Hybrid Real-time Operating System for Resource-constraint Wireless Sensor Nodes

Wireless sensor network (WSN) has been used in widespread domains, and the real-time response is required by many WSN applications. However, due to the memory resources limitation on the sensor nodes, the current WSN OSs such as TinyOS, Contiki, SOS, mantisOS, etc., are not real-time ones. To achieve the objective of designing a realtime OS with low memory resource consumption, a new WSN OS named HEROS is developed and presented in this paper. For HEROS, it adopts a hybrid scheduling strategy. Both the event-driven and multithreading schedulers are implemented in parallel, and these two schedulers can switch to each other when necessary. By this means, HEROS take advantages of both the event-driven system's low memory resource consumption as well as multithreading system's high real-time performance. Besides these, HEROS uncouples the applications from the underlying systems by using the pre-linked mechanism (PLM). With this mechanism, a user-friendly development environment can be provided to the WSN users. Finally, to evaluate the performance of HEROS, it is compared with some other WSN OSs on the iLive platform (8-bit AVR microcontroller). The final experimental and evaluation results prove that HEROS is a memory resources efficient, real-time supported and user-friendly OS, and can be used on most resource-constrained sensor nodes to support the diverse kinds of WSN applications.