• 융합신호처리학회논문지
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• 제1권2호
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• pp.115-121
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• 2000

본 논문에서는 초고속 멀티미디어 서비스를 제공하는 차세대 무선 통신 인프라의 하나인 성층권 비행선을 사용하여 이동 통신 시스템을 구축하였을 때, Rician 페이딩과 간섭의 영향, 그리고 간섭 제거 기법들을 고려한 outage 확률에 대해 분석하고 이를 시뮬레이션 하였다. 결과로부터, 페이딩이 없을 때의 반송파 대 간섭전력비 C/I 와 페이딩 심도K 가 outage 확률에 결정적인 영향을 미친다. 즉, 일정한 C/I에 대해 K값이 클수록, 일정 K값에 대해 C/I값이 클수록 outage 확률은 낮게 나타남을 알 수있었다.

• 전기학회논문지
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• 제58권11호
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• pp.2168-2174
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• 2009

Electrical railway system consists of rolling stock, track, signal and streetcar line system. Track circuit system is a vital system due to checking the location of trains. Track circuits are divided by using frequency and isolated electrically. Currently, there is not a regulation for the distance between track circuits using identical frequency. In case of installing additional track circuits in large stations or marshalling yard, the problem which is that the signal is not exactly transmitted to the track circuit occurs due to the mutual interference. In other words, the track circuit properly is not operated on account of wrong induction current by the mutual inductance between track circuits. In this paper, we suggest the electrical model between track circuits and numerically calculate demanded parameters in electrical model. The distance between track circuits satisfying the mutual inductance which does not happen to the mutual interference phenomenon is presented about the distance of track circuit. It is proved by using Matlab and PSpice program as the amplitude of mutual induced current.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.471-473
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• 2009

본 논문에서는 핸즈프리 전화통신을 위한 동시통화(double-talk) 및 잡음에 강건한 반향제거 시스템을 제안한다. 제안하는 반향제거 시스템은 동시통화 상황을 판별하기 위해 마이크 입력신호와 추정한 마이크 입력신호의 분산을 기반으로한 동시통화 검출 알고리즘을 사용하고 반향 경로 추정을 위한 적응 필터는 잔여반향 오차 전력과 AP 알고리즘의 투영차수를 곱하여 입력 신호의 자기공분산 행렬에 더해 정규화시킨 알고리즘을 적용한다. 컴퓨터 시뮬레이션을 통한 동시통화 및 주변 잡음이 큰 핸즈프리 환경에서 제안하는 방법이 AIC(acoustic interference cancellation) 측면에서 우수함을 보인다.

• Journal of the Optical Society of Korea
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• 제17권4호
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• pp.317-322
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• 2013

We have proposed and demonstrated a low numerical aperture technique to measure the depth of through silicon vias (TSVs) using white-light scanning interferometry. The high aspect ratio hole like TSV's was considered to be impossible to measure using conventional optical methods due to low visibility at the bottom of the hole. We assumed that the limitation of the measurement was caused by reflection attenuation in TSVs. A novel interference theory which takes the structural reflection attenuation into consideration was proposed and simulated. As a result, we figured out that the low visibility in the interference signal was caused by the unbalanced light intensity between the object and the reference mirror. Unbalanced light can be balanced using an aperture at the illumination optics. As a result of simulation and experiment, we figured out that the interference signal can be enhanced using the proposed technique. With the proposed optics, the depth of TSVs having an aspect ratio of 11.2 was measured in 5 seconds. The proposed method is expected to be an alternative method for 3-D inspection of TSVs.

• Healthcare Informatics Research
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• 제24권4호
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• pp.387-393
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• 2018

Objectives: This paper describes an experience of implementing seamless service trials online and offline by adopting Internet of Things (IoT) technology based on near-field communication (NFC) tags and Bluetooth low-energy (BLE) beacons. The services were provided for both patients and health professionals. Methods: The pilot services were implemented to enhance healthcare service quality, improve patient safety, and provide an effective business process to health professionals in a tertiary hospital in Seoul, Korea. The services to enhance healthcare service quality include healing tours, cancer information/education, psychological assessments, indoor navigation, and exercise volume checking. The services to improve patient safety are monitoring of high-risk inpatients and delivery of real-time health information in emergency situations. In addition, the services to provide an effective business process to health professionals include surveys and web services for patient management. Results: Considering the sustainability of the pilot services, we decided to pause navigation and patient monitoring services until the interference problem could be completely resolved because beacon signal interference significantly influences the quality of services. On the other hand, we had to continue to provide new wearable beacons to high-risk patients because of hygiene issues, so the cost increased over time and was much higher than expected. Conclusions: To make the smart connected hospital services sustainable, technical feasibility (e.g., beacon signal interference), economic feasibility (e.g., continuous provision of new necklace beacons), and organizational commitment and support (e.g., renewal of new alternative medical devices and infrastructure) are required.

• 제어로봇시스템학회논문지
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• 제14권10호
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• pp.1073-1080
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• 2008

A GPS receiver platform has been developed to design an interference rejection filter and the platform is also able to evaluate performance of those filters. This platform consists of RF/IF part, data acquisition part and PC part. The RF/IF part converts RF signals to IF signals, the data acquisition part transmits the IF signals to PC using USB device. The PC part rejects the interferences with a filter and then it does navigation with GPS software receiver. The RF/IF part and data acquisition part had been validated with signal spectrum, and the PC part had been validated with the navigation results of GPS receiver. Finally, the entire platform including interference rejection filter has been confirmed with the navigation results in case that the GPS signals and interference entered this platform. As a result, the GPS receiver operated well against interference with 45dB JSR.

• IEIE Transactions on Smart Processing and Computing
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• 제1권2호
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• pp.117-124
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• 2012

A client collaboration (CC) system is proposed for a user relay system. The proposed scheme focuses on the management of transmit power and leakage interference. In the proposed CC system, edge users transmit signals to the masters considered as user relays. The masters relay the signals of the edge users to the base station using the resource blocks (RBs) that are assigned to the edge users. The leakage interference and power consumption were analyzed in the CC system. In addition, an optimal master location problem was formulated based on the signal-to-leakage-plus-noise ratio (SLNR). Because the optimal master location problem is quite complex, a sub-optimal master location problem was proposed and a closed-form sub-optimal master location was obtained. The edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC. The numerical results showed that the edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC, and the average throughput increases.

• 한국통신학회논문지
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• 제38A권12호
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• pp.1117-1124
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• 2013

최근 무선트래픽 수요가 폭발적으로 증가하면서 셀룰라 무선망에서 이를 효율적으로 지원하기 위한 스몰셀 연구가 활발히 수행중이다. 본 논문은 스몰셀 구현의 가장 큰 걸림돌인 다중셀 간섭을 효율적으로 해결하기 위한 간섭상쇄 기법에 대해 연구하였다. 각 사용자의 메시지가 기지국 혹은 릴레이를 통하여 전달되는 경우, 무선채널의 시변특성을 이용한 간섭상쇄 기법을 제안하였다. Amplify-and-forward (AF) 에 기반한 기존 접근방식은 잡음증폭 특성으로 인하여 신호대잡음비가 낮은 영역에서는 심한 성능열화를 보였다. 본 논문은 최근 개발된 compute-and-forward (CF) 에 기반한 간섭상쇄를 제안하여 이러한 문제를 해결하고 신호대잡음비가 작은 영역에서 전송율을 크게 개선하였다.

• Journal of Communications and Networks
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• 제10권2호
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• pp.118-126
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• 2008

The use of beamforming is effective for users in limited power environments. However, when it is applied to the downlink of a cellular system with universal frequency reuse, users near the sector boundary may experience significant interference from more than one sector. The use of a minimum mean square error (MMSE)-type receiver may not sufficiently cancel out the interference unless a sufficient number of receive antennas are used. In this paper, we consider the use of inter-sector beamforming that cooperates with a neighboring sector in the same cell to mitigate this interference problem in time-division duplex (TDD) environments. The proposed scheme can avoid interference from an adjacent sector in the same cell, while enhancing the transmit array gain by using the TDD reciprocity. The performance of the proposed scheme is analyzed in terms of the output signal-to-interference-plus-noise power ratio (SINR) and the output capacity when applied to an MMSE-type receiver. The beamforming mode can be analytically switched between the inter-sector and the single-sector mode based on the long-term channel information. Finally, the effectiveness of the proposed scheme is verified by computer simulation.

• 한국통신학회논문지
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• 제35권11A호
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• pp.1085-1090
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• 2010

Ultra wideband (UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geolocation, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional mobile wireless systems sharing the frequency bands such as Cellular CDMA and Korean PCS. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a direct-sequence spread-spectrum UWB source and an impulse radio UWB source, to a Cellular CDMA and K-PCS digital transmission system. The average frame error rate degradation of each system arc presented. From these experimental results, we show that in all practical cases UWB system can coexist with Cellular CDMA and K-PCS terminal without causing any dangerous interference.