LIMOS: A Lightweight Multi-Threading Operating System dedicated to Wireless Sensor Networks

The operating systems of wireless sensor networks should be suitable for strict-constrained system resources and support two operation modes: event-driven & multi-threading. Traditional embedded operating systems are generally not fit for WSN applications. This paper presents a smart, resource-aware, low-power-consuming and distributed real-time micro-kernel: LIMOS. LIMOS adopts an event & thread two-level system architecture and a two-level scheduling policy: ´non pre-emption priority based´ high level scheduling for events; and ´preemptive priority-based´ low level scheduling for threads. The scheduling scheme is predictable and deterministic with respect to real-time applications. A unique system interface and a system primitive-pair, i.e. tuple and IN & OUT, are proposed for all kinds of system synchronization and communication. LIMOS integrates the advantages of tinyOS and SDREAM. It allows running in different modes. The combination of two kernels extends greatly the application range of LIMOS from simple single-task to multitask applications. In present, LIMOS has been evaluated on several hardware platforms and ported for different applications.