• 제어로봇시스템학회논문지
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• 제14권3호
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• pp.318-325
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• 2008

In this paper, a dynamic backoff adjustment method of IEEE 802.15.4 is proposed for time-critical sporadic data in a noisy factory environment. For this, a superframe of IEEE 802.15.4 is applied to a real-time mixed data (periodic data, sporadic data, and non real-time message) transmission in factory communication systems. To guarantee a channel access of real-time sporadic(non-periodic) data, a transmission method using the dynamic backoff is applied to wireless control networks. For the real-time property, different initial BE, CW parameters are used for the dynamic backoff adjustment method. The simulat-ion results show an enhancement of the real-time performance of sporadic emergency data. The proposed method provides the channel access of real-time sporadic data efficiently, and guarantee real-time transmission simultaneously within a limite-d timeframe.

• ETRI Journal
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• 제32권5호
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• pp.823-826
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• 2010

This letter proposes a handover ranging power adjustment scheme to improve handover performance. Incorrect ranging power can degrade handover performance due to the increased handover latency; therefore, the proposed scheme exploits the uplink channel information to adjust the uplink handover ranging power. Simulation results demonstrate that the proposed scheme reduces call outage probability by 33% compared to that of the conventional scheme. It also improves the number of users who satisfy the system requirements for handover interruption time.

• 한국유기농업학회지
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• 제26권4호
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• pp.571-583
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• 2018

The purpose of this study is to explore the dynamic properties of causality and asymmetric price transmission in the distributional channel of the tomato market in Korea. Using the wholesale and retail price series of the tomato market, we obtain the following results. First, the price transmission mechanism reveals the causal relationship channeling from the wholesale price to the retail price. Second, we find an asymmetric price transmission from the analysis using the threshold partial adjustment model. The retail price responds strongly when the wholesale price increases. On the other hand, the retail price shows sluggish adjustment when the wholesale price decreases.

• 인터넷정보학회논문지
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• 제10권3호
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• pp.85-94
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• 2009

본 논문에서는 무선 센서 네트워크에서의 에너지 효율적인 전송방안을 제안하고 이에 대한 이론적 분석을 제시하고자 한다. 본 논문에서 제안하는 전송기법은 채널 상태가 상대적으로 좋을 때만 전송을 시도하는 opportunistic transmission에 기반한 이진 결정 (binary-decision) 기반 전송이다. 이진 결정 기반 전송에서는 Markov decision process (MDP)를 이용하여 성공적인 전송을 위한 최적의 채널 임계값을 도출하였다. 다양한 시뮬레이션을 통해 제안하는 전송기법의 성능을 에너지 효율성과 전송율 측면에서 분석하였다.

• ETRI Journal
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• 제37권5호
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• pp.845-855
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• 2015

To enable the coexistence of Licensed Assisted Access (LAA) and Wi-Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi-Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi-Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non-saturation loads. By computing the activity ratio of Wi-Fi, the proposed analytical model is able to control the time ratio between LAA and Wi-Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility.

• 전자공학회논문지CI
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• 제47권6호
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• pp.28-39
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• 2010

본 논문은 IEEE 802.11p에 기반한 CSMA의 미디어 접근 제어로서, 경쟁 차량단말기(OnBord Unit, OBU)의 증가에 따른 전송 지연(transmission delay)과 감소(data throughput decrease) 문제를 해결하고자 한다. 경쟁 기반의 전송매체에서는 OBU 증가에 따라 충돌 확률이 높아진다. 이러한 미디엄 계층의 성능 향상을 위해 교통량과 데이터 종류를 고려하여 접속 단말기의 개별 충돌 윈도(Contention Windows, CW)를 동적으로 조절하는 EDCA(Enhanced Distributed Channel Access)를 제안하였다. EDCA는 채널별 서비스 차별화를 위해 네 개의 클래스를 AC(Access Category)마다 고정된 최소 경쟁 윈도우(CWmin) 값과 최대 경쟁 윈도우(CWmax) 값을 적용한다. EDCA는 트래픽 특성별로 구분되어 AC 간의 차별화를 보장하지만, IEEE 802.11p 에 구성된 채널별 특성과 네트워크 상태를 보장하지 않기 때문에, 짧은 채널 서비스별 혼잡에 따른 충돌 발생을 능동적으로 대처할 수 없다. 이에 따른 해결방안으로 CWminAS(CWmin Adaptation Scheme)와 ACATICT(Adaptive Contention window Adjustment Technique based on Individual Class Traffic)가 능동적인 CW의 제어 기법으로 제시되었다. 선행연구는 개별 AC 값에 따라 발생하는 충돌 확률을 고려하지 않거나 단일 채널 기반의 개별 AC 값만 고려하고, IEEE 802.11p의 채널별 요구 사항과 이에 따른 충돌 확률을 반영하지 않았다. 본 연구는 이전 서비스 구간에서 OBU 경쟁에 따라 발생하는 충돌 횟수와 현재 무선망의 혼잡을 고려하여, 다음 채널의 CW를 능동적으로 제어하는 기법으로 ACCW(Adaptive Control of Contention windows in considering the WAVE situation)를 제안한다.

• 대한전자공학회논문지
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• 제24권3호
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• pp.472-477
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• 1987

In order to prevent the short-channel effects due to threshold voltage adjustment implantation in conventional n+ doped silicon gate process, a new approach involving automatic doping of polycide by boron during source and drain implantation is introduced. P-MOSFET devece fabricated by theis approach shows improved short channel characteristics than conventional device with n+ doped gate. Some concerns of adopting this approach in CMOS technology are addressed togetheer with some suggestions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 춘계학술대회 논문집
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• pp.86-90
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• 1992

We have studied the characteristics of n-and p-channel FETs with submicron channel length fabricated by twin-well process. Threshold voltage variation and potential distribution with channel ion implantation conditions and impurity profile of n-and p-channel region wee simulated using SUPREM-II and MINIMOS 4.0 simulater, P-channel FET had buried-channel in the depth of 0.15 $\mu\textrm{m}$ from surface by counter-doped boron ion implantation for threshold voltage adjustment. As a result of device measurement, we have obtained good drain saturation characteristics for 3.3 [V] opreation, minimized short channel effect with threshold voltage shift below 0.2[V], high punchthrough and breakdown voltage above 10[V] and low subthreshold value.

• 산업기술연구
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• 제22권A호
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• pp.219-228
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• 2002

The divided channel is not often used on the river and when the installation is for the controlling of the flow quantity. The determination of the channel size is not a easy task. Model tests are examined to confirm the variation of distribution rate by the method of the channel installation and the position of the structure and the adjustment of numerical simulation is executed by the comparing of the results. This study is to execute numerical model according to installation of divided channel by using AQUADYN program, the 2nd dimension numerical model, and HEC-RAS program, the 1st dimension numerical model, by the shape of divided channel. Also, it compares with difference by method about each case.

• 전자공학회논문지D
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• 제34D권8호
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• pp.35-40
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• 1997

To suppress the short channel effects in nMOSFET with 0.1.mu.m channel length, we have fabricated and characterized the ISRC n MOSFET with several process condition. When the recess oxide thickness is 100nm and the channel dose for threshold voltge adjustment is 6*10$^{12}$ /c $m^{-2}$ , B $F_{2}$$^{+}$, the maximum transconductance at $V_{DS}$ =2.0V is 455mS/mm and the BIDL is kept within 67mV. By comparing the ISRC n MOSFET with the conventioanl SHDD (shallowly heavily dopped drain) nMOSFET, we verify the suppression of short channel effects ISRC structure.e.