• Journal of the Korea Convergence Society
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• v.8 no.8
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• pp.9-15
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• 2017

With the development of semiconductor integration technology, central processing units and storage devices have been miniaturized and performance has been rapidly developed, interconnection network technology is becoming a more important factor in terms of the performance of high performance computing system. In this paper, we analyze the trend of interconnection network technology used in high performance computing. Interconnect technology, which is the most widely used in the Supercomputer Top 500(2017. 06.), is an Infiniband. Recently, Ethernet is the second highest share after InfiniBand due to the emergence of 40/100Gbps Gigabit Ethernet technology. Gigabit Ethernet, where latency performance is lower than InfiniBand, is preferred in cost-effective medium-sized data centers. In addition, top-end HPC systems that demand high performance are devoting themselves from Ethernet and InfiniBand technologies and are attempting to maximize system performance by introducing their own interconnect networks. In the future, high-performance interconnects are expected to utilize silicon-based optical communication technology to exchange data with light.

• Journal of Korea Port Economic Association
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• v.29 no.4
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• pp.73-95
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• 2013

This paper analyzes a competitive shipping market in East Asia in order to explore how container carriers make decisions on ship size, number of ships, service frequency, and service route. A sequential-move game based on non-cooperative game theory is applied to establish the models for the decision-makings involving the transportation volumes, freight rates, costs, and market shares of the service routes from Shanghai or Hong Kong to the ports in Busan, Gwangyang, and Incheon. According to the sub-game perfect Nash equilibrium solutions proposed by these models, carriers' decisions in such a competitive environment vary depending on sailing distance, transport demand, and freight rates. Therefore, carriers are recommended to reflect the optimal equilibrium solutions and a variety of decision factors when formulating strategies for transportation networks and operating fleets. Furthermore, ports should establish management strategies for these factors to provide optimal equilibrium solutions for carriers' transportation networks.

• Journal of KIISE
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• v.45 no.2
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• pp.187-194
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• 2018

Recently, Hypertext Transfer Protocol (HTTP) adaptive streaming service is attracting attention. The existing quality adaptive scheme of HTTP adaptive streaming service adjusts the video quality according to the network bandwidth or the client buffer size. However, the problem with the existing quality adaptive scheme is the QoE (Quality of Experience) degradation caused by the unnecessary quality change that occurs due to frequent bandwidth change or fixed buffer threshold. We propose a video quality maintenance scheme that improves average video quality and minimizes unnecessary quality change in order to improve the QoE of HTTP adaptive streaming service in the changing network environment. The proposed scheme maintains high quality for a long time by setting the quality maintenance duration to be long when buffer occupancy and video quality are high. The experimental results show that the proposed scheme improves QoE by improving the average video quality and minimizing the quality change.

• Journal of KIISE
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• v.44 no.12
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• pp.1296-1306
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• 2017

Recently, as the number of Internet of Things users has increased, IETF (Internet Engineering Task Force) has released the CoAP (Constrained Application Protocol). So Internet of Things have been researched actively. However, existing studies are difficult to adapt to streaming service due to low transmission rate that result from buffer underflow. In other words, one block is transmitted one block to client's one request according to the internet environment of limited resources. The proposed scheme adaptively adjusts the rate of CON(Confirmable) message among all messages for predicting the exact network condition. Based on this, the number of blocks is determined by using buffer occupancy rate and content download rate. Therefore it improves the quality of user experience by mitigating playback interruption. Experimental results show that the proposed scheme solves the buffer underflow problem in Internet of Things streaming environment by controlling transmission rate according to the network condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5C
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• pp.493-505
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• 2003

A new inter-client synchronization framework for multicast media streaming is proposed employing a server-client coordinated adaptive playout control. The proposed adaptive player controls the playback speed of audio and video by adopting the time-scale modification of audio. Based on the overall synchronization status as well as the buffer occupancy level, the playout speed of each client is manipulated within a perceptually tolerable range. Additionally, the server implicitly helps increasing the time available for retransmission while the clients perform an interactive error recovery mechanism with the assistance of playout control. The network-simulator based simulations show that the proposed framework can reduce the playout discontinuity without degrading the media quality, and thus mitigate the client heterogeneity.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.103-110
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• 2014

Recent TSV based 3D Integrated Circuit (IC) technology needs more powerful thermal management techniques. However, because cooling cost and form factor are restricted, thermal management are emphasis on software based techniques. But in case of throttling thermal management which one of the most candidate technique, increasing bus occupation induce total performance decrease. To solve communication bottleneck issue in TSV based 3D SoC, we proposed adaptive throttling technique Experimental results show that the proposed method can improve throughput by about 72% compare with minimal path routing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9B
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• pp.829-837
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• 2006

Due to the internet network congestion, packets may be dropped or delayed at routers. This phenomenon degrades the quality of streaming applications that require high QoS requirements. The proposed algorithm in this paper, called DBRC(Delay-Based Rate Control), tries to cause router queue occupancy to reach a steady state or equilibrium by throttling the transmission rate of the multimedia traffics when network delays tend to increase and also probing for more bandwidth when network delays tend to decrease. Simulation results show that the proposed algorithm provides smooth transmission rate, nearly constant delay and low packet loss rates, compared with TFRC(TCP Friendly Rate Control) that is one of dominant multimedia congestion control algorithms.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.04a
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• pp.336-339
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• 2017

스마트폰 서드 파티 애플리케이션에 대한 포렌식 분석은 최근 수 년 간 탐구되어야 할 새로운 영역으로 떠올랐다. 현재 스마트폰 시장은 그 규모를 측정하는 것이 무의미할 만큼 커졌으며 각 스마트폰 플랫폼의 앱(App)마켓에는 셀 수 없이 많은 서드 파티 애플리케이션이 존재한다. 모바일 포렌식 소프트웨어 도구들은 일반적으로 연락처, 문자메시지, 통화기록 등의 전형적인 데이터를 수집한다. 이러한 도구들은 서드 파티 애플리케이션이 기기 내부에 저장하는 정보들을 간과하기 쉽다. 여러 제조사 중, 애플사의 모바일 기기에 설치된 많은 서드 파티 애플리케이션은 수사에 도움이 되는 많은 정보와 관련있는 디지털 증거를 남긴다. 이런 잠재적 증거들은 기기 내부에 저장되기도 하며, 비교적 손쉬운 방법으로 법정에 제출 가능하다. 스마트폰으로 이루어지는 많은 활동은 상당 부분 서드 파티 애플리케이션으로 이루어지며, 사이버 범죄 사건의 중심에 스마트폰이 있다면 서드 파티 애플리케이션 분석을 통한 핵심 증거 획득이 사건을 해결할 가능성이 높아진다. 본 논문에서는 스마트폰에서 널리 쓰이고 있는 소셜네트워크 애플리케이션인 '인스타그램(Instagram)'에서 행해진 포렌식 분석에 초점을 맞추고, 기기는 전 세계 적으로 가장 사용자 점유율이 높은 스마트폰인 아이폰에서 이루어졌다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.542-545
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• 2010

In this paper, we propose a parking information system which suggests an available parking lot on the shortest path between an entrance and adestination. In order to analyse the change of the parking management efficiency of each model as the number of unavailable parking lots increases from 10% to 99%, we compare the experimental results of three parking information system: an entrance-oriented system, a destination-oriented system, and the proposed system. Also, we compare user's satisfaction according to whether 50 user park their car with the proposed system or not.

• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.765-772
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• 2004

Multicast communication is simultaneous transmission of data to multiple receivers and saves considerably sender resources and network bandwidth. It has high risk to attack using group address and inherent complexity of routing packets to a large group of receivers. It is therefore critical to provide source authentication, allowing a receiver to ensure that received data is authentic. In this paper, we propose the multiple chain authentication scheme for secure and efficient multicast stream. To evaluate the performance of our scheme, we compare our technique with two other previously proposed schemes using simulation results. Our scheme provides non-repudiation of origin, low overhead by amortizing the signature operation over multiple packets, and high packet loss resistance.