• Journal of Korea Multimedia Society
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• v.6 no.7
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• pp.1200-1208
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• 2003

Java Card technology allows us to run Java applications on smart cards and other memory-constrained devices. Java Card technology supports high security, portability and ability of storing and managing multiple applications. However, constrained memory resources of the Java Card Platform hinder wide deployment of the Java Card applications. Therefore, in this paper we propose a bytecode optimization algorithm to use the memory of a Java Card efficiently. Our algorithm can reduce the size of the bytecode by sharing the memory of the parameters of the catch clause in the try-catch-finally sentence.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.729-732
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• 2003

Security and privacy issues complicate wireless local area network deployment. for a wired network, certain levels of security are maintained since access to the physical medium is restricted to the devices physically connected to the network. Though wireless local area networks offer some built-in security features, security breaches are possible if appropriate precautions are not taken. This paper describes security issues related to wireless local area networks and presents a software approach for restricting and controlling wireless access. The system authenticates users on the basis of identity, privileges and access hardware by distributed software agents that implement security policy and restrict unauthorized access.

• Journal of information and communication convergence engineering
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• v.10 no.4
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• pp.359-364
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• 2012

Harvesting energy from the environment is essential for many applications to slow down the deterioration of energy of the devices in sensor networks and in general, the network itself. Energy from the environment is an inexhaustible supply which, if properly managed and harvested from the sources, can allow the system to last for a longer period - more than the expected lifetime at the time of deployment, or even last indefinitely. The goal of this study is to develop a simple algorithm for ns-2 to simulate energy harvesting in wireless sensor network simulations. The algorithm is implemented in the energy module of the simulator. Energy harvesting algorithms have not yet been developed for ns-2. This study will greatly contribute to the existing knowledge of simulating wireless sensor networks with energy harvesting capabilities in ns-2. This paper will also serve as a basis for future research papers that make use of energy harvesting.

• Journal of Multimedia Information System
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• v.1 no.1
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• pp.23-43
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• 2014

With the rapidity of the development on electronic technology, various mobile devices are produced to make human life more convenient. The user is always in constant search of middle with ease of deployment. Therefore, the development of infrastructure and application with ubiquitous nature gets a growing keen interest. Recently, the number of pervasive network services is expanding into ubiquitous computing environment. To get desired services, user presents personal details about this identity, location and private information. The information transmitted and the services provided in pervasive computing environments (PCEs) are exposed to eavesdropping and various attacks. Therefore, the need to protect this environment from illegal accesses has become extremely urgent. In this paper, we propose an anonymous authentication and access control scheme to secure the interaction between mobile users and services in PCEs. The proposed scheme integrates a biometric authentication in PKI model. The proposed authentication aims to secure access remote in PCE for guaranteeing reliability and availability. Our authentication concept can offer pervasive network service users convenience and security.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.855-857
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• 2007

In recent years, Wireless Mesh Network (WMN) is a compelling topic to many network researchers due to its low cost in deployment, ease and simplicity in installation and scalability and robustness in operation. In WMN, Gateway nodes (Access Point-AP) are in charge of steering the traffic from the external network (e.g. Internet...) to client devices or mesh clients. The limited bandwidth of wireless links between Gateways and intermediate mesh routers makes the Gateways becomes the bottleneck of the mesh network in both uplink stream and downlink stream. In this paper, we propose a mechanism to permit Gateways collaboratively work to manipulate the traffic to fit our network. They will move the traffic from congested links to the unused capacity on other links.

• International Journal of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.26-38
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• 2016

Recently, mobile traffic has increased tremendously due to the deployment of smart devices such as smartphones and smart tablets. Android is the world's most powerful mobile platform in smartphone. The Android operating system provide seamless access to many applications and access to the Internet. It would involve network packet sharing communicated over the network. Network packet contains a lot of useful information about network activity that can be used as a description of the general network behaviours. To study what is the behaviours of the network packet, an effective tools such as network packet analyzers software used by network administrators to capture and analyze the network information. In this research, more understanding about network information in live network packet captured from Android smartphone is the target and identify the best network analyzer software.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.256-259
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• 2013

Data and network security for e-Healthcare Systems are a primary concern due to the easiest deployment area accessibility of the sensor devices. Furthermore, they are often interacting closely in cooperation with the physical environment and the surrounding people, where such exposure increases security vulnerabilities in cases of improperly managed security of the information sharing among different healthcare organizations. Hence, healthcare-specific security standards such as authentication, data integrity, system security and internet security are used to ensure security and privacy of patients' information. This paper discusses security threats on e-Healthcare Systems where an attacker can access both data and network using masquerade attack. Moreover, an efficient and cost effective approach for countermeasures is discussed for the delivery of secure services.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2453-2467
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• 2017

Wireless communication is a telecommunication technology, which enables wireless transmission between the portable devices to provide wireless access in all types of environments. In this research, the measurements and various empirical models are analysed and compared in order to find out a suitable propagation model to provide guidelines for cell planning of wireless communication systems. The measured data was taken in urban region with low vegetation and some trees at 900 MHz frequency band. Path loss models are useful planning tools, which permit the designers of cellular communication to obtain optimal levels for the base station deployment and meeting the expected service level requirements. Outcomes show that these empirical models tend to overestimate the propagation loss. As one of the key outputs, it was observed that the calculations of Weissberger model fit with the measured data in urban environment.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.117-120
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• 2003

PON (Passive Optical Network) is an emerging local subscriber access architecture that provides more bandwidth and services to subscriber than DSL (Digital Subscriber Line and HFC (Hybrid-Fiber Coaxial) network. A PON is a point-to-multipoint optical network with no active elements in the signals' path from source to destination. Advantages of using PON for a subscriber access network include large coverage area, reduced fiber deployment, multicast and broadcast capabilities, reduced cost of maintenance (due to devices being passive), and ease of upgrades to higher bit rate or additional wavelengths. PON uses WDM (Wavelength Division Multiplexing) technique that transmits the downstream and upstream data at each different wavelength. For transmitting the CATV (Community Antenna television) service through PON network, we give out additional wavelength. This study shows the available TPS (Triple play service) architecture using CATV overlay EPON (Ethernet PON) architecture and analyzes the effects of EPON-based CATV transmission by measuring the power loss fur each wavelength and the power range of the available analog wavelength and RF.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.141-149
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• 2007

Multiple-input multiple-output (MIMO) transmit pre-coding/beamforming can significantly improve system spectral efficiency. However, several obstacles prevent precoding from wide deployment in early wireless networks: The significant feedback overhead, performance degradation due to feedback delay, and the large storage requirement at the mobile devices. In this paper, we propose a precoding method that addresses these issues. In this approach, only 3 or 6 bits feedback is needed to select a precoding matrix from a codebook. There are fifteen codebooks, each corresponding to a unique combination of antenna configuration (up to 4 antennas) and codebook size. Small codebooks are prestored and large codebooks are efficiently computed from the prestored codebook, modified Hochwald method and Householder reflection. Finally, the feedback delay is compensated by channel prediction. The scheme is validated by simulations and we have observed significant gains comparing to space-time coding and antenna selection. This solution was adopted as a part of the IEEE 802.16e specification in 2005.