Browsing by Author "Chang, Tzu-Chien"

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Efficient Color-theory-based Dynamic Localization for Mobile Wireless Sensor Networks
(2011-07-01)
Shee, Shen-Hai
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Chang, Tzu-Chien
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
Location information is critical to mobile wireless sensor networks (WSN) applications. With the help of location information, for example, routing can be performed more efficiently. In this paper, we propose a novel localization approach, Color-theory based Dynamic Localization (CDL), which is based on color theory to exploit localization in mobile WSNs. CDL makes use of the broadcast information, such as locations and RGB values, from all anchors (a small portion of nodes with GPS receivers attached), to help the server to create a location database and assist each sensor node to compute its RGB value. Then, the RGB values of all sensor nodes are sent to the server for localization of the sensor nodes. A unique feature of our color-theory based mechanism is that it can use one color to represent the distances of a sensor node to all anchors. Since CDL is easy to implement and is a centralized approach, it is very suitable for applications that need a centralized server to collect user (sensor) data and monitor user activities, such as community health-care systems and hospital monitoring systems. Evaluation results have shown that for mobile WSNs, the location accuracy of CDL (E-CDL, an enhanced version of CDL) is 40-50% (75-80%) better than that of MCL (Hu, L., & Evans, D. (2004). Localization for mobile sensor networks. In Proceedings of the 10th annual international conference on mobile computing and networking, pp. 45-57). In addition, we have implemented and validated our E-CDL algorithm on the MICAz Mote Developer's Kit.
Enhanced color-theory-based dynamic localization in mobile wireless sensor networks
(2007)
Chang, Tzu-Chien
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
There are few localization schemes targeted at mobile wireless sensor networks. In this paper, we propose an Enhanced Color-theory-based Dynamic Localization (E-CDL) which is based on the CDL algorithm [1]. However, the location accuracy of this algorithm depends on the accuracy of the average hop distance derivation. Therefore, we present two novel schemes to estimate the average hop distance. We analyzed the behavior of sensor nodes communication, and computed the expected value of the average hop distance, which is 7r/9, where r is the radio range. In addition, since CDL is based on the DV-hop scheme, the derived shortest path length is usually larger than the corresponding Euclidean distance. With this observation, the derived shortest path length can be adjusted by the ratio of the Euclidean distance and the shortest path distance to further enhance the location accuracy. Finally, in mobile wireless sensor networks, sensor nodes may become isolated. By employing mobile anchor nodes, the isolation problem can be relieved and hence the location accuracy can be improved. Simulation results have shown that the location accuracy of E-CDL is 50% - 55% better than that of CDL, and 75% - 80% better than that of MCL (Monte Carlo Localization) [2]. In addition, we have implemented and verified our algorithm on the MICAz Mote Developer's Kit [3].