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UbiFOS: A Small Real-Time Operating System for Embedded Systems
Hee-Joong Ahn, Moon-Haeng Cho, Myoung-Jo Jung, Yong-Hee Kim, Joo-Man Kim, and Cheol-Hoon Lee
Abstract :	The ubiquitous flexible operating system (UbiFOS) is a real-time operating system designed for cost-conscious, low-power, small to medium-sized embedded systems such as cellular phones, MP3 players, and wearable computers. It offers efficient real-time operating system services like multi-task scheduling, memory management, inter-task communication and synchronization, and timers while keeping the kernel size to just a few to tens of kilobytes. For flexibility, UbiFOS uses various task scheduling policies such as cyclic time-slice (round-robin), priority-based preemption with round-robin, priority-based preemptive, and bitmap. When there are less than 64 tasks, bitmap scheduling is the best policy. The scheduling overhead is under 9 μs on the ARM926EJ processor. UbiFOS also provides the flexibility for user to select from several inter-task communication techniques according to their applications. We ported UbiFOS on the ARM9-based DVD player (20 kB), the Calm16-based MP3 player (under 7 kB), and the ATmega128-based ubiquitous sensor node (under 6 kB). Also, we adopted the dynamic power management (DPM) scheme. Comparative experimental results show that UbiFOS could save energy up to 30% using DPM.
Key word :	real-time operating systems, embedded systems, wearable computers, power management
DOI :	http://dx.doi.org/10.4218/etrij.07.0506.0025
Cite this :	Hee-Joong Ahn, Moon-Haeng Cho, Myoung-Jo Jung, Yong-Hee Kim, Joo-Man Kim, and Cheol-Hoon Lee, "UbiFOS: A Small Real-Time Operating System for Embedded Systems," ETRI Journal, vol. 29, no. 3, June 2007, pp. 259-269. http://dx.doi.org/10.4218/etrij.07.0506.0025
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