Browsing by Author "Huang, Chi-Fu"

Now showing 1 - 7 of 7

A Load-Balanced Guiding Navigation Protocol in Wireless Sensor Networks
(2008)
Chen, Wen-Tsuen
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Chen, Po-Yu
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Wu, Cheng-Han
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Huang, Chi-Fu
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資訊工程學系
One of the major applications of wireless sensor networks is guiding navigation service with its goal to assist moving objects in leaving a hazardous region safely and quickly. In this paper, we propose a distributed guiding navigation protocol that can guide moving objects to multiple exits with load balancing among multiple navigation paths to the exits. With the assistances of sensor nodes, moving objects are guided to different navigation paths so that they can move to exits as soon as possible without causing congestion. In some traditional navigation algorithms, a sensor may select a wrong guiding direction when an information-updating packet has not flooded through the whole network. Hence, the guiding direction of the sensor may oscillate in a short time and guided objects will confuse with this phenomenon, called direction oscillation problem. This problem will be eliminated in our proposed protocol. Simulation results indicate that our protocol can guide moving objects to exits in shorter time and solve the direction oscillation problem effectively.
A Wireless Human Motion Capturing System for Home Rehabilitation
(2009)
Tseng, Yu-Chee
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Wu, Chin-Hao
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Wu, Fang-Jing
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Huang, Chi-Fu
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King, Chung-Ta
Following the trend of miniature intelligent sensing, wearing small, integrated wireless sensor nodes, such as one with accelerometers and compasses, to capture human body motions may have many applications in medical care and computer animation. In this paper, we demonstrate the use of intelligent sensors to capture human motions for home rehabilitation. We design a game to help a patient to conduct his/her rehabilitation program. For each exercise, the patient is instructed to wear sensors on specified movable body parts. The system will then estimate the quality of the movements and give scores as if it is advised by a therapist. In this way, patients will no longer feel painful and boring as that in traditional rehabilitation, which is typically done in hospitals.
Data Gathering by Mobile Mules in a Spatially Separated Wireless Sensor Network
(2009)
Wu, Fang-Jing
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Huang, Chi-Fu
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
While wireless sensor networks (WSNs) are typically targeted at large-scale deployment, due to many practical or inevitable reasons, a WSN may not always remain connected. In this paper we consider the possibility that a WSN may be spatially separated into multiple subnetworks. Data gathering, which is a fundamental mission of WSN, thus may rely on a mobile mule ("mule" for short) to conduct data gathering by visiting each subnetwork. This leads to the problem of minimizing the path length traversed by the mobile mule. We show that minimizing the path length, which may reflect the data gathering latency and the energy consumption of the mule is a generalization of the traveling salesman problem and is NP-complete. Some heuristics based on geometrical properties of node deployment are proposed. Our simulation results show that these heuristics perform very close to optimal solutions in most practical cases.
Decentralized Energy-Conserving and Coverage-Preserving Protocols for Wireless Sensor Networks
(2006-05-01)
Huang, Chi-Fu
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Lo, Li-Chu
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Tseng, Yu-Chee
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Chen, Wen-Tsuen
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資訊工程學系
In this article, we propose several decentralized protocols that schedule sensors' active and sleeping periods to prolong the network lifetime while maintain the sensing field sufficiently covered. The proposed protocols are based on a model similar to that of Yan et al. [ 2003], but improve its results in several senses. First, our approach can significantly reduce the computational complexity incurred, and at the same time achieve better accuracy in determining the coverage of the sensing area. Second, we extend the result such that it can support multilayer coverage of the sensing field. Third, we further enhance it [Yan et al. 2003] by proposing several optimization mechanisms to balance or reduce sensors' energy expenditure.
Distributed protocols for ensuring both coverage and connectivity of a wireless sensor network
(2007-03-01)
Huang, Chi-Fu
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Tseng, Yu-Chee
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Wu, Hsiao-Lu
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資訊工程學系
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Department of Computer Science
Wireless sensor networks have attracted a lot of attention recently. Such environments may consist of many inexpensive nodes, each capable of collecting, storing, and processing environmental information, and communicating with neighboring nodes through wireless links. For a sensor network to operate successfully, sensors must maintain both sensing coverage and network connectivity. This issue has been studied in Wang et al. [2003] and Zhang and Hou [2004a], both of which reach a similar conclusion that coverage can imply connectivity as long as sensors' communication ranges are no less than twice their sensing ranges. In this article, without relying on this strong assumption, we investigate the issue from a different angle and develop several necessary and sufficient conditions for ensuring coverage and connectivity of a sensor network. Hence, the results significantly generalize the results in Wang et al. [2003] and Zhang and Hou [2004a]. This work is also a significant extension of our earlier work [Huang and Tseng 2003; Huang et al. 2004], which addresses how to determine the level of coverage of a given sensor network but does not consider the network connectivity issue. Our work is the first work allowing an arbitrary relationship between sensing ranges and communication distances of sensor nodes. We develop decentralized solutions for determining, or even adjusting, the levels of coverage and connectivity of a given network. Adjusting levels of coverage and connectivity is necessary when sensors are overly deployed, and we approach this problem by putting sensors to sleep mode and tuning their transmission powers. This results in prolonged network lifetime.
Non-Location-Based Mobile Sensor Relocation in a Hybrid Static-Mobile Wireless Sensor Network
(2009)
Wu, Fang-Jing
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Hsu, Hsiu-Chi
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Tseng, Yu-Chee
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Huang, Chi-Fu
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資訊工程學系
An inherent concern for a wireless sensor network (WSN) is the unbalanced energy consumption problem, where sensors closer to the sink are more likely to exhaust their energy faster than other nodes. To mitigate this problem, this paper considers including some resource-rich mobile nodes, called mobile data-pumps, to conduct data relaying from static sensors to the sink. The network thus becomes a two-tier network, with the original static sensors at the low tier and data-pumps at both low and high tiers. We propose a novel distributed navigation protocol that does not rely on any location information of sensor nodes to relocate data-pumps to meet both goals of connectivity and load balance. The main idea is a concept called virtual Voronoi cells, which can help data-pumps to locally balance their loads using the underlaying low-tier topology and thus significantly balance energy consumption of sensors. Simulation results are presented to verify the effectiveness of our result.
Providing Group Tour Guide by RFIDs and Wireless Sensor Networks
(2009-06-01)
Chen, Po-Yu
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Chen, Wen-Tsuen
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Tseng, Yu-Chee
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Huang, Chi-Fu
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資訊工程學系
This paper proposes a new application framework for group tour guiding services based on RFIDs and wireless sensor networks. We consider a sensing field mixed with multiple independent tourist groups, each with a leader and several members. Members of a group will follow the moving path of their leader, but may occasionally roam around randomly on their own interests. Sensor nodes have to track leaders' locations and maintain guiding paths from members to leaders. A member may inquire where his/her leader is, and a leader may "recall" his/her members. We propose a feasible solution to such an application by using existing technologies and off-the-shelf components. A group guiding protocol is presented. The design enables reliable group guiding at low-cost and low traffic load. Our prototyping system is reported and system performance is discussed.