• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.196-203
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• 1999

In this paper, the DS(direct sequence)-CDMA and MC(multi-carrier)-CDMA, which are being researched recently as a synchronous IMT-2000 scheme for next-generation mobile multimedia communications, are studied in terms of BER(bit error rate) performance. The BER performance of MC-CDMA with EGB, MRC, and improved MMSEC detection scheme are analyzed and compared to that of conventional DS-CDMA adopting RAKE receiver through the computer simulations under the environments of synchronous IMT-2000 transmission channel. Not only single user case but also multiuser case is considered in the given system. As a result, it is shown that MC-CDMA with MMSEC detection outperforms all other schemes improved the $E_b/N_o$ by about 5 [dB] and 6 [dB] when the BER is $2{\times}10^{-3}$, for the indoor/outdoor fading channel and synchronous IMT-2000 transmission channel, respectively. Also in the multiuser case, MC-CDMA with MMSEC detection scheme exhibits better performance than all the other schemes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.221-231
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• 1997

This paper presents an analysis of a hybrid direct-sequence/slow frequency hopped code division multiple access(DS/SFH-CDMA) system employing noncoherent M-ary frequency shift keying(MFSK) modulation in a multiple m-distribution fading environment. Multipath interfer- ence(MPI) and multiuser interference(MUI) is taken into accout and the spectral efficiency is calculated for uncoded as well as simple channel coding systems. The predetection multipath CCI canceller in conjunction with convolution coding is employed for improving the bit error rate(BER) performance. The BER of noncoherent hybrid system is obtained using a Gaussian interference approximation. From the results, we know that the error performance more deteriorates as the depth of fading becomes deeper. The DS part of the modulation combats the multipath interference, whereas the FH part is a predetection against large multiuser interference. It is shown that, for the con- sidered types of a channel coding, the use of a predetection coding is still essential for obtained a satisfactory bit error performance. The results show that the capacity of the DS/SFG-CDMA MFSK communication system increases in proportion to the length of PN code sequence in the presence of AWGN and MUI. In m-distribution fading environment the capacity increases in proportion to the fading index. The capacity is increased and error performance is improved when the CCI Canceller and Convolution code technique are adopted, respectively. From the results, it is known that the error performance of $4\times10^{-2}$ by adopting Canceller technique. Also convolutional coding technique is the improvement of error performance attains about $10^{-5}$ in code rate 1/2.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.630-643
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• 2001

In this paper, the performance of a Multi-Carrier DS-CDMA system with Hybrid $SC/MRC- L_{c}/L$ diversity in the multipath Rayleigh fading environment is analyzed and compared with that of a Wideband DS-CDMA system. Each carriers of the number of the input diversity branches in the Multi-Carrier DS-CDMA system is L and among L, the branches of $L_c$ are chosen to be maximum-ratio-combined. And the diversity outputs are coherent-detected and despread by the correlator of each carrier. As the result, we have known that the structure of the Wideband DS-CDMA system with Hybrid $SC/MRC-L_{c}/L$ diversity reception becomes simple due to no synchronization of bit or phase and in terms of the error performance, the performance of Hybrid $SC/MRC- L_{c}/L$ diversity is better than that of selection diversity, but worse than that of MRC diversity. Moreover, the performance of a Multi-Carrier DS-CDMA system is better than that of a Wideband DS-CDMA system in multipath Rayleigh fading channel since Hybrid $SC/MRC- L_c/L$ diversity can obtain gain from each diversity branch. In case four carriers are used and required BER is $10^{-6}$ in wireless data communication, Hybrid SC/MRC-2/4 diversity can increase more 17 users than Hybrid SC/MRC-2/3 diversity because the better input branches can be selected through increase of input branches.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.3-8
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• 2013

Bit patterned media (BPM) storage is one of the promising technologies to overcome the limitations of the conventional magnetic recording. However, there are some problems in a high areal density BPM storage, inter-track interference, inter-symbol interference and noise which are severely degrading performance of the system with reducing the bit error rate. In this paper, we present a simple iterative two-dimensional equalizer based on the contraction mapping theorem to mitigate these adverse effects. Furthermore, we examine that the channel characteristics of the proposed two-dimensional equalizer satisfies the convergence conditions. In the simulation we demonstrate the bit separation characteristics of the one-dimensional equalizer and the two-dimensional equalizer and evaluate the BER performance of the proposed equalizer comparing with the conventional equalizers. According to the results of experiments, the proposed equalizer is an promising equalizer with maintaining proper complexity for a high areal density BPM storage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.12A
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• pp.1387-1395
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• 2004

Turbo decoder inherently requires large memory and intensive hardware complexity due to iterative decoding, despite of excellent decoding efficiency. To decrease the memory space and reduce hardware complexity, various design issues have to be discussed. In this paper, various design issues on Turbo decoder are investigated and the tradeoffs between the hardware complexity and the performance are analyzed. Through the various simulations on the fixed-length analysis, we decided 5-bits for the received data, 6-bits for a priori information, and 7-bits for the quantization state metric, so the performance gets close to that of infinite precision. The MAX operation which is the main function of Log-MAP decoding algorithm is analyzed and the error correction term for MAX* operation can be efficiently implemented with very small hardware overhead. The size of the sliding window was decided as 32 to reduce the state metric memory space and to achieve an acceptable BER.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.9 s.339
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• pp.73-80
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• 2005

The Turbo decoders based on Log-MAP decoding algorithm inherently requires large amount of memory and intensive complexity of hardware due to iterative decoding, despite of excellent decoding efficiency. To decrease the large amount of memory and reduce hardware complexity, the result of previous research. And this paper design the Turbo decoder applicable to the 3G W-CDMA systems. Through the result of previous research, we decided 5-bits for the received data 6-bits for a priori information, and 7-bits for the quantization state metrics. The error correction term for $MAX^{*}$ operation which is the main function of Log-MAP decoding algorithm is implemented with very small hardware overhead. The proposed Turbo decoder is synthesized in $0.35\mu$m Hynix CMOS technology. The synthesized result for the Turbo decoder shows that it supports a maximum 9Mbps data rate, and a BER of $10^{-6}$ is achieved(Eb/No=1.0dB, 5 iterations, and the interleaver size $\geq$ 2000).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.8
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• pp.1-11
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• 2012

The multi-code spread spectrum communication system, which spreads data bit stream by multiplexing orthogonal codes, can transmit data in high rate. However it needs the high-cost good linear amplifier because of the multi-level output signal. In order to overcome this drawback several systems making the amplitude of output signal constant with Walsh codes have been proposed. Recently constant amplitude pre-coded multi-code spread spectrum systems using extended m-sequence have been proposed. In this paper we consider an extended m-sequence based constant amplitude multi-code spread spectrum system with code set partitioning. By grouping the orthogonal codes into 4 subsets, not only is the computational complexity of the transceiver reduced but BER performance also improves. It has been shown that parity checking on four detected codes at the receiver can correct code detection error and result in BER performance enhancement. In this paper we propose a improved parity check receiver. We carried out computer simulation to verify feasibility of the proposed algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.510-516
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• 2005

In this paper, we discuss parameters of line code and simulate a same optical ethernet having minimum bandwidth(MB810) and non-minimum bandwidth line code(8B/10B) to present the possibility of improving of transmission performance using minimum bandwidth line code on the high speed optical ethernet. We design the high speed optical ethernet using Serial type LAN PHY 10GBASE-E(WDM type LAN PHY 10GBASE-LX4) for the single(multi) channel link. To compare the transmission performance of MB810, 8B/10B line code we measure the bit error rate(BER) according to the received optical power of single and multi channel link.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.669-672
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• 2008

In this paper, we propose a constant-amplitude multi-rode trans-bi-orthogonal modulation scheme by introducing a simple constant-amplitude coding scheme with redundant bits and trans-code, which if a modified orthogonal modulation scheme. Generally speaking, the orthogonal modulation scheme is not appropriate for the high speed data transmission applications because of bad bandwidth efficiency. Therefore, we use the multi-rode trans-bi-orthogonal modulation with trans-code for high bandwidth efficiency. Moreover, redundant bits are used for constant-amplitude-coding. Finally, we compare the performance of the proposed scheme with the orthogonal modulation and constant-amplitude multi-code trans-orthogonal modulation by using the computer simulation.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.3
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• pp.226-231
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• 2010

This paper proposes a new coding technique for constructing error correcting high rate DC-free multimode code using a generator matrix generated from a sparse parity-check matrix. The scheme exploits high rate generator matrixes for producing distinct candidate codewords. The decoding complexity depends on whether the syndrome of the received codeword is zero or not. If the syndrome is zero, the decoding is simply performed by expurgating the redundant bits of the received codeword. Otherwise, the decoding is performed by a sum-product algorithm. The performance of the proposed scheme can achieve a reasonable DC-suppression and a low bit error rate.