• 한국인터넷방송통신학회논문지
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• 제16권6호
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• pp.153-158
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• 2016

다중홉 무선센서네트워크에서 플러딩(또는 브로드캐스팅) 전송은 경로 탐색, 주소설정, 메시지 전송과 같은 기본 작업이다. 그러나 플러딩 기법은 'Broadcasting Storm' 현상을 발생시키며, 메시지 충돌, 혼잡, 불필요한 네트워크 자원을 소모하게 된다. 따라서 이러한 단순 플러딩 기법의 단점을 보완하기 위한 다양한 Flooding 기법이 제안되었다. 이러한 플러딩 기법은 확률기반, 카운터 기반, 거리기반, 이웃 기반 기법으로 분류할 수 있다. 본 논문에서는 이러한 대표적인 플러딩 기법의 장단점을 소개하고, 컴퓨터 시뮬레이션을 통하여 단순 플러딩 기법을 포함한 각 기법의 성능과 효율성을 비교 분석하였다.

• 제어로봇시스템학회논문지
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• 제15권7호
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• pp.661-666
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• 2009

The linear model following controller(LMFC) scheme controls a plant based on the output of a reference model, thereby replacing a PI controller that has better time response characteristics, which are irrelevant to the structural perturbation of a plant. However, the main weakness of the LMFC scheme is a slow response time to load changes. Thus, to solve this problem, a robust linear model following controller(RMFC) was developed that is robust in load changes. However, when compared with the LMFC scheme, the RMFC scheme has a weaker performance in the case of system parameter changes. Therefore, this paper presents a new LMFC scheme, where the controller is designed based on the output of a plant rather than the output of a model, as in the case of the conventional LMFC scheme. As a result, in the case of load changes, the response characteristics of the proposed scheme are slower than those of the RMFC scheme, yet laster than those of the conventional LMFC scheme, however, for parameter changes, the proposed scheme has a superior performance over the RMFC scheme. The usefulness of the proposed LMFC scheme is verified through a comparison using MATLAB/SIMULINK.

• Asian-Australasian Journal of Animal Sciences
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• 제17권1호
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• pp.18-26
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• 2004

This study evaluated the impact of an AI heifer calf rearing scheme on dairy stock development, in a coconut grazing and a peri-urban smallholder dairy production system in the Western Province of Sri Lanka. The heifer rearing scheme included free advice on calf rearing, drugs, acaricides, minerals and subsidised concentrates for 30 months. The farmers in the coconut growing area integrate dairying with their plantation, they sell their milk to the main processors. The peri-urban farmers are intensive milk producers, who sell their milk at informal markets. To estimate the effect of the heifer rearing scheme on dairy replacement stock development, scheme farmers were compared with farmers who did not participate in the scheme. Calf mortality was twice as high in non-scheme farms (23-28%) as in scheme farms (12-14%). The scheme had a positive effect on weight development and scheme heifers calved 4.5 months earlier than non-scheme heifers. The calf rearing package is cost effective in both farming systems, however, the required cash inputs are a major constraint. The costs per in-calf heifer under the scheme are much lower than the production of such animals by either multiplication in state farms or importing them. The coconut grazing system showed the highest potential for producing surplus dairy stock.

• 정보보호학회논문지
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• 제26권1호
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• pp.17-30
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• 2016

본 논문에서는 효율적인 공개키 기반 공모자 추적 및 제외 스킴을 제안하고자 한다. 공모자 추적 및 제외 스킴은 암호 전송 스킴(Broadcast encryption scheme)에 공모자 추적과 제외 기능을 추가한 것으로 악의적인 사용자들이 유출한 개인키 또는 공모한 해적판 키를 시스템에서 제외함으로서 스킴의 안전성을 유지하는 것이다. 또한 제외 기능은 일부 사용자만을 위한 암호문을 만들 수 있어 다양한 응용 환경에 적용할 수 있는 스킴이다. 본 논문에서는 합성수 위수의 겹선형 군을 기반으로 설계된 스킴[Augmented broadcast encryption scheme]을 소수 위수의 겹선형 군을 기반으로 하는 스킴으로 변화시켰고, 효율성의 척도인 공개키, 개인키, 암호문의 크기를 크게 개선했다. 또한 제외 기능에 대한 분석을 통해 기존 논문의 제한적인 제외 기능을 충분한 제외 기능으로 확장하는 결과를 얻을 수 있었다. 본 논문에서 제안하는 스킴의 구조는 계층적 구조 또는 피라미드 구조를 갖는 우리나라 정부, 군 조직 등에 쉽게 적용 가능하다.

• 제어로봇시스템학회논문지
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• 제15권6호
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• pp.598-603
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• 2009

The checkpointing scheme is a well-known technique to cope with transient faults in digital systems. This paper proposes an adaptive checkpointing scheme for the reliability improvement of real-time control systems. The proposed adaptive checkpointing scheme is based on the previous work about the reliability problem of an equidistant checkpointing scheme. For the derivation of the adaptive scheme, some conditions are introduced which are to be satisfied for the reliability improvement by exploiting an equidistant checkpointing scheme. Numerical data show the proposed adaptive scheme outperforms the equidistant scheme from a reliability point of view.

• ETRI Journal
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• 제30권2호
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• pp.282-289
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• 2008

We propose a new mini-slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN-PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini-slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN-PON with a mini-slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.

• 전자공학회논문지A
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• 제33A권2호
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• pp.40-49
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• 1996

In this paper, we studied channel assignment and handover schemes for the indoor microcell systems. For efficient frequency spectrum reuse we proposed the high quality reassignment (HQR) scheme. Proposed HQR scheme tries to keep the reuse distances small by monitoring C/I of channels being used. To assign a channel for a new or handove call, the scheme checks C/I of all available channels. Then HQR assigns the channel that has C/I near the threshold value, A_TH. The scheme also checks C/I of ongoing calls and continuously reassigns a new channel when needed. It attempts handover not only when C/I gets below a handover threshold value, HO_TH, but also when C/I becomes above a high quality reassignment threshold, H_TH. The performance of the proposed HQR scheme was analyzed by a computer simulation configuraed. The performance of the scheme was also analyzed for various threshold values selected and the results are presented in this paper. The results show that HQR scheme perfomrs better than the scheme adopted for DECT.

• International Journal of Internet, Broadcasting and Communication
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• 제8권3호
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• pp.50-57
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• 2016

In 2013, Li et al. proposed an improved smart card-based remote user password authentication scheme, and claimed that their scheme not only overcomes security weaknesses of the Chen et al.'s scheme but also is a more user friendly scheme compared with other schemes. In this paper, we analyze the security of Li et al.'s authentication scheme and we show that Li et al.'s authentication scheme is still insecure against the various attacks, such as the off-line password guessing attack, the forgery attack, and the session key generation attack etc. Also, we propose an improved scheme that can resist these security drawbacks of Li et al.'s authentication, even if the secret information stored in the smart card is revealed. As a result of security analysis, the improved scheme is relatively more secure against several attacks than other related schemes in terms of the security.

• 전자공학회논문지A
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• 제31A권7호
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• pp.1-16
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• 1994

In this paper, we propose a new multiple access scheme for VSAT(Very Small Aperture Terminal) data communications. The proposed scheme has better performance in terms of delay throughput than Controlled Multiaccess Scheme which has excellent performance. The proposed scheme use the spare reservation method, adaptation method to offered load, and fixed bandwidth reservation method. In this paper, we analyze the performance using simple queueing model and present the simulation results. When network traffic is very low, the new scheme and the controlled multiaccess scheme have almost the same access delay characteristic. As the network load becomes higher, the new scheme's access delay gain becomes larger. Futhermore, even when the network traffic is very high it is possible to access satellite link within the delay similar to one round-trip delay. In addition to access delay performance enhancement, the new scheme has facility that supports fixed bandwidth reservation. So it shows more enhanced performance in the environment that stream traffic is dominant such as in VSAT communication environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권1호
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• pp.497-522
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• 2018

Fully homomorphic encryption(FHE) scheme may be the best method to solve the privacy leakage problem in the untrusted servers because of its ciphertext calculability. However, the existing FHE schemes are still not being put into the practical applications due to their low efficiency. Therefore, it is imperative to find a more efficient FHE scheme or to optimize the existing FHE schemes so that they can be put into the practical applications. In this paper, we optimize GSW scheme by using the parallel computing, and finally we get a high-performance FHE scheme, namely PGSW scheme. Experimental results show that the time overhead of the homomorphic operations in new FHE scheme will be reduced manyfold with the increasing of processing units number. Therefore, our scheme can greatly reduce the running time of homomorphic operations and improve the performance of FHE scheme through sacrificing hardware resources. It can be seen that our FHE scheme can catalyze the development of FHE.