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.

As sensor networks edge closer towards wide-spread deployment, security issues become a central concern. So far, the main research focus has been on making sensor networks feasible and useful, and less emphasis was placed on security. We design a suite of security...

We study the problem of media access control in the novel regime of sensor networks, where unique application behavior and tight constraints in computation power, storage, energy resources, and radio technology have shaped this design space to be very different from that found in traditional mobile computing regime. Media access control in sensor networks must not only be energy efficient but should also allow fair bandwidth allocation to the infrastructure for all nodes in a multihop network. We propose an adaptive rate control mechanism aiming to support these two goals and find that such a scheme is most effective in achieving our fairness goal while being energy effcient for both low and high duty cycle of network traffic.

All emphasize low-cost components operating on shoestring power budgets for years at a time in potentially hostile environments without hope of human intervention. Wireless sensor networks combine processing, sensing, and communications into tiny embedded devices. Peer-to-peer communication protocols then combine the individual devices into an interconnected mesh network where data is seamlessly routed among all the nodes. These networks require no external infrastructure and can scale to hundreds or even thousands of nodes.

We introduce a novel technique for computation of consecutive preimages of hash chains. Whereas traditional techniques have a memory-times-computation complexity of O(n) per output generated, the complexity of our technique is only O(log 2 n), where n is the length of the chain.

We consider the problem of coverage and exploration of an unknown dynamic environment using a mobile robot(s). The environment is assumed to be large enough such that constant motion by the robot(s) is needed to cover the environment. We present an e#cient minimalist algorithm which assumes that global information is not available (neither a map, nor GPS). Our algorithm deploys a network of radio beacons which assists the robot(s) in coverage. This network is also used for navigation. The deployed network can also be used for applications other than coverage. Simulation experiments are presented which show the collaboration between the deployed network and mobile robot(s) for the tasks of coverage/exploration, network deployment and maintenance (repair), and mobile robot(s) recovery (homing behavior). We present a theoretical basis for our algorithm on graphs and show the results of the simulated scenario experiments.

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.

Sensor networks are gaining a central role in the research community. This paper addresses some of the issues arising from the use of sensor networks in control applications. Classical control theory proves to be insufficient in modeling distributed control problems where issues of communication delay, jitter, and time synchronization between components are not negligible. After discussing our hardware and software platform and our target application, we review useful models of computation and then suggest a mixed model for design, analysis, and synthesis of control algorithms within sensor networks. We present a hierarchical model composed of continuous time-trigger components at the low level and discrete event-triggered components at the high level. Keywords—Distributed control, distributed pursuit–evasion game (DPEG), embedded, Mica, mote, NesC, pursuit–evasion game (PEG), sensor network, TinyOS. I.

We describe an algorithm for robot navigation using a sensor network embedded in the environment. Sensor nodes act as signposts for the robot to follow, thus obviating the need for a map or localization on the part of the robot. Navigation directions are computed within the network (not on the robot) using value iteration. Using small low-power radios, the robot communicates with nodes in the network locally, and makes navigation decisions based on which node it is near. An algorithm based on processing of radio signal strength data was developed so the robot could successfully decide which node neighborhood it belonged to. Extensive experiments with a robot and a sensor network confirm the validity of the approach.

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.