Browsing by Author "Jeng, Andy An-Kai"

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Adaptive Topology Control for Mobile Ad Hoc Networks
(2011-12-01)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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資訊工程學系
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Department of Computer Science
In MANETs, mobile devices are usually powered by batteries with limited energy supplies. Topology control is a promising approach, which conserves energy by either reducing transmission power for each node or preserving energy-efficient routes for the entire network. However, there is empirically a trade-off between the energy efficiency of the nodes and routes in a topology. Besides, it may consume considerable energy to maintain the topology due to node mobility. In this paper, we propose an adaptive topology control protocol for mobile nodes. The protocol allows each node to decide whether to support energy-efficient routing or conserve its own energy. Moreover, it can drastically shrink the broadcasting power of beacon messages for mobile nodes. We prove that any reconstruction and change of broadcasting radius converge in four and five beacon intervals, respectively. The experimental results show that our protocol can significantly reduce the total energy consumption for each successfully transmitted packet, and prolong the life times of nodes, especially in high mobility environments.
Adaptive Urban Traffic Signal Control System with Bus Priority
(2013-01-01)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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Chen, Chien
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Chang, Tzu-Lin
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資訊工程學系
In recent years, with the economic development and urbanization, traffic congestion has become a serious problem in urban environments. Traffic signal control plays a key role in Intelligent Transportation System (ITS). Particularly, bus system can carry a higher capacity of passengers, which help to relief traffic jam in cities. However, different from ordinary vehicles, bus system has several unique features, including higher capacity of passengers, fixed routes and specific requirements on arrival time and headway. In this paper, we propose an adaptive traffic signal control approach with bus Priority that determines the phase sequence and time in non-fixed order based on synergic information to improve the performance of bus system with a very small cost to ordinary vehicles. Simulation results show that our approach can significantly reduce the waiting time of buses, keep bus schedules on time, and regular bus headway.
An adaptive topology control scheme for energy-efficient routing in mobile ad hoc networks
(2007)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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資訊工程學系
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Department of Computer Science
In mobile ad hoc networks, nodes are usually powered by batteries with limited energy. To prolong the network life, the energy consumption of the routing task is crucial. In previous works, enormous topology control methods were given to support the energy-efficient routing, while the most of them are designed for static network. In this paper, we proposed a novel topology control scheme for mobile nodes. It is based on an adjustable structure, named the r-neighborhood graph. Simulation results show the proposed scheme can significantly improve the energy consumption especially in high mobility environment.
Distortion-based Video Streaming over Vehicular Ad Hoc Networks in Highway
(2014-01-01)
Chang, Je-Wei
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Sun, Kuan-Yu
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Chen, Chien
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Jeng, Andy An-Kai
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資訊工程學系
There are already many routing protocols tailored for Vehicular Ad Hoc Networks (VANET). However, few of them are suitable for real-time video streaming delivery. The network partition nature and dynamic changing network topology of VANET make it hard for existing protocols to satisfy the stringent delay requirements of video streaming or other multimedia applications. To address this issue, this study first develops a rate distortion model based on a shadowing model and 802.11 DCF with RTS/CTS scheme over a highway road segment. Based on the proposed rate distortion model and traffic statistic information (vehicle density over a road), we can decide the best next-hop forwarding distance. Since a vehicle may not have a neighbor vehicle at the best forwarding distance, this study proposes a cell based packet forwarding scheme based on the derived best forwarding distance to prioritize the neighboring vehicles of a sender We set up the simulations using NS2 to validate the performance of the proposed protocol. The results show that the proposed protocol can yield a 30% PSNR improvement.
Efficient Broadcast Mechanism for Cooperative Collision Avoidance Using Power Control
(2009)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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Chen, Chien
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Chiang, Tsun-Chieh
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資訊工程學系
Improving driver's safety has been an active research area in wireless communication. In particular, the vehicle cooperative collision avoidance (CCA) is one of the most important issues in safety applications. A variety of broadcast protocols has been proposed for vehicular network. However, there is only a few of them dedicatedly designed for the CCA system. In this paper, we propose a novel broadcast mechanism for CCA using the power control technique. The power control rule is based on the safe distance between vehicles. Simulation results show that our approach can significantly reduce the delivery delay and avoid car collision.
iPCA: an integration information system for patient controlled analgesia using wireless techniques
(2013)
Yang, Shu-Fen
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Ku, Tien-Hsiung
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Jeng, Andy An-Kai
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Jan, Rong-Hong
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Tseng, Yu-Chee
Recently, pain management has become an important aspect of medical care. Patient Controlled Analgesia (PCA) is a particularly effective and flexible treatment that allows patients to adjust the dosages of the analgesics that control their pain after surgery. However, PCA requires manual operation for sustained attention, and should be analysed with other pathology information for synergic usage. In this paper, we propose an integrated information system for pain management, called Integrated Patient Controlled Analgesia (iPCA). The system integrates various PCA-related devices by wireless techniques to provide real-time information for medial staffs, and offer more efficient and convenient pain control for both in-hospital and at-home patients. To evaluate our system, we have developed a prototype and conducted a series of field trails at a large private hospital in southern Taiwan. The results show that the iPCA system indeed works well with patients, and can provide better post-operative pain control by efficiently collecting PCA usage information.
Optimization on Hybrid Channel Assignment for Multi-channel Multi-radio Wireless Mesh Networks
(2006)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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資訊工程學系
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Department of Computer Science
The emergence of multi-channel multi-radio wireless mesh networks has given us many new opportunities and challenges. Particularly, the issue on how to appropriately assign channels to interfaces has gathered great importance in the recent publications. To efficiently utilize the channels diversity, the communicating channels should be negotiated between interfaces, which would cause considerable overhead. To conquer this, a hybrid scheme was proposed to rule the way for assigning channels in literatures. In this paper, we formally model the hybrid scheme into an integer linear programming formulation. We provide the necessary as well as sufficient conditions of any feasible assignment. To optimize the link-layer performance, we suggest an objective function which minimizes the total potential interference. We also show that the approximability of the considered problem.
Release-time-based multi-channel MAC protocol for wireless mesh networks
(2011-06-23)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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Li, Chi-Yu
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Chen, Chien
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資訊工程學系
The wireless mesh network (WMN) has been considered one of the most promising techniques for extending broadband access to the last mile. In order to utilize multiple channels to increase the throughput in WMNs, a variety of multi-channel MAC (MMAC) protocols have been proposed in the literature. In particular, the dedicated control channel (DCC) approach can greatly simply many design issues in multi-channel environments by using a common control channel to exchange control signals. On the other hand, it allows each sender-receiver pair to dynamically select a data channel for their data transmission in an on-demand matter. However, the common control channel would become a bottleneck of the overall performance. Besides, the selection of data channels would be highly related to the final throughput. In this paper, we propose a new MMAC protocol, named the release-time-based MMAC (RTBM) to overcome the control channel bottleneck and data channel selection problems in the DCC approach. The RTBM consists of three major components: (1) Control initiation-time predication (CIP); (2) Dynamic data-flow control (DDC); (3) Enhanced channel selection (ECS). The CIP can predict a proper initiation time for each control process to reduce control overhead. The DDC can dynamically adjust the flow of each data transmission to fully exploit the channel bandwidth. The ECS can achieve a higher reusability of data channels to further enhance the throughput. Simulation results show that the RTBM can substantially improve the throughput in both single-hop and multihop networks. (C) 2011 Elsevier B.V. All rights reserved.
Role and channel assignments for wireless mesh networks using hybrid approach
(2009-08-13)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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資訊工程學系
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Department of Computer Science
The wireless mesh network has been considered one of the most promising techniques to extend the broadband access to the last mile. To utilize multiple channels on more than one interface, a number of approaches have been proposed. In particular, the hybrid strategy that combines the benefits of high channel diversity and low coordination cost has seen growing interest in recent studies. In this paper, we define two optimization problems, named the role assignment and the semi-fixed channel assignment, to characterize the unique feature in the hybrid strategy. We proved that the two problems are NP-hard even if the transmission ranges of interfaces are equal. In order to solve our problems in reasonable time, we design efficient algorithms. For the role assignment problem, we give an 1/2-approximate algorithm to find a nearly optimal solution. For the semi-fixed channel assignment problem, a heuristic algorithm, based on transferring from a coloring-based problem, is proposed. Experimental results show that optimizing the defined problems is indeed beneficial to improve the network throughput, and the proposed algorithms are significantly superior to existing methods. (C) 2009 Elsevier B.V. All rights reserved.
The r-neighborhood graph: An adjustable structure for topology control in wireless ad hoc networks
(2007-04-01)
Jeng, Andy An-Kai
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Jan, Rong-Hong
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資訊工程學系
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Department of Computer Science
In wireless ad hoc networks, constructing and maintaining a topology with lower node degrees is usually intended to mitigate excessive traffic load on wireless nodes. However, keeping lower node degrees often prevents nodes from choosing better routes that consume less energy. Therefore, the trade-off is between the node degree and the energy efficiency. In this paper, an adjustable structure, named the r-neighborhood graph, is proposed to control the topology. This structure has the flexibility to be adjusted between the two objectives through a parameter r, 0 <= r <= 1. More explicitly, for any set of n nodes, the maximum node degree and power stretch factor can be bounded from above by some decreasing and increasing functions of r, respectively. Specifically, the bounds can be constants in some ranges of r. Even more, the r-neighborhood graph is a general structure of both RNG and GG, two well-known structures in topology control. Compared with YGk, another famous adjustable structure, our method always results in a connected planar with symmetric edges. To construct this structure, we investigate a localized algorithm, named PLA, which consumes less transmitting power during construction and executes efficiently in O(n log n) time.