Technological progress in integrated, low-power, CMOS communication devices and sensors makes a rich design space of networked sensors viable. They can be deeply embedded in the physical world or spread throughout our environment. The missing elements are an overall system architecture and a methodology for systematic advance. To this end, we identify key requirements, develop a small device that is representative of the class, design a tiny event-driven operating system, and show that it provides support for efficient modularity and concurrency-intensive operation. Our operating system fits in 178 bytes of memory, propagates events in the time it takes to copy 1.25 bytes of memory, context switches in the time it takes to copy 6 bytes of memory and supports two level scheduling. The analysis lays a groundwork for future architectural advances.

Wireless networks of miniaturized, low-power sensor/actuator devices are poised to become widely used in commercial and military environments. The communication security problems for these networks are exacerbated by the limited power and energy of the sensor devices. In this paper, we describe the design and implementation of public-key-(PK)-based protocols that allow authentication and key agreement between a sensor network and a third party as well as between two sensor networks. Our work is novel in that PK technology was commonly believed to be too inefficient for use on low-power devices. As part of our solution, we exploit the efficiency of public operations in the RSA cryptosystem and design protocols that place the computationally expensive operations on the parties external to the sensor network, when possible. Our protocols have been implemented on UC Berkeley MICA2 motes using the TinyOS development environment.

Wireless sensor networks have the potential to become the pervasive sensing (and actuating) technology of the future. For many applications, a large number of inexpensive sensors is preferable to a few expensive ones. The large number of sensors in a sensor network and most application scenarios preclude hand placement of the sensors. Determining the physical location of the sensors after they have been deployed is known as the problem of localization. In this paper, we present a localization technique based on a single mobile beacon aware of its position (e.g. by being equipped with a GPS receiver). Sensor nodes

Emerging low power, embedded, wireless sensor devices are targeting a wide range of applications, yet have very limited processing, storage, and energy resources. An architecture must be developed that can efficiently meet system demands while simultaneously remaining flexible to application specific optimizations. Analysis of past designs identifies core architectural issues and their impact on system performance. This paper outlines these issues and presents a generalized architecture designed to provide efficient communication mechanisms while allowing for system-level optimizations. The importance of providing a tight coupling between application and communication processing is shown and the tradeoffs associated with virtual versus physical parallelism are investigated. We conclude that a shared controller closely integrated with special-purpose hardware accelerators is the preferred building block for a flexible yet efficient node. A subset of the architecture is implemented using commercial building blocks and shows substantial improvements in communication performance and the ability to perform system-level optimizations that obtain tight synchronization and low power channel monitoring.

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Abstract. We present TinyOS, a flexible, application-specific operating system for sensor networks, which form a core component of ambient intelligence systems. Sensor networks consist of (potentially) thousands of tiny, low-power nodes, each of which execute concurrent, reactive programs that must operate with severe memory and power constraints. The sensor network challenges of limited resources, event-centric concurrent applications, and low-power operation drive the design of TinyOS. Our solution combines flexible, fine-grain components with an execution model that supports complex yet safe concurrent operations. TinyOS meets these challenges well and has become the platform of choice for sensor network research; it is in use by over a hundred groups worldwide, and supports a broad range of applications and research topics. We provide a qualitative and quantitative evaluation of the system, showing that it supports complex, concurrent programs with very low memory requirements (many applications fit within 16KB of memory, and the core OS is 400 bytes) and efficient, low-power operation. We present our experiences with TinyOS as a platform for sensor network innovation and applications. 1

We present an implementation and evaluation of an Active Messages based communication system for tiny, wireless, networked sensors. The implementation includes two major software components. The first is the device based operating program which includes the communication subsystem, dispatch loop and AM handlers. The second is a communication library for general purpose host computers. Using an Atmel 8535 based device and an Intel Pentium II PC, we demonstrate an ad hoc networking application that uses Active Message primitives for multi-hop route discovery and packet delivery on silver dollar sized devices. We also make observations about the applicability of TCP/IP to the Tiny Networked Sensor regime.

Networks of hundreds or thousands of sensor nodes equipped with sensing, computing and communication ability are conceivable with recent technological advancement. Methods are presented in this report to recover and visualize data from wireless sensor networks, as well as to estimate node positions. A communication system is assumed wherein information from sensor nodes can be transferred to a centralized computer for data processing, though suggestions are made for extensions to distributed computation. Specifically, this report presents four topics. First, the notion of using network connectivity to reconstruct node positions via linear or semidefinite programming is explored. Random feasible node placement and bounding methods are both found to increase in precision with the indiviual geographical constraints. Second, the potential effectiveness of two correlation-based sensor data encoding schemes is reported. Blind correlation methods are found to provide meager compression while ...

Large-scale networks of integrated wireless sensors and actuators become increasingly

Wireless Sensor Networks (WSNs) are characterized by resource constraints and large scalability. Many applications of WSN require secure communication, a crucial component especially in hostile environments. However, the low computational capability and small storage budget within sensors render many popular public-key based cryptographic systems impractical. Symmetric key cryptography, on the other hand, is attractive due to efficiency. Nevertheless, establishing a shared key for communicating parties is a challenging problem. In this paper, we propose and analyze an in-situ PAirwise Key bootstrapping scheme (iPAK) for large-scale WSNs. Our theoretical analy-sis and simulation study demonstrate that iPAK can achieve high key-sharing probability between neighboring sensors and strong resilience against node capture attacks at the cost of a low storage overhead.