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Modified EDCF to Improve the Performance of IEEE 802.11 e Contention-based Channel Access
Wen-Yen Lin,Jung-Shyr Wu 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
In this paper we propose a modified EDCF scheme, M-EDCF, to improve the Quality of Service (QoS) of the IEEE 802.11e wireless network. The IEEE 802.11e standard is presented to support QoS at medium access control level using a priority scheme by differentiating the inter-frame space and the initial window size. In addition to providing relative priorities by adjusting the size of the Contention Window (CW) of each traffic class, our proposed scheme, M-EDCF, also consider the effect of a back_off_timer to avoid unnecessary collisions. Our study shows that in either in heavy or light traffic load our proposed scheme can provide better quality for both high priority and low priority packets than either the AEDCF [1][14].
Design of a De-ringing Filter for Wavelet-based Compressed Image
Yen-Yu Chen,Ying-Wen Chang,Wen-Chien Yen 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
JPEG2000 Standard is a new generation image compression technique, enabling encoding images at low bitrates with acceptable quality. Since JPEG2000 is based on wavelet transforms, the reconstructed image will contain perceivable ringing artifacts in medium and low bit-rate regimes of lossy compression. This work utilizes a quad-tree partitioning scheme for post-processing the reconstructed image in a spatially varying manner and presents a voting strategy to determine a set of morphological filters to be used for reducing the ringing artifacts. Simulation results demonstrate that the proposed technique enhances reconstructed image quality compared to unprocessed JPEG2000 output at an equivalent bit-rate accounting for the side-information overhead, in terms of both Peak Signal-to-Noise Ratio (PSNR) and Visible Ringing Measure (VRM).
DCT-based Image Compression with Efficient Enhancement Filter
Wen-Chien Yen,Yen-Yu Chen 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
This work adopts DCT and modifies the SPIHT algorithm to encode DCT coefficients. The algorithm represents the DCT coefficients to concentrate signal energy and proposes combination and dictator to eliminate the correlation in the same level subband for encoding the DCTbased images. The proposed algorithm also provides the enhancement function in low bit rate in order to improve the perceptual quality. This work contribution is that the coding complexity of the proposed algorithm for DCT coefficients is just close to JPEG but the performance is higher than JPEG2000. Experimental results indicate that the proposed technique improves the quality of the reconstructed image in terms of both PSNR and the perceptual results close to JPEG2000 at the same bit rate.
Study of Data Placement Schemes for SNS Services in Cloud Environment
( Yen-wen Chen ),( Meng-hsien Lin ),( Min-yan Wu ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.8
Due to the high growth of SNS population, service scalability is one of the critical issues to be addressed. The cloud environment provides the flexible computing and storage resources for services deployment, which fits the characteristics of scalable SNS deployment. However, if the SNS related information is not properly placed, it will cause unbalance load and heavy transmission cost on the storage virtual machine (VM) and cloud data center (CDC) network. In this paper, we characterize the SNS into a graph model based on the users` associations and interest correlations. The node weight represents the degree of associations, which can be indexed by the number of friends or data sources, and the link weight denotes the correlation between users/data sources. Then, based on the SNS graph, the two-step algorithm is proposed in this paper to determine the placement of SNS related data among VMs. Two k-means based clustering schemes are proposed to allocate social data in proper VM and physical servers for pre-configured VM and dynamic VM environment, respectively. The experimental example was conducted and to illustrate and compare the performance of the proposed schemes.
Shared Protection of Lightpath with Guaranteed Switching Time over DWDM Networks
Chen Yen-Wen,Peng I-Hsuan The Korea Institute of Information and Commucation 2006 Journal of communications and networks Vol.8 No.2
Survivability is a very important requirement for the deployment of broadband networks because out of service links can affect volumes of traffic even if it is a very short time. And the data paths of broadband networks, which are critical for traffic engineering, are always necessary to be well protected. The procedure of protection or restoration for a path is initiated when failure is detected within the working path. In order to minimize the influence on transmission quality caused by the failure of links and to provide a definite time for the recovery from the failure, the protection switching time (PST) should be carefully considered in the path arrangement. Several researches have been devoted to construct the protection and restoration schemes of data paths over dense wavelength division multiplexing (DWDM) networks, however, there was rare research on the design of data paths with guaranteed protection switching time. In this paper, the PST-guaranteed scheme, which is based on the concept of short leap shared protection (SLSP), for the arrangement of data paths in DWDM networks is proposed. The proposed scheme provides an efficient procedure to determine a just-enough PST-guaranteed backup paths for a working path. In addition to selecting the PST-guaranteed path, the network cost is also considered in a heuristic manner. The experimental results demonstrate that the paths arranged by the proposed scheme can fully meet the desired PST and the required cost of the selected path is competitive with which of the shared path scheme.
Arm Exoskeleton Rehabilitation Robot with Assistive System for Patient after Stroke
Guan De Lee,Wei-Wen Wang,Kai-Wen Lee,Sheng-Yen Lin,Li-Chen Fu,Jin-Shin Lai,Wen-Shiang Chen,Jer-Junn Luh 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
Exercise dosage is proven to be an important factor in the physical treatment. Robot assistive approach can improve the rehabilitation quality and evaluate patient’s recovery quantitatively. This paper presents kinematic structure, assistive control system, and integrated F/T sensor for an upper limb rehabilitation robot. By using the human arm dynamic, there are three rehabilitation modes presented in this paper: active mode, assistive mode, and passive mode. In assistive mode, we have two strategies to implement it. One is to amplify interactive torque, and the other is to apply assist-as-needed concept. The goal of this mode is to assist patients to finish motion tasks. The rehabilitation robot under investigation has 7 degree of freedom (DOF) actuated by DC motors, which are programmed to drive the robot arm in the 3D space. To validate our control design, some realistic experiments are conducted and its satisfactory performance is demonstrated. This work is approved clinical testing by the Department of Health, Executive Yuan, R.O.C. So far, we are demonstrating the effect of our controller.