• ETRI Journal
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• v.33 no.5
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• pp.661-669
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• 2011

In this paper, we propose an efficient soft-output signal detection method for spatially multiplexed multiple-input multiple-output (MIMO) systems. The proposed method is based on the ordered successive interference cancellation (OSIC) algorithm, but it significantly improves the performance of the original OSIC algorithm by solving the error propagation problem. The proposed method combines this enhanced OSIC algorithm with a multiple-channel-ordering technique in a very efficient way. As a result, the log likelihood ratio values can be computed by using a very small set of candidate symbol vectors. The proposed method has been synthesized with a 0.13-${\mu}m$ CMOS technology for a $4{\times}4$ 16-QAM MIMO system. The simulation and implementation results show that the proposed detector provides a very good solution in terms of performance and hardware complexity.

• ETRI Journal
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• v.31 no.2
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• pp.173-181
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• 2009

The growth of the World Wide Web and web-based applications is creating demand for high performance web servers to offer better throughput and shorter user-perceived latency. This demand leads to widely used cluster-based web servers in the Internet infrastructure. Load balancing algorithms play an important role in boosting the performance of cluster web servers. Previous load balancing algorithms suffer a significant performance drop under dynamic and database-driven workloads. We propose an estimation-based load balancing algorithm with admission control for cluster-based web servers. Because it is difficult to accurately determine the load of web servers, we propose an approximate policy. The algorithm classifies requests based on their service times and tracks the number of outstanding requests from each class in each web server node to dynamically estimate each web server load state. The available capacity of each web server is then computed and used for the load balancing and admission control decisions. The implementation results confirm that the proposed scheme improves both the mean response time and the throughput of clusters compared to rival load balancing algorithms and prevents clusters being overloaded even when request rates are beyond the cluster capacity.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.4
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• pp.35-44
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• 1989

In this paper, a precisely speed-controlled DC servo motor system utilizing direct adaptive control (DAC) algorithm which require that neither satisfaction of the perfect model following conditions (PMFC) nor explicit parameter identification is proposed. Computer simulation as well as experiments using MC-68000 are implemened with the above input trajectory fairly well in spite of load disturbances and parameter variations. Presented algorithm is simple and effective both in software and hardware applications.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.9
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• pp.1207-1214
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• 1995

We present an optimized integer cosine transform(OICT) as an alternative approach to the conventional discrete cosine transform(DCT), and its fast computational algorithm. In the actual implementation of the OICT, we have used the techniques similar to those of the orthogonal integer transform(OIT). The normalization factors are approximated to single one while keeping the reconstruction error at the best tolerable level. By obtaining a single normalization factor, both forward and inverse transform are performed using only the integers. However, there are so many sets of integers that are selected in the above manner, the best OICT matrix obtained through value minimizing the Hibert-Schmidt norm and achieving fast computational algorithm. Using matrix decomposing, a fast algorithm for efficient computation of the order-8 OICT is developed, which is minimized to 20 integer multiplications. This enables us to implement a high performance 2-D DCT processor by replacing the floating point operations by the integer number operations. We have also run the simulation to test the performance of the order-8 OICT with the transform efficiency, maximum reducible bits, and mean square error for the Wiener filter. When the results are compared to those of the DCT and OIT, the OICT has out-performed them all. Furthermore, when the conventional DCT coefficients are reduced to 7-bit as those of the OICT, the resulting reconstructed images were critically impaired losing the orthogonal property of the original DCT. However, the 7-bit OICT maintains a zero mean square reconstruction error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8B
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• pp.1204-1210
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• 2010

In this paper, in order to reduce the power consumption of LCD TV, we present a two-dimensional dimming algorithm for LED BLU(Backlight Unit) using light spread function and a pragmatic implementation method. In conventional two dimensional dimming algorithms, LED BLU is divided into MxN blocks and proper backlight luminance for each block is computed according to input image and used for dimming control. But, LED light of each block is diffused and affects the neighboring blocks so that luminance of each block becomes larger than that of intent. In the proposed algorithm, dimming control values are reduced by the amount of quantity affected by the neighboring blocks using light spread function, resulting in additional reduction of power consumption.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.5
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• pp.636-642
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• 1999

The synthesis of the 3D images is the most important part of the virtual reality. The ray tracing is the best method for reality in the 3D graphics. But the ray tracing requires long computation time for the synthesis of the 3D images. So, we implement the ray tracing with software and hardware. Specially we design the hit-test unit with FPGA tool for the ray tracing. Hit-test unit is a very important part of ray tracing to improve the speed. In this paper, we proposed a new hit-test algorithm and apply the parallel architecture for hit-test unit to improve the speed. We optimized the arithmetic unit because the critical path of hit-test unit is in the multiplication part. We used the booth algorithm and the baugh-wooley algorithm to reduce the partial product and adapted the CSA and CLA to improve the efficiency of the partial product addition. Our new Ray tracing processor can produce the image about 512ms/F and can be adapted to real-time application with only 10 parallel processors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.81-88
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• 2004

Turbo code has been adopted in the 3GPP standard, since its performance is very close to the Shannon limit. However, the turbo decoder requires a lot of computations and the amount of the memory increases as the block size of turbo codes becomes larger. In order to reduce the complexity of the turbo decoder, the Log-MAP, the Max-Log-MAP and the sliding window algorithm have been proposed. In this paper, the performance of turbo codes adopted in the 3GPP standard is analyzed by using the floating point and the fixed point implementation. The efficient decoding method is also proposed. It is shown that the BER performance of the proposed method is close to that of the Log-MAP algorithm.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1740-1751
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• 2018

This paper proposes a novel fault tolerant tracking control (FTTC) scheme for a class of nonlinear systems with actuator failures based on the policy iteration (PI) algorithm and the adaptive fault observer. The estimated actuator failure from an adaptive fault observer is utilized to construct an improved performance index function that reflects the failure, regulation and control simultaneously. With the help of the proper performance index function, the FTTC problem can be transformed into an optimal control problem. The fault tolerant tracking controller is composed of the desired controller and the approximated optimal feedback one. The desired controller is developed to maintain the desired tracking performance at the steady-state, and the approximated optimal feedback controller is designed to stabilize the tracking error dynamics in an optimal manner. By establishing a critic neural network, the PI algorithm is utilized to solve the Hamilton-Jacobi-Bellman equation, and then the approximated optimal feedback controller can be derived. Based on Lyapunov technique, the uniform ultimate boundedness of the closed-loop system is proven. The proposed FTTC scheme is applied to reconfigurable manipulators with two degree of freedoms in order to test the effectiveness via numerical simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.599-602
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• 2005

This paper utilizing model picture of finished clothes in fashion design field various material (textile fabrics) doing Draping directly can invent new design, and do not produce direction sample or poetic theme width and confirm clothes work to simulation. Also, construct database about model and material image that can confirm Mapping result by real time. Development did the 2.5D Mapping system that used path extraction algorithm, warp algorithm, a lighting extraction and application algorithm in order to implement natural Draping of model picture and material image.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.3
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• pp.120-130
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• 2001

We present an approach to parallelizing optimal power flow that is suitable for distributed implementation and is applicable to very large interconnected power systems. This approach can be used by utilities to optimize economy interchange without disclosing details of their operating costs to competitors. Recently, it is becoming necessary to incorporate contingency constraints into the formulation, and more rapid updates of telemetered data and faster solution time are becoming important to better track changes in the system. This concern led to a research to develop an efficient algorithm for a distributed optimal power flow based on the Auxiliary Problem Principle and to study the convergence rate improvement of the distributed algorithm. The objective of this paper is to find a set of control parameters with which the Auxiliary Problem Principle (Algorithm - APP) can be best implemented in solving optimal power flow problems. We employed several IEEE Reliability Test Systems, and Korea Power System to demonstrate the alternative parameter sets.