Browsing by Author "Tsai, Chia-Hung"

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A Path-Connected-Cluster Wireless Sensor Network and Its Formation, Addressing, and Routing Protocols
(2012-06-01)
Tsai, Chia-Hung
;
Tseng, Yu-Chee
;
資訊工程學系
;
Department of Computer Science
Although wireless sensor networks (WSNs) have been extensively researched, their deployment is still a main concern. We observe that many monitoring applications for WSNs have adopted a path- connected- cluster (PCC) topology, where regions to be monitored are deployed with clusters of sensor nodes. Since these clusters might be physically separated, paths of sensor nodes are used to connect them together. We call such networks PCC-WSNs. PCC-WSNs may be widely applied in real situations, such as bridge-connected islands, street-connected buildings, and pipe-connected ponds. In this paper, we show that the address assignment scheme defined by ZigBee will perform poorly in terms of address utilization. We then propose a systematical solution, which includes network formation, automatic address assignment, and light-weight routing. Simulation results verify the effectiveness of the proposed solution.
A Path-Connected-Cluster Wireless Sensor Network and Its Formation, Addressing, and Routing Protocols
(2012-06-01)
Tsai, Chia-Hung
;
Tseng, Yu-Chee
;
資訊工程學系
;
Department of Computer Science
Although wireless sensor networks (WSNs) have been extensively researched, their deployment is still a main concern. We observe that many monitoring applications for WSNs have adopted a path-connected-cluster (PCC) topology, where regions to be monitored are deployed with clusters of sensor nodes. Since these clusters might be physically separated, paths of sensor nodes are used to connect them together. We call such networks PCC-WSNs. PCC-WSNs may be widely applied in real situations, such as bridge-connected islands, street-connected buildings, and pipe-connected ponds. In this paper, we show that the address assignment scheme defined by ZigBee will perform poorly in terms of address utilization. We then propose a systematical solution, which includes network formation, automatic address assignment, and light-weight routing. Simulation results verify the effectiveness of the proposed solution.
A sensor-based sun-tracking energy harvest system
(2015-01-01)
Tsai, Chia-Hung
;
Hu, Shu-Chiung
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Huang, Chung-Hsiang
;
Tseng, Yu-Chee
;
資訊工程學系
Recent study has shown that the energy gain of a solar panel will be significantly influenced by the incidence angle of the sun radiation. The main goal of this paper is to present a sensor-based sun-tracking system. First, we design a sensing tower for measuring the direction of sun radiation. Then we design a sun-tracking algorithm, which adopts an iterative process to identify the direction of sun radiation to the earth\'s surface. This information is then passed to the nearby solar panels to adjust their angles. We have also developed a prototype and conducted several simulations to verify our sun-tracking system. Simulation results show that our system has better performance on the solar energy generation than existing ones.
An Energy-Efficient Multicast Protocol for ZigBee-based Networks
(2016)
Hu, Shu-Chiung
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Tsai, Chia-Hung
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Lu, Yi-Chen
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Pan, Meng-Shiuan
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Tseng, Yu-Chee
Recently, many Internet of Things (IoT) or wireless sensor network (WSN) applications adopt ZigBee as their communication protocol. In these applications, messages may need to be disseminated to some specific objects or nodes using multicast transmissions. However, we observe that the original ZigBee multicast protocol causes extremely high packet overhead and energy consumption. In this work, we propose a ZigBee-compatible energy efficient multicast protocol, which allows nodes to execute the designed procedures in a distributed manner. By our scheme, each node uses the designed maintenance module to manage its neighbors. When multicasting, a node utilizes the designed multicasting module to compete for being a relay node by the proposed backoff mechanism. In addition, each node overhears its neighbors\' broadcasts to avoid unnecessary transmissions and to ensure that the transmitted multicast packets are successfully received. Our results indicate that the proposed protocol can indeed lengthen network lifetime, reduce redundant packets, and preserve network reliability.
Cross-Layer, Energy-Efficient Design for Supporting Continuous Queries in Wireless Sensor Networks: A Quorum-Based Approach
(2009-11-01)
Tsai, Chia-Hung
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Hsu, Tsu-Wen
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Pan, Meng-Shiuan
;
Tseng, Yu-Chee
;
資訊工程學系
Power saving and query processing are two major concerns in a wireless sensor network. Each of these two issues has been intensively studied separately in the literature. In this work, we are interested in linking the asynchronous power-saving protocol and the continuous query-processing problem together. A cross-layer solution is proposed. On the MAC layer, we propose to use the grid-quorum system (Tseng et al., Computer Networks, 43(3):317-337, 2003) to serve as the underlying power-saving framework. On the network layer, we propose to find query paths based on the power cost incurred by grid quorums used by nodes along a path. We show how these two layers interwork with each other to support continuous queries in an energy-efficient way.
Nanofabrication of uniform and stabilizer-free self-assembled platinum monolayers as counter electrodes for dye-sensitized solar cells
(2014-08-01)
Li, Lu-Lin
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Wu, Hsin-Hui
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Tsai, Chia-Hung
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Diau, Eric Wei-Guang
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交大名義發表
We report a two-step dip-coating approach for the fabrication of self-assembled monolayers of platinum nanocrystals (SAM-Pt) with a particle size of similar to 3 nm and that are uniformly deposited on a transparent conducting oxide (TCO) surface to serve as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). In the first step, we prepared a polyol solution containing H2PtCl6 and ethylene glycol at 110 degrees C, in which the reduction kinetics were controlled by adding various proportions of NaOH. In the second step, we immersed a thiol-modified TCO substrate into the polyol solution with monodispersed Pt nanoparticles prepared at pH 3.7 at approximately 295 K to complete the nanofabrication. The DSSC devices using Z907 dye as a photosensitizer and the CE prepared using this SAM-Pt approach attained notable photovoltaic performance (eta = 9.2%) comparable with those fabricated using a conventional thermal decomposition method (eta = 9.1%) or a cyclic electrodeposition method (eta = 9.3%) under the same experimental conditions. We emphasize that the SAM-Pt films feature a clean surface, uniform morphology, narrow size distribution, small Pt loading and great catalytic activity; the present approach is hence not only suitable for DSSCs but also applicable for many other energy-related applications that require platinum as an efficient catalyst.
The Orphan Problem in ZigBee Wireless Networks
(2009-11-01)
Pan, Meng-Shiuan
;
Tsai, Chia-Hung
;
Tseng, Yu-Chee
;
資訊工程學系
;
Department of Computer Science
ZigBee is a communication standard which is considered to be suitable for wireless sensor networks. In ZigBee, a device (with a permanent 64-bit MAC address) is said to join a network if it can successfully obtain a 16-bit network address from a parent device. Parent devices calculate addresses for their child devices by a distributed address assignment scheme. This assignment is easy to implement, but it restricts the number of children of a device and the depth of the network. We observe that the ZigBee address assignment policy is too conservative, thus usually making the utilization of the address pool poor. Those devices that cannot receive network addresses will be isolated from the network and become orphan nodes. In this paper, we show that the orphan problem can be divided into two subproblems: the bounded-degree-and-depth tree formation (BDDTF) problem and the end-device maximum matching (EDMM) problem. We then propose algorithms to relieve the orphan problem. Our simulation results show that the proposed schemes can effectively reduce the number of orphan devices compared to the ZigBee strategy.