Browsing by Author "Wang, Kuochen"

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A color-theory-based energy efficient routing algorithm for mobile wireless sensor networks
(2008-02-22)
Chang, Tai-Jung
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
Wireless sensor networks (WSNs) with nodes spreading in a target area have abilities of sensing, computing, and communication. Since the GPS device is expensive, we used a small number of fixed anchor nodes that are aware of their locations to help estimate the locations of sensor nodes in WSNs. To efficiently route sensed data to the destination (the server), identifying the location of each sensor node can be of great help. We adopted a range-free color-theory based dynamic localization (CDL) [Shen-Hai Shee, Kuochen Wang, I.L. Hsieh, Color-theory-based dynamic localization in mobile wireless sensor networks, in: Proceedings of Workshop on Wireless, Ad Hoc, Sensor Networks, August 2005] approach, to help identify the location of each sensor node. Since sensor nodes are battery-powered, we propose an efficient color-theory-based energy efficient routing (CEER) algorithm to prolong the life time of each sensor node. The uniqueness of our approach is that by comparing the associated RGB values among neighboring nodes, we can efficiently choose a better routing path with energy awareness. Besides, the CEER has no topology hole problem. Simulation results have shown that our CEER algorithm can save up to 50-60% energy than ESDSR [Mohammed Tarique, Kemal E. Tepe, Mohammad Naserian, Energy saving dynamic source routing for ad hoc wireless networks, in: Proceedings of Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, April 2005, pp. 305-310] in mobile wireless sensor networks. In addition, the latency per packet of CEER is 50% less than that of ESDSR. (c) 2007 Elsevier B.V. All rights reserved.
A dynamic MBS zone framework for cost-effective inter-MBS zone handover in WiMAX networks
(2016-04)
Lee, Lung-Sheng
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Wang, Kuochen
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Hsu, Yi-Huai
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資訊工程學系
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Department of Computer Science
To synchronize multicast broadcast service (MBS) zone data transmissions, the WiMAX standard defines a coordination mechanism to coordinate data transmissions over the WiMAX network; however, the packet loss recovery procedures, which are parts of the coordination mechanism, enlarge packet transmission latency and packet buffer pool requirement. Therefore, we propose an in-frame control (IFC) scheme to decrease packet error rate and packet retransmission count, so as to reduce the packet transmission latency and packet buffer pool requirement. To support level-2 frame-offset coordination, we also propose a dynamic MBS zone (DMZ) framework that can provide data continuity between any two adjacent MBS zones. Based on the proposed DMZ framework, a seamless dynamic inter-MBS zone handover (called DMZ HO) scheme is proposed to resolve the data discontinuity (or packet loss) problem during inter-MBS zone HO. Compared to the WiMAX standard scheme, the proposed IFC scheme reduces packet error rate and packet retransmission count by 49.8 and 49.73 %, respectively. The proposed DMZ HO scheme also outperforms an overlapping zones (OLZ) scheme in terms of channel occupation time and channel bandwidth consumption (in terms of channel idle ratio). Therefore, by resolving data discontinuity, the proposed DMZ HO scheme is more cost-effective and more feasible in providing smooth multimedia content delivery services without disruption to multiple mobile stations (MSs) during HO, and thus will enhance user experience.
A Fast and Load-aware Controller Failover Mechanism for Software-Defined Networks
(2016)
Fang, Ko-Chih
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Wang, Kuochen
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Wang, Jian-Hong
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資訊工程學系
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Department of Computer Science
We propose a Fast and Load-aware Controller Failover (FLCF) for software-defined networks to resolve the single point of failure problem. The FLCF utilizes one detecting controller to collect all the other controllers\' failure notifications about a failed controller so as to help the detecting controller to make the final decision. Each controller pre-computes its recovery plan and synchronizes the plan with other controllers that will take over the switches if the controller is determined failed. Using Estinet, experiment results show that the proposed FLCF has better performance in terms of failover time and controller load standard deviation than related works.
A Fast Converging Mechanism for Load Balancing among SDN Multiple Controllers
(2018-01-01)
Chen, Yan-Ting
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Li, Chi-Yu
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
Load balancing among multiple controllers is a critical issue in the software-defined networking (SDN), since traffic dynamics prevent control-plane loads from being evenly distributed among controllers. Load imbalance may cause some controllers to be overloaded while the other controllers are still underutilized. Though there have been several proposed solutions, they do not consider the convergence time of load balancing. We thus propose a fast-converging load balancing (FCLB) mechanism that seeks to achieve fast convergence for balancing loads (i.e., assigning switches) among the SDN controllers. Fast convergence can rapidly release controllers from being overloaded, thereby shortly recovering network performance and preventing some unanticipated results (e.g., controller crash). Searching for the optimal solution from a large set of switch-controller combinations can lead to a large delay, which can aggravate negative impacts from overloading. We thus leverage the genetic algorithm to find a near-optimal solution. Our simulation results show that FCLB has at least 20.7% faster convergence time than the other mechanisms while achieving better load balancing performance.
A fast failure detection and failover scheme for SIP high availability networks
(2007)
Wu, Wei-Ming
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Wang, Kuochen
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Jan, Rong-Hong
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Huang, Chia-Yuan
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資訊工程學系
The SIP proxy server, which is an important building block of a SIP network, can be in a form of a cluster to prevent service unavailability caused by software or hardware failures. The design of a SIP proxy server cluster with a single dispatcher in a SIP network faces the single-point-of-failure problem. The use of dual SIP dispatcher architecture was proposed and VRRP (Virtual Router Redundancy Protocol) was used as an JP failover mechanism. In this paper, we have designed and implemented a dependable SIP network that includes n + k SIP dispatchers (n active dispatchers + k backup dispatchers) to control and monitor a cluster of m SIP proxy servers for VoIP and video conferencing applications. A fast failure detection and failover (FFF) scheme has also been proposed. FFF uses OpenAIS as a high availability middleware to perform health check and failover of dispatchers and proxy servers. Experimental results have shown that the FFF scheme reduces the dispatcher failover time by 80% compared to the VRRP mechanism and also shorten the proxy failover time by 85% compared to the mechanism provided by OpenSER itself
A Fast Window-based Scalar Multiplication Algorithm for Elliptic Curve Cryptography in Wireless Sensor Networks
(2015-01-01)
Ye, Hung-Nan
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Wang, Kuochen
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Jan, Rong-Hong
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Hu, Yuh-Jyh
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Tseng, Yu-Chee
In this paper, we propose an enhanced window-based mutual opposite form (EW-MOF) for scalar multiplication with ECC in WSNs. The proposed EW-MOF combines MOF with an enhanced window method that can reduce not only pre-computation time and memory usage, but also average key generation time that includes pre-computation time in each sensor node. Our analysis has shown that the proposed EW-MOF requires a smaller number of essential pre-computed points than the one's complement. Therefore, it is very suitable for WSNs. Simulation results show that the proposed EW-MOF is 24.69% faster than the one's complement method, which is the best method available, in the average key generation time of ECC that includes pre-computation time under different field sizes. In summary, the proposed EW-MOF is more feasible than the one's complement for wireless sensor networks in terms of key generation time and power saving.
A fuzzy pattern-based filtering algorithm for botnet detection
(2011-10-27)
Wang, Kuochen
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Huang, Chun-Ying
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Lin, Shang-Jyh
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Lin, Ying-Dar
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資訊工程學系
Botnet has become a popular technique for deploying Internet crimes. Although signature-based bot detection techniques are accurate, they could be useless when bot variants are encountered. Therefore, behavior-based detection techniques become attractive due to their ability to detect bot variants and even unknown bots. In this paper, we propose a behavior-based botnet detection system based on fuzzy pattern recognition techniques. We intend to identify hot-relevant domain names and IP addresses by inspecting network traces. If domain names and IP addresses used by botnets can be identified, the information can be further used to prevent protected hosts from becoming one member of a botnet. To work with fuzzy pattern recognition techniques, we design several membership functions based on frequently observed bots' behavior including: (1) generate failed DNS queries; (2) have similar DNS query intervals; (3) generate failed network connections; and (4) have similar payload sizes for network connections. Membership functions can be easily altered, removed, or added to enhance the capability of the proposed system. In addition, to improve the overall system performance, we develop a traffic reduction algorithm to reduce the amount of network traffic required to be inspected by the proposed system. Performance evaluation results based on real traces show that the proposed system can reduce more than 70% input raw packet traces and achieve a high detection rate (about 95%) and a low false positive rates (0-3.08%). Furthermore, the proposed FPRF algorithm is resource-efficient and can identify inactive botnets to indicate potential vulnerable hosts. (C) 2011 Elsevier B.V. All rights reserved.
A Hierarchical Social Network-based P2P SIP System for Mobile Environments
(2010)
Li, Bo-Wei
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
P2P SIP (peer to peer session initiation protocol) systems have emerged as a new trend in multimedia realm due to their abilities to overcome the shortcomings of conventional SIP systems. Most of P2P SIP systems were implemented using Chord, a Distributed Hash Table (DHT) based routing algorithm which can provide scalability and reliability. Previous studies on P2P SIP systems did not address node heterogeneity, location information and mobility issues all together. For node heterogeneity, nodes with different capabilities (processing power, storage and bandwidth) should be treated suitably. For location information, the signaling latency is correlated with the distance between end users. This will influence call setup latency greatly. As to mobility, the node churn property will involve additional messages to maintain a stable DHT-based network and increases call setup latency. To conquer these problems, we propose a hierarchical social network-based P2P SIP system. The social network property can increase routing efficiency when calling friends. In addition, the proposed hybrid (structured/unstructured) overlay is more resilient to cope with node churn. Simulation results show that our approach can improve 32% call setup latency with non-buddies and reduce 63% maintenance cost in comparison with the conventional Chord-based approach. In addition, we improve lookup efficiency from O(logN) to O(1) when making calls with buddies, where N is the number of nodes in a DHT-based network.
A network assisted fast handover scbeme for IEEE 802.16e networks
(2007)
Lee, Lung-Sheng
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
The IEEE 802.16e provides QoS for real-time traffic; however, the packet transmission delay due to the handover process is still a big concern. Therefore, a fast handover approach to minimize the blocking time of real-time traffic is necessary for providing QoS. In this paper, we present a novel network architecture for IEEE 802.16e, which is still compatible to the IEEE 802.16e standard. Based on this architecture, a network assisted fast handover scheme (NFHO) is proposed to shorten the handover time. Performance evaluation has shown that our proposed NFHO scheme reduces the service disruption time by 98.2% and 96.8% compared to association levels 1 and 2 / Choi et al. of the IEEE 802.16e, respectively, for scanning just one base station (BS). Our improvements will be even better if scanning more BSs. In addition, the proposed NFHO scheme reduces the service disruption time by 78.4% with five neighbouring BSs scanning compared to Lee et al.
A power efficient MAC protocol for IEEE 802.11 multihop ad hoc networks
(2006)
Wu, Hung-Jui
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Wang, Kuochen
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Lee, Lung-Sheng
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資訊工程學系
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Department of Computer Science
In this paper, we propose a power efficient MAC protocol (PEMP) for IEEE 802.11 multihop ad hoc networks. Most of related work targeted at single hop ad hoc networks. In PEMP, when a node intends to transmit data, it will piggyback a data profile, which includes data size, on ATIM* and ATIM-ACK*. ATIM* and ATIM-ACK* are ATIM and ATIM-ACK with piggybacked data profiles, respectively. In this way, senders and receivers can inform their neighbor nodes of their data profiles. Then, each node calculates its transmission priority according to the collected data profiles. Based on transmission priorities, PEMP can schedule a better transmission sequence to reduce power consumption. By decreasing the idle time in the active state and adjusting the ATIM window dynamically based on network conditions, the power consumption of PEMP is 20% and 10% similar to 30% less than that of DPSM and IEEE 802.11 PSM, respectively. PEMP is applicable to multihop ad hoc networks and can achieve a good tradeoff between power consumption, throughput and delay.
A QoS-aware routing in SDN hybrid networks
(2017-01-01)
Lin, Chienhung
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Wang, Kuochen
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Deng, Guocin
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資訊工程學系
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Department of Computer Science
Changing the whole network into a software defined network (SDN) is impractical due to high replacement cost. Therefore, there exist SDN hybrid networks, where SDN switches and legacy switches coexist at the same time. In this paper, we propose an SDN hybrid network architecture which can discover existence of legacy switches by using the Spanning Tree Protocol and thus have a global view of the SDN hybrid network. We also enable OpenFlow switches to cooperate with legacy switches by using the Learning Bridge Protocol without requiring any modification on legacy switches. By utilizing the characteristics of SDN, SDN applications can dynamically find routing paths according to pre-defined QoS requirements and current network status. We also propose a simulated annealing based QoS-aware routing (SAQR) algorithm which can adaptively adjust weights of delay, loss rate and bandwidth requirements in a cost function to find the best fit path according to QoS requirements. We evaluate the proposed SAQR in a simulated SDN hybrid network which runs applications with different QoS requirements. Simulation results show that the SAQR performs better than related work MINA in terms of the fitness ratios of delay, loss rate and bandwidth, with 88%, 90.8% and 86.5% of flows meeting their respective QoS requirements, in contrast to MINA, with only 63%, 82.4% and 87.5% of flows meeting their respective QoS requirements. (C) 2017 The Authors. Published by Elsevier B.V.
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 Reliable Routing Scheme Based on Vehicle Moving Similarity for VANETs
(2011)
Wei, Min-Hsuan
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
In this paper, we propose a reliable routing scheme based on vehicle moving similarity (RR-VMS), which focuses on stable rebroadcast nodes selection and route discovery to make inter-vehicle data transmissions more reliable. We select nearby vehicles having similar velocities with the source vehicle as rebroadcast nodes. We call these vehicles having moving similarity with the source vehicle. To reflect vehicle moving similarity, a vehicle persistence score (VPS) is derived. A vehicle with a high VPS, chosen as a rebroadcast node, will stay long enough in an inter-vehicle transmission path. Moreover, to reduce the number of rebroadcast nodes, we define a donut-like selection area to choose relay nodes in order to reduce the route hop count and network traffic. Simulation results show that in large speed range scenarios, the proposed RR-VMS increases (reduces) 8.3% (16%) and 8.3% (15%) of the delivery ratio (number of broken links) compared to AODV and PAODV, respectively. In addition, RR-VMS also reduces 30% and 13% routing overhead compared to AODV and PAODV respectively. The proposed method is simple and feasible to other ad hoc routing protocols as well that involve broadcast.
A Road-based QoS-aware Multipath Routing for Urban Vehicular Ad Hoc Networks
(2012)
Hsieh, Yi-Ling
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
Stable and efficient routing plays a key role for the success of VANETs. Road-based routing has been shown well-suited for urban VANETs, and multipath routing provides alternative routes once the current route fails. However, existing multipath routing protocols are node-based, which are not suitable for urban VANETs. In this paper, we propose a road-based QoS-aware multipath routing protocol for urban VANETs (RMRV). The proposed RMRV can find multiple paths and intelligently utilize them. We also propose a space-time planar graph approach to predict the connectivity of each road section (RS) in a path, and then derive the path's future lifetime and life periods. In this way, the source node may dynamically switch to use a path with the longest lifetime. The life periods of a path can further be utilized to estimate the packet delay for QoS routing. Simulation results show that comparing to RBVT-R, which is a single-path road-based routing protocol, the packet delivery ratio of the proposed RMRV (only one path used at a time) is 12.2% higher than that of RBVT-R, and the average end-to-end delay of RMRV is 11.5% lower than that of RBVT-R, on average. To the best of our knowledge, there is no existing road-based multipath routing protocol for VANETs.
A Simulated Annealing-based Efficient Failover Mechanism for Hierarchical SDN Controllers
(2019-01-01)
Hsieh, Hsiao-Hu
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
The multi-controller architecture is a must to improve scalability and reliability of software defined networks (SDNs). A hierarchical multi-controller architecture allows a global controller to handle rare events, such as routing events from local controllers. A failover mechanism, which includes failure detection and recovery, is necessary for the multi-controller architecture in case of a controller failure. Existing controller failure detection and recovery mechanisms are performed in local controllers, which may degrade the performance of the local controllers. In controller failure recovery, existing mechanisms did not consider the time-varying load standard deviation metric, which may be used to reduce the flow setup time. To address these problems, we propose a Simulated Annealing-based Efficient Failover (SAEF) mechanism, run as an app in global controllers, to relieve the burden of local controllers for high availability hierarchical SDN controllers. The SAEF uses multiple global controllers to detect a local controller failure and compute a switch migration plan to redo switch-controller association for controller failure recovery. In controller failure detection, global controllers exchange their failure detection results of local controllers to jointly make a local controller failure decision to reduce the mistake rate. In controller failure recovery, the SAEF considers two metrics: switch-controller propagation delay and load standard deviation among local controllers with adaptive weights to adapt to time-varying local controllers' loads. In addition, in our design, a switch is connected to two local controllers so that asynchronous messages, such as packet-in and port-status messages, will not be lost during controller failover. Experiment results using EstiNet show that, the SAEF can achieve efficient failover with the best load balance result in term of load balance metric (LBM) of 1.035, while the best LBM of related works is 1.087. The SAEF also has the lowest flow setup time of 7.837 ms, while the best of related works is 10.418 ms. The lower flow setup time implies that the SDN data plane can receive the response message of a packet-in message faster.
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).
Adaptive Routing for Video Streaming with QoS Support over SDN Networks
(2015)
Yu, Tsung-Feng
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Wang, Kuochen
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Hsu, Yi-Huai
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資訊工程學系
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Department of Computer Science
In this paper, we propose an adaptive routing approach for video streaming with QoS (Quality of Service) support over Software Defined Networks (SDN), called ARVS. In our approach, base layer packets and enhancement layer packets of video bit streams are treated separately as two levels of QoS flows (level-1 and level-2 QoS flows). During video streaming, if the shortest path does not satisfy the delay variation constraint, the base layer packets have the first priority to be rerouted to a calculated feasible path based on the available bandwidth of this path, and the enhancement layer packets will stay on the shortest path. However, if there is no available bandwidth in this path, the base layer packets will stay on the shortest path while the enhancement layer packets will be rerouted to this path. In this way, the video quality would be enhanced due to the congestion of the shortest path has been mitigated. Simulation results have shown that, compared with OpenQoS, our approach can reduce up to 77.3% of the packet loss rate for the base layer packets of video bit streams and also enhance at least 51.4% coverage under various network loads of the shortest path and the feasible path.
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 Energy Saving Mechanism for LTE-A Self-Organizing HetNets
(2015)
Hsu, Yi-Huai
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
Since the information and communication technology industry is one of contributors to global warming, how to utilize self-organizing networks (SONs), which can simplify network management, to achieve energy saving over future cellular networks has been a significant issue. We propose an adaptive energy saving mechanism (AES) for LTE-A self-organizing heterogeneous networks (HetNets). The proposed AES is designed for multi-hop cellular networks, in which each cell has an enhanced Node B (eNB) and multiple relay nodes (RNs). The AES uses two-level multi-threshold load management for each RN under different eNBs (inter-cell level) and for each RN within the same eNB (intra-cell level) so as to reduce the congestion in hot spot eNBs and RNs. In addition, the AES can dynamically switch an RN between active and sleep modes to maximize the number of sleep RNs for adaptive energy saving. It can also dynamically change an RN\'s coverage area to reduce energy consumption and to increase radio resource utilization. Besides, the AES adopts a neural network predictor to forecast the loading of each RN to determine whether it is appropriate to switch an RN to sleep mode. Simulation results show that with slightly sacrificing average throughput (1.16% lower) and radio interface delay (1.4% higher), the proposed AES\'s percentage of sleep RNs is from 0.28 to 0.19 under the percentage of active UEs from 0.7 to 1. Comparing with a representative related work, reinforcement learning (RL), the proposed AES\'s average energy consumption is 26.44% lower than RL\'s.
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.