• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.142-152
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• 2010

When a mobile station(MS) performs a handover, in the IEEE 802.11 WLAN, MS's channel scanning for discovering new available APs is the dominating factor in handover latency, accounting 90% of overall latency. In order to reduce such a scanning latency, we focus on the method for reducing the number of channels for the MS in handover process to scan. With the help of IEEE 802.21 information server(IS), a proper order of groups of channels to be scanned is offered by the current AP depending on the information of neighbor APs in terms of the distance from serving AP, traffic load and network topology. By using this scanning order, the passive scanning of a MS in normal operation enables the MS to filter out the unavailable channels, and thus to classify the candidate channels of neighbor APs into three groups. Then, a handover-imminent MS can perform the active scanning from the most reliable group of channels. Simulation results show that the proposed scanning scheme reduce the scanning latency in comparison with the conventional scheme.

• Journal of KIISE:Information Networking
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• v.35 no.1
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• pp.11-20
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• 2008

An inevitable trend in the next generation wireless network environments is coexistence of different wireless access networks in a complementary, manner. In addition, mobile devices equipped with multiple air interfaces simultaneously executing diverse applications have been emerging, In such network environment, It is required that a solution for mobile users to seamlessly roam between different access networks as well as to satisfy QoS requirements of each application by efficiently utilizing coexisting various wireless access networks. In this paper, therefore, we propose a mobility management platform based on per-application end-to-end mobility management and cross-layer handover controls. Four core functional modules composing the proposed platform for end user devices are defined: Monitoring Agents, Profile Database, Decision Engine, and IP Agent. We show through simulations that the presented platform provides an improved QoS as it selectively utilizes the best available networks.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.271-280
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• 2010

For the next generation mobile communication system, diverse wireless network techniques such as beyond 3G LTE, WiMAX/WiBro, and next generation WLAN etc. are proceeding to the form integrated into the All-IP core network. According to this development, Beyond 3G integrated into heterogeneous wireless access technologies must support the vertical handover and network to be used of several radio networks. However, unified management of each network is demanded since it is individually serviced. Therefore, in order to solve this problem this study is introducing the theory of Common Radio Resource Management (CRRM) based on Generic Link Layer (GLL). This study designs the structure and functions to support the vertical handover and propose the vertical handover algorithm of which policy-based and MCDM are composed between LTE and WLAN systems using GLL. Finally, simulation results are presented to show the improved performance over the data throughput, handover success rate, the system service cost and handover attempt number.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.146-153
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• 2009

Recently, the research relative to NGN(Next Generation Network) is progressing in 3GPP(The 3rd Generation Partnership Progect), IETF(Internet Engineering Task Force), and so on. Although user needs frequently mobility which is various service pattern, In accordance with the development of these various applications, IMS(IP Multimedia Subsystem) and hierarchical networks ie, Femtocell/WiBro/3G etc is constructed for more user demands which provide service in anytime, anywhere. It is necessary to optimum network selection criterion which consider to wireless signal quality add to user service profile and service network traffic balance. NGN also needs a method to perform heterogeneous handover and to constraint Ping-pong phenomenon when using existing terminal-based handover decision. This paper proposes scheme for network selection and heterogeneous handover procedure in hierarchical wireless multi-access network based on SIP-MIH(Session Initiation Protocol-Media Independent Handover) with IMS by using user service profile that the considerations are dealing with not only selection and registration of various access network but also easy of developing the terminal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4492-4497
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• 2013

An important features of next-generation wireless networks will be heterogeneous environment in which a mobile terminal will be able to connect to multiple radio access networks and network selection mechanisms play an important role in ensuring QoS for users in this environment. In this paper, our study is concerned with an extension of the well known AHP to the group decision making methods. The users requested specific QoS divide into a group and the access networks with similar characteristics split into a group. Between each group, the one group is selected and within that group, the best access networks will be assigned according to priority order by network selection algorithm. The experimental results of MATLAB simulation show that the every user in each services can select the same network with decision value as large as 0.9. Consequently, the proposed network selection mechanism is more effective than conventional one in integrated UMTS and WLAN networks.

• Korean Journal of Construction Engineering and Management
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• v.21 no.4
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• pp.50-61
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• 2020

Safety management has been one of the most critical issues in the construction industry for a long time. Despite continuous efforts, it still shows a higher accident rate than other sectors. To reduce the accident rate, a lot of studies have been performed, mostly focused on contractors or construction phase. Although the initial stage of the construction project has the most significant impact on construction safety and decision-makers at the initial stage play an important role, the safety management system throughout the project entire life-cycle is still insufficient. In addition, although a great deal of information is generated in the construction project and the value is increasing, while it shows an inefficient aspect. This is believed to be due to insufficient information exchange and a lack of standards. In this context, this study aims to analyze the efficiency of information handover in construction safety. For this purpose, a safety management framework for systematically and efficiently managing and utilizing for construction safety information is referred to as 'safety business functions', 'project life-cycle', and 'industrial hierarchy'. The 'safety business functions' are classified into three levels. And then, in order to analyze the efficiency of safety information handover, 'importance of safety business function' and 'efficiency of safety information handover' were evaluated by interviewing with experts. This study can be used as reference data for implementing systematical and efficient safety management, and can also increase construction safety competency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3171-3191
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• 2016

Due to growing demand on wireless data traffic, a large number of different types of base stations (BSs) have been installed. However, space-time dependent wireless data traffic densities can result in a significant number of idle BSs, which implies the waste of power resources. To deal with this problem, we propose an active state control algorithm based on semi-Markov decision process (SMDP) for a heterogeneous network. A MDP in discrete time domain is formulated from continuous domain with some approximation. Suboptimal on-line learning algorithm with a random policy is proposed to solve the problem. We explicitly include coverage constraint so that active cells can provide the same signal to noise ratio (SNR) coverage with a targeted outage rate. Simulation results verify that the proposed algorithm properly controls the active state depending on traffic densities without increasing the number of handovers excessively while providing average user perceived rate (UPR) in a more power efficient way than a conventional algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.10
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• pp.858-864
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• 2013

In the 4G wireless environment, one of the important issues is to discover and select an access network suited for users. In this thesis, we propose a new network selection mechanism using group decision making and evaluate the effect of network selection schemes for vertical handover in heterogeneous wireless networks. We consider the group of users with similar QoS requirements search for the available access network simultaneously and a service area consist of multiple access networks with various characteristics. We divide the access networks with similar characteristics split into a group. Between each group, the one group is selected and within that group, the best access networks will be assigned according to priority order by network selection algorithm. We evaluate and compare the performance of three representative MADM schemes: GRA, SAW and TOPSIS. The MATLAB simulation results indicate the proposed algorithm can make a more effective choice according to the networks' characteristics and user's preference.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3B
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• pp.158-164
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• 2012

Heterogeneous Network and CSG cell are hot issues in the 3GPP LTE/LTE-Advanced system. In this paper, we analyze the system information measurement methods which are essential for handover to CSG cell. Since there have been no sufficient discussion about this problem, we present and analyze five possible solutions. Moreover, we propose a novel solution to reduce system information measurement delay. In the proposed Autonomous Measurement with Parallel Small Gap(AMPSG) method, the UE measures system information of neighbor cells in a parallel manner. As a result, the proposed method shows better delay performance. Therefore, the proposed AMPSG method can reduce handover delay since the UE have to measure the system information of neighbor cells before CSG handover decision.

• International Journal of Computer Science & Network Security
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• v.24 no.1
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• pp.226-234
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• 2024

The frequent handover problem and playing ping-pong effects in 5G (5th Generation) ultra-dense networking cannot be effectively resolved by the conventional handover decision methods, which rely on the handover thresholds and measurement reports. For instance, millimetre-wave LANs, broadband remote association techniques, and 5G/6G organizations are instances of group of people yet to come frameworks that request greater security, lower idleness, and dependable principles and correspondence limit. One of the critical parts of 5G and 6G innovation is believed to be successful blockage the board. With further developed help quality, it empowers administrator to run many systems administration recreations on a solitary association. To guarantee load adjusting, forestall network cut disappointment, and give substitute cuts in case of blockage or cut frustration, a modern pursuing choices framework to deal with showing up network information is require. Our goal is to balance the strain on BSs while optimizing the value of the information that is transferred from satellites to BSs. Nevertheless, due to their irregular flight characteristic, some satellites frequently cannot establish a connection with Base Stations (BSs), which further complicates the joint satellite-BS connection and channel allocation. SF redistribution techniques based on Deep Reinforcement Learning (DRL) have been devised, taking into account the randomness of the data received by the terminal. In order to predict the best capacity improvements in the wireless instruments of 5G and 6G IoT networks, a hybrid algorithm for deep learning is being used in this study. To control the level of congestion within a 5G/6G network, the suggested approach is put into effect to a training set. With 0.933 accuracy and 0.067 miss rate, the suggested method produced encouraging results.