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.

Distributed real-time systems are becoming more pervasive in many domains including process control, discrete manufacturing, defense systems, air traffic control, and online monitoring systems in medicine. The construction of such systems, however, is impeded by the lack of simple yet powerful programming models and the lack of efficient, scalable, dependable and analyzable interfaces and their implementations. We argue that these issues need to be resolved with powerful application-level toolkits similar to that provided by ISIS [2]. In this paper, we consider the inter-process communication requirements which form a fundamental block in the construction of distributed real-time systems. We propose the real-time publisher/subscriber model, a variation of group-based programming and anonmyous communication techniques, as a model for distributed real-time inter-process communication which can address issues of programming ease, portability, scalability and analyzability. The model has been used successfully in building a software architecture for building upgradable real-time systems. We provide the programming interface, a detailed design and implementation details of this model along with some preliminary performance benchmarks. The results are encouraging in that the goals we seek look achievable.

Interprocess communication (IPC) provides the fundamental mechanism for the Mach microkernel to be extensible and flexible. Mach IPC provides efficient communication mechanisms for many applications. However, it does not provide sufficient functionality for real-time applications which have rigid timing constraints among threads. In RealTime Mach (RT-Mach), we have extended Mach IPC to be priority inversion free for real-time applications. This paper describes the Real-Time IPC (RT-IPC) facilities, its implementation, and the evaluation results. We used the Distributed Hartstone (DHS) real-time benchmark for the evaluation and the results show that RT-IPC can reduce priority inversion and improve CPU utilization for real-time applications. 1. Introduction In traditional operating systems, it is difficult to support real-time applications such as continuous media applications and mobile computing, due to the lack of facilities which can manage time constrained resources, such as proce...

The goal of TAXYS is to provide a framework for developing real-time embedded code and verifying its correct behavior with respect to quantitative timing requirements. To achieve so, TAXYS connects France Telecom's FSTEREL compiler SAXO-RT with VERIMAG's model-checker KRONOS. TAXYS has been successfully applied on real industrial telecommunication systems, such as a GSM radio link from Alcatel and a phone prototype from France Telecom.

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