• Journal of Korea Multimedia Society
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• v.11 no.3
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• pp.281-291
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• 2008

In this paper, we propose a new double talk detection algorithm which detects near end signals with less degradation, tracking echo path variation of echo canceler simultaneously. Our method makes use of a cross-correlation between channel input signals and estimated error signals and a normalized cross-correlation between microphone input signals and estimated error signals. By combing thresholds for these cross-correlations pertinently, this algorithm discriminates between variation of echo path and occurrence of double talk. These two cross-correlation are used to detect double talk periods, tracking echo path variation. During the detection period, adjustive adaptive filter is ceased to prevent the echo canceler from being disturbed by near end signals. Also, the echo canceler will still be kept on for tracking any variation in echo path. Through computer simulation results, it was confirmed that the proposed algorithm shows better performance, tracking echo path variation and detecting the double talk periods, than the Ye et. al's and the NLMS algorithms from ERLE viewpoint.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1078-1084
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• 2010

The tracking performance of a big parabola tracking antenna system for tracking and receiving of the signal from the vehicle is impacted by many factors of the internal and the external of the system. In this paper, we analyze the tracking error due to the radio refraction in the application of the tracking and positioning of the vehicle by using radio frequency. The real measurement data are used for the analysis which had been acquired by using GPS and the tracking systems of C- and S-band frequencies in NARO Space centre. To verify the correlation between the tracking errors measured and the radio refraction, we review the error factors and the accuracies of the tracking systems, and the characteristics of the refractivity. The analysis shows that there are angular errors which are due to the radio refraction and not to be neglected, compared to the accuracies of the tracking systems, in case of low elevation angle less than 10 degrees. Also, the tracking errors depend on the target altitude as well as the elevation angle for the case of the target in the troposphere. It is recommended to correct the tracking angle considering the target altitude and elevation angle for the precise target positioning.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.217-219
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• 2011

현재 차량 위치 추적 시 사용빈도가 가장 많은 방법은, 지도상에 자신의 위치를 수치로 보여주는 GPS 수신기를 사용하여 지도상 실외의 위치를 측위 한다. 위의 GPS를 이용한 내비게이션은 차량의 진행방향, 출발 도착 지점을 설정하여 차량을 운행한다. 또한 GPS 음영지역 및 신호 지연의 문제를 해결하기 위한 지자기센서와 가속도센서를 사용하는 시스템도 있다. 그러나 센서를 활용할 경우 차량의 방향 정보를 얻을 수 있지만 음영 및 신호 왜곡 시간이 길어질 경우 정확한 차량의 위치를 판단 할 수 없다. 즉, GPS의 신호에 오류가 있을 경우 차량의 이동거리를 알 수 없으므로 차량의 회전 정보는 효용 가치가 떨어진다. 따라서 이를 보정하기 위해서는 정확한 차량의 위치를 판단할 수 있는 시스템이 필요하다. 본 논문에서는 기존 GPS의 문제를 해결하기 위해 차량의 속도정보와 스마트폰의 지자기센서를 활용한 실외 위치 추적 시스템과 WiFi 정보를 활용한 차량용 WPS시스템을 설계 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1563-1569
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• 2000

Teager-Kaiser algorithm that can track the energy of tone signals with simple nonlinear operations, has been applied to detection of tone signals closely spaced in frequency. The performance of the previous detector depends upon the performance of internal filters. An improved scheme is proposed in this paper by employing the nonlinear energy trackers in cascade. The proposed detector is analytically designed and verified by computer simulation. It shows that the new detection scheme improves the detection performance while reducing the implementation complexity.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.9
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• pp.595-602
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• 2013

WiFi fingerprinting is well known as an effective localization technique used for indoor environments. However, this technique requires a large amount of pre-built fingerprint maps over the entire space. Moreover, due to environmental changes, these maps have to be newly built or updated periodically by experts. As a way to avoid this problem, crowd-sourced fingerprint mapping attracts many interests from researchers. This approach supports many volunteer users to share their WiFi fingerprints collected at a specific environment. Therefore, crowd-sourced fingerprinting can automatically update fingerprint maps up-to-date. In most previous systems, however, individual users were asked to enter their positions manually to build their local fingerprint maps. Moreover, the systems do not have any principled mechanism to keep fingerprint maps clean by detecting and filtering out erroneous fingerprints collected from multiple users. In this paper, we present the design of a crowd-sourced fingerprint mapping and localization(CMAL) system. The proposed system can not only automatically build and/or update WiFi fingerprint maps from fingerprint collections provided by multiple smartphone users, but also simultaneously track their positions using the up-to-date maps. The CMAL system consists of multiple clients to work on individual smartphones to collect fingerprints and a central server to maintain a database of fingerprint maps. Each client contains a particle filter-based WiFi SLAM engine, tracking the smartphone user's position and building each local fingerprint map. The server of our system adopts a Gaussian interpolation-based error filtering algorithm to maintain the integrity of fingerprint maps. Through various experiments, we show the high performance of our system.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.4
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• pp.1-6
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• 2003

In this Paper, the moving image is detected by a collision preventive system. The noise of these images is reduced by a mean filter. In case of detecting a movement with a binary difference image the moving area is detected exactly by the labeling and the projective method. When the image move slowly with the tracking mode of the system, the center of the tracking window move to the previous tracking window. And the tracking windows are divided into a tracking mode and a coasting mode which are determine by the Contrast-Difference Correlation of the date obtained from a difference image. The coasting mode determine whether continue the tracking step or not comparing the coasting-time values to reducing the error by the disturbance. The coasting and tracking of these moving images are verified by the result of the simulation.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2180-2183
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• 2003

본 논문에서는 광 디스크의 기록 밀도 증가에 따른 신호품질의 열화나 노이즈가 심한 환경에서 DPLL(Digital Phase Locked Loop)의 성능을 개선하기 위한 FD(Frequency Detector)와 PD(Phase Detector) 알고리즘을 제안한다. 제안된 PD 알고리즘은 노이즈에 의해 왜곡되어 RLL 조건을 위배하는 입력신호, 즉 RLL 조건에 의해 결정되는 최소 런 길이보다 주기가 작은 신호에 의해 발생하는 위상오차를 위상오차 보정 시 사용하지 않도록 설계하여 잘못된 정보에 의한 위상오차 보정이 일어나지 않도록 하였다 제안된 FD 알고리즘은 주파수를 추적하기 위해 삽입되는 신호인 Sync 신호의 symmetry 특성을 이용하여 샘플패턴을 검출하도록 하여 기존의 주파수 오차 보정 알고리즘보다 향상된 주파수 추적 성능을 가지도록 하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.367-374
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• 2012

In this paper, we propose a novel cancellation scheme of correlation side-peaks for binary offset carrier (BOC) signals. The proposed scheme is based on a combination of the sub-correlation functions composing the BOC autocorrelation and applicable to both sine- and cosine-phased BOC signals without requiring any auxiliary signal in the receiver. From numerical results, it is confirmed that the proposed scheme provides a better tracking accuracy than the conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.957-963
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• 2015

The autocorrelation of an alternative binary offset carrier (AltBOC) signal provides an improved positioning accuracy because of its narrow main-peak. However, The AltBOC signal has a disadvantage that the autocorrelation of the AltBOC signal has multiple side-peaks which incur a severe positioning error. In this paper, we propose a generating method of an unambiguous correlation function for AltBOC signal tracking. Specifically, we first obtain symmetric partial correlation functions, and subsequently, we obtain an unambiguous correlation function by combining them. In numerical results, it is confirmed that the proposed correlation function provides better tracking error standard devation (TESD) performances comparing with the conventional correlation functions.

• Journal of Convergence for Information Technology
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• v.12 no.4
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• pp.9-13
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• 2022

In this paper, the tracking error of monopulse radar caused by cross-eye jamming using terrain bounce is analyzed. Cross-eye jamming is a method of generating an error in a radar tracking system by simultaneously transmitting two signals with different phases and amplitudes. When the monopulse radar receives the cross-eye jamming signal generated by the terrain bounce, a tracking error occurs in the elevation direction. In the presence of multipath, this signal is a combination of the direct target return and a return seemingly emanating from the target image beneath the terrain surface. Terrain bounce jamming has the advantage of using a single jammer, but the space affecting the jamming is limited by the terrain reflection angle and the degree of scattering of the terrain. This study can be usefully used to protect ships from low-altitude missiles or aircraft in the sea.