An Event-driven Multi-threading Real-time Operating System Dedicated to Wireless Sensor Networks

At present, the OSs (Operating system) employed for WSN (wireless sensor networks) are either satisfied with only one or two application classes or unsuitable for strict-constrained resources. In view of a variety of WSN applications, there is a need of developing a self-adaptable and self-configurable embedded real-time operating system (RTOS). This paper presents a resource-aware and low-power RTOS termed LIMOS. This kernel adopts a component-based three-level system architecture: action (system operation), thread (component) and event (container). In accordance, a predictable and deterministic two-level scheduling mechanism is proposed: 'non pre-emption priority based' high level scheduling for events and 'preemptive priority-based' low level scheduling for threads. Employing the concepts of LINDA language, LIMOS provides a simplified tuple space and a light IN/OUT system primitive-pair to achieve system communication and synchronization. LIMOS is capable of self-adapting to run on two operation modes: event-driven and multi-threading, with respect to the application diversity. The performance evaluation and comparison shows LIMOS has tiny resource consumption and is fit for the real-time applications. Currently LIMOS has been ported on several hardware platforms for different WSN applications.