Browsing by Author "Huang, Chen-Che"

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A Proxy-Based Approach to Continuous Location-Based Spatial Queries in Mobile Environments
(2013-02-01)
Huang, Jiun-Long
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Huang, Chen-Che
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資訊工程學系
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Department of Computer Science
Caching valid regions of spatial queries at mobile clients is effective in reducing the number of queries submitted by mobile clients and query load on the server. However, mobile clients suffer from longer waiting time for the server to compute valid regions. We propose in this paper a proxy-based approach to continuous nearest-neighbor (NN) and window queries. The proxy creates estimated valid regions (EVRs) for mobile clients by exploiting spatial and temporal locality of spatial queries. For NN queries, we devise two new algorithms to accelerate EVR growth, leading the proxy to build effective EVRs even when the cache size is small. On the other hand, we propose to represent the EVRs of window queries in the form of vectors, called estimated window vectors (EWVs), to achieve larger estimated valid regions. This novel representation and the associated creation algorithm result in more effective EVRs of window queries. In addition, due to the distinct characteristics, we use separate index structures, namely EVR-tree and grid index, for NN queries and window queries, respectively. To further increase efficiency, we develop algorithms to exploit the results of NN queries to aid grid index growth, benefiting EWV creation of window queries. Similarly, the grid index is utilized to support NN query answering and EVR updating. We conduct several experiments for performance evaluation. The experimental results show that the proposed approach significantly outperforms the existing proxy-based approaches.
ALM: An adaptive location management scheme for approximate location queries in wireless sensor networks
(2010-10-15)
Yeh, Lo-Yao
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Huang, Chen-Che
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Wu, Cheng-En
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Huang, Jiun-Long
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資訊工程學系
Location management is an important issue for object tracking applications of wireless sensor networks. Since locations obtained by most positioning techniques are inherently imprecise, users may send approximate location queries with precision constraints to trade for energy consumption of sensor nodes. Therefore, we propose an Adaptive Location Management scheme called ALM to process approximate location queries. ALM employs a two-tier storage architecture (i.e., centric storage node and local storage node) to facilitate approximate query resolving and to reduce the energy consumption of sensor nodes. We propose a storage node relocation and replication mechanism, which can create, remove replicas of storage nodes and adjust the positions of storage nodes according to the location queries and updates. As such, the number of forwarding location update and query messages is reduced by the proposed storage node relocation and replication mechanism, thereby conserving more energy. The experimental results show that compared with EASE (Xu et al. (2008) [18]), ALM is able to reduce the number of transmission messages and the energy consumption of sensor network, and prolong the network lifetime. (C) 2010 Elsevier B.V. All rights reserved.
ALM: An adaptive location management scheme for approximate location queries in wireless sensor networks
(2010-10-15)
Yeh, Lo-Yao
;
Huang, Chen-Che
;
Wu, Cheng-En
;
Huang, Jiun-Long
;
資訊工程學系
Location management is an important issue for object tracking applications of wireless sensor networks. Since locations obtained by most positioning techniques are inherently imprecise, users may send approximate location queries with precision constraints to trade for energy consumption of sensor nodes. Therefore, we propose an Adaptive Location Management scheme called ALM to process approximate location queries. ALM employs a two-tier storage architecture (i.e., centric storage node and local storage node) to facilitate approximate query resolving and to reduce the energy consumption of sensor nodes. We propose a storage node relocation and replication mechanism, which can create, remove replicas of storage nodes and adjust the positions of storage nodes according to the location queries and updates. As such, the number of forwarding location update and query messages is reduced by the proposed storage node relocation and replication mechanism, thereby conserving more energy. The experimental results show that compared with EASE (Xu et al. (2008) [18]), ALM is able to reduce the number of transmission messages and the energy consumption of sensor network, and prolong the network lifetime. (C) 2010 Elsevier B.V. All rights reserved.
Efficient algorithms for team formation with a leader in social networks
(2013-11-01)
Juang, Ming-Chin
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Huang, Chen-Che
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Huang, Jiun-Long
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資訊工程學系
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Department of Computer Science
Given a project with a set of required skills, it is an important and challenging problem of find a team of experts that have not only the required skill set but also the minimal communication cost. Furthermore, in view of the benefits of greater leaders, prior work presented the team formation problem with a leader where the leader is responsible for coordinating and managing the project. To find the best leader and the corresponding team, the prior work exhaustively evaluates each candidate and the associated team, incurring substantial computational cost. In this paper, we propose two efficient algorithms, namely the BCPruning algorithm and the SSPruning algorithm, to accelerate the discovery of the best leader and the corresponding team by reducing the search space of team formation for candidates. The BCPruning algorithm aims at selecting better initial leader candidates to obtain lower communication cost, enabling effective candidate pruning. On the other hand, the SSPruning algorithm allows each leader candidate to have a lower bound on the communication cost, leading some candidates to be safely pruned without any computation. Besides, the SSPruning algorithm exploits the exchanged information among experts to aid initial candidate selection as well as team member search. For performance evaluation, we conduct experiments using a real dataset. The experimental results show that the proposed BCPruning and SSPruning algorithms are respectively 1.42-1.68 and 2.64-3.25 times faster than the prior work. Moreover, the results indicate that the proposed algorithms are more scalable than the prior work.
Energy-efficient and cost-effective web API invocations with transfer size reduction for mobile mashup applications
(2014-04-01)
Huang, Chen-Che
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Huang, Jiun-Long
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Tsai, Chin-Liang
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Wu, Guan-Zhong
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Chen, Chia-Min
Recently, the proliferation of smartphones and the extensive coverage of wireless networks have enabled numerous mobile users to access Web resources with smartphones. Mobile mashup applications are very attractive to smartphone users due to specialized services and user-friendly GUIs. However, to offer new services through the integration of Web resources via Web API invocations, mobile mashup applications suffer from high energy consumption and long response time. In this paper, we propose a proxy system and two techniques to reduce the size of data transfer, thereby enabling mobile mashup applications to achieve energy-efficient and cost-effective Web API invocations. Specifically, we design an API query language that allows mobile mashup applications to readily specify and obtain desired information by instructing a proxy to filter unnecessary information returned from Web API servers. We also devise an image multi-get module, which results in mobile mashup applications with smaller transfer sizes by combining multiple images and adjusting the quality, scale, or resolution of the images. With the proposed proxy and techniques, a mobile mashup application can rapidly retrieve Web resources via Web API invocations with lower energy consumption due to a smaller number of HTTP requests and responses as well as smaller response bodies. Experimental results show that the proposed proxy system and techniques significantly reduce transfer size, response time, and energy consumption of mobile mashup applications.
Hierarchical role-based data dissemination in wireless sensor networks
(2013-10-01)
Huang, Chen-Che
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Huang, Tsun-Tse
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Huang, Jiun-Long
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Yeh, Lo-Yao
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資訊工程學系
Data dissemination from multiple sources to mobile sinks is fundamental and challenging in WSN applications due to limited energy supply of sensor nodes and sink mobility. Previous data dissemination protocols either rely on an energy-consuming coordinate system or build an inefficient backbone. In this paper, we propose a hierarchical role-based data dissemination (HRDD) protocol in wireless sensor networks. In HRDD, a small number of sensor nodes are assigned to serve as cluster heads and agents to form the data dissemination backbone and mitigate unnecessary query forwarding. In addition, HRDD designs an efficient data delivery mechanism that provides shorter paths to accelerate data delivery as well as reduce the number of data transmissions. An adaptive backbone maintenance mechanism is also introduced for low-energy cluster heads and agents to reduce their load, thereby prolonging the network lifetime. The experimental results show that HRDD achieves the longer network lifetime, the shorter delay, and the high success ratio compared to the prior work.
On Simplifying Mobile Mashup Application Development
(2013)
Wu, Guan-Zhong
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Huang, Chen-Che
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Teng, Yui-Chey
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Huang, Jiun-Long
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Ting, Wei-Chih
In this paper, we propose a novel integrated API service system as well as a Web API script to enable mobile mashup application developers to invoke Web APIs in a consistent way, and provide a consistent format for the responses of Web APIs, thereby relieving developers of striving to study the usage of various Web APIs.
PipelineOR: A Pipelined Opportunistic Routing Protocol with Network Coding in Wireless Mesh Networks
(2010)
Lin, Yu-Jen
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Huang, Chen-Che
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Huang, Jiun-Long
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資訊工程學系
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Department of Computer Science
Traditional routing protocols in wireless mesh networks establish a single data path between a source and a destination. However, the performance suffers from degradation and instability due to variation of wireless links and interference. Opportunistic routing has been proposed to overcome the problem by exploiting the broadcast nature of wireless links and multiple forwarders. Current opportunistic routing protocols with network coding improve the system performance but suffer from redundant packet transmissions because a source stops transmitting packets in the same segment until it receives an ACK message from the destination. In this paper, we propose a pipelined opportunistic routing protocol with network coding (PipelineOR) in which segments are transmitted in a pipelined manner. A source is allowed to send packets in the next segment without waiting for the ACK message from the destination. In addition, we present two mechanisms, namely ETX-based mechanism and DCounter-based mechanism, to suppress forwarders to transmit redundant packets. The simulation results show that the proposed PipelineOR outperforms MORE [7] and CodeOR [8] in terms of transmission time.