RFID 기반 물류정보 공유를 위한 인증 모델

김희열(Heeyoul Kim),김남기(Namgi Kim),김광훈(Kwang-Hoon Kim),방효찬(Hyo-Chan Bang),김선진(Sun-Jin Kim) 한국정보기술학회 2011 한국정보기술학회논문지 Vol.9 No.3

An authentication model for sharing logistic information based on RFID system is presented. Logistic systems where many companies collaborate with each other require an authentication model providing that only authenticated entities can share logistic information securely. The presented model applies federated identity technology in consideration of such environment. Each entity is only authenticated in its own domain, and then it can access logistic information in other domains. Based on the presented model, an authentication system is implemented preventing leakage of logistic information.

Machine Learning Approach for Active Vaccine Safety Monitoring

Kim Yujeong,Jang Jong-Hwan,Park Namgi,Jeong Na-Young,Lim Eunsun,Kim Soyun,Choi Nam-Kyong,Yoon Dukyong 대한의학회 2021 Journal of Korean medical science Vol.36 No.31

Background: Vaccine safety surveillance is important because it is related to vaccine hesitancy, which affects vaccination rate. To increase confidence in vaccination, the active monitoring of vaccine adverse events is important. For effective active surveillance, we developed and verified a machine learning-based active surveillance system using national claim data. Methods: We used two databases, one from the Korea Disease Control and Prevention Agency, which contains flu vaccination records for the elderly, and another from the National Health Insurance Service, which contains the claim data of vaccinated people. We developed a casecrossover design based machine learning model to predict the health outcome of interest events (anaphylaxis and agranulocytosis) using a random forest. Feature importance values were evaluated to determine candidate associations with each outcome. We investigated the relationship of the features to each event via a literature review, comparison with the Side Effect Resource, and using the Local Interpretable Model-agnostic Explanation method. Results: The trained model predicted each health outcome of interest with a high accuracy (approximately 70%). We found literature supporting our results, and most of the important drug-related features were listed in the Side Effect Resource database as inducing the health outcome of interest. For anaphylaxis, flu vaccination ranked high in our feature importance analysis and had a positive association in Local Interpretable Model-Agnostic Explanation analysis. Although the feature importance of vaccination was lower for agranulocytosis, it also had a positive relationship in the Local Interpretable Model-Agnostic Explanation analysis. Conclusion: We developed a machine learning-based active surveillance system for detecting possible factors that can induce adverse events using health claim and vaccination databases. The results of the study demonstrated a potentially useful application of two linked national health record databases. Our model can contribute to the establishment of a system for conducting active surveillance on vaccination.

Analysis and Improvement of MPEG-DASH-based Internet Live Broadcasting Services in Real-world Environments

( Namgi Kim ),( Byoung-dai Lee ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

Adaptive bitrate streaming is a crucial element in the implementation of high-quality streaming of media content over the Internet. Dynamic adaptive streaming over HTTP (MPEG-DASH) has lately emerged as the de facto solution for over-the-top (OTT) video streaming services. In this paper, we perform macro-level analysis on a real-world MPEG-DASH-based Internet live broadcasting service to gain insight into its behavior throughout the end-to-end service-provision chain, from broadcasters to viewers. Based on this analysis, we propose methods to improve the quality-of-experience (QoE) of MPEG-DASH-based services, particularly with regard to reducing broadcasting delays between recording and viewing of videos, as well as synchronizing client terminals.

Improving Handover Quality in 4G Mobile Systems

KIM, Dongwook,LEE, Hanjin,KIM, Namgi,YOON, Hyunsoo The Institute of Electronics, Information and Comm 2008 IEICE transactions on fundamentals of electronics, Vol.91 No.7

<P>In this paper, we propose a new handover algorithm to guarantee handover quality in 4G mobile systems. The proposed algorithm limits the handover interruption time by improving the HARQ retransmission latency of the first packet transmitted from new serving cell. Through the simulations, we proved that our algorithm meets the requirement of handover interruption time for TCP services with high rate.</P>

레이블 스위칭 네트웍 상에서 L2A 캐쉬 대체 기법

김남기(Namgi Kim),황인철(Inchul Hwang),윤현수(Hyunsoo Yoon) 한국멀티미디어학회 2000 한국멀티미디어학회 학술발표논문집 Vol.2000 No.1

차세대 패킷 기반 이동 통신 시스템에서 트래픽 분산을 위한 적응적 핸드오프 기법

김남기(Namgi Kim),최혜은(Hyeeun Choi),윤현수(Hyunsoo Yoon) 한국정보과학회 2005 정보과학회논문지 : 정보통신 Vol.32 No.3

3 세대 이상의 차세대 패킷 기반 이동 통신 시스템은 패킷 네트워크의 특성 때문에 사용자가 받는 서비스의 질이 셀(Cell)의 트랙픽 부하량에 의해 직접적인 영향을 받는 구조로 되어 있다. 또 이동통신 시스템에서 트래픽 집중화 현상은 시스템 자원을 충분히 활용하지 못하면서 호(Call) 탈락률을 높여 전체 시스템 성능이 떨어지는 핫셀(Hot cell) 문제를 야기한다. 그러므로 패킷 네트워크를 기반으로 하는 이동 통신 시스템에서 자원을 효율적으로 사용하기 위해 트래픽을 분산시키는 것은 매우 중요하다. 따라서 본 논문에서는 패킷 기반의 이동 통신 시스템에서 핸드오프 시 주변 셀의 부하 정보를 고려해 몰려있는 트래픽을 주위로 분산시키는 적응적 핸드오프 알고리즘을 제안한다. 또, 패킷 네트워크에서 트래픽 부하를 측정하는 방법으로 MAC 상태도에서 트래픽 전송 및 트래픽 대기 상태에 있는 사용자의 수를 이용하는 기법도 제안한다. 그리고 모의 실험 결과를 통하여 제안하는 핸드오프 기법이 트래픽을 분산시켜 시스템 전체 측면에서의 자원을 효율성을 높이고, 사용자의 서비스 질을 보장함을 보인다. In the packet data network systems beyond 3G, the service quality of current users is affected by traffic load due to the packet burstiness. There also exists a hot cell problem, a well-known problem of cellular systems, caused by traffic centralization. Hot cell problem is one of the major reasons of degrading system performance because hot cell increases the call drop rate without fully utilization of system resource. Therefore, it is very important to distribute the traffic on the several neighboring cells so that system uses its resource effectively and maintains the quality of service. In this paper, we propose the adaptive handoff algorithms for distributing traffic in the packet data network systems. In addition, we propose a new load estimation method with MAC state diagram suitable for packet data network systems. Through the simulation results, we could find that proposed algorithm is able to improve efficiency of system resource and to assure the service quality of users through traffic distribution.

무선 ATM 망에서 무선 단말을 위한 새로운 위치 관리 기법의 설계

김남기(Namgi Kim),진성기(Sungkee Jean),장익현(Ik Hyeon Jang),윤현수(Hyunsoo Yoon) 한국정보과학회 1999 한국정보과학회 학술발표논문집 Vol.26 No.1A

본 논문에서는 무선 ATM 환경에서 단말의 이동성을 지원하기 위해 사용되는 위치 관리 기법(location management) 중에서 대표적인 Mobile PNNI 기법, Location Register 기법, Integrated 기법에 대해 알아 보고 서로 간의 장단점을 비교해 본다. 그리고 Integrated 기법을 개선한 위치 관리 기법을 제안한다. 제안된 기법의 가장 큰 특징은 기존의 Integrated 기법에 부가적인 변화를 가하지 않고 오히려 더 작은 변화로 더 나은 성능 향상을 얻을 수 있다는 점이다.

단말간 직접 통신 시스템에서 동기 신호 전파 알고리즘 검증을 위한 시뮬레이터 구현

김남기(Namgi Kim) 한국정보기술학회 2014 한국정보기술학회논문지 Vol.12 No.11

In the massive accident or disaster area, the PPDR network, which is needed for efficient rescue activities, must support the device-to-device communication function to guarantee network survivability and robustness. In order to implement the device-to-device communication, the time synchronization among devices is needed. For setting time synchronization among devices, we need an algorithm that effectively propagates the distributed synchronization signal; therefore, we design and implement a simulator which is able to measure the performance of the distributed synchronization signal propagation algorithm. We knew that the more efficient distributed synchronization algorithm could be proposed when the implemented simulator was used because the performance of the distributed synchronization algorithm could be measured quantitatively and visually.

IP 및 AMC 기반 이동 통신 시스템에서 효율적인 핸드오버 알고리즘

김남기(Namgi Kim),정유승(Yuseung Jeong) 한국정보기술학회 2007 한국정보기술학회논문지 Vol.5 No.4

The next generation mobile communication systems have been developed into pure IP packet networks. Moreover, in order to improve transmission efficiency, the AMC (Adaptive Modulation and Coding) scheme, which changes transmission rate depending on channel condition, is also adapted positively. In the IP based system, the rate that mobile users are serviced varies according to the number of users in a single cell. In addition, as the AMC scheme adjusts the data rate in terms of channel conditions. Thus, an user's service quality is dominated by two components; service rate by cell load and data rate by channel conditions. Therefore, In this paper, we propose the efficient handover algorithm considering both the service rate and the data rate for maximizing user performance in the IP and AMC based mobile communication systems.

IEEE 802.16e 무선 네트워크에서 효율적인 데이터 전송 제어를 위한 가변 CRC 기법

김남기(Namgi Kim) 한국정보기술학회 2009 한국정보기술학회논문지 Vol.7 No.3

Today, most wireless network systems use the CRC (Cyclic Redundancy Check) code as an error detection scheme for efficient data transmission control. By the way, the size of CRC code for maintaining a certain level of error detection rate is varied depending on the size of transmitting data. However, the most wireless systems on development adopt fixed-size CRC code, regardless of the size of transmitting data. Therefore, in this paper, we propose a variable CRC scheme for IEEE 802.16e wireless network system which dynamically changes the size of CRC code based on the size of transmitting data. The proposed variable CRC scheme makes the most use of wireless resource with maintaining a certain level of error detection rate.