• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.5
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• pp.21-29
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• 1992

This paper proposes a new MAC propocol for high-speed MAN. The proposed protocol is based on the P$_1$-persistent tranmission scheme and each node calculates the transmission probability periodically by using delay information(DI). A window mechanism for the calculation of message delay in each node is proposed to improve the adaptability of the proposed protocol to traffic changes. The capactiy of the proposed protocol is analyzed. The simulation results show that the proposed protocol gives fair message delay under heavy load conditions and, when the transmission speed or distance is increased, the message delay variation of the proposed protocol is less than that of IEEE 802.6 DQDB.

• ETRI Journal
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• v.34 no.2
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• pp.210-215
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• 2012

In this paper, a group delay time controller (GDTC) is proposed based on a reflection topology employing a parallel resonator as the reflection termination. The design equations of the proposed GDTC have been derived and validated by simulation and experimental results. The group delay time can be varied by varying the capacitance and inductance at an operating frequency. To show the validity of the proposed circuit, an experiment was performed for a wideband code division multiple access downlink band operating at 2.11 GHz to 2.17 GHz. According to the experiment, a group delay time variation of $3{\pm}0.17$ ns over bandwidth of 60 MHz with excellent flatness is obtained.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.765-768
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• 2012

사회관계망에서 영향력 전파 문제는 네트워크에 가장 영향력을 끼칠 수 있는 노드들을 찾아 전체 네트워크에 영향력을 최대화 하는 것을 목적으로 한다. 본 논문에서는 Delay-Tolerant Networks에서 각 노드의 영향력을 측정하여 가장 영향력 있는 노드 집합을 선택하는 문제를 다룬다. 노드 간 연결성이 항시 보장되지 않는 Delay-Tolerant Networks 환경에서는 전체 네트워크 정보를 정확히 알 수 없기 때문에 노드의 영향력을 정확히 측정하는 것은 매우 어렵다. 본 논문에서는 Delay-Tolerant Networks 환경에서 분산 방식으로 각자 노드가 k-Clique 구조로 커뮤니티를 구성하여 국지적 정보 (Local Information)만을 활용하여 자신의 영향력을 추정하는 방법을 제시하고 실험을 통해 제안 기법으로 산출한 노드들의 영향력이 전체 네트워크 관점에서 산출한 노드들의 영향력에 근접함을 실험을 통해 증명한다.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.14-21
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• 1997

In delay-optimized designs, timing failures due to manufacturing delay defects are more likely to occur because the average timing slacks of paths decrease and the system becomes more sensitive to smaller delay defect sizes. In this paper, the impact of delay optimized logic circuits on delay fault testing will be discussed and compared to the case for non-optimized designs. First, we provide a timing optimization procedure and show that the resultant density function of path delays is a delta function. Next we also discuss the impact of timing optimization on the yield of a manufacturing process and the defect level for delay faults. Finally, we will give some recommendations on the determination of the system clock time so that the delay-optimized design will have the same manufacturing yield as the non-optimized design and on the determination of delay fault coverage in the delay-optimized design in order to have the same defect-level for delay faults as the non-optimized design, while the system clock time is the same for both designs.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.72-82
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• 2009

In OFDMA systems, cyclic delay diversity can improve the system performance due to diversity effects. However, applying cyclic delay diversity to block-hopping SC-FDMA systems can affect the performance in two contrary ways: positive effect due to increased frequency diversity and negative effect caused by increased frequency selectivity. Hence, the delay value for cyclic delay diversity should be carefully selected to maximize the system performance. This paper discusses these two contrary effects and proposes a method of determining the delay value of cyclic delay diversity for block-hopping SC-FDMA systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.997-1010
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• 2014

Today, as the hierarchical cellular system is getting more attention than before, some recent studies introduce delay based admission control (AC) scheme which delays the admission to the macro-embedded small cell for a relatively short time to prevent unnecessary handover caused by the short-term visitors of the small cell area. In such delay based ACs, when we use improper delay parameter, the system frequently makes incorrect handover decisions such as where unnecessary handover is allowed due to too short delaying, or where necessary handover is denied due to too long delaying. In order to avoid these undesirable situations as much as possible, we develop a new delay parameter decision method based on probabilistic cell residence time approximations. By the extensive numerical and analytical evaluations, we determine the proper delay parameter which prevents the incorrect handover decision as much as possible. We expect our delay parameter decision method can be useful system administration tips in hierarchical cellular system where delay based AC is adopted.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.643-651
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• 2008

In this paper, we propose a method to determine the optimal cyclic delay value of cyclic delay diversity(CDD) in orthogonal frequency division multiplexing(OFDM) systems. As the cyclic delay value increases, we can get signal to interference and noise ratio(SINR) gain by diversity effect, while SINR loss increases because of channel estimation errors. If the optimal delay value obtained by the proposed method is applied to CDD scheme, we can minimize the required SINR for a given FER(frame error rate) under the above mentioned trade-off.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.5
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• pp.291-299
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• 2005

An obstacle avoidance algorithm for a network-based autonomous mobile robot is proposed in this paper. The obstacle avoidance algorithm is based on the VFH(Vector Field Histogram) algorithm and two delay compensation methods with the VFH algorithm are proposed for a network-based robot with distributed environmental sensors, mobile actuators, and the VFH controller. Firstly, the environmental sensor information is compensated by prospection with acquired environmental sensor information, measured network delays, and the kinematic model of the robot. The compensated environmental sensor information is used for building polar histogram with the VFH algorithm. Secondly, a sensor fusion algorithm for localization of the robot is proposed to compensate the delay of odometry sensor information and the delay of environmental sensor information. Through some simulation tests, the performance enhancement of the proposed algorithm in the viewpoint of efficient path generation and accurate goal positioning is shown here.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.53-54
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• 2006

In this paper, we analytically evaluate packet delay and energy consumption of S-MAC protocol with a modified Markov chain model. Although some models, based on IEEE 802.11 MAC protocol, to analyze the S-MAC protocol in wireless sensor network (WSN) have been proposed, they fail to consider the differences in architecture between the S-MAC and the 802.11 MAC. Therefore, by reflecting the significant features in the S-MAC function, we model the operation of S-MAC protocol, and derive its packet delay and energy consumption in single-hop WSN. Numerical results show the delay and the dissipated energy at various duty cycle values according to offered load, where a practical mote is used.

• International Journal of Control, Automation, and Systems
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• v.2 no.2
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• pp.182-188
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• 2004

This paper presents a design method of delay-dependent control for T-S fuzzy systems with time delays. Based on parallel distributed compensation (PDC) and a descriptor model transformation of the system, a delay-dependent control is utilized. An appropriate Lyapunov-Krasovskii functional is chosen for delay-dependent stability analysis. A sufficient condition for delay-dependent control is represented in terms of linear matrix inequalities (LMIs).