• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.1-8
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• 2010

Multi antenna techniques using space-time codes can achieve diversity gains in a multi-path environment without additional bandwidth requirement. Most of the 4G candidate standards including the IEEE 802.16e adopt multi-input multi-output (MIMO) schemes to achieve either high throughput performance or diversity gains. In these 4G candidate standards, turbo codes using an iterative decoder with soft input soft output are used to overcome serious channel fading. For this reason, the estimated signal values from MIMO detectors should be soft decision detection values. In this paper, we propose efficient methods to estimate soft decision detection values for various space time coding schemes, and provide the simulation results of turbo coded space time coding scheme over an IEEE 802.16e link.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5C
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• pp.469-477
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• 2007

Most multimedia source coders exhibit unequal bit error sensitivity. Efficient transmission system design should therefore incorporate the use of matching unequal error protection (UEP). In this paper, we present and evaluate a flexible space-time coding system with unequal error protection. Multiple transmit and receive antennas and bit-interleaved coded modulation techniques are used combined with rate compatible punctured convolutional codes. A near optimum iterative receiver is employed with a multiple-in multiple-out inverse mapper and a MAP decoder as component decoders. We illustrate how the UEP system gain can be achieved either as a power or bandwidth gain compared to the equal error protection system (EEP) for the identical source and equal overall quality for both the UEP and EEP systems. An example with two/three transmit and two receive antennas using BPSK modulation is given for the block fading channel.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.6
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• pp.2446-2462
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• 2016

In this paper, a frequency domain Expectation-Maximization (EM)-based channel estimation algorithm for Space Time Block Coded-Orthogonal Frequency Division Multiplexing (STBC-OFDM) systems is investigated to support higher data rate applications in wireless communications. The computational complexity of the frequency domain EM-based channel estimation is increased when higher order constellations are used because of the ascending size of the search set space. Thus, a search set reduction algorithm is proposed to decrease the complexity without sacrificing the system performance. The performance results of the proposed algorithm is obtained in terms of Bit Error Rate (BER) and Mean Square Error (MSE) for 16QAM and 64QAM modulation schemes.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.176-183
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• 1996

A new iterative scheme is proposed for finite element analysis of wrinkling or tension structures. This enables us to update the stress state and the internal forces correctly taking into account the existence of wrinkling. The finite element implementation of the scheme is straightforward and simple, and only minor modifications of the existing total Lagrangian finite element codes for membranes are needed. The validity of the scheme is demonstrated via numerical examples for the torsion of a membrane and the quasi-static inflation of an automotive airbag, both made of isotropic or anisotropic elastic membranes

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.485-490
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• 2000

This paper describes the application of discretized continuum-type optimality criteria (DCOC) for minimum-cost design of the reinforced concrete frame structures consisting of beams and columns. The cost of construction as objective function which includes the costs of concrete, reinforced steel and formwork is minimized. The design constraints include limits on the maximum deflection at a prescribed node, bending and shear strengths in beams, uniaxial bending strength of columns according to design codes(CEB/FIP, 1990). In the first stage, only beams with uniform cross-sectional parameters per span are considered. But the steel ratio is allowed to vary freely. The cross-sectional parameters and steel ratio in each column are assumed to be uniform for practical reasons. Optimality criteria is given based on the well known Kuhn-Tucker necessary conditions, followed by an iterative procedure for designs when the design variables are the depth and the steel ratio. The versatility of the DCOC technique has been demonstrated by considering numerical examples which have one-bay four-storey frame.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.9B
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• pp.1321-1328
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• 2001

터보 부호는 종료 알고리즘(termination algorithm)과 반복복호 알고리즘(iterative decoding algorithm)을 사용함으로써 AWGN 채널환경에서 BER 성능이 우수한 것으로 알려져 있다. 그러나 터보 부호는 복호과정에서 큰 복호지연을 요구하며 음성 신호를 전송할 때 프레임의 크기가 작아서 성능의 열화가 생긴다. 또한, 높은 SNR에서는 BER 성능의 개선이 없는 Error Floor 현상이 나타나기 때문에 오류정정 능력의 한계에 도달하는 큰 단점을 가진다. Flattening Effect는 종료 알고리즘을 사용하는 터보 부호(terminated conditions : TC)보다는 종료 알고리즘을 사용하지 않는 터보 부호(non terminated conditions : NTC)에서 상대적으로 많이 나타난다. 따라서 본 논문에서는 NTC 하에서 터보 부호의 Flattening Effect를 개선시키기 위한 새로운 블록 인터리빙 방법을 제시한다. 모의실험결과, 새로운 블록 인터리빙 방법을 적용함으로써 효과적으로 Flattening Effect를 제거할 수 있음을 알 수 있었다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.4
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• pp.117-125
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• 2014

In this paper, a novel hardware architecture of the LT codec is presented where non-BP based decoding algorithm is applied. Novel LT codec architecture is designed with an efficient degree distribution unit using Verilog HDL. To perform permutation operation, different initial valued or time shifted counters have been used to get pretty well permutations and an effect of randomness. The codec will take 128 bits as input and produce 256 encoded output bits. The simulation results show expected performances as the implemented distribution and the original distribution are pretty same. The proposed LT codec takes 257.5 cycle counts and $2.575{\mu}s$ for encoding and decoding instead of 5,204,861 minimum cycle counts and 4.43s of the design mentioned in the previous works where iterative soft BP decoding was used in ASIC and ASIP implementation of the LT codec.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.4
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• pp.1296-1309
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• 2023

In this paper, based on the soft cancellation (SCAN) bit-flipping (SCAN-BF) algorithm, a generalized SCAN bit-flipping (GSCAN-BF-Ω) decoding algorithm is carried out, where Ω represents the number of bits flipped or corrected at the same time. GSCAN-BF-Ω algorithm corrects the prior information of the code bits and flips the prior information of the unreliable information bits simultaneously to improve the block error rate (BLER) performance. Then, a joint threshold scheme for the GSCAN-BF-2 decoding algorithm is proposed to reduce the average decoding complexity by considering both the bit channel quality and the reliability of the coded bits. Simulation results show that the GSCAN-BF-Ω decoding algorithm reduces the average decoding latency while getting performance gains compared to the common multiple SCAN bit-flipping decoding algorithm. And the GSCAN-BF-2 decoding algorithm with the joint threshold reduces the average decoding latency further by approximately 50% with only a slight performance loss compared to the GSCAN-BF-2 decoding algorithm.

• Geophysics and Geophysical Exploration
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• v.4 no.3
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• pp.70-79
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• 2001

The integral equation method is a powerful tool for numerical electromagnetic modeling. But the difficulty of this technique is the size of the linear equations, which demands excessive memory and calculation time to invert. This limitation of the integral equation method becomes critical in inverse problem. The conventional Born approximation, where the electric field in the anomalous body is approximated by the background field, is very rapid and easy to compute. However, the technique is inaccurate when the conductivity contrast between the body and the background medium is large. Quasi-linear, quasi-analytical and extended Born approximations are novel approaches to 3-D EM modeling based on the linearization of the integral equations for scattered EM field. These approximation methods are much less time consuming than full integral equation method and more accurate than conventional Born approximation. They we, however, still approximate methods for 3-D EM modeling. Iterative series methods such as modified Born, quasi-linear and quasi-analytical can be used to increase the accuracy of various approximation methods. Comparisons of numerical performance against a full integral equation and various approximation codes show that the iterative series methods are very accurate and almost always converge. Furthermore, they are very fast and easy to implement on a computer. In this study, extended Born series method is developed and it shows more accurate result than that of other series methods. Therefore, Iterative series methods, including extended Born series, open principally new possibilities for fast and accurate 3-D EM modeling and inversion.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.66-74
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• 2010

Recently distributed video coding (DVC) is spotlighted for the environment which has restriction in computing resource at encoder. Wyner-Ziv (WZ) coding is a representative scheme of DVC. The WZ encoder independently encodes key frame and WZ frame respectively by conventional intra coding and channel code. WZ decoder generates side information from reconstructed two key frames (t-1, t+1) based on temporal correlation. The side information is regarded as a noisy version of original WZ frame. Virtual channel noise can be removed by channel decoding process. So the performance of WZ coding greatly depends on the performance of channel code. Among existing channel codes, Turbo code and LDPC code have the most powerful error correction capability. These channel codes use stochastically iterative decoding process. However the iterative decoding process is quite time-consuming, so complexity of WZ decoder is considerably increased. Analysis of the complexity of LPDCA with real video data shows that the portion of complexity of LDPCA decoding is higher than 60% in total WZ decoding complexity. Using the HDA (Hard Decision Aided) method proposed in channel code area, channel decoding complexity can be much reduced. But considerable RD performance loss is possible according to different thresholds and its proper value is different for each sequence. In this paper, we propose an adaptive HDA method which sets up a proper threshold according to sequence. The proposed method shows about 62% and 32% of time saving, respectively in LDPCA and WZ decoding process, while RD performance is not that decreased.