• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.3
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• pp.1174-1192
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• 2021

With the assistance of non-orthogonal multiple access (NOMA), the spectrum efficiency and the number of users in cloud radio access network (CRAN) can be greatly improved. In this paper, the system performance of NOMA-assisted CRAN is investigated. Specially, the outage probability (OP) and ergodic sum rate (ESR), are derived for performance evaluation of the system, respectively. Based on this, by minimizing the OP of the system, a suboptimal power allocation (PA) scheme with closed-form PA coefficients is proposed. Numerical simulations validate the accuracy of the theoretical results, where the derived OP has more accuracy than the existing one. Moreover, the developed PA scheme has superior performance over the conventional fixed PA scheme but has smaller performance loss than the optimal PA scheme using the exhaustive search method.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.3
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• pp.148-159
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• 2013

An analysis of the throughput and stability region of random access systems is currently of interest in research and industry. This study evaluated the performance of a multiuser random access channel with a retransmission gain. The channel was composed of a media access control (MAC) determined by the transmission probabilities and a multiuser communication channel characterized by the packet reception probabilities as functions of the number of packet transmissions and the collision status. The analysis began with an illustrative two-user channel, and was extended to a general multiuser channel. For the two-user channel, a sufficient condition was derived, under which the maximum throughput was achieved with a control-free MAC. For the channel with retransmission gain, the maximum steady throughput was obtained in a closed form. The condition under which the random access channel can acquire retransmission gain was also obtained. The stability region of the general random access channel was derived. These results include those of the well-known orthogonal channel, collision channel and slotted Aloha channel with packet reception as a special instance. The analytical and numerical results showed that exploiting the retransmission gain can increase the throughput significantly and expand the stability region of the random access channel. The analytical results predicted the performance in the simulations quite well.

• Journal of IKEEE
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• v.24 no.1
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• pp.360-363
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• 2020

We present the power of the correlated superposition coding (SC) in non-orthogonal multiple access (NOMA). This paper derives closed-form expressions for the total allocated power with the constant total transmitted power. It is shown that the total allocated power is the function of a correlation coefficient. In result, the correlated SC NOMA should be designed with consideration of the correlation coefficient.

• The Korean Journal of Archival Studies
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• no.10
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• pp.65-111
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• 2004

In the modern society, Archives are an available subject to the people of a nation and it is indispensable to build and appropriate access environment in order to connect the users and the registered records stored in the facilities. Specially, the Closed Shelves Access system, based on the notion of "a Policy of Archives Preservation", needs to be fully equipped with an access environment more adequate to its necessities. Hence, this study has analyzed all sorts of environments-institutional, organizational, human, physical and intellectual- from a general perspective in order to activate users to read the archives and based on this, the objective of the research is in proposing a program that effectively provides archives to the users and provides the basis for putting into practice an active access environment. The use of archives is the fountainhead in order to preserve archives. By using the archives, the meaning of preserving them is maximized. Whether these archives may be used or not will depend on the quality of information and the advancement of the access environment. Therefore, in order to motivate users to access the archives, first of all the facilities and the archivists must establish norms regarding the access, based on statutes and once they have been settled, they should provide other changes such as ; the development and fixation in the organization's structure, the education of specialized human labor, the expansion of physical space and the facilities and diverse positive services.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.10
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• pp.2357-2375
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• 2013

Message ferry is a controllable mobile node with large capacity and rechargeable energy to collect information from the sensors to the sink in wireless sensor networks. In the existing works, route of the message ferry is often designed from the solutions of the Traveling Salesman Problem (TSP) and its variants. In such solutions, the ferry route is often a simple cycle, which starts from the sink, access all the sensors exactly once and moves back to the sink. In this paper, we consider a different case, where the ferry route is a closed walk that contains more than one simple cycle. This problem is defined as the Closed Walk Ferry Route Design (CWFRD) problem in this paper, which is an optimization problem aiming to minimize the average weighted delay. The CWFRD problem is proved to be NP-hard, and the Integer Linear Programming (ILP) formulation is given. Furthermore, a heuristic scheme, namely the Initialization-Split-Optimization (ISO) scheme is proposed to construct closed walk routes for the ferry. The experimental results show that the ISO algorithm proposed in this paper can effectively reduce the average weighted delay compared to the existing simple cycle based scheme.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.1-6
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• 2024

In this paper, we designed and implemented the security network NVR system that can flexibly use the internal network and VPN network. In general, the NVR systems that only use internal networks cannot be access from the outside, which has the disadvantage of unnecessary inspections and inability to access from the outside. External access has made possible using the VPN security network, and a NVR system software was designed and implemented so that the existing internal network could be used. We compared with the NVR system usage environment in the internal network through the client and the NVR system. It also has implemented usage environment with the VPN network through the mobile APP, and confirmed that the same NVR was operating normally with the same functions. We also studied on IP based NVR for flexible access with closed loop network based on VPN system.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.4
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• pp.67-74
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• 2015

Due to an inability to accommodate for the rapidly increasing number of printed materials, Korean academic libraries are facing serious space shortage problems. Very few academic institutions have the funds to expand existing libraries or construct new facilities in order to accommodate the influx of printed materials. Despite not having the luxury to create new space, many establishments continue to implement the open access system. Seeing that such a system is only user friendly when used in a spacious facility, the maintenance of the open access system is unreasonable. Only few libraries consider the space efficient closed access system which helps to resolve storage space shortage. In the current state of the problem, improving the efficiency to which books are stored in existing storage areas within a library facility is the only appropriate solution. Enacting methods to improve physical space utilization within a fixed volume library facility will undoubtedly diminish the space shortage issue at hand. In this article, several space efficiency improvement approaches are discussed. Methods of book storage plan re-layout (floor, plan, ceiling, height, bookshelf design), book arrangement possibilities, and the reduction of the physical volume of reserved materials are each examined.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2007.05a
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• pp.84-102
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• 2007

Security is crucial for the successful deployment of large distributed systems. Many of these systems provide services to people across different administrative domains. The traditional identity-based access control mechanisms are un scalable and difficult to manage. Unlike the closed systems, open systems provide services to people from different security domains. Healthcare systems need to be highly available in order for the patients to get a timely treatment. The health care information should be available to authorized users both inside the administrative domain and outside the domain, such as pharmacies and insurance companies. In this paper, we first analyzed the necessities and advantages of importing attribute-based trust-management models into open distributed systems. Then we reviewed traditional access-control models and presented the basic elements of the new trust-management model.

• ETRI Journal
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• v.28 no.1
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• pp.17-30
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• 2006

In time division duplex (TDD) code division multiple access (CDMA) systems, chip-synchronous transmission in the uplink is obtainable, thus leading to free multiple access interference in flat Rayleigh fading channels plus additive white Gaussian noise. This motivates us to develop a novel cooperative transmission strategy that allows single-antenna devices to benefit from spatial diversity using orthogonal signature sequences. The proposed cooperation is applicable to many digital modulation methods and achieves the fullest diversity level, low implementation complexity, and a full data rate. Closed-form bit-error-rate expressions were also derived and compared to simulation results in order to evaluate its validity. A variety of numerical results demonstrated the cooperation's superiority over single transmission under the same transmit power constraint.

• ETRI Journal
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• v.36 no.4
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• pp.625-634
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• 2014

This paper studies a dual-hop multiple-access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single-antenna amplify-and-forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low-complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches.