• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.298-311
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• 2003

Iterative Fourier transform algorithm, (IFTA) is tile iterative numerical algorithm for the design of the diffractive optical elements (DOE), by which the phase distribution of a DOE converges on a local optimal solution. The convergence of IFTA depends on several factors 3s initial phase distribution, the structure of the degree of freedom on the observation plane, and the values of internal parameters. In this paper, we analyze tile dependence of the convergence of IFTA on an internal parameter of IFTA, the relaxation parameter, and propose a new hybrid scheme of genetic algorithm and IFTA to obtain more accurate solution.

• The KIPS Transactions:PartC
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• v.17C no.2
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• pp.145-152
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• 2010

In this paper, we first propose a fast division algorithm in GF($2^{163}$) using standard basis representation, and then it is mapped into divider for GF($2^{163}$) with iterative hardware structure. The proposed algorithm is based on the binary ExtendedGCD algorithm, and the arithmetic operations for modular reduction are performed within only one "while-statement" unlike conventional approach which uses two "while-statement". In this paper, we use reduction polynomial $f(x)=x^{163}+x^7+x^6+x^3+1$ that is recommended in SEC2(Standards for Efficient Cryptography) using standard basis representation, where degree m = 163. We also have implemented the proposed iterative architecture in FPGA using Verilog HDL, and it operates at a clock frequency of 85 MHz on Xilinx-VirtexII XC2V8000 FPGA device. From implementation results, we will show that computation speed of the proposed scheme is significantly improved than the existing two approaches.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4293-4304
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• 2014

In order to ensure the wireless connectivity and seamless service to mobile users, the next generation network system will be an integration of multiple wireless access networks. In a heterogeneous wireless access system, bandwidth allocation becomes crucial for load balancing to avoid network congestion and improve system utilization efficiency. In this article, we propose a new dynamic bandwidth allocation scheme for hierarchical wireless network systems. First, we derive a multi-objective decision criterion for each access point. Second, a bargaining strategy selection algorithm is developed for the dynamic bandwidth re-allocation. Based on the intervenient Stackelberg game model, the proposed scheme effectively formulates the competitive interaction situation between several access points. The system performance of proposed scheme is evaluated by using extensive simulations. With a simulation study, it is confirmed that the proposed scheme can achieve better performance than other existing schemes under widely diverse network environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.450-456
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• 2005

In this paper, we propose a high-speed turbo decoding algorithm and present results of its implementation. The latency caused by (de)interleaving and iterative decoding in conventional MAP turbo decoder can be dramatically reduced with the proposed scheme. The main cause of the time reduction is to use radix-4, center to top, and parallel decoding algorithm. The reduced latency makes it possible to use turbo decoder as a FEC scheme in the real-time wireless communication services. However the proposed scheme costs slight degradation in BER performance because the effective interleaver size in radix-4 is reduced to an half of that in conventional method. To ensure the time reduction, we implemented the proposed scheme on a FPGA chip and compared with conventional one in terms of decoding speed. The decoding speed of the proposed scheme is faster than conventional one at least by 5 times for a single iteration of turbo decoding.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.432-432
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• 2004

• Journal of Korea Multimedia Society
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• v.17 no.8
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• pp.1012-1019
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• 2014

The emerging smart utility networks (SUN) provide two-way communications between smart meters and smart appliances for purpose of low power usage, low cost, and high reliability. This paper deals with a bandwidth-efficient communication method based on the hidden pilot-aided scheme using a precoder in downlink SUN suitable for high-rate multimedia applications. With the aid of the design of a precoder and a superimposed hidden pilot, it is possible to estimate the channel without loss of bandwidth. In the channel estimation procedure, the inevitable data interference, which degrades the performance of channel estimation, can be reduced by the precoder design with an iterative scheme. Computer simulations show that the proposed scheme outperforms the conventional method in terms of achievable data rate, especially when a large number of subcarriers are employed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1725-1727
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• 2015

In this letter, a QR decomposition based sequential BP detection scheme is proposed for MIMO systems. The proposed scheme performs the sequential updates from the observation node having the smallest degree among all the observation nodes. Our simulation results verify that the proposed scheme achieves an improved error performance with a significantly accelerated detection convergence speed compared to the conventional schemes.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.4
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• pp.1-18
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• 2007

In this paper, we develop an adaptive genetic algorithm (aGA). The aGA has an adaptive scheme which can automatically determine the use of local search technique and adaptively regulate the rates of crossover and mutation operations during its search process. For the adaptive scheme, the ratio of degree of dispersion resulting from the various fitness values of the populations at continuous two generations is considered. For the local search technique, an improved iterative hill climbing method is used and incorporated into genetic algorithm (GA) loop. In order to demonstrate the efficiency of the aGA, i) a canonical GA without any adaptive scheme and ii) several conventional aGAs with various adaptive schemes are also presented. These algorithms, including the aGA, are tested and analyzed each other using various test problems. Numerical results by various measures of performance show that the proposed aGA outperforms the conventional algorithms.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.85-99
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• 2008

The dynamic response analysis for large structures using finite element method requires a large amount of computational resources. This paper presents an efficient vibration analysis procedure by combining node-based substructuring reduction method with a response analysis scheme for structures with undamped, proportional or nonproportional damping. The iterative form of substructuring reduction scheme is derived to reduce the full eigenproblem and to calculate the dynamic responses. In calculating the time response, direct integration scheme is used because it can be applied directly to the reduced model. Especially for the non proportional damping matrix, the transformation matrices defined in the displacement space are used to reduce the system. The efficiency and the effectiveness of the present method are demonstrated through the numerical examples.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.75-83
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• 2001

In this paper, numerical analysis is used to find the effects of inclination of rear end on flow characteristic around an automobile. The reference slant angle of rear end is 28.6$^{\circ}$, the slant angle of rear end is decreased to 24$^{\circ}$, 26.6$^{\circ}$ and also increased to 31.6$^{\circ}$, 36.4$^{\circ}$. The 3-D incompressible Navier-Stockes equations are solved by the iterative time marching scheme. The computed surface pressure coefficients were compared with experimental results and a good agreement has been achieved. The A- and C-pillar vortex and other flow phenomena around the ground vehicle are evidently shown. The variation of aerodynamic coefficients of drag, lift with respect to inclination angle of rear end are systematically studied. The flow characteristic on the automobile surface with respect to change of inclination of rear end have been also studied.