• 한국통신학회논문지
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• 제32권1A호
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• pp.125-133
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• 2007

본 논문에서는 TDD-OFDMA (Time Division Duplex-Orthogonal Frequency Division Multiple Access) 기반의 차세대 셀룰러 이동통신 시스템을 구성하는 다수의 기지국과 이동국으로부터 발생하는 간섭을 계산하여 육상고정 시스템과의 주파수 공유 분석을 수행하였다. 기존의 A-MCL에 제시된 간섭 평가 방법을 TDD-OFDMA 방식으로 동작하는 다수의 이동국과 기지국이 존재하는 간섭 시나리오에 적합하게 확장하였으며, 이를 통해 섹터 당 평균 이동국 수와 기지국 간의 간격 및 육상 고정 시스템 안테나의 주빔 방향에 따른 공유 분석을 수행하였다. 분석 결과를 통해 섹터 당 평균 20명의 사용자를 동시에 서비스하는 경우에 기준 간섭치를 만족하는 기지국간 거리는 5.8km이고 이때 육상 고정 시스템으로부터 가장 인접해 있는 기지국까지의 거리는 2.5km임을 관찰할 수 있었다. 또한 육상 고정 시스템 안테나의 수평 방향에 따른 간섭전력의 변화량은 25dB 정도이며, 약 40 %에 해당하는 방향에서 간섭전력이 최대 허용 간섭전력 보다 작은 사실을 확인할 수 있었다.

• Journal of information and communication convergence engineering
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• 제8권2호
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• pp.155-158
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• 2010

In this article, we proposed a new interference canceller using the adaptive algorithm. We designed constant modulus algorithm-correlation normailized least mean square (CMA-CNLMS) for wireless system. This structure is normalized LMS algorithm using correlation between the desired and input signal for cancelling the interference signals in the wideband code division multiple access (WCDMA) system. We showed that the proposed algorithm could improve the Mean Square Error (MSE) performance of LMS algorithm. MATLAB (Matrix Laboratory) is employed to analyze the proposed algorithm and to compare it with the experimental results. The MSE value of the LMS with mu=0.0001 was measured as - 12.5 dB, and that of the proposed algorithm was -19.5 dB which showed an improvement of 7dB.

• ETRI Journal
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• 제35권5호
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• pp.775-785
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• 2013

Because of their exclusive features, millimeter wave directive mesh networks can be considered for small cell backhaul support in urban environments. For this purpose, a network of closely spaced stations has been considered with very directive line-of-sight links operating in the 60-GHz band. An attempt is made to evaluate channel response and interference behavior in such a network, taking into account the effect of building blockage. A simple grid of building blocks is considered as the propagation environment, and wave propagation is simulated using 2.5-dimensional (2.5D) ray tracing (2D with ground effect) to calculate the received signal at different nodes in the network. The results are compared with free space predictions and used to evaluate interference at all nodes in the channel and describe certain characteristics of links, such as the delay profile and the correlation length.

• 한국방사선학회논문지
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• 제8권3호
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• pp.111-115
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• 2014

본 연구에서는 콩팥 초음파 검사에서 발견된 콩팥 낭종 증례에서 낭종 내 초음파 간섭에 의한 허상이 진단에 미치는 영향 정도를 공학적 방법으로 해석하는 방안을 제안하였다. 제안된 방법으로 실험한 결과 육안적 방법으로 판단한 방법은 초음파 간섭의 효과로 발생하는 낭종 내의 에코를 구별하지 못하고 간과할 수 있음을 알 수 있었다. 따라서 종괴 내의 미미한 신호의 차이를 본 연구에서 수행한 결과를 이용한다면 오진을 사전에 예방할 수 있을 것이다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.67-70
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• 1998

In this paper, an interference analyzer for communication and/or broadcasting services is developed and presented based on Monte Carlo technique, which is now under study in the International Telecommunication Union(ITU). Monte Carlo technology is a statistical approach which functions by considering many trials. For each simulation trial, a scenario is built up using a number of different random variables, such as signal and interference strengths, transmitting and receiving antenna heights, antenna gains, etc.. Furthermore, this paper shows and application example of the analyzer to examine interference influence of the PCS(IS-95) base stations affecting to the IMT-2000 FDD base station, depending on serveral service environments like rural, suburban, and urban areas. The wave propagation model used in this simulation is the modified Hata model, which is known to the suitable to Korean environments.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.591-592
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• 2010

다양한 무선통신 시스템이 사용되고 있는 환경에서 수신 단으로 유입되는 강력한 인접 주파수 신호는 원래의 통신 신호 복원을 어렵게 할뿐만 아니라 시스템 성능을 현저하게 열화 시킨다. 따라서 이러한 인접 주파수 간섭을 제거하기 위한 기법을 본 논문에서 고찰하였다. 송신 단에서의 강력한 출력이 수신 단으로 유입되는 경우를 가정하였으며 구현이 비교적 간단한 일반적인 LMS 알고리즘을 이용하여 적응제거를 시도하였다. 적응계수들은 비교적 빠르게 수렴하였으며 $10^{-5}sec$ 정도 이내에 적응 제거가 이루어짐을 확인하였으며 50dB 정도의 제거성능을 보였다.

• 한국통신학회논문지
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• 제21권11호
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• pp.2942-2953
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• 1996

This paper studies the effect of intersymbol interference due to sampling-time jitter on the worst-case bit error probability in a digital modultation over an additive white Gaussian noise channel, with the squared-root raised-cosine filters in the transmitter and the receiver. It derives approximation formulas using the Taylor series approximations. the principal results of this paper is the relationship between the worst-casse bit error probability, the degree of jitter, the roll factor of the raised cosine filter, and other quantities. Numerical results show, as expected, that the intersymbol interference decreases as the roll-off factor increases and the jitter decreases. They also show that the approximation formulas are accurate for smally intersymbol interference, i.e., for large roll-noise ratio $E_{b/}$ $N_{0}$.leq.7 dB and begin to lose accuracy for larger signal-to-noise ratio.o.o.

• IEIE Transactions on Smart Processing and Computing
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• 제3권2호
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• pp.83-87
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• 2014

This paper introduces a refined opportunistic interference alignment (OIA) technique that uses minimum mean square error (MMSE) detection at the receivers in multiple-input multiple-output multi-cell uplink networks. In the OIA scheme under consideration, each user performs the optimal transmit beamforming and power control to minimize the level of interference generated to the other-cell base stations, as in the conventional energy-efficient OIA. The result showed that owing to the enhanced receiver structure, the OIA scheme shows much higher sum-rates than those of the conventional OIA with zero-forcing detection for all signal-to-noise ratio regions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권11호
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• pp.5324-5337
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• 2017

In this paper, we investigate the feasibility of interference alignment(IA) in signal space in the scenario of multiple cell and multiple user cellular networks, as the feasibility issue is closely related to the solvability of a multivariate polynomial system, we give the mathematical analysis to support the constraint condition obtained from the polynomial equations with the tools of algebraic geometry, and a new distribute IA algorithm is also provided to verify the accessibility of the constraint condition for symmetric system in this paper. Simulation results illustrate that the accessibility of the constraint condition is hold if and only if the degree of freedom(DoF) of each user can be divided by both the transmit and receive antenna numbers.

• ETRI Journal
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• 제26권1호
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• pp.13-20
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• 2004

We propose a new optical code division multiple access (OCDMA) scheme for reducing multiple access interference (MAI) and enhancing performance for optical subscriber access networks using modified pseudorandom noise (PN)-coded fiber Bragg gratings with bipolar OCDMA decoders. Through the bipolar OCDMA decoder and the modified PN codes, MAI among users is effectively depressed. As the data are encoded either by a unipolar signature sequence of the modified PN code or its complement according to whether the data bit is 1 or 0, the bit error ratio (BER) can be more improved with the same signal to interference plus noise ratio over the conventional on-off shift keying-based OCDMA system. We prove by numerical analysis that the BER of the proposed bipolar OCDMA system is better than the conventional unipolar OCDMA system. We also analyze the spectral power distortion effects of the broadband light source.