• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.110-118
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• 2009

The PB/MC-CDMA(Partial Block Multi Carrier Code Division Multilple Access) system can improve the performance by reducing the ICI(Inter-Code Interference) between users. Also, this system can achieve the frequency diversity gain by avoiding ISI(Inter Symbol Interference). Therefore, the performance of PB/MC-CDMA system is better than that of conventional MC-CDMA(Multi Carrier Code Division Multiple Access) system. However, similarly to other multi-carrier systems, it still has a PAPR(Peak to Average Power Ratio) issue. In this paper, we propose a peak power reduction technique involving optimized spreading code selection without side information for the PB/MC-CDMA. The PB/MC-CDMA system in each block of units reuses the code so the extra code will be remained. This extra code is divided into several groups to calculate the PAPR and solving the PAPR problem by transferring the selected code which has minimum peak power.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1996.06a
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• pp.33-38
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• 1996

A multi-media binary DS/CDMA system with variable processing gain and coherent correlation receivers are considered under additive white Gaussian noise channels. Two types of information sources with different rates and transmitting powers are assumed to be transmitted simultaneously in the same channel. Average signal-to-noise ratios at the correlation receiver outputs for each type of information sources are analytically derived as functions of discrete partial cross-correlations between spreading code sequences. The analysis is expected to provide analytical tools for use in preliminary system design and spreading code selection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.333-340
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• 2003

In this paper, we propose a new turbo-coded orthogonal frequency division multiplexing (OFDM) transmission scheme that can improve greatly the performance by making all the turbo-coded symbols have the same reliability for OFDM transmission over a frequency selective fading channel. The same reliability, that is, the same fading can be accomplished through multiplexing of turbo-coded symbols using distinct orthogonal codes and spreading over the whole effective subcarriers (hereafter, called as the orthogonal code multiplexing (OCM)). As for the orthogonal code selection, we choose the set of the discrete Fourier transform (DFT) basis sequences, since the code set holds the orthogonality irrespective of the length and also has the equal energy property. We perform computer simulations using the Log-maximum-a-posteriori (Log-MAP) algorithm for iterative decoding in order to assess the performance of the proposed transmission scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.502-511
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• 2012

As the importance of GNSS system increases, the necessity of independent system is increased also. When the independent GNSS system is required, GNSS signal design is necessary with requirement definition. This paper suggests the design method of GNSS signal using the analysis result of receiver performance. First, the candidates are defined based on the design elements. Then the receiver performance of the candidates is analyzed based on the performance evaluation parameters. The weights of performance evaluation parameter are defined in order to consider the receiver performance in a various aspects. Finally, the calculation of normalized performance evaluation parameters and weights are derived to obtain the compared value for signal selection. Spreading code, modulation method and carrier frequency are considered as design parameters. Also, correlation width, DLL PLL thermal noise jitter, frequency bandwidth and side lobe peak ratio are considered as performance evaluation parameters. And positioning performance, robustness to noise, bandwidth efficiency are considered as the performance aspects. This paper analyzes the performance of each candidate using software based simulator and suggest the method to compare objectively the performance of each candidates.