• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권5호
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• pp.1532-1553
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• 2014

Radio spectrum is a precious resource and characterized by fixed allocation policy. However, a large portion of the allocated radio spectrum is underutilized. Conversely, the rapid development of ubiquitous wireless technologies increases the demand for radio spectrum. Cognitive Radio (CR) methodologies have been introduced as a promising approach in detecting the white spaces, allowing the unlicensed users to use the licensed spectrum thus realizing Dynamic Spectrum Access (DSA) in an effective manner. This paper proposes a generalized framework for DSA between the licensed (primary) and unlicensed (secondary) users based on Continuous Time Markov Chain (CTMC) model. We present a spectrum access scheme in the presence of sensing errors based on CTMC which aims to attain optimum spectrum access probabilities for the secondary users. The primary user occupancy is identified by spectrum sensing algorithms and the sensing errors are captured in the form of false alarm and mis-detection. Simulation results show the effectiveness of the proposed spectrum access scheme in terms of the throughput attained by the secondary users, throughput optimization using optimum access probabilities, probability of interference with increasing number of secondary users. The efficacy of the algorithm is analyzed for both imperfect spectrum sensing and perfect spectrum sensing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권8호
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• pp.1913-1925
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• 2012

In order to efficiently utilize limited radio resources, resource allocation schemes in OFDMA-based wireless networks have gained intensive attention recently. Instead of improving the throughput performance, the utility is adopted as the metric for resource allocation, which provides reasonable methods to build up the relationship between user experience and various quality-of-service (QoS) metrics. After formulating the optimization problem by using a weighted bipartite graph, a modified bipartite matching method is proposed to find a suboptimal solution for the resource allocation problem in OFDMA-based wireless systems with feasible computational complexity. Finally, simulation results are presented to validate the effectiveness of the proposed method.

• 한국통신학회논문지
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• 제35권8A호
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• pp.828-834
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• 2010

In this paper, an adaptive cross-layer resource allocation algorithm for the downlink multi-user OFDM system is proposed. The proposed algorithm does not only concern the wireless characteristics of physical (PHY) layer, but also pays attention to the user's quality of service (QoS) requirement, fairness, and packet queue state information of medium access control (MAC) layer. The algorithm is composed of two parts: one is to decide the priority of the user, and the other is to assign the radio resource according to its priority. Simulation results show that the proposed algorithm has both steady QoS and low computation complexity, even though the mobile users have different receiving signal to noise ratio (SNR).

• 한국컴퓨터정보학회논문지
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• 제21권12호
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• pp.73-79
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• 2016

This paper proposes a novel resource allocation scheme which enables to guarantee the quality of experience (QoE) for handovers from femtocell to macrocell and vice versa, and between femtocells in the overlaid macro-femto networks. The proposed scheme guarantees QoE to a certain extent during handover by utilizing a fixed amount of radio resource reserved in advance for the dedicated use to support QoE. We take both the type of the handover and the temporal sensitiveness characteristics of user services into consideration in order to support QoE. Performance of our scheme is analyzed by simulation with respect to the outage probability and total throughput.

• ETRI Journal
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• 제30권1호
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• pp.1-12
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• 2008

In this paper, we propose an efficient single-resource task scheduling algorithm for the Communication, Ocean, and Meteorological Satellite. Among general satellite planning functions such as constraint check, priority check, and task scheduling, this paper focuses on the task scheduling algorithm, which resolves conflict among tasks which have an exclusion relation and the same priority. The goal of the proposed task scheduling algorithm is to maximize the number of tasks that can be scheduled. The rationale of the algorithm is that a discarded task can be scheduled instead of a previously selected one depending on the expected benefit acquired by doing so. The evaluation results show that the proposed algorithm enhances the number of tasks that can be scheduled considerably.

• 한국국방경영분석학회지
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• 제31권1호
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• pp.58-72
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• 2005

RFID(Radio Frequency Identification) is one of key technologies in ubiquitous computing. RFID system comprises tag, reader, and computer application. The tag is a small electronic chip, which is attached to a thing such as item, pallet, container. The reader has an tiny antenna obtaining the identification information of the things by radio frequency, and provides the information to the computer application for a business. In this paper we have proposed the military application of RFID and its implementation policy for the Korean armed forces. We believe that The principle application area would be logistics TAV(total asset visibility) and resource management, and the implementation should be achieved step by step considering the advancement of RFID technology and government policy.

• Journal of Communications and Networks
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• 제8권4호
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• pp.442-450
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• 2006

Inter-operability between heterogeneous radio access technologies (RATs), in the sense of seamless vertical han-dover (VHO) support with common radio resource management (CRRM) functionalities, has recently attracted a significant research attention and has become a prominent issue in standardization fora. In this paper, we formulate the problem of load balancing between cooperative RAT's as a mathematical program and by trading off a pre-defined delay tolerance per request we propose a vertical handover batch processing (VHBP) scheme. To quantify the performance of the proposed VHBP scheme we compare it with a baseline processing scheme, where each VHO request is processed independently under a number of different network scenarios. Numerical investigations reveal significant net benefits of the proposed scheme compared with the baseline, both in terms of achieved load balancing levels but also with regard to the acceptance rate of the VHO requests.

• ETRI Journal
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• 제39권3호
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• pp.345-352
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• 2017

Traffic management is a highly beneficial mechanism for satisfying quality-of-service requirements and overcoming the resource scarcity problems in networks. This paper introduces an optimal connection admission control mechanism to decrease the packet loss ratio and end-to-end delay in cognitive radio sensor networks (CRSNs). This mechanism admits data flows based on the value of information sent by the sensor nodes, the network state, and the estimated required resources of the data flows. The number of required channels of each data flow is estimated using a proposed formula that is inspired by a graph coloring approach. The proposed admission control mechanism is formulated as a semi-Markov decision process and a linear programming problem is derived to obtain the optimal admission control policy for obtaining the maximum reward. Simulation results demonstrate that the proposed mechanism outperforms a recently proposed admission control mechanism in CRSNs.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.744-748
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• 2003

Developing an interactive satellite multi­media system, such as a digital video broadcasting (DVB) return channel via satellite (RCS) system, is gaining popularity over the world To accommodate the increasing traffic demand we are motivated to investigate an alternative for improving return channel utilization We develop an efficient method for optimal packet scheduling in an interactive satellite multimedia system using hybrid CDMA/TDMA channels. We formulate the timeslot-code assignment problem as a binary integer programming (BIP) problem, where the throughput maximization is the objective, and decompose this BIP problem into two sub-problems for the purpose of solution efficiency. With this decomposition, we promote the computational efficiency in finding the optimal solution of the original BIP problem Since 2001, ETRI has been involved in a development project where we have successfully completed an initial system integration test on broadband mobile Internet access via Ku-band channels using the proposed resource allocation algorithm.

• 한국포장학회지
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• 제14권1호
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• pp.15-22
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• 2008

The excitement over radio frequency identification (RFID) technology has gained momentum in the last five years, with a diversification in the range of applications. Besides academic research into radio frequency identification (RFID) has proliferated over the last few years, however there is much to be desired on Packaging industry. In this paper, we present a literature reviews of researches of RFID system on Packaging, especially focused on RFID system standardization into packaging. There is not any packaging standard or guidance about tag locations, classification with the materials and so on. Therefore it hampers reduction of the distribution costs on political and corporate sides, and lack consistency of applying RFID system. The main focus of this review paper is to establish a constituency about legislating RFID system standard on packaging. It is hoped that the review will be a good resource for future research in order to applly RFID system to Packaging industry effectively.