• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.63-66
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• 2015

As smart-phones become popular, mobile data traffic has been dramatically increasing and intensive researches on the next-generation mobile communication network is in progress to meet the increasing demand for mobile data traffic. In particular, heterogeneous network (HetNet) is attracting much interest because it can significantly enhance the network capacity by increasing the spatial resue with macro and small cells. In the HetNet, we have several problems such as load imbalance and interference because of the difference in transmit power between macro and small cells and cell range expansion (CRE) can mitigate the problems. In this paper, we propose a new cell selection scheme with adaptive cell range expansion bias (CREB) for ultra dense HetNet and we analyze the performance of the proposed scheme in terms of average cell transmission rate through system-level simulations and compare it with those of other schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4B
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• pp.411-423
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• 2004

This paper defines test methodologies and performance indices for SIP server system, and describes elements that can have influence on the test of SIP network equipments. Moreover, we implement a tester to evaluate the performance of SIP Servers such as Registrar and Proxy server. The performance indices for testing SIP servers are message processing rate, transaction delay, and call success probability. The parameters that can have an effect on the performance of SIP servers are user population, transport protocol, method of database access, method of DNS, call creation pattern, definition of transactions, and size of packets. We tested several SIP servers that act as Registrar, Proxy, and Redirect server using the implemented SIP tester, and, as a result, verified functions of the tester and performance indices and input parameters defined in this paper. Performance indices and methodologies presented in this paper can be used to evaluate SIP servers in NGN

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.12
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• pp.94-102
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• 2016

Recently, the I/O performance of a single node is rapidly improving due to the advent of high-performance SSD. As a result, the next-generation storage platform based on SSD has received a great deal of attention and such storage platforms are increasingly adopted to commodity servers or data centers that look for the high-bandwidth computation and I/O. However, building all SSD-based storage platform may not be cost-effective because the price per storage capacity is very high as compared to that of HDD. In this paper. we propose a hybrid file management solution, called HyPLVM(Hybrid Priority Logical Volume Manager), which combines the strength of SSD with the desirable aspects of low-price, high-storage capacity HDD. HyPLVM prioritizes the files and directories to be accessed by users, in order to determine the target storage device (SSD/HDD) in which files are allocated, while mitigating the cost of building storage platforms.

• Journal of Broadcast Engineering
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• v.20 no.6
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• pp.871-879
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• 2015

With the increase of mass contents data, a method of a scene change detection is required for analysis, indexing and editing. Although many researchers are studying a variety of scene change detection method, it is too difficult to accurately detect various movements of the cameras and scene changes. Also, earlier scene change detection methods take too much time to apply to UHD video contents. That is because the UHD video contents with 4K (3820x2160) resolution or higher have greater amount of data. Therefore a method for detecting a scene change by using the next-generation codec, HEVC, is required. In this paper, we propose four scene change detection methods using the coding additional information of HEVC, and a new pixel-based scene change detection system. Furthermore, through the experimental results, we check the possibility of detecting the scene changes of UHD videos encoded in HEVC format.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.3-10
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• 2012

The visible light communication takes advantages of LED and PD for communication and is considered as a next generation wireless communication technology. It can support variety indoor applications. Especially, Visible LAN service has drawn much attention due to high data rate and no interference with existing WPAN system as well as high efficiency in illumination. However, existing MAC protocol occurs a high communication delay due to uplink collision and backoff time. In this paper, to reduce packet delay, we propose an enhanced MAC protocol based on FDD where the time difference between uplink frame and downlink frame transmission is utilized. Through computer simulations, we verified that the proposed MAC protocol outperforms the existing MAC protocol in terms of average packet delay.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.2
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• pp.373-381
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• 2017

Currently, various types of user authentication methods based on public certificates are used in domestic financial transactions. Such an authorized certificate method has a problem that a different security module must be installed every time a user connects an individual financial company to a web server. Also, the financial company relying on this authentication method has a problem that a new security module should be additionally installed for each financial institution whenever a next generation authentication method such as biometric authentication is newly introduced. In order to solve these problems, we propose an integrated authentication system that handles user authentication on behalf of each financial institution in financial transactions, and proposes an integrated authentication protocol that handles secure user authentication between user and financial company web server. The new authentication protocol is a modified version of OAuth2.0 that increases security and efficiency. It is characterized by performing a challenge-response protocol with a pre-shared secret key between the authentication server and the financial company web server. This gives users a convenient and secure Single Sign-On (SSO) effect.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.156-166
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• 2005

Ethernet passive optical network is an economical and efficient access network that has received significant research attention in recent years. A MAC(Media Access Control) protocol of PON, the next generation access network, is based on TDMA(Time Division Multiple Access) basically. In this thesis, we addressed the problem of dynamic bandwidth allocation in QoS based Ethernet PONs. We augmented the bandwidth allocation to support QoS in a differentiated services framework. Our differentiated bandwidth guarantee allocation(DBGA) allocates effectively and fairly bandwidths among end users. Moreover, we showed that DBGA that perform weighted bandwidth allocation for high priority packets result in better performance in terms of average and maximum packet delay, as well as network throughput compared with existing dynamic bandwidth allocations. We used simulation experiments to study the performance and validate the effectiveness of the proposed bandwidth allocations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.943-951
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• 2006

Multi-input-multi-output (MIMO) systems are considered to improve the capacity and reliability of next generation mobile communication. However, the multiple RF chains associated with multiple antennas are costly in terms of size, power and hardware. Antenna selection is a low-cost low-complexity alternative to capture many of the advantages of MIMO systems. We proposed new joint Tx/Rx antenna selection algorithm with low complexity. The proposed algorithm is a method selects $L_R{\times}L_T$ channel matrix out of $L_R{\times}L_T$ entire channel gain matrix where $L_R{\times}L_T$ matrix selects alternate Tx antenna with Rx antenna which have the largest channel gain to maximize Frobenius norm. The feature of this algorithm is very low complexity compare with Exhaustive search which have optimum capacity. In case of $4{\times}4$ antennas selection out of $8{\times}8$ antennas, the capacity decreases $0.5{\sim}2dB$ but the complexity also decreases about 1/10,000 than optimum exhaustive search.

• Journal of the Korea Society of Computer and Information
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• v.12 no.2 s.46
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• pp.63-70
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• 2007

The Data Encryption Standard (DES) is a block cipher that encrypts a 64 bit block of plaintext into a 64 bit block of ciphertext. The DES has been a worldwide standard for 20 years since it was adopted in 1976. strong. But, due to the rapid development of hardware techniques and cryptanalysis, the DES with 64-bit key is considered to be not secure at the present time. Therefore it became necessary to increase the security of DES. The NG-DES(New Generation DES)[1] is an encryption system which upgrades the encryption security of DES by the key extension and the usage of non-linear f function. It extends not only the size of plaintext and ciphertext to 128 bit but also the Fiestel structure used in each round. This structure has a weak point that the change of each bit of plaintext does not affect all bits of ciphertext simultaneously. In this paper, we propose a modified Fiestel structure of DES and thus increased confusion and diffusion by effectively cross-connecting between outputs in a round and inputs in next round.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.1
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• pp.63-72
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• 2007

Recently, as recognizing the risk about the infection of an infectious wastes, the problems about the management and treatment of the infectious wastes stand out socially. In this paper, as being possible monitoring whole processing from the origin of the infectious waste to the processing plant, using the RFID which is the kernel technology of the next generation, we tried to solve the second infection problem by inefficient treatment of the infectious wastes. Through the research suggesting in this paper, as storing and monitoring the procedural business articles and the problem about miss-writing and input error being found in management system like documentary writing by the existing manager and computation input by the web application, we can understand the management state, immediately. And the Bio information for the personal authentication is carried out through storing the feature vector calculation by the PCA algorithm, into the tag. It suggested more systematic and safer management plan than previous thing, as giving attention about the wastes to manager.