Jinchul Choi

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In RFID systems, the performance of each reader such as interrogation range and tag recognition rate may suffer from interferences from other readers. Since the reader interference can be mitigated by output signal power control, spectral and/or temporal separation among readers, the system performance depends on how to adapt the various reader arbitration(More)
The performance of the clustering scheme is influenced by the cluster-head election method and the size or the number of clusters. Thus we should optimize these factors to maximize the energy efficiency of the clustering scheme. In this paper, we propose a new energy consumption model for the LEACH which is a well-known clustering protocol and determine the(More)
In wireless ad hoc networks, one of the most important issues impacting performance is wireless interference between adjacent nodes. Such interference problem has often been approached to find independent sets in a topological graph. In general, the topological graph have exponentially many independent sets and and thus it is very difficult to find the(More)
Heroes of Koskenniska is a game-based pervasive learning space that combines mobile and sensor technologies to raise environmental and cultural awareness in a Finnish Biosphere Reserve. An environmental sensor network (ESN) is used to gather and process environmental parameters to be used in the game. The developed wireless infrastructure is presented(More)
IEEE 802.11e is being proposed to improve QoS (Quality of Service) by IEEE 802.11 working group. HCCA (HCF Controlled Channel Access), a centralized polling based mechanism of IEEE 802.11e, needs a scheduling algorithm that decides on how the available radio resources are allocated to the polled stations. In IEEE 802.11e a standard Reference Scheduler is(More)
Since the performance of the clustering scheme is influenced by various factors such as the size or the number of clusters, good models for the clustered sensor networks are necessary to optimize these factors. Hence, determining the optimal number of clusters with the energy consumption has been one of the important issues in the clustered sensor network.(More)
Ubiquitous computing has become popular and is in demand in many fields of human activity. This kind of computing could significantly enhance applications such as an organizer by making it more agile through sensing the environment. The <i>context-aware agriculture organizer</i> (CAAO), which was pursued by this study, facilitates farmers work by providing(More)