Browsing by Author "Lee, YF"

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A configurable Java architecture for mobile terminal software download
(2002)
Lee, YF
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Juang, FS
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Chang, RC
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資訊工程學系
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Department of Computer Science
The objective of software radio is reconfigurability -the ability to dynamically configure software and hardware functionalities of mobile terminals. To achieve this, the concept of software download is emerging. With software download, a mobile terminal can be reconfigured using downloadable modules instead of saving all the software in its non-volatile memory. This paper presents the design of a configurable Java architecture. With this architecture, we may dynamically build secure and flexible execution environments for different software requirements. The implementation of the configurable Java virtual architecture is based on K virtual machine (KVM) and the constructed execution environment supports user application, man-machine interface (MMI), and protocol stack reconfigurability.
Developing dynamic-reconfigurable communication protocol stacks using Java
(2005-05-01)
Lee, YF
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
This paper proposes the development of a dynamic-reconfigurable protocol stack, which allows the programmer to create, to remove, and to replace protocol modules during their operation. Moreover, this protocol stack also aims to preserve the module state, such as the data structures that manage the existing connections. To achieve these goals, a Java-based component framework is developed so that the programmers are able to implement their components under the proposed framework. This framework can dynamically reconfigure the components at a safe period and can help the components transfer their states, and the dynamic reconfiguration is transparent to the user application running on top of the stack. To demonstrate the component framework, a TCP component is implemented. While maintaining active connections for the user application, the TCP component is able to be dynamically replaced by another version. Copyright © 2005 John Wiley & Sons, Ltd.
Hotswapping Linux kernel modules
(2006-02-01)
Lee, YF
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Chang, RC
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資訊工程學系
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Department of Computer Science
Contemporary operating system kernels are able to improve their functionality by installing kernel extensions at runtime. However, when an existing kernel extension needs to be upgraded, it must be completely removed before the new kernel extension is installed. Consequently, the new kernel extension needs to be run from the beginning, which also influences the applications using this kernel extension. This work describes the design and implementation of a Linux module system that supports hotswapping, in which a module can be replaced while it is in use. Rather than completely removing the old module, the new module can inherit the state held by the old module so the dependent applications are not affected. For example, a Linux file system module can be hotswapped without unmounting the corresponding partitions and terminating the applications that use these partitions. The proposed system is implemented on Linux kernel 2.6.11. Existing modules can be loaded into the hotswap system without change and can be hotswapped by changing only a few lines. Additionally, the hotswap system does not impose any runtime overhead on module invocations. (C) 2005 Elsevier Inc. All rights reserved.
Improving the accuracy of cell-based positioning for wireless networks
(2004-12-20)
Jan, RH
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Chu, HC
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Lee, YF
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資訊工程學系
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Department of Computer Science
One fundamental issue for location-based services and applications is solving the location-sensing problem, i.e., determining where a given node is physically located in a network. In a previous paper, we have presented a location-sensing method, called the cell-based positioning method, and its positioning accuracy for the wireless networks with a hexagonal structure and mesh structure. Unfortunately, in real situations, a wireless network may not have a hexagonal or mesh structure. Thus, in this paper we consider networks with irregular structures and present an algorithm to determine the positioning accuracy of the cell-based method in such networks. In addition, we use the simulated annealing (SA) method to determine the locations and transmission ranges of base stations in order to achieve the best possible positioning accuracy. Simulation results show that the accuracy can be improved up to 30% by the SA method. The results are useful for deploying a wireless network for location-based applications. (C) 2004 Elsevier B.V. All rights reserved.
Java-based component framework for dynamic reconfiguration
(2005-06-01)
Lee, YF
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Updating software via the Internet is becoming a necessary feature of contemporary software. However, most software updating processes need to restart the programs or systems after the new software modules are installed. Dynamic reconfiguration is a technique that can deploy new software modules without restarting. This is usually achieved by modifying programming language syntax, language runtime systems or the code that is compiled. In the paper, a Java-based component framework is proposed to support dynamic reconfiguration, which does not need to modify the Java language, the Java virtual machine or the Java bytceode. The component framework has two implementations. The first one is based on the Java language itself; it is slower but can be used on almost every Java virtual machine. The second one is based on both the Java code and native programming interfaces provided by the Java virtual machine; it is much more efficient but is platform-dependent. The component framework is able to replace a single component as well as multiple components. In addition, several kinds of component change are permitted, including data members and component interfaces. To demonstrate the use of the component framework, a dynamically reconfigurable TCP is implemented.