• Journal of Institute of Control, Robotics and Systems
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• v.12 no.10
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• pp.1050-1055
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• 2006

Since the muiltipath signal arrives at the GPS receiver later than the line-of-sight signal, the multipath signal makes the shape of the correlation function asymmetric. This paper proposes a multipath mitigation method through asymmetry estimation of the correlation function, in which multiple correlators are utilized. The asymmetry is estimated from correlation values of correlators which have different chip spacings. Based on the estimated asymmetry, the correlation function is modified in order to get a better code tracking performance. Even through the proposed method uses multiple correlators including the narrow correlator, the acquisition performance is not degraded since the number of search cell of the narrow correlator part can be reduced in the algorithm of the proposed method. The simulation results show that the proposed method gives better performance than the generic correlator in multipath environment.

• Management & Information Systems Review
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• v.3
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• pp.201-214
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• 1999

Adaptive correlator receiver with neural network based on complex multilayer perceptron is persented for suppressing interference of narrow-band of direct spread spectrum communication systems. Recursive least square algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise and transmission power, computer simulation results show that bit error ratio of adaptive correlator using neural network improved that of adative transversal filter of direct sequence spread spectrum considering of jamming and narrow-band interference. Bit error ratio of adaptive correlator with neural network is reduced about 10-1 than that of adaptive transversal filter where interference versus signal ratio is 5dB.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.79-84
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• 1996

In this paper, adaptive correlator model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of adaptive correlator uswing backpropagation neural network improved than that of adaptive transversal filter of direct sequence spread spectrum considering of co-channel and narrow-band interference. Bit error ratio of adaptive correlator using backpropagation neural network is reduced about $10^{-1}$ than that of adaptive transversal filter where interference versus signal ratio is 5 dB.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.542-546
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• 2009

In this Paper, a back propagation neural network learning algorithm based on the complex multilayer perceptron is represented for controling and detecting interference of the received signals in cellular mobile communication system. We proposed neural network adaptive correlator which has fast convergence rate and good performance with combining back propagation neural network and the receiver of cellular. We analyzed and proved that NNAC has lower bit error probability than that of traditional RAKE receiver through results of computer simulation in the presence of the tone and narrow - band interference and the co-channel interference.

• Publications of The Korean Astronomical Society
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• v.31 no.2
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• pp.11-19
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• 2016

This paper presents the results of test observations toward a point source, 4C39.25, for observation modes with various bandwidths and numbers of IF streams in order to examine a reliability of the Daejeon hardware correlator performance for correlating VLBI (Very Long Baseline Interferometry) data obtained with the several observation modes of the KVN (Korean VLBI Network). We used a DiFX software correlator (DiFX) as a reference, for investigating the output visibilities from the Daejeon corelator. It is found that the band shapes of the output visibilities from two correlators are similar to each other and the correlated flux density for each baseline obtained from the Daejeon hardware correlator is lower by 3 - 7% than that from the DiFX. The flux difference is attributed to the limitation of FPGA resources and the difference of fringe rotation algorithm of the Daejeon hardware correlator. The conversion factor, 0.93 ~ 0.97, is proposed for future correlation with the Daejeon hardware correlator.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2570-2572
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• 2005

본 논문에서는 다중 경로 오차 제거를 위해, 4개의 상관값을 제공하는 가중 협대역 상관기(Weighted Narrow Correlator) 구조에 대해 제안한다. 가중 협대역 상관기는 서로 다른 칩 간격을 가지는 여러 상관값 출력에 가중치를 주어 다중경로 신호에 의한 코드 위상 측정 오차를 줄이는 방법이다. 우선 다양한 지연시간 및 신호 감쇄를 가지는 다중 경로 신호에 대하여, 가중치에 대한 수신기의 성능 변화를 분석하고 이를 통해 최적의 가중치를 선택하였다. 제안한 상관기는 일반 수신기와 동일한 신호 획득능력을 가지며, 협대역 상관기보다 개선된 다중경로 오차 제거 능력을 보인다. 가중 협대역 상관기의 성능은 시뮬레이션을 통한 의사거리 측정치의 비교를 통해 검증하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.109-116
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• 1998

In this paper, a back propagation neural network teaming algorithm based on the complex multilyer perceptron is represented for suppressing narrowband interference of the received signals in DS-SS mobile communication system. We proposed neural network adaptive correlator(NNAC) which has fast convergence rate and good performance with combining back propagation neural network and the receiver of DS-SS. We analyzed and proved that NNAC has lower bit error probability than that of traditional RAKE receiver through results of computer simulation in the presence of the tone and narrow-band interference and the co-channel interference.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1372-1377
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• 2013

In this Paper, a back propagation neural network learning algorithm based on the complex multilayer perceptron is represented for controling and detecting interference of the received signals in cellular mobile communication system. We proposed neural network adaptive correlator which has fast convergence rate and good performance with combining back propagation neural network and the receiver of cellular. We analyzed and proved that NNAC has lower bit error probability than that of traditional RAKE receiver through results of computer simulation in the presence of the tone and narrow-band interference and the co-channel interference.

• Publications of The Korean Astronomical Society
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• v.23 no.2
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• pp.91-107
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• 2008

In this paper, we introduce the performance evaluation and development of Raw VLBI Data Buffer(RVDB) system for the synchronized playback processing of observed data in Korea-Japan Joint VLBI Correlator(KJJVC). The high-speed correlation processing system is under development so that the radio data obtained with 8192 channels and 8 Gbps speed from 16 stations will be able to be processed. When the recorded data of each station are played to correlator, the time synchronization of each station is very important because the correlator should process the data obtained with same time and condition. There are many types of recorder systems in the East Asia VLBI Network (EAVN). Therefore it is required to prepare the special time synchronized playback processing system to synchronize the time tag of observed data. The developed RVDB system consists of Data Input Output(DIO), 10GbE switch, and Disk Data Buffer(DDB). It can record the data with maximum 2 Gbps speed, and can play back the data to correlator with nominal 2 Gbps speed. To enable to play back the data of different playback system to the correlator, we developed the high-speed time synchronized playback processing system. We carried out the experiments of playing back and correlation for gigabit correlator and VCS trial product so as to confirm the performance of developed time synchronized playback processing system. In case of online and offline playing back experiment for gigabit correlator, we confirmed that the online and offline correlation results were the same. In case of playing back experiment for VCS trial product, we verified that the wide band and narrow band correlation results were also the same. Through the playing back experiments of RVDB system, the effectiveness of developed RVDB system was verified. In this paper, the system design, construction and experimental results are shown briefly.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.409-414
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• 2007

The effect of multipath is especially serious in urban area and sea surface where buildings and water reflect GPS signal. Multipath brings about the performance degradation on many GPS application because the presence of multipath causes the diminution of pseudorange measurement accuracy in turn position accuracy. In this paper, a multipath mitigation named weighted correlation method is implemented on software GPS receiver, in which the asymmetric correlation function is compensated by modifying the late correlation value. Asymmetry compensation is obtained as weighted sum of two correlators which have different early-late chip spaces. This structure is adopted to lessen the computation load lower keeping up performance similar to that. The performance of implemented multipath mitigation technique is evaluated using GPS signal and multipath signal generated by GPS signal generator and software GPS receiver. The test results show that the weighted correlation method gives hefter performance than the standard correlator and the narrow correlator.