• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.423-429
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• 2019

Recently, a variety of methods for the performance improvement of ultra-high speed wideband wireless transmission systems have been suggested. This paper proposes a space-frequency (SF) block coded single side band (SSB) single carrier (SC)-frequency division multiple access (FDMA) transmission system. In the proposed SSB SC-FDMA system, SF block code is implemented with the complex conjugates, which are formed from discrete Fourier transform (DFT) spreading of pulse amplitude modulation (PAM) signals. As a result, transmit diversity gain can be obtained in the proposed SF block coded SSB SC-FDMA system without any significant increase of the system computational complexity. The simulation result shows that the signal-to-noise power ratio (SNR) performance of the proposed SF block coded SSB SC-FDMA system is approximately 4 dB better than the SNR performance of the conventional SSB SC-FDMA system with single transmit antenna at a symbol error rate (SER) of $10^{-2}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1077-1082
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• 2007

This paper presents the analysis of the potential ultra-wideband(UWB) interference to WiMAX at 3.5 GHz bands and the mitigation method using transmit power control(TPC) of UWB system. UWB interference effect is evaluated with WiMax's outage probability over UWB density when multiple UWB systems and single WiMAX receiver distribute in unit area of 1$km^2$, When UWB distribution density is 20$devices/km^2$ and the dynamic range of TPC is 30 dB, UWB interference effect with TPC is decreased by 42 % rather than that without mitigation scheme. Finally, we describe that the proposed TPC is an effective method to mitigate UWB interference to WiMAX.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2601-2619
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• 2012

A differencing multiuser detection (MUD) method is proposed for multiple-input multiple-output (MIMO) direct sequence (DS) ultra-wideband (UWB) system to cope with the multiple access interference (MAI) and the computational efficiency in Nakagami fading channel. The method, which combines a multiuser-interference-cancellation-based decision feedback equalizer using error feedback filter (MIC DFE-EFF), a coefficient optimization algorithm (COA) and a differencing algorithm (DA), is termed as MIC DFE-EFF (COA) with DA for short. In the paper, the proposed MUD method is illuminated from the rudimental MIC DFE-EFF to the advanced MIC DFE-EFF (COA) with DA step by step. Firstly, the MIC DFE-EFF system performance is analyzed by minimum mean square error criterion. Secondly, the COA is investigated for optimization of each filter coefficient. Finally, the DA is introduced to reduce the computational complexity while sacrificing little performance. Simulations show a significant performance gain can be achieved by using the MIC DFE-EFF (COA) with DA detector. The proposed MIC DFE-EFF (COA) with DA improves both bit error rate performance and computational efficiency relative to DFE, DFE-EFF, parallel interference cancellation (PIC), MIC DFE-EFF and MIC DFE-EFF with DA, though it sacrifices little system performance, compared with MIC DFE-EFF (COA) without DA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9C
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• pp.899-906
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• 2005

In this paper, the optimum maximum-likelihood rake receiver for impulsive, fading channel is derived, and a sub-optimun rake receiver with reduced complexity is obtained for practical purposes. Numerical results show that, when the noise is impulsive, the rake receivers designed for impulsive noise offer performance improvement over those optimized for Gaussian environment. It is also observed that, as the number of fingers increases, the performance of the rake receivers designed for impulsive environment improves while the rake receiver optimized for Gaussian environment experiences performance degradation in impulsive environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5162-5168
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• 2013

Hopping sequences of Time Hopped Ultra Wideband Impulse Radio (TH-UWB-IR) system are to mitigate multipath fading and to provide the multiple access chances for multi users. For the reliable communications, the same pulses are repeatedly transmitted for a bit duration based on hopping sequences. The proposed decoding scheme utilizes the intervals of inter-codes in a frame where the short interval between two pulses leads to the large interference by the multipath fading. For a single user case, the proposed method obtains 0.5dB gain over the conventional method at BER=$10^{-3}$. Decoding performance of repeated pulses can be increased using the property of the hopping sequences of multi users.