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Operating systems for sensor networks must provide energy and memory-space efficient execution environments for applications because of the resource constraints of the sensor nodes. The shared-stack cooperative threads have been proposed to conserve stack memory-space and to minimize the possibility of stack overflow in the sensor operating systems. However, stack switching brings about external fragmentations in the stack space. Compaction may remove the fragmentation but the compaction overhead could degrade the performance. In this paper, we propose an efficient scheme to determine the compaction time of a shared-stack to reduce the number of compactions. For determining the time of a compaction, we evaluated the expected stack overflow time according to our stack model, which is based on the continuous time Markov chain. Our simulation results show that the number of compactions is greatly reduced and the lifetime of the sensor networks is increased with using our proposed scheme.

Keywords: operating systems, sensor networks, cooperative threads, stack overflow, memory external fragmentation, continuous time Markov chain

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Received January 15, 2008; revised May 16 & August 20, 2009; accepted September 26, 2009.
Communicated by Tei-Wei Kuo.
^* This research was financially supported by Hansung University in the year of 2009, it was supported by NIPA under the program of Software Engineering Technologies Development and Experts Education, and it was supported by the MKE, Korea, under the ITRC support program supervised by the IITA (IITA-2008-C1090-0803-0006).
⁺ Corresponding author.