A hybrid embedded real-time operating system for wireless sensor networks

Traditional operating systems for wireless sensor networks (WSN) are based on either event-driven or multitask concept. Instead, this paper presents an embedded real-time operating system, named HEROS 'Hybrid Embedded Real-time Operating System', which is configurable to run in different modes: event-driven, multitask or hybrid to adapt to diverse domains of WSN applications. HEROS adopts a modular and hierarchical architecture: action (system operation), thread (component) and event (etask) and provides a predictable and deterministic scheduling mechanism: 'non pre-emption priority based' scheduling for events and 'pre-emptive priority-based' scheduling for threads. Furthermore, to ease distributed cooperative application, HEROS adopts LINDA concept by providing a simplified tuple space and a lightweight IN/OUT primitive-pair to implement system communication & synchronization. Currently, HEROS has been implemented and evaluated in different applications and on different platforms. The experimentation results show that HEROS has a small footprint and meets different real-time application requirements.