Browsing by Author "Shih, Hung-Cheng"

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A QoS-Guaranteed Energy-Efficient Packet Scheduling Algorithm for WiMax Mobile Devices
(2010)
Shih, Hung-Cheng
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
A mobile device may run energy consuming multimedia applications, such as video streaming. Thus, power management is an important issue in mobile devices. In this paper, we propose a QoS-guaranteed energy-efficient packet scheduling algorithm for IEEE 802.16-2009 (WiMax) network interfaces. The integration of packet scheduling and sleep mode operation can make IEEE 802.16-2009-enabled mobile devices more energy efficient. Simulation results show that the proposed packet scheduling algorithm has 14.37% less energy consumption than the naive algorithm, and it does not sacrifice average packet delay. The contributions of our proposed algorithm are that our algorithm is suitable for wireless environments where connections come and go rapidly and the time complexity of our algorithm is low.
A WAP-based, push-enabled mobile Internet application platform
(2006-09-01)
Chen, Hsuan-Hao
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Wang, Kuochen
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Shih, Hung-Cheng
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資訊工程學系
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Department of Computer Science
We propose a WAP-based, Push-enabled mobile Internet application platform, called MAP, to provide extensive services for users in the mobile environment. The goal of this platform is to provide a flexible, scalable and rapid-service-creation environment for mobile Internet applications to operate in. MAP has four main components, which have been designed and implemented: (1) a WAP micro-browser for mobile devices, (2) a WAP simulator for desktops or notebooks, (3) a WAP Push proxy gateway, the MBL Gateway, and (4) a distributed mobile agents server, Wagent. This platform enables mobile clients to access legacy information systems, Intranets and WWW services conveniently. It applies the advantages of the mobile agent paradigm and WAP Push technologies to extend Internet services to wireless environments. It also makes it possible to push critical information, such as news and stock prices, to mobile users in real time. We have also evaluated the performance of the MBL Gateway, which is a key component of the platform, using a realistic traffic model. Experiment results show that the MBL Gateway is more efficient than the other two notable open source WAP gateways in terms of average response time. The MBL Gateway reduces the average response time by up to 25% and 87% compared to the Standalone Kannel Gateway and Original Kannel Gateway, respectively, under the highest load (270 requests/sec when the session a rival rate lambda = 0.015).
An adaptive bluetooth packet selection and scheduling scheme in interference environments
(2006-07-26)
Shih, Chen-Han
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Wang, Kuochen
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Shih, Hung-Cheng
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資訊工程學系
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Department of Computer Science
Bluetooth is a new technology for Wireless Personal Area Networks (WPANs). It intends to eliminate the need of wires and connectors between a variety of devices, like PCs and their peripherals, walkmans and their earphones, etc. Bluetooth provides robust and secure wireless radio communication of both data and voice, even when the devices are not within line-of-sight. Bluetooth employs the 2.4 GHz ISM band, sharing the same band with the Wireless LAN (WLAN) implementing the IEEE 802.11 series standard. While WLANs and WPANs are complementary rather than competing technologies, the likelihood of mutual interference may occur unexpectedly, which may impact the performance of either severely. In this paper, we propose a Bluetooth channel state dependent data segmentation and reassembly (CSD-SAR) scheme and a queue state dependent priority (QSD-PR) scheduling policy. The CSD-SAR maintains a receiving frequency table to predict channel conditions and selects the best packet type and packet size to transmit data. In this way, it not only masks bad frequencies without delaying transmission but also leads to the best performance with high link utilization in error-prone environments. In addition, the QSD-PR also uses the receiving frequency table to avoid bad frequencies and gives a selected master-slave pair, which has more queued data to send between each other, a higher priority to eliminate the wastage of slots. The conventional scheduling policy, Round Robin (RR), yields poor performance with the time division duplex based MAC protocol and results in slot wastage and may not ensure fairness. Simulation results show that our proposed scheme achieves better link utilization and higher throughput with bounded delay compared to the RR scheme in error-free and error-prone environments. Our scheme can also eliminate interference to other wireless networks that share the same spectrum, such as WLANs, by avoiding selecting channels occupied by other networks. (c) 2006 Elsevier B.V. All rights reserved.
An adaptive hybrid dynamic power management algorithm for mobile devices
(2012-02-02)
Shih, Hung-Cheng
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
We propose a novel power efficient adaptive hybrid dynamic power management (AH-DPM) algorithm. To adapt well to bursty request arrival patterns with self-similarity and a service provider (SP, i.e., hard disk or WLAN NIC, in this paper) with multiple inactive states, the proposed AH-DPM first derives the average idle time of the SP in the bursty (ON) period and non-bursty (OFF) period separately. Then, to achieve better power saving, we use the average idle time in the ON period to adjust the timeout value more precisely and use the average idle time in the OFF period to decide which inactive state the SP should be switched to. Experimental results based on real traces show that, for the hard disk, the average power consumption of the proposed AH-DPM is better than that of the Adaptive Timeout (ATO), Machine Learning (ML), Predictive, Static Timeout (STO), and Stochastic algorithms. In addition, the average response time of the proposed AH-DPM algorithm is still lower than that specified in a typical hard disk specification. As to the WLAN NIC, experimental results show that the average power consumption of the proposed AH-DPM is comparable to that of the Oracle (theoretically optimal), ATO, and Predictive algorithms, and is better than that of the ML, STO, and Stochastic algorithms. However, the average packet transmission delay of the proposed AH-DPM is better than that of the ATO and Predictive algorithms. Therefore, by providing a better tradeoff between average power consumption and average response time (or average packet transmission delay), the proposed AH-DPM algorithm is very feasible for extending the battery lifetime of ever increasing mobile devices that are equipped with hard disks and WLAN NICs. (C) 2011 Elsevier B.V. All rights reserved.
Enhanced fair scheduling for IEEE 802.11e wireless LANs
(2007-11-01)
Tseng, Kun-Nan
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Wang, Kuochen
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Shih, Hung-Cheng
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資訊工程學系
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Department of Computer Science
As wireless LANs are gaining popularity, the demand for supporting multimedia and QoS-sensitive applications becomes more important than before. Although enhancements to the legacy IEEE 802.11 MAC to support QoS mechanisms have been proposed, they suffer from unfair allocation of bandwidth between high and low priority traffic. We propose a distributed enhanced fair scheduling (EFS) scheme that can conquer the above problem. With a fast backoff mechanism in the backoff timer decrement state and by dynamically adjusting backoff intervals according to the network load, we can enhance the performance of the EFS. We have evaluated the performance of the EFS through simulation. Experimental results show that the proposed EFS has better throughput performance than DFS by 13%, lower average MAC delay than DFS by 6% and the two have nearly equal fairness. Although the enhanced distributed channel access (EDCA) in IEEE 802.11 e has better throughput and delay performance than EFS and DFS, it has very poor fairness. The contention free burst (CFB) mechanism in EDCA is the main factor that results in good throughput performance, lower average MAC delay and poor fairness. Our EFS is very suitable for applications that need strict fair bandwidth allocation, such as pay services.