• The Journal of Engineering Geology
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• v.17 no.4
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• pp.511-516
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• 2007

Active method MASW(Multi channel Analysis of Surface Waves), which is one of the surface wave exploration methods, has the difficulties to supply enough shear wave velocity log, caused by short spread length and lack of low frequency energy. To make up this defect, the passive method MASW survey is taked and analysised in Daeku subway construction site, Jungpyung-dong Gyeongsan city. The passive method MASW using the microtremor, improve the quality of the overtone record by applying the azimuth correction caused offline sources. And combing with active overtone record which is acquired by same geometry has the benefits of improve shallow depth resolution and extend possible investigation depth. To take the optimized acquisition parameters, the 2m, 4m, and 6m geophone spacing is tested. And 2m spacing overtone image could make the reliable shear wave velocity log.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.11
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• pp.1407-1413
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• 2019

In this paper, we assume that another transmitter can transmit its data signal in the same frequency band in order to maximize the frequency efficiency of non-orthogonal multiple access(NOMA) systems. We also focus on the improvement in fairness performance of receiver's data rates, not the maximization of sum data rate for NOMA systems. Thus, in this paper, we propose a power allocation scheme to enhance the fairness performance of average data rates of receivers considering the NOMA systems in the presence of interference. Assuming Rayleigh fading channels, the average data rates of receivers are defined, and the power allocation coefficients to improve the data-rate fairness are derived by using high signal-to-noise power ratio approximation. In addition, through simulations, it is shown that the proposed power allocation scheme can improve the data-rate fairness in the NOMA system with interference.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.519-529
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• 1998

In this paper, we analyze the effects of interference canceller on the performance of multitone DS/CDMA system. Although there are various kinds of interference cancellers suggested by different researchers, we adopt a canceller used by Yoon et at.［9］. We consider three kinds of inteferences, that is, multiPath interference(MPI), interchannel interference(ICI) and multiple access interference(MPI). The equations for variances ate derived for the inteferences and thermal noise used for signal to noise ratio calculation. We also consider RAKE reception over multipath channel and three stage interference canceller used for performance improvement. We draw some conclusions that interference canceller is effective in multitone DS/CDMA system and the performance is further improved with the higer order of diversity and larger number of PN chips.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.853-864
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• 2001

In this paper, system model is based on proposed standardization by 3GPP(Asynchronous IMT-2070 system), and we have analyzed the performance of the DS-CDMA/QPSK which cancelled self-interference, so that occurs when the received signal time is delay by multipath fading. We proposed the new scheme that designed for self-interference cancellation and the system performance is calculated in Rician fading and Rayleigh fading channel. The proposed rake receiver can be achieved a gain of about 1 [dB]∼6 [dB] more than generally rake receiver, and will be a very effective method to improve the performance of IMT-2000, and these data can be available for modem design of DS-CDMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.932-939
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• 1998

In this paper, we analyze the performance of a multicode-CDMA system which have been proposed for the multimedia communications. The performance of a multicode-CDMA system, providing good spectrum efficiency as well as serving various bit rates, is analyzed with multipath, frequency selective, slowly fading Rayleigh channel. Also the proposed scheme adopting RAKE receiver with MRC(Maximal Ratio Combine) is advantageous to multipath channel. For a practical channel modeling, the JTC(Joint Technical Committee) recommended channel model(JTC(AIR) 23-065R6) is applied to simulation. The proposed schemehas serial-to-parallel convertor which splits input data stream of 2 Mits/s into 20 branches o 100 kbits/s. From the result of simulation, the case of RAKE receiver with 3 fingers to reduce the system complexity required the relatively large $E_{b}/N_O$ of 0 dB~1.5 dB, compared to the case of RAKE receiver with the number of path finger to keep the average error rate to be $1{\times}10^{-3}$ in channel A.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.167-170
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• 2010

잡음 분산 값은 SNR(signal-to-noise ratio) 추정이나 MMSE(minimum mean square error) 계산, 채널 임펄스 응답의 추정 등에 사용되는 중요한 파라미터이다. 채널이 시간에 따라 변하는 무선 통신 환경에서, 신호와 섞여 있는 잡음과 간섭 신호의 정확한 추정에는 그 한계가 있으며 이로 인해 발생하는 추정 오차는 수신기의 데이터 검출 성능을 저하시킨다. 훈련열을 이용하여 채널을 추정하였을 경우 추정된 채널 임펄스 응답 신호 중 다중 경로 신호는 소수에 불과하고 나머지 대부분의 계수는 잡음 성분만을 포함하는 신호이다. 이러한 특징을 이용하여 채널의 추정 계수로 잡음 분산을 추정하는 방법이 기존에 제시되어 있다. 여기서 제안하는 알고리즘은 기존 알고리즘인 PSA(partial sample average)와 비교해 연산량에서 차이가 거의 없이 구현되며, 3GPP TDD[1]에서의 모의 실험을 통하여 기존 알고리즘보다 더 정확한 분산 값을 찾아냄을 확인하였다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.10
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• pp.19-26
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• 1998

In this paper, we studied the design and implementation of fading compensation systems at aspects of narrowband mobile communication using TTIB SSB. The mobile radio channel with multipath fading places fundamental limitations on the performance of wireless communication systems. The multipath fading is compensated using pilot tone in TTIB SSB. The TTIB transceiver was implemented using the prevailing digital signal processing (DSP) techniques and compensation for the multipath fading was incorporated in the receiver in the form of DSP algorithm. In order to evaluate fading compensation performance in TTIB transceiver, we first used computer simulation. In the simulation results, we found that the TTIB transceiver could compensate for the multipath fading as expected. Second, we carried out some experiments on TTIB transceiver implementation with DSP boards and later with hardwares including RF circuits with center frequency of 145MHz. Through these experiments, we found that fading compensation performance in TTIB transceiver was almost as good as that obtained from simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.167-171
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• 2002

As a channel of a DS-CDMA system is shared among several users, the receivers face the problem of MAI. Also the multipath scenario leads to ISI. Both components are undesired, but unlike the additive noise process, which is usually completely unpredictable, their space-time structure helps to estimate and remove them. This paper investigates a DS-CDMA system with a fading multipath channel. The investigations have been separated into a channel estimation part and a reception part. In the first part, the estimation of multipath parameters(DOA, TOA) are considered, space-time beamformers(Decorrelating, Match-Filter, Wiener-Hopf) are performed in the second part. To assess many different estimation techniques and beamformers, the simulation compared with theoretical values is performed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1340-1346
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• 2022

In this paper, we consider a downlink non-orthogonal multiple access (NOMA) using multiple transmit antennas, where the transmit antenna selection scheme is used to reduce the system complexity. Thus, in this paper, we propose radio resource allocation and receiver selection schemes in order to improve the outage probability performance of the downlink NOMA system using the transmit antenna selection scheme. In particular, the receiver selection scheme is a method of grouping the receivers to improve the outage probability performance, and the radio resource allocation scheme is a method of allocating radio resources to each group in order to enhance the outage probability performance. In addition, through the computer simulation under the assumption of independent Rayleigh fading channels, we show that the proposed radio resource allocation and receiver selection schemes can improve the outage probability performance at the expense of the sum rate performance.

• Journal of Broadcast Engineering
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• v.14 no.4
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• pp.438-449
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• 2009

To analyze reception environments of ATSC Digital TV, CIR (Channel Impulse Response) analysis systems are widely applied. The receiving performances of conventional CIR analysis systems are not as good as those of commercial state-of-the-art receivers. There are difficulties in measuring and analyzing reception problems caused by multi-path interferences. To solve these problems, commercial DTV chip sets embedded CIR analysis system is proposed. Generally, commercial chip sets provide baseband (In-phase) channel data and field or segment sync data. For more precise analysis of measured I channel data, it is necessary to extract Q (quadrature) channel data components as well. This paper presents the technical requirements of CIR analysis system for DTV. In order to satisfy such requirements and measure more accurate magnitude and phase of CIR, a method to derive the quadrature data from the measured in-phase channel data is proposed. The proposed channel analysis system is implemented with a commercial DTV chip set and expedites the data analysis for use on DTV field test vehicles. Computer simulation and laboratory test results are provided to demonstrate the performance of the proposed channel analysis system.