the system design of "Smart Kindergarten", a smart problem solving environment for ea... more We describe the system design of "Smart Kindergarten", a smart problem solving environment for early childhood education. Two crucial building blocks that make up smart kindergarten are iBadge, a lightweight power-aware sensor-instrumented badge, and Sylph, a sensor middleware infrastructure. Equipped with sensors, radio, and DSP, iBadge has been designed to be worn by kids and teachers to unobtrusively capture the interaction between the kids and their surroundings. The captured data is then wirelessly transmitted to Sylph, a middleware infrastructure, which provides means of accessing the data in coherent and user-friendly manner. In this paper, we present the design challenges of iBadge and Sylph and our efforts in integrating these two systems.
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Park, Savvides, and Srivastava Figure 3: Sensor Network Model Architecture transmit modes corresp... more Park, Savvides, and Srivastava Figure 3: Sensor Network Model Architecture transmit modes corresponding to different symbol rates, modulation schemes, and transmit power. Similarly, the CPU may be in sleep mode, or one of several different ac-tive modes corresponding ...
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Sigmetrics Performance Evaluation Review, 2001
focus of conventional wireless networks, these wireless sensor networks pose significantly differ... more focus of conventional wireless networks, these wireless sensor networks pose significantly different design, implementation, and deployment challenges. Their application-specific nature, severe resource limitations, long network life requirements, and the presence of sensors lead to interesting interplay between sensing, communications, power consumption, and topology that designers need to consider. Existing tools for modeling wireless networks focus only on the communications problem,
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Ad-hoc localization in multihop setups is a vital component of numerous sensor network applicatio... more Ad-hoc localization in multihop setups is a vital component of numerous sensor network applications. Although considerable effort has been invested in the development of multihop localization protocols, to the best of our knowledge the sensitivity of localization to its different setup parameters (network density, ranging system measurement error and beacon density) that are usually known prior to deployment has not been systematically studied. In an effort to reveal the trends and to gain better understanding of the error behavior in various deployment patterns, in this paper we study the Cramer Rao Bound behavior in carefully controlled scenarios. This analysis has a dual purpose. First, to provide valuable design time suggestions by revealing the error trends associated with deployment and second to provide a benchmark for the performance evaluation of existing localization algorithms.
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... Sensors Andreas Savvides, Chih-Chieh Han and Mani B. Strivastava Networked and Embedded Syste... more ... Sensors Andreas Savvides, Chih-Chieh Han and Mani B. Strivastava Networked and Embedded Systems Lab Department of Electrical Engineering University of Calfornia, Los Angeles {asavvide, simonhan, mbs}@ee.ucla.edu ...
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Mobile Networks and Applications, 2003
The recent advances in MEMS, embedded systems and wireless communication technologies are making ... more The recent advances in MEMS, embedded systems and wireless communication technologies are making the realization and deployment of networked wireless microsensors a tangible task. In this paper we study node localization, a component technology that would enhance the effectiveness and capabilities of this new class of networks. The n-hop multilateration primitive presented here, enables ad-hoc deployed sensor nodes to accurately estimate their locations by using known beacon locations that are several hops away and distance measurements to neighboring nodes. To prevent error accumulation in the network, node locations are computed by setting up and solving a global non-linear optimization problem. The solution is presented in two computation models, centralized and a fully distributed approximation of the centralized model. Our simulation results show that using the fully distributed model, resource constrained sensor nodes can collectively solve a large non-linear optimization problem that none of the nodes can solve individually. This approach results in significant savings in computation and communication, that allows fine-grained localization to run on a low cost sensor node we have developed.
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IEEE Transactions on Mobile Computing, 2005
Ad hoc localization of wireless sensor nodes is a fundamental problem in wireless sensor network... more Ad hoc localization of wireless sensor nodes is a fundamental problem in wireless sensor networks. Despite the recent proposals for the development of ad hoc localization algorithms, the fundamental behavior in systems using measurements has not been characterized. In this ...
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Papers by Andreas Savvides