• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.101-104
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• 2010

MOST는 동기식 데이터, 비동기식 데이터, 제어 데이터를 전송할 수 있는 차량용 멀티미디어 네트워크이다. MOST 네트워크에는 높은 대역폭과 동영상이나 오디오를 버퍼링 없이 전송할 수 있는 동기식데이터 영역이 존재한다. 이러한 동기식 영역을 통해 실시간 데이터를 전송하기 위해서는 소스노드와 싱크노드와의 커넥션 및 해당 채널 할당이 요구된다. 본 논문은 이러한 동기식 영역을 사용하기 위한 모듈을 설계한 후 실제 MOST 네트워크를 구축하여 노드 간 동기식 데이터 전송을 위한 절차와 채널 할당에 대한 이해를 돕고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.453-460
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• 1988

The error probability for coherent frequency-hopped spread-spectrum multiple-access communications is computed by using characteristic function method. We employ PSK as a modulation scheme. The channel capacity is performance measure and the minimum bit signal-to-noise ratio for reliable communications is obtained.

• Journal of Korea Society of Industrial Information Systems
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• v.28 no.4
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• pp.21-34
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• 2023

Federated Learning is divided into synchronous federated learning and asynchronous federated learning. Asynchronous federated learning has a time advantage over synchronous federated learning, but asynchronous federated learning still has some challenges to obtain better performance. In particular, preventing performance degradation in non-IID training datasets, selecting appropriate clients, and managing stale gradient information are important for improving model performance. In this paper, we deal with K-asynchronous federated learning by using non-IID datasets. In addition, unlike traditional method using static K, we proposed an algorithm that adaptively adjusts K and we can reduce the learning time. Additionally, the we show that model performance is improved by using stale gradient handling method. Finally, we use a method of judging model performance to obtain strong model stability. Experiment results show that overall algorithm can obtain advantages of reducing training time, improving model accuracy, and improving model stability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.414-422
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• 2013

This paper describes a 10-bit 10-MS/s asynchronous successive approximation register (SAR) analog-to-digital converter (ADC) using a split-capacitor-based differential digital-to-analog converter (DAC). SAR logic and comparator are asynchronously operated to increase the sampling frequency. The time-domain comparator with an offset calibration technique is used to achieve a high resolution. The proposed 10-bit 10-MS/s asynchronous SAR ADC with the area of $140{\times}420{\mu}m^2$ is fabricated using a 0.18-${\mu}m$ CMOS process. Its power consumption is 1.19 mW at 1.8 V supply. The measured SNDR is 49.95 dB for the analog input frequency of 101 kHz. The DNL and INL are +0.57/-0.67 and +1.73/-1.58, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.135-138
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• 1999

본 논문에서는 차세대 멀티미디어 통신인 IMT-2000의 억세스방식으로 제안되고 있는 비동기 W-CDMA(3GPP) System을 적용, 기존의 IS-95와는 달리 Pilot symbol을 이용하여 페이딩채널을 추정하여, 이를 통한 다중사용자 간섭제거 방법으로 PIC(Parallel Interference Cancellation)을 적용하고 DPCCH(Contorl)과 DPDCH(Data)의 Power Ratio에 따른 성능을 분석하였다. 시뮬레이션 결과 Hard decision 인 경우 사용자5명의 설정에서 C:D : 3:7 과 4:6에서 가장 좋은 성능을 보였으며, 사용자를 10명으로 늘렸을 경우 C:D = 4:6 보다는 3:7의 비율에서 가장 나은 성능을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.698-706
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• 2016

Orthogonal frequency division multiplexing (OFDM) has high peak to power ratio (PAPR). High PAPR makes problems such as signal distortion and circuit cost increasing. To solve the problemsm several PAPR reduction methods have been proposed. However, synchronization and orthogonality in OFDM systems may be a limitation to reduce latency for 5G networks. Generalized frequency division multiplexing (GFDM) is one of the possible solutions for asynchronous and non-orthogonal systems, which are more preferable to reduce the latency. However, multiple subsymbols in GFDM result in more superposition in time domain, GFDM has higher PAPR. Selective mapping (SLM) is one of PAPR reduction techniques in OFDM, which uses phase shift. The PAPR of GFDM SLM is compared to conventional GFDM and OFDM SLM in terms of PAPR reduction enhancement via numerical simulations. In addition, the out-of-band performance is analyzed in the aspect of asynchronous condition interference.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1998.10a
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• pp.623-635
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• 1998

이 논문에서 우리는 분산 실시간 소프트웨어 설계방법인 CODARTS/DA(Concurrent Design Approach for Real-Time Systems/Distributed Application)를 위한 타스크 행위 명세방법을 제안한다. 각 타스크는 CODARTS/DA 모듈들, 즉, 다수 클라이언트/서버 모듈(Multiple Client/Sever Module), 단일 클라이언트/서버 모듈(Single Client/Server Module), 그룹 통신모듈(Group Comm. Module), 우선 순위 모듈등과 통신을 수행하는데, 분산환경의 동기, 비동기 문제들을 제안한 방법으로 설계 명세할 수 있다. 또한 제안된 명세방법은 C언어와 비슷한 문법구조를 제공하므로 쉽게 문서들이 구조적 프로그램으로 변환될 수있다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.190-190
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• 2004

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.660-672
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• 2011

The Web is widely used to share information, utilizing the client-server model. In the client-server model, since the server only responds according to explicit requests from the client, the model seems hard to support sharing of massive information rapidly changing in today's Internet. The technology known as Server Push enables the server to actively provide information to clients without explicit requests from the clients using Web pages. Although various studies have been done to realize the Server Push technologies, there are many problems in the development of push application without push engines which support infrastructures for the effective development of push application. In this paper, we develop JPE(Java Push Engine) which presents the effective support for push services over the Internet. JPE is composed of two main components: the JPE Core supporting Epoll and the JPE Library supporting asynchronous communication. In addition, JPE defines various push functions and provides programming interfaces supporting the functions. Push applications developed using JPE effectively manages client connections with Epoll mechanism, providing push services through AJAX-based asynchronous communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1087-1094
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• 2008

In this paper, we propose the acquisition method of the Cyclic-Prefix CDMA using Good-Autocorrelation-Sequence (GAS-CP-CDMA) system. The sequences for GAS-CP-CDMA are m-sequence and constant amplitude zero autocorrelation code (CAZAC) with good autocorrelation property. The GAS-CP-CDMA system is proposed for interference cancellation in multi-user and -path environment in co-cell. However, the reliable initial acquisition in multi-path fading channel and multi-user system environment is crucial. In this paper, non-coherent power detector and threshold value are used for discriminating signal acquisition. The sequence used for computer simulation is CAZAC. The simulation results show proper threshold value depends on the number of users. Through the computer simulation, we draw setting up method of the optimum threshold value for the GAS-CP-CDMA system.