Distributed sensor system applications (e.g., wireless sensor networks) have been studied extensively in recent years. Such applications involve resource-limited embedded sensor nodes that communicate with each other through self-organizing protocols. Depending on application requirements, distributed sensor system design may include protocol and prototype implementation. Prototype implementation is especially useful in establishing and maintaining system functionality as the design is customized to satisfy size, energy, and cost constraints. In this paper, we present a streamlined, application-specific approach to incorporating fault tolerance into a TDMA-based distributed sensor system for line-crossing recognition. The objective of this approach is to prevent node failures from translating into failures in the overall system. Our approach is specialized and light-weight so that fault tolerance is achieved without significant degradation in energy efficiency. We also present an asynchronous handshaking approach for providing synchronization between the transceiver and digital processing subsystem in sensor node. This provides a general method for achieving such synchronization with reduced hardware requirements and reduced energy consumption compared to conventional approaches, which rely on generic interface protocols. We demonstrate the capabilities of our approaches to fault tolerance and transceiver-processor integration through experiments involving a complete prototype wireless sensor network test-bed, and a distributed line-crossing recognition application that runs on this test-bed.

Many application-specific wireless sensor network (WSN) systems require small size and low power features due to their limited resources, and their use in distributed, wireless environments. In this paper, we present a light-weight distributed algorithm for line-crossing recognition, together with its analysis, implementation, and experimental evaluation within a prototype wireless sensor network platform. The algorithm is developed in conjunction with a TDMA-based communication protocol such that the proposed system provides for low duty cycle and energy efficient operation. An accurate lifetime model is proposed with consideration of detailed energy usage to analyze and estimate the system lifetime. Our experimental results demonstrate the accuracy of this lifetime model, and its utility in optimizing network implementation. The design and experimental evaluation of our prototype network demonstrates the compactness and functionality of the proposed distributed WSN system for line-crossing recognition.

For the Butterfly of N input/output vertices we present a layout on the square grid of area k N2 + o(N').A lower bound of the same order is proved.The encompassing rectangle which defines the area is 45' slanted w.r.t. the grid axes and the input/output vertices are not on the boundary of this rectangle.For the Butterfly of A4 input/output edges we present a layout of area +M" + o(M').In this layout the input edges are on the 1.h.s. of the upright encompassing rectangle and the output edges are on its r.h.s.Again this is also a lower bound.Both layouts are scalable.i.e. if one allocates for each switch a square of Q x a area, the layouts remain of area f N2 + o( N2) and iA4' + o(M'), respectively, where the value of a affects only the o(N2) and o(A4') terms.Both layouts are free of knock-knees.