Browsing by Author "Shen, Chien-Chung"

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A lightweight, self-adaptive lock gate designation scheme for data collection in long-thin wireless sensor networks
(2013-01-01)
Wang, You-Chiun
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Chuang, Che-Hsi
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Tseng, Yu-Chee
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Shen, Chien-Chung
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資訊工程學系
Constrained by the physical environments, the long-thin topology has recently been promoted for many practical deployments of wireless sensor networks (WSNs). In general, a long-thin topology is composed of a number of long branches of sensor nodes, where along a branch each sensor node has only one potential parent node toward the sink node. Although data aggregation may alleviate excessive packet contention, the maximum payload size of a packet and the dynamically changing traffic loads may severely affect the amount of sensor readings that may be collected along a long branch of sensor nodes. In addition, many practical applications of long-thin WSNs demand the exact sensor readings at each location along the deployment areas for monitoring and analysis purposes, so sensor readings may not be aggregated when they are collected. This paper proposes a lightweight, self-adaptive scheme that designates multiple collection nodes, termed lock gates, along a long-thin network to collect sensor readings sent from their respective upstream sensor nodes. The self-adaptive lock gate designation scheme balances between the responsiveness and the congestion of data collection while mitigating the funneling effect. The scheme also dynamically adapts the designation of lock gates to accommodate the time-varying sensor reading generation rates of different sensor nodes. A testbed of 100 Jennic sensor nodes is developed to demonstrate the effectiveness of the proposed lock gate designation scheme. Copyright (c) 2011 John Wiley & Sons, Ltd.
Range-Free Mobile Actor Relocation in a Two-Tiered Wireless Sensor and Actor Network
(2016-05)
Wu, Fang-Jing
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Hsu, Hsiu-Chi
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Shen, Chien-Chung
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Tseng, Yu-Chee
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資訊工程學系
Two-tiered wireless sensor and actor networks (WSANs) have been proposed to enhance network capabilities, where a set of resource-rich mobile nodes (termed actors) form a connected backbone to relay sensing data from static sensors to the sink and sometimes are requested by sensors to perform a particular action. Such a two-tiered WSAN facilitates scalability and can efficiently reduce the energy consumption incurred by conventional hop-by-hop relaying via only sensors. However, relocating actors to achieve both connectivity and load balance is a challenge, especially when there is no location information of the nodes. Connectivity ensures that the actors are connected, whereas load balance ensures that actors collect and originate a similar amount of sensory data from the sensors. In this article, we formulate the Connected and Balanced Mobile Actor Relocation (CBMAR) optimization problem to address both connectivity and load balance and prove that the problem is NP-hard. We thus propose a dual-mode distributed actor relocation protocol that does not rely on any location information of nodes to relocate actors. The idea is to locally form virtual Voronoi cells of actors (termed covering cells) based on the lower-tiered topology, where each actor locally recruits its own sensor members to form its own covering cell. By maintaining the covering cell, each actor locally relocates itself toward a sensor along the lower-tiered topology. Extensive simulation results show that the protocol can achieve both objectives of connectivity and load balance with low moving and communication overheads.
Shortest Path Routing with Reliability Requirement in Delay Tolerant Networks
(2009)
Lian, Huai-En
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Chen, Chien
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Chang, Je-Wei
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Shen, Chien-Chung
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Jan, Rong-Hong
The topology of a delay tolerant network (DTN) over time has been modeled by a space-time graph. However, the mobility of nodes, such as buses, may not be completely predictable due to factors such as traffic load, road condition, the number of passengers getting on and off the buses, and the operations of traffic lights. In this paper, we adapt the space-time graph by augmenting each horizontal edge with a direct contact probability to model the uncertainty of connectivity. With such an augmented space-time graph, our goal is to compute a shortest routing path satisfying a given end-to-end delivery reliability in a DTN. To facilitate such computation, we adapt the Floyd-Warshall algorithm to compute the maximum contact probability matrix at each time interval. By using an iterative matrix multiplication scheme on a maximum contact matrix, we can compute the shortest path satisfying the reliability constraint. Simulation results validate the performance of our solution which achieves a good balance between delay and reliability.
Special Issue on Vehicular Wireless Networks and Vehicular Intelligent Transportation Systems Foreword
(2010-05-01)
Chang, Chih-Yung
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Shen, Chien-Chung
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Shen, Xuemin (Sherman)
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Tseng, Yu-Chee
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資訊工程學系