• Convergence Security Journal
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• v.16 no.7
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• pp.85-91
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• 2016

Block cipher is one of the prominent and important elements in cryptographic systems and study on the minimal construction is a major theme in the cryptographic research. Even and Mansour motivated by the study suggested a kind of block cipher called the Even-Mansour scheme in the early 1990s. It is a very simple cipher with one permutation and two secret keys. There have been many studies on the Even-Mansour scheme and security analysis of the scheme. We explain the Even-Mansour scheme and simplify those attacks on the Even-Mansour scheme with mathematical language. Additionally, we show that Pollard's rho attack to the discrete logarithm problem can be used to attack the Even-Mansour scheme with the same complexity of the Pollard's rho attack.

• Journal of Environmental Science International
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• v.19 no.2
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• pp.137-148
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• 2010

This paper investigates the characteristics of turbulence schemes. Turbulence closures are fundamental for modeling the atmospheric diffusion, transport and dispersion in the boundary layer. In particular, in non-homogeneous conditions, a proper description of turbulent transport in planetary boundary layer is fundamental aspect. This study is based on the Regional Atmospheric Modeling System (RAMS) and combines four different turbulence schemes to assess if the different schemes have a impact on simulation results of vertical profiles. Two of these schemes are Isotropc Deformation scheme (I.Def) and Anisotropic deformation scheme (A.Def) that are simple local scheme based on Smagorinsky scheme. The other two are Mellor-Yamada scheme (MY2.5) and Deardorff TKE scheme (D.TKE) that are more complex non-local schemes that include a prognostic equation for turbulence kinetic energy. The simulated potential temperature, wind speed and mixing ratio are compared against radiosonde observations from the study region. MY2.5 shows consistently reasonable vertical profile and closet to observation. D.TKE shows good results under relatively strong synoptic condition especially, mixing ratio simulation. Validation results show that all schemes consistently underestimated wind speed and mixing ratio but, potential temperature was somewhat overestimated.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.7
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• pp.9-16
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• 2011

In this paper, various kinds of high throughput turbo decoding schemes are introduced, and a new turbo decoding scheme using the advantages of each scheme is proposed. The proposed scheme uses the decoding structure of double flow scheme, sliding window scheme and shuffled turbo decoding scheme. Simulation results show that the proposed scheme offers a BER performance equivalent to those of existing turbo decoding schemes with less clock cycles. We also show that the required memory can be reduced by choosing proper size of sliding window. Consequently, we can design a high throughput turbo decoder requiring low power and low area.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.12
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• pp.15-21
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• 2004

The Guaranteed Bandwidth Rate scheme has been designed to accomodate non-real-time applications, such as Internet based traffic in Pm networks. The Guaranteed Bandwidth Rate scheme not only guarantees a minimum throughput at the frame level, but also supports a fair share of available resources. In this paper, we propose a cell control algorithm which can improve the fairness and the throughput through the traffic control in PM networks. For the evaluation of the proposed scheme, we compare proposed scheme with the existing scheme in the fairness and the throughput. Simulation results show that proposed scheme can improve the fairness and throughput than the existing scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.407-414
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• 2007

A sensor fault detection scheme(SFDS) for a class of nonlinear systems that can be represented by Takagi-Sugeno fuzzy model is proposed. Basically, the SFDS may be considered as a multiple observer scheme(MOS) in which the bank of state observers and the detection & isolation logic are included. However, the proposed scheme has two great differences from the conventional MOSs. First, the proposed scheme includes fuzzy fault detection observers(FFDO) that are constructed based on the T-S fuzzy model that provides very good approximation to nonlinear dynamic systems. Secondly, unlike the conventional MOS, the FFDOS are driven not parallelly but sequentially according to the predetermined sequence to avoid the massive computational burden, which is known to be the biggest obstacle to the practical application of the multiple observer based FDI schemes. During the operating time, each FFDO generates the residuals carrying the information of a specified fault, and the corresponding fault detection logic unit performs the logical operations to detect and isolate the fault of interest. The proposed scheme is applied to an inverted pendulum control system for sensor fault detection/isolation. Simulation study shows the practical feasibility of the proposed scheme.

• Journal of KIISE:Information Networking
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• v.31 no.2
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• pp.217-223
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• 2004

This paper proposes a new backoff scheme to improve the throughput of stations over wireless local area networks. It is designed to carry out the proposed backoff scheme using information of basic service area, such as number of stations, in terms of the throughput. Basic idea of the proposed backoff scheme is that we change the contention window size for backoff time as collisions increase. We evaluate the performance of the proposed backoff scheme using Markov model analysis and compare it with the IEEE 802.11e backoff scheme. The numerical results indicate that the Proposed backoff scheme may offer better performance than the conventional backoff scheme in terms of the throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.1010-1018
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• 2007

In this paper, we propose a companding scheme to effectively reduce PAPR (Peak-to-Average Power Ratio) of the OFDM (Orthogonal frequency Division Multiplexing) signals. The proposed scheme is basically based on the companding scheme to consider both complexity and Bit Error Rate (BER) performance, and composed of the clipping followed by the companding scheme. In the first step of the proposed scheme, some of peak signals which do not influence the BER even without them, are clipped. In the second step, the proposed scheme utilizes the ${\mu}-law$ companding to effectively reduce the PAPR. Simulation results show that the proposed clipped companding scheme can provide more PAPR reduction without degradation of the BER performance, as compare to the conventional ${\mu}-law$ companding.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.1-16
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• 2005

Adaptive control methods are studied for the Satellite to isolate vibration in spite of the nonlinear system dynamics and parameter uncertainties of disturbance. First, a centralized control scheme is developed based on the particle swarm optimization(PSO) algorithm and feedback theory to automatically tune controller gains. A simulation study of a 3 degree-of-freedom device was conducted to evaluate the performance of the proposed control scheme. Next, since a centralized control scheme is hard to construct model dynamics and not goad at performance when controller and systems environment are easily changed, a decentralized control scheme is presented to avoid these defects of the centralized control scheme from the point of view of production and maintenance. It is based on the adaptive control methodologies to find PID controller parameters. Experiment studies were conducted to apply the adaptive control scheme and evaluate the performance of the proposed control scheme with those of the conventional control schemes.

• Journal of Internet Computing and Services
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• v.7 no.6
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• pp.79-86
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• 2006

Many of concurrency control for client-sewer database systems have been proposed and studied in the literature. However, commonly known schemes do not manage to the case of dramatic changes in data contention because the data contention of database systems is changed for each cases. In this paper, we propose o hybrid concurrency control. The proposed scheme uses a optimistic scheme for the first-run transactions and a pessimistic scheme for the second-run transactions. By pre-claiming locks in the second phase, deadlocks which ore possible in pessimistic based concurrency control are prevented in our approach. In addition, the scheme ensures at most one re-execution even if the validation in the optimistic phase fails. By a detailed simulation, this paper examines the behaviors of the Distributed Optimistic Concurrency Control and the proposed scheme. The simulation study shows our scheme outperforms Distributed Optimistic Concurrency Control in our experimental result.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.10
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• pp.5013-5034
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• 2019

In the Peer-to-Peer (P2P) streaming systems, peers randomly form a network overlay to share video resources with a data scheduling scheme. A data scheduling scheme can have a great impact on system performance, which should achieve two optimal objectives at the same time ideally. The two optimization objectives are to improve the perceived video quality and maximize the network throughput, respectively. Maximizing network throughput means improving the utilization of peer's upload bandwidth. However, maximizing network throughput will result in a reduction in the perceived video quality, and vice versa. Therefore, to achieve the above two objects simultaneously, we proposed a new data scheduling scheme based on multi-objective particle swarm optimization data scheduling scheme, called MOPSO-DS scheme. To design the MOPSO-DS scheme, we first formulated the data scheduling optimization problem as a multi-objective optimization problem. Then, a multi-objective particle swarm optimization algorithm is proposed by encoding the neighbors of peers as the position vector of the particles. Through extensive simulations, we demonstrated the MOPSO-DS scheme could improve the system performance effectively.