• Journal of Communications and Networks
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• 제14권4호
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• pp.443-450
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• 2012

As for cluster-based wireless sensor networks (WSNs), cluster lifetime is one of the most important subjects in recent researches. Besides reducing the energy consumptions of the clusters, it is necessary to make the clusters achieve equal lifetimes so that the whole network can survive longer. In this paper, we focus on the cluster lifetimes in multi-hop WSNs with cooperative multi-input single-output scheme. With a simplified model of multi-hop WSNs, we change the transmission schemes, the sizes and transmission distances of clusters to investigate their effects on the cluster lifetimes. Furthermore, linear and uniform data aggregations are considered in our model. As a result, we analyze the cluster lifetimes in different situations and discuss the requirements on the sizes and transmission distances of clusters for equal lifetimes.

• Journal of Communications and Networks
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• 제10권2호
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• pp.163-174
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• 2008

Performance of downlink transmission strategies exploiting cooperative transmit diversity is investigated for distributed multiple-input single-output (MISO) systems, for which geographically distributed remote antennas (RA) in a cell can either communicate with distinct mobile stations (MS) or cooperate for a common MS. Statistical characteristics in terms of the signal-to-interference-plus-noise ratio (SINR) and the achievable capacity are analyzed for both cooperative and non-cooperative transmission schemes, and the preferred mode of operation for given channel conditions is presented using the analysis result. In particular, we determine an exact amount of the maximum achievable gain in capacity when RAs for signal transmission are selected based on the instantaneous channel condition, by deriving a general expression for the SINR of such antenna selection based transmission. For important special cases of selecting a single RA for non-cooperative transmission and selecting two RAs for cooperative transmission among three RAs surrounding the MS, closed-form formulas are presented for the SINR and capacity distributions.

• ETRI Journal
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• 제38권3호
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• pp.435-443
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• 2016

In this paper, an efficient beam tracking algorithm for a regularized zero-forcing (RZF) approach in slowly fading multiple-input and single-output (MISO) broadcast channels is considered. By modifying an RZF equation, an RZF beam tracking algorithm is proposed using matrix perturbation theory. The proposed algorithm utilizes both beams from the previous time step and channel difference (between the previous and current time steps) to calculate the RZF beams. The tracking performance of the proposed algorithm is analyzed in terms of the mean square error (MSE) between a tracking approach and an exact recomputing approach, and in terms of the additional MSE caused by the beam tracking error at the receiver. Numerical results show that the proposed algorithm has almost the same performance as the exact recomputing approach in terms of the sum rate.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.397-401
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• 1994

This paper proposes an identification method for a thin plate where multiple actuators and sensors are bonded. Since a thin plate has small damping ratios of all modes, each mode can be identified seperately with a bandpass filter for each modal signal. With the bandpass filter and the characteristics of the plate, the Multi-Input Multi-Output (MIMO) model of the plate can be converted to several Multi-Input Single-Output(MISO) models of second order linear difference equations of the modes. Parameters for each mode are obtained by using the Least Square method. Form there MISO models, the MIMO model is obtained in the form of the state space. Experiments were performed for an all-clamped plate with two pairs of piezoelectric actuators and sensors. The outputs of the identified model and the experimental data match well.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2012년도 추계학술대회
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• pp.75-76
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• 2012

본 논문에서는 MIMO(multi-input multi-output) RQD(rotation constellation and Q-delay) 시스템을 적용하여 지상파 UHDTV 시스템을 구현하기 위한 전송 시스템의 성능을 분석한다. 차세대 UHDTV 시스템이 필요로 하는 높은 전송량을 달성하기 위하여 STBC(space time block code)를 사용하는 기존의 MISO(multi-input single-output)와 MIMO(multi-input multi-output) 시스템에 RQD 기술을 더하여 성능을 개선한다. 개선된 MISO RQD 기법과 MIMO RQD 기법의 성능을 컴퓨터 시뮬레이션을 통하여 비교 분석하였다. 또한 실험 결과를 통하여 앞으로 차세대 지상파 UHDTV를 위한 방향을 제시한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1932-1935
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• 2002

This paper introduces the downlink Eigen-beamformer with Space-Time Block Code (STBC) 〔1,2〕employed on the MISO (Multiple Input Multiple Output) systems. The proposed scheme is acquired both transmit diversity gain from STBC and beamforming gain from Eigen-beamformer. In general, it is well described that the diversity gain be maximized when channel parameters associated to fingers are mutually independent. Major role f utilizing Eigen-beamformer is to enforce channel parameters being uncorrelated. According to this, the proposed STBC combined with Eigen-beamformer on the downlink significantly improves its performance under the spatially correlated channel. Simulation results are accomplished under three distinct channel conditioned with varying the degree of their correlations. The result indicates hat our proposed scheme is good performance in spatially correlated channel.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.115-116
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• 2010

• 한국생명과학회:학술대회논문집
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• 한국생명과학회 2005년도 국제학술심포지움 The 44th Annual Meeting of Korean Society for Life Science
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• pp.37-40
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• 2005

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.305-306
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• 2013

• 한국통신학회논문지
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• 제39B권4호
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• pp.216-227
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• 2014

데이터-운송 중계기(mechanical relay: McR)는 운송 지연 및 간헐적 접속단절을 반영하는 중계기법 중에 하나다. 기존의 비이동성 중계기법과 달리, 데이터-운송 중계기법은 다양한 종류의 차량 및 교통기반시설의 이동성을 이용하여 근거리의 송수신이 가능하게 하는 점에서 잠재적인 이득이 존재한다. 본 논문에서는 McR을 운용하는 무선 선형 네트워크(wireless line networks: WLN)를 고려하고, 각 사용자간의 다중 홉 무선전송 기법과 데이터-운송 중계기법을 비교하고, 에르고딕 네트워크 전송률의 관점에서 분석한다. 또한 Vehicle SISO(Ve-SISO) 뿐만 아니라 Vehicle SIMO/MISO(Ve-SIMO/MISO)의 경우에 대해서도 McR의 사용을 고려한다. 에르고딕 네트워크 전송률에 대한 실험 결과로부터 McR의 속도, 사용자와 McR의 밀도, 그리고 McR의 사용방식에 따라서 나타나는 트레이드-오프관계를 살펴본다.