• The Transactions of the Korea Information Processing Society
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• v.6 no.11S
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• pp.3390-3398
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• 1999

To achieve high-speed communication and to improve QoS characteristics, ATM is now being used as underlying transfer mechanism of Internet protocols, or TCP/IP. When TCP uses the ABR service in ATM networks, the ABR service control is important to improve the performance of TCP/IP traffic as long as there is no interaction between ABR rate control and TCP flow control. In such environment, the interoperability of EFCI and ER switches becomes unavoidable in order to more effectively control ABR traffic in ATM network. In this paper, we use the model of mixed EFCI-ER environment and discuss the performance issues, e.g., the fairness of bandwidth allocation, drop rate, throughput by using various ER switch algorithms. Among various ERSwitch algorithms, we present one algorithm that have a less network topology and allocate the fair share of VC bandwidth by simulation results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4331-4346
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• 2015

The femtocell network, which is designed for low power transmission and consists of consumer installed small base stations, coexists with macrocells to exploit spatial reuse gain. For its realization, cross-tier interference mitigation is an important issue. To solve this problem, we propose a joint access and power control scheme that requires limited information exchange between the femto and macro networks. Our objective is to maximize the network throughput while satisfying each user's quality of service (QoS) requirement. To accomplish this, we first introduce two distributed interference detection schemes, i.e., the femto base station and macro user equipment based schemes. Then, the proposed scheme dynamically adjusts the transmission power and makes a decision on the access mode of each femto base station. Through extensive simulations, we show that the proposed scheme outperforms earlier works in terms of the throughput and outage probability.

• Proceedings of the IEEK Conference
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• summer
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• pp.35-38
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• 2004

The MAC protocol of HIPERLAN/2 is based on TDMA/TDD and AP (Access Point) can dynamically allocate the number of RCHs (Random CHannels). We propose a dynamic random channel allocation scheme improved by limiting the number of minimum RCHs. On a simulated scenario adopted practical Internet traffic, the proposed scheme is shown to achieve over $19\%$ lower delay than previously studied algorithm. This study will be a first step towards designing scope of RCHs for high-performance wireless packet network

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.314-321
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• 2011

There have been considerable standardization works to measure subjective video quality. However, these standardization methods are based on the situation where they have original or reference video sequences, and measure the video quality by looking the sequence during short time duration, e.g. 10 seconds. Since people's TV watching time durations in IPTV services are very long (e.g. more than 30 minutes), the quality measurements by the standards are not practical. In this paper, we analyze the effect of video quality rating period to MOS (Mean Opinion Score), and suggest a proper rating duration of subjective video quality for IPTV services.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.1-12
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• 2008

The multimedia streaming service in NGN architecture is not only to deliver video streaming (VoD, Broadcasting TV, etc.) but also to provide new services and service bundles, such as Triple Play (IPTV + VoIP + Internet). Among these services, Internet Protocol Television (IPTV) is becoming a convergence of communication, content, computing, as well as an integration of broadcasting and telecommunication services. In this paper, we addresses enhanced IPTV management scheme aspect of E2E from Home Network to Head End Center over NGN to support efficient service management with a full quality of service (QoS) guarantee.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.37-38
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• 2019

본 논문에서는 자원제한적인 IoT 환경에서 스케줄링 정확도 향상을 위해 Softmax를 이용한 Q-learning 기반의 패킷 스케줄링 기법을 제안한다. 기존 Q-learning의 Exploitation과 Exploration의 균형을 유지하기 위해 e-greedy 기법이 자주 사용되지만, e-greedy는 Exploration 과정에서 최악의 행동이 선택될 수도 있는 문제가 발생한다. 이러한 문제점을 해결하기 위해 본 연구에서는 Softmax를 기반으로 다중 센서 노드 환경에서 데이터 패킷에 대한 Quality of Service (QoS) requirement 정확도를 높이기 위한 연구를 진행한다. 이 때 Temperature 매개변수를 사용하는데, 이는 새로운 정책을 Explore 하기 위한 매개변수이다. 본 논문에서는 시뮬레이션을 통하여 제안된 Softmax를 이용한 Q-learning 기반의 패킷 스케줄링 기법이 기존의 e-greedy를 이용한 Q-learning 기법에 비해 스케줄링 정확도 측면에서 우수함을 보인다.

• Korean Management Science Review
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• v.23 no.3
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• pp.243-257
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• 2006

ITU-T's NgN(Next generation Network) architecture is expected to offer a new Internet platforms such as QoS(Quality of Service) guaranteed services as it overcame the limitations of the existing best-effort Internet architecture. However, policy development crucial for the NgN framework(e.g., interconnections and billing) is lagging far behind technology development. For example, arguments over network neutrality clearly indicate little understanding of the Internet industry structure where diverse providers including ISP and CP coexist. This study employs a network economics approach to predict how the competitive landscape involving various providers will evolve under the traffic-based billing system under the NgN environment. Applied is the non-cooperative game theory, in particular, Stackelberg's repeated game in order to build and analyze model for competition among those providers. We also studied possible impacts that CPs would have on the competitive landscape if they have an option to replace ISP: i.e., CDN(Content Delivery Network) provider. Lastly, based on the model analysis and experiments, presented are their implications to policy development and tile future prospect.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.386-393
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• 2003

Future wireless networks are expected to achieve high bit rates at low cost, enabling multimedia and QoS-based services over the wireless medium. The impulse radio ultra-wide band (IR-UWB) technique is a promising candidate in the deployment of such networks, thanks to its potential robustness and capacity. In the past, most of the UWB research focused on hardware and physical layer aspects in order to solve the technological challenges posed by IR-UWB. UWB peculiar characteristics may, however, also stimulate innovative higher layers’ design. This work addresses MAC issues for UWB communication systems. Key areas such as medium sharing, MAC organization, packet scheduling and power control are reviewed. The impact of UWB on the above functions is discussed, and areas which require UWB specific design are identified. Finally, novel MAC functions enabled by UWB specific features, i.e., precise ranging and positioning, are presented.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.25-28
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• 2000

As Internet users and network traffics are explosively increased, many researches have been done to provide fast and guaranteed Internet services. The results of these efforts are Multiprotocol Lab el Switching(MPLS) and differentiated service(Diff serv) emerging as a next generation backbone net work. In this paper, we make a research on gearing (or interworking) two technology needed to support end-to-end QoS and explain sequential procedure. And we simulate the L-LSP/E-LSP proposed by Working Group of IETF to be deployed to the DiffServ module which is implemented based on the MPLS network simulator and analyze the performance of the simulation result.

• Information and Communications Magazine
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• v.31 no.10
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• pp.34-42
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• 2014

FirstNet는 2012년에 출범하여 미 전역에 단일의 공공안전용 브로드밴드 네트워크 (NPSBN) 구축을 추진하고 있다. 출범과 동시에 700 MHz 대역에 20 MHz 대역폭이 할당되고 미화 70억불의 예산이 책정되었다. 그리고 망구축을 PS-LTE를 기반으로 하되, 추진 일정상 공공안전의 요구사항을 모두 만족하지는 못 하기 때문에 미션크리티컬 음성을 제외하고 미션크리티컬 데이터를 위주로 하는 기능을 정의하였다. 망 구조는 네트워크 코어가 중앙에 위치하며, 지역에 RAN 위주의 장비들이 배치되게 된다. 지방정부가 지역에 배치될 장비와 시설을 구축할 것이며 이를 위하여 FirstNet는 지방정부와 긴밀하게 협의를 추진하고 있다. 현재 RFP 에 앞서 RFI를 진행하고 있다. 2015년에 RFP를 완성하고 2016년에 네트워크 코어를 구축할 예정이다. 그리고 이전에 BTOP PSBN 프로그램으로 추진되고 있던 일곱 개의 프로젝트에 대하여 FirstNet 의 PS-LTE 망과의 호환성과 협조를 보장하는 조건으로 주파수 사용 협상을 추진하여 다섯 개의 프로젝트와 협상을 완료했으며, 두 개의 프로젝트는 중지시켰다. 이중 가장 규모가 큰 프로젝트는 LA-RICS PSBN으로서 231 국의 eNodeB가 시설되며 2015년 2사분기에 개통될 예정이다. 이 시설을 활용하여 2차 재난대응기관의 이용, QoS (서비스 품질), 우선순위/선취에 대하여 분석될 예정이다.