• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.1 no.2
• /
• pp.145-158
• /
• 1997

Method for synchronizing multimedia data is needed to support continuous transmission of multimedia data through a network in a bounded time and it also required for supporting continuous presentation of multimedia data with the required norminal playout rate in distributed network environments. This paper describes a new synchronization method for supporting delay-sensitive multimedia Presentation without degration of Quality of services of multimedia application. It mainly aims to support both intermedia and intermedia synchronization by absorbing network variations which may cause skew or jitter. In order to remove asynchonization problems, we make use of logical time system, dynamic buffer control method, and adjusting synchronization intervals based on the quality of services of a multimedia. It might be more suitable for working on distribute[1 multimedia systems where the network delay variation is changed from time to time and no global clock is supported. And it also can effectively reduce the amount of buffer requirements needed for transfering multimedia data between source and destination system by adjusting synchronization intervals with acceptable packet delay limits and packet loss rates.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1991.10a
• /
• pp.133-136
• /
• 1991

한국통신 연구개발단에서 개발한 국제망관리시스템(INMS)에서 필요로하는 망관리 데이터는 각 국제교환기로부터 발생즉시 온라인으로 수집되어 분석 처리되어야한다. 이들 망관리 데이터는 양이 많을뿐아니라 여러곳에 분산되어져 있는 교환기로부터 실시간으로 신뢰성있는 데이터를 온라인으로 수집하여야한다. 본 논문에서는 INMS의 온라인 수집시스템을 소개하고, 비동기식 데이터 통신에서의 전송에러검출 기법을 적용한 온라인 프로토콜에 의한 온라인 데이타 수집기법을 소개하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.1
• /
• pp.53-65
• /
• 2012

Recently wireless intra-vehicle communication has received a great interest from the automotive industry and ultra wideband (UWB) technology is considered as one of the potential candidate for this system. Many research works have been done on the measurement and modeling of intra-vehicle communication channel. However, very little work has been reported for the performance analysis of various PHY layer methods under the intra-vehicle communication environment. This paper is to study IEEE 802.15.4a standard in intra-vehicle channel and to evaluate its performance. Channel model in chassis and engine compartment is considered for evaluation. Through simulation BER performance of system with different receiver structures is analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.11C
• /
• pp.851-859
• /
• 2008

This paper investigates the effect a guard period (GP) in the form of a cyclic prefix for asynchronous multicarrier-code division multiple access (MC-CDMA) systems. At first, we analyze the performance of asynchronous MC-CDMA systems with a GP, which results in closed-form bit error rate (BER) performance. Furthermore, it confirms that the frequency diversity of MC-CDMA systems is identical to the path diversity. The analytical approach proposed here is extended to the case without a GP. The derived analytical results show that a GP is required for MC-CDMA systems in order to mitigate not only the effect of intersymbol interference (ISI) and intercarrier interference (ICI) but also the desired signal power degradation. In addition, the accuracy of the proposed analysis is verified by simulations.

• 정보화사회
• /
• s.177
• /
• pp.56-57
• /
• 2005

유럽진영을 중심으로 이미 시장활성화에 접어든 비동기식 3G서비스인 WCDMA. 국내에서도 SK텔레콤과 KTF가 서비스하고 있지만 이런저런 이유로 투자를 미뤄오면서 두 사업자 합쳐 가입자 5000명 수준에 머물고 있다. WCDMA가 기존 EVDO 서비스 대비 장점이 미약했기 때문이다. 그러나 내년부터 상황은 달라질 전망이다. WCDMA보다 5배 이상 속도가 빠른 HSDPA가 떠오르고 있기 때문이다.

• ETRI Journal
• /
• v.11 no.2
• /
• pp.41-50
• /
• 1989

본고에서는 BISDN 구현에 핵심이 되고 있는 비동기식 정보전달 모드인 ATM 방식을 이해하기 위하여 ISDN의 진화와 ATM의 정의 및 특징 등을 살펴보고 ATM 망의 실현에 필히 고려되어야 하는 서비스, 서비스의 질, UNI, 교환 및 전송, 그리고 신호방식등을 분석하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.23 no.4
• /
• pp.23-28
• /
• 2023

In a wireless smart utility network communication system, an asynchronous low power MAC is standardized and used according to IEEE 802.15.4e. An asynchronous MAC called RIT (Receiver Initiated Transmission) has a characteristic in which delay time and power consumption are greatly affected by a check-in interval (RIT period). By waking up from sleep every check-in interval and checking whether there is data to be received, power consumption in the receiving end can be drastically reduced, but power consumption in the transmitting end occurs due to an excessive wakeup sequence. If an excessive wake-up sequence is reduced by shortening the check interval, power consumption of the receiving end increases due to too frequent wake-up. In the RIT asynchronous MAC technique, power consumption performance according to traffic load and operation of check-in interval is analyzed and applied to Wi-SUN construction.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.6
• /
• pp.1583-1591
• /
• 1998

In this paper, we consider the quasi maximum likelihood(quasi-ML) detector which uses antenna arrays in asynchronous time-varing channels. It is shown that the proposed quasi-ml detector can be regarded as a beamformer followed by a decorrelator: a method based on the eigendecomposition of the correlation matrix of the inverse-filtered signal is proposed to estimate the channel vectors. We also show that the proposed algorithm estimates the channel vector within small mismatch loss in severe propagation environment through computer simulations.

• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.579-583
• /
• 2008

본 논문은 이더넷이 비동기식으로 전송됨으로 인해, 동일한 전송속도를 가진 장비라 할지라도 링크가 제공하는 명목상의 최대속도로 전송될 경우, 상호 접속한 장비간의 전송클럭 차이로 인해 프레임의 손실이 발생한다. 본 논문에서는 PHY에서 복원된 수신 클럭과 송신 클럭의 차이를 비교하고 동시에 프레임버퍼에 쌓인 큐를 참조하여 프레임 손실이 방생할 수 있는 임계치를 넘어설 경우, 전송프레임의 프리엠블 길이를 조정함으로써 이더넷 장비에서 전송클럭의 차이로 인한 프레임손실을 줄일 수 있음을 확인하였다.

• Journal of KIISE:Computer Systems and Theory
• /
• v.27 no.4
• /
• pp.394-400
• /
• 2000

The main goal of synchronization is to guarantee exclusive access to shared data and critical sections, and then it makes parallel programs work correctly and reliably. Exclusive access restricts parallelism of parallel programs, therefor efficient synchronization is essential to achieve high performance in shared-memory parallel programs. Many techniques are devised for efficient synchronization, which utilize features of systems and applications. This paper shows the simulation results that existing synchronization methods have inefficiency under CC-NUMA(Cache Coherent Non-Uniform Memory Access) system, and then compares the performance of Freeze&Melt synchronization that can remove the inefficiency. The simulation results present that Test-and-Test&Set synchronization has inefficiency caused by broadcast operation and the pre-defined order of Queue-On-Lock-Bit (QOLB) synchronization to execute a critical section causes inefficiency. Freeze&Melt synchronization, which removes these inefficiencies, has performance gain by decreasing the waiting time to execute a critical section and the execution time of a critical section, and by reducing the traffic between clusters.