• 한국항공우주학회지
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• 제32권9호
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• pp.88-93
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• 2004

본 논문에서는 기저선 제한조건을 이용하여 GPS 반송파 측정값에 바이어스 존재 여부를 보다 정확하게 판단하는 방법을 확인하고, 시뮬레이션을 통하여 이를 분석하였다. 기저선 제한조건은 추가적인 측정값으로 사용되며, 기존의 GPS 반송파 측정 방정식을 확장하는 형태로 사용된다. GPS 반송파 측정값만을 사용하는 경우와 기저선 제한조건을 함께 사용하는 경우에 대하여, 각각 검출확률(Detection Probability)를 계산하고 기저선 제한조건을 사용하는 경우 검출확률이 향상되는 것을 보이게 된다. 기저선 제한조건을 사용하는 것에 대한 장점을 통계적으로 증명하고 시뮬레이션을 통하여 수치적인 결과를 확인한다.

• 대한전자공학회논문지
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• 제13권5호
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• pp.24-29
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• 1976

Phase locked AM신호 검파방식에서는 위상고정회로를 사용하여 입력신호로부터 반송신호를 분리 재생시킨다. 입력잡음은 백색 Gaussian잡음이고, 전려제어발진기의 자유발진주파수와 입력반송신호주파수가 같다는 가정하에 위상고정회로의 동작특성을 해석하고, 본 검파방식의 신호대 잡음비를 정량적으로 고찰하였다. Phase locked AM신호 검파방식은 종래의 검파방식에 비해서 잡음의 영향을 적게 받게됨을 본 해석에서 알 수 있다. In the phase locked AM signal detection, phase locked loop is used to extract a synchronous carrier from an input AM signal. Under the assumption that input noise is white Gaussian and free-running frequency of voltage controlled oscillator is the same that of an input carrier, operational behaviours of phase locked loop is analyzed and signal to noise ratio of the detection is derived quentitatively. The results show that the phase locked AM signal detection method offers a higher degree of noise mmunity than conventional AM signal detections.

• Journal of Positioning, Navigation, and Timing
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• 제8권3호
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• pp.129-138
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• 2019

In this work, we propose detection method for ionosphere storm that occurs locally using widespread GNSS reference stations. For ionosphere storm detection, we compare ionosphere condition with other reference stations and estimate direction of movement based on ionosphere time variation. The method use carrier phase measurement of dual frequency, for accuracy and precision of test statistics, are evaluated with multiple GNSS reference stations data.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1239-1243
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• 2005

A multipath mitigation method using the fault detection and isolation technique is proposed for the CDGPS. The base station is assumed to be immune to the effect of the multipath. With this reasonable assumption, the effect of multipath in moving station is mitigated. For that, the double difference measurement is produced, and then another additional difference between code pseudorange and acclumulated carrier phase is calculated. The test statistic is constituted with those differences. The hypothesis testing is applied to that test statistic. The proposed test statistic makes use of the effect of multipath in code pseudoranges and it does not use time differences. Therefore the detection ability for multipath is improved in most environments. However, the increased number of differences makes the measurement noises larger. The performance of the method is compared with that of the conventional parity space method with code pseudorange.

• 한국항행학회논문지
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• 제14권5호
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• pp.640-647
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• 2010

최근 많은 연구자들에 의하여 위성항법 측정값 중 반송파 측정값에 대한 고장검출 연구가 진행되어 왔으나, 육상교통 환경에서의 적용연구는 활발히 진행되지 않았다. 본 논문에서는 움직이는 물체의 동적특성과 복수의 위성항법 수신기 사이의 기준 거리 제한 조건을 활용하여 위성항법 반송파 측정값의 고장검출을 수행하였다. 반송파 측정값의 고장은 다중경로 등을 포함하고 있으며 측정값 영역에서 고장검출을 수행함으로써 위치결정을 수반하는 기존의 고장검출 방법에 비하여 그 구현이 용이함을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권2호
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• pp.601-617
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• 2014

In digital radio broadcasting systems, long delays are incurred in service start time when tuning to a particular frequency because several synchronization steps, such as symbol timing synchronization, frame synchronization, and carrier frequency offset and sampling frequency offset compensation are necessary. Therefore, the operation of the synchronization blocks causes delays ranging from several hundred milliseconds to a few seconds until the start of the radio service after frequency tuning. Furthermore, if spectrum inversed signals are transmitted in digital radio broadcasting systems, the receivers are unable to decode them, even though most receivers can demodulate the spectral inversed signals in analog radio broadcasting systems. Accordingly, fast synchronization techniques and a method for spectral inversion detection are required in digital radio broadcasting systems that are to replace the analog radio systems. This paper presents a joint detection method of frame, integer carrier frequency offset, and spectrum inversion for DRM Plus digital broadcasting systems. The proposed scheme can detect the frame and determine whether the signal is normal or spectral inversed without any carrier frequency offset and sampling frequency offset compensation, enabling fast frame synchronization. The proposed method shows outstanding performance in environments where symbol timing offsets and sampling frequency offsets exist.

• Journal of Communications and Networks
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• 제18권3호
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• pp.502-512
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• 2016

The wireless carrier sense multiple access with collision detection (WCSMA/CD) and carrier sense multiple access with collision resolution (CSMA/CR) protocols are considered representative distributed collision detection protocols for fully connected dense wireless local area networks. These protocols identify collisions through additional short-sensing within a collision detection (CD) period after the start of data transmission. In this study, we analyze their throughput numerically and show that the throughput has a trade-off that accords with the length of the CD period. Consequently, we obtain the optimal length of the CD period that maximizes the throughput as a closed-form solution. Analysis and simulation results show that the throughput of distributed collision detection protocols is considerably improved when the optimal CD period is allocated according to the number of stations and the length of the transmitted packet.

• 한국통신학회논문지
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• 제24권8A호
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• pp.1099-1106
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• 1999

본 논문에서는 다중사용자/다중경로 환경에서 다중반송파 CDMA 시스템의 오류확률을 해석적으로, 구하고, 다중 사용자, 다중반송파, 다중경로에 의한 간섭의 영향을 분석하였다. 또한 다중반송파 시스템에 대한 역상관 검출기(decorrelating detector)를 결합한 다중반송파/다중사용자/다중경로 결합 검출 방식을 제시하고 성능 및 역상관 과정에 의한 백색가우시안 잡음(AWGN)의 증가를 분석하였다. 제안한 결합 검출 방식의 오류 확률은 하나의 상용자만이 있는 경우의 이상적인 성능에 근접하였다.

• 대한임베디드공학회논문지
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• 제17권2호
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• pp.101-107
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• 2022

In this article, we propose a new protocol at fast scan mode for a sea-surface small target detection. The conventional fast scan mode is composed of coherent intrascan integration to suppress sea clutter and non-coherent interscan integration to exclude sea spikes. The proposed method realizes the coherent interscan integration by the new Fourier relationship between carrier-frequency and initial-radial-range, which can be analytically derived by using multiple carrier frequencies at fast scan mode, leading to improved detection performance, compared to the conventional non-coherent methods. In simulations, our proposed method is verified.

• Journal of Communications and Networks
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• 제18권3호
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• pp.439-445
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• 2016

In this paper, we consider subcarrier-index modulation (SIM) for precoded orthogonal frequency division multiplexing (OFDM) with a few activated subcarriers per user and its generalization to multi-carrier multiple access systems. The resulting multiple access is called sparse index multiple access (SIMA). SIMA can be considered as a combination of multi-carrier code division multiple access (MC-CDMA) and SIM. Thus, SIMA is able to exploit a path diversity gain by (random) spreading over multiple carriers as MC-CDMA. To detect multiple users' signals, a low-complexity detection method is proposed by exploiting the notion of compressive sensing (CS). The derived low-complexity detection method is based on the orthogonal matching pursuit (OMP) algorithm, which is one of greedy algorithms used to estimate sparse signals in CS. From simulation results, we can observe that SIMA can perform better than MC-CDMA when the ratio of the number of users to the number of multi-carrier is low.