• 한국통신학회논문지
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• 제37A권12호
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• pp.1106-1114
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• 2012

In order to provide high data rate and real time services under maritime environment, link-level performance of ship ad-hoc network (SANET) based on 3GPP LTE and IEEE 802.11p (WAVE) specifications are investigated and discussed in this paper. The measured maritime channel, whose delay spread is longer than the length of guard interval (GI) of both 3GPP LTE and IEEE 802.11p specifications, is adopted for the link-level simulations. For the purpose of eliminating inter-symbol interference (ISI) due to insufficient GI length, double antenna pattern (DAP) scheme and advanced time-domain decision-feedback equalizer (DFE) are proposed for LTE and WAVE systems, respectively. The proposed DFE removes the ISI in a same manner as the residual inter-symbol interference cancellation (RISIC) algorithm, but the inter-carrier interference (ICI) is reduced via cyclicity removal instead of cyclicity restoration used in the RISIC algorithm. Compared with existing schemes, our proposed DFE is a robust technique to overcome the severe ISI channel which has a comparatively large delay spread. Based on simulation results, not only comparisons between systems are discussed, but also some reformative suggestions are given.

• 한국정보처리학회논문지
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• 제7권10호
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• pp.3218-3225
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• 2000

본 논문에서는 MMSE 다중사용자 검파기의 성능을 AWGN채널 및 페이딩채널 하에서 신호대 잡음비와 다중 사용자에 따른 지수면에서 상용 검파기와 비교 분석한다. MMSE 다중사용자 검파기는 상용검파기에 비해 다중접속간섭에 강한 면을 보였고, 하드웨어 복잡도와 계산량이 많은 것이 단점으로 나타난다. 또한 동일한 주파수와 시간을 점유하는 DS/CDMA 시스템은 확신부호의 비직교성으로 인한 다중접속간섭 때문에 통화품질과 사용자 수에 따른 간섭이 발생하게 된다. 이러한 문제점을 해결하기 위해 적응형 MMSE 다중사용자 검파기를 제시하고, 시스템의 처리 이득에 대한 하드웨어 복잡도는 검파기 내의 탭수을 설정하여 간섭을 줄일 수 있다.

• 전자공학회논문지
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• 제50권7호
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• pp.34-42
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• 2013

본 논문에서는 웨이블릿 OFDM (Orthogonal Frequency Division Multiplexing) 및 FD-OFDM(Frequency Diversity OFDM) 시스템과 일반 OFDM 시스템의 성능을 비교 분석 한다. 푸리에 변환에 기반하는 일반 OFDM방식과는 달리 웨이블릿 OFDM 방식은 웨이블릿 변환을 사용하며, CDM (Code Division Multiplexing)과 OFDM의 중간적인 특성을 통해 심볼간 간섭을 효과적으로 제거할 수 있으며 채널간 간섭 역시 최소화 할 수 있다. FD-OFDM 방식의 경우, 각 병렬 브랜치에 입력된 심볼들이 직교 시퀀스로 곱해진 뒤 모든 부반송파에 분배되고, 각 부반송파는 주어진 프레임에서 각 병렬 브랜치의 심볼 조각들의 합의형태로 이루어진 정보를 전달한다. FD-OFDM의 한 부반송파 내에 포함된 모든 심볼들은 직교 시퀀스에 의해 구별되며, 간섭에 강하며 주파수 다이버시티 특성을 가진다는 장점을 지닌다. 협대역 간섭과 하모닉 잡음 환경에서 BER (Bit Error Rate) 성능을 통해 시스템 간 성능 비교 분석을 진행하였으며, 이를 통해 웨이블릿 OFDM과 FD-OFDM의 성능이 일반 OFDM보다 간섭에 대해 강건하고 특히 하모닉 노이즈 환경에서는 웨이블릿 OFDM이 가장 강건한 특성을 보이는 것을 알 수 있다.

• 한국정보통신학회논문지
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• 제4권3호
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• pp.653-660
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• 2000

본 논문에서는 대역확산 통신을 위하여 웨이브렛 패킷 영역에서 다중적응필터뱅크를 이용하여 간섭신호를 제거할 수 있는 적응간섭제거기를 제안하고 Monte-Carlo 시뮬레이션을 이용하여 AWGN과 간섭채널에서 LMS와 RLS 적응알고리즘이 적용된 간섭제거기에 따른 대역확산통신시스템의 성능을 분석하였다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.223-226
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• 2007

This paper first outlines the technology used in Power Line Communications(PLC) systems, and the political support being offered to the technology, from the point of view of its effect on electromagnetic compatibility (EMC). The radio spectrum needs protection from other interferers, and there is a regime in place to provide this interference avoidance/mitigation. Nevertheless, PLC has several features that mean that it is capable of creating such interference. These features are discussed, and some published field trial results are reviewed. Difficulties in achieving compatibility between the requirements for radio protection and the requirements for operation of the PLC system mean that there is no consensus as yet as to how PLC system components can be made compliant with EMC requirements. It is concluded that there is little prospect of an accommodation between the competing demands, so that if PLC is to become widespread it will be at the expense of the radio environment.

• 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.

• Journal of Communications and Networks
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• 제10권1호
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• pp.63-70
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• 2008

Narrow-band interference (NBI) from the coexisting narrow-band services affects the performance of ultra wideband (UWB) systems considerably due to the high power of these narrow-band signals with respect to the UWB signals. Specifically, IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals may interfere with UWB systems significantly. In this paper, we suggest a novel NBI suppression technique based on singular value decomposition (SVD) algorithm in time hopping UWB (TH-UWB) systems. SVD is used to approximate the interference which then is subtracted from the received signals. The algorithm precision and closed-form bit error rate (BER) expression are derived in the wireless multipath channel. Comparing with the conventional suppression methods such as a notch filter and a RAKE receiver, the proposed method is simple and robust and especially suitable for UWB systems.

• 한국통신학회논문지
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• 제35권11A호
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• pp.1038-1044
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• 2010

무선 통신 환경에서 간섭은 성능을 악화 시키는 요소이다. Han-Kobayashi 방식은 간섭의 영향을 줄이기 위해서 전송하는 신호를 개인신호와 공용신호로 분리하여 전송하고 수신기에서는 간섭 사용자의 공용신호를 제거하므로써 부분적으로 간섭을 제거한다. 본 논문에서는 개인신호만 전송할 때에 필요한 신호대 잡음비를 이용하여, 개인신호와 공용신호에 최적으로 전력을 할당하는 간단한 방법을 제안한다. 시뮬레이션을 통해서 제안하는 전력 할당 방법이 전수조사를 통한 기법의 성능에 근접함을 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1679-1691
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• 2016

Successive interference cancellation (SIC) is an effective means of multi-packet reception to combat interference at the physical layer. We investigate the joint optimization issue of channel access and power control for capacity maximization in SIC-enabled wireless networks. We propose a new interference model to characterize the sequential detection nature of SIC. Afterward, we formulize the joint optimization problem, prove it to be a nondeterministic polynomial-time-hard problem, and propose a novel approximation approach based on the genetic algorithm (GA). Finally, we discuss the design and parameter setting of the GA approach and validate its performance through extensive simulations.

• 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.