• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.2039-2042
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• 2002

In this paper, we propose a technique used to simplify the trellis diagram, thus, reduce the complexity of Viterbi decoder in term of the number of Compare-Select (CS) operations needs in decoding process. It is shown that if the branch metrics are properly decomposed into orthogonal components. The trellis diagram can be modified that each original state with large number branches terminating to it can be broken into a number of sub-states having smaller number of branches terminating to them. Simulation results shown that the newly proposed technique can be used reduced the complexity of 8 and 16 PSK-TCMs without degrading the BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2C
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• pp.160-165
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• 2007

In this paper, we propose a novel signal detection method that achieves the maximum likelihood (ML) performance but requires much less computational complexity than the ML detection. When the well-known linear decoding method is used for space-time block coded (STBC) OFDM systems in fast-fading channels, co-channel interference (CCI) as well as inter-carrier interference (ICI) occurs. A maximum likelihood (ML) method can be employed to deal with the CCI; however, its computational complexity is very high. In this paper, we propose a signal detection method for orthogonal space-time coded OFDM systems that achieves the similar error performance as the ML method, but requires much less computational complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.2
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• pp.432-443
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• 2017

The primary goal of the MPEG-H 3D Audio standard is to provide immersive audio environments for high-resolution broadcasting services such as UHDTV. This standard incorporates a wide range of technologies such as encoding/decoding technology for multi-channel/object/scene-based signal, rendering technology for providing 3D audio in various playback environments, and post-processing technology. The reference software decoder of this standard is a structure combining several modules and can operate in various modes. Each module is composed of independent executable files and executed sequentially, real time decoding is impossible. In this paper, we make DLL library of the core decoder, format converter, object renderer, and binaural renderer of the standard and integrate them to enable frame-based decoding. In addition, by measuring the computation complexity of each mode of the MPEG-H 3D-Audio decoder, this paper also provides a reference for selecting the appropriate decoding mode for various hardware platforms. As a result of the computational complexity measurement, the low complexity profiles included in Korean broadcasting standard has a computation complexity of 2.8 times to 12.4 times that of the QMF synthesis operation in case of rendering as a channel signals, and it has a computation complexity of 4.1 times to 15.3 times of the QMF synthesis operation in case of rendering as a binaural signals.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.179-190
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• 2012

In Distributed Video Coding(DVC), a low complexity encoder can be realized by shifting complex processes of encoder such as motion estimation to decoder. Since not only motion estimation/compensation processes but also channel decoding process needs to be performed at DVC decoder, the complexity of a decoder is significantly increased in consequence. Therefore, various fast channel decoding methods are proposed for the most computationally complex part, which is the channel decoding process in DVC decoding. As the channel decoding process becomes faster using various methods, however, the complexity of the other processes are relatively highlighted. For instance, the complexity of side information generation process in the DVC decoder is relatively increased. In this paper, therefore, a fast method for the DVC decoding is proposed by using adaptive search range method in side information generation process. Experimental results show that the proposed method achieves time saving of about 63% in side information generation process, while its rate distortion performance is degraded only by about 0.17% in BDBR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9C
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• pp.888-894
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• 2007

The computational complexity of a sphere decoder (SD) is conventionally reduced by decoding order scheme which sorts candidate symbols in the ascending order of the Euclidean distance from the output of a zero-forcing (ZF) receiver. However, since the ZF output may not be a reliable sorting reference, we propose two types of sorting schemes to allow faster decoding. The first is to use the newly found lattice points in the previous search round instead of the ZF output (Type I). Since these lattice points are closer to the received signal than the ZF output, they can serve as a more reliable sorting reference for finding the maximum likelihood (ML) solution. The second sorting scheme is to sort candidate symbols in descending order according to the number of candidate symbols in the following layer, which are called child symbols (Type II). These two proposed sorting schemes can be combined with layer sorting for more complexity reduction. Through simulation, the Type I and Type II sorting schemes were found to provide 12% and 20% complexity reduction respectively over conventional sorting schemes. When they are combined with layer sorting, Type I and Type II provide an additional 10-15% complexity reduction while maintaining detection performance.

• The Journal of the Convergence on Culture Technology
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• v.7 no.3
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• pp.565-570
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• 2021

A soft-decision decoding scheme of a channel code for correcting an error occurring in a receiver of a digital communication systems is proposed. A method for efficiently decoding by use of the linear and arithmetic structure of linear block codes is presented. In this way, the probability of decoding errors has been reduced. In addition, it is possible to reduce the complexity of decoding as well. Sufficient conditions for achieving optimal decoding has been derived. As a result, the sufficient conditions enable efficient search for candidate codewords. With the proposed decoding scheme, we can effectively perform the decoding while lowering the block error probability.

• The KIPS Transactions:PartC
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• v.11C no.1
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• pp.75-80
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• 2004

An iterative soft-decision decoding algorithm of block codes is proposed. With careful examinations of the first hard-decision decoding result, the candidate codewords are efficiently searched for. An approach to reducing decoding complexity and lowering error probability is to select a small number of candidate codewords. With high probability, we include the codewords which are at the short distance from the received signal. The decoder then computes the distance to each of the candidate codewords and selects the codeword which is the closest. We can search for the candidate codewords which make the error patterns contain the bits with small reliability values. Also, we can reduce the cases that we select the same candidate codeword already searched for. Computer simulation results are presented for (23,12) Golay code. They show that decoding complexity is considerably reduced and the block error probability is lowered.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.213-216
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• 2001

In this paper, the performance of an OFDM/CDMA system with turbo coding is analyzed and simulated in a multipath fading channel. Bit error probability is derived fDr a Rayleigh fading channel. In an OFDM/CDMA system, an OFDM and a CDMA techniques are combined to exploit the advantages of both techniques. For decoding of turbo code, MAP decoding algorithm is employed. From the simulation results. it is demonstrated that turbo coding offers considerable coding gain with reasonable encoding/decoding complexity. Also, it is shown that the BER performance is substantially improved by increasing the interleaver length for a fixed code rate and the increasing number of iterations used in the decoding process. The results in the paper can be applied to the design of OFDM-based CDMA system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5401-5421
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• 2016

Both low-density parity-check (LDPC) codes and the multiple access technique of spatially coupling data transmission (SCDT) can be expressed in bipartite graphs. To improve the performance of iterative demodulation and decoding for SCDT, a novel joint sparse graph (JSG) with SCDT and LDPC codes is constructed. Based on the JSG, an approach for iterative joint demodulation and decoding by belief propagation (BP) is presented as an exploration of the flooding schedule, and based on BP, density evolution equations are derived to analyze the performance of the iterative receiver. To accelerate the convergence speed and reduce the complexity of joint demodulation and decoding, a novel serial schedule is proposed. Numerical results show that the joint demodulation and decoding for SCDT based on JSG can significantly improve the system's performance, while roughly half of the iterations can be saved by using the proposed serial schedule.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.2
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• pp.9-15
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• 1990

A soft-decision decoding algorithm for linear binary block codes is proposed, for minimizing the block error probability. To compare the proposed algorithm with already established decoding methods, computer simulations are performed for the (7,4)Hamming code and the (23,12) Golay code. The average number of hard-decision decoding is always less then 2, and approaches to 1 when the signal to noise ratio is sufficiently large. These results show that the proposed algorithm reduces the decoding complexity.