• 전자공학회논문지
• /
• 제51권10호
• /
• pp.41-44
• /
• 2014

전이중 무선 통신 시스템은 반이중 통신 시스템에 비해 향상된 대역폭 효율을 얻을 수 있다. 전이중 방식의 다중 사용자 다중 안테나 시스템에서는 단말 간 간섭에 의한 성능 열화 문제가 발생한다. 본 논문에서는 단말 간 간섭 채널의 통계적 정보만을 이용하여 시스템의 대역폭 효율을 최대화하는 하향 링크 전력 할당 기법을 제안한다.

• 한국통신학회논문지
• /
• 제36권4A호
• /
• pp.337-344
• /
• 2011

본 논문은 모든 노드가 다중 안테나를 갖는 다중 안테나 (MIMO, multiple-input and multiple-output) 공간 다중화 (SM, spatial multiplexing) 릴레이 시스템을 비트 오율 (BER, bit error rate) 관점에서 연구한다. 제한된 전력 자원을 효율적으로 이용하기 위해서는 각 노드와 안테나에서 최적화된 전력 할당 전략이 필요하다. 본 논문은 이런 관점에서 다중 안테나 공간 다중화 릴레이 시스템을 위한 비트 오율 최소화에 기반을 둔 전력 할당 알고리즘을 제안한다. 제안된 알고리즘은 평균 비트 오율을 직접 최소화하여 얻어지며, 노드 간 (inter-node) 전력 할당 알고리즘과 안테나 간 (inter-antenna) 전력 할당 알고리즘으로 구성된다. 비트 오율 성능에 있어서, 기존의 균등 전력 할당 (EPA, equal power allocation) 알고리즘보다 추가적인 전력 소비 없이도 월등한 성능을 보인다.

• 대한전자공학회논문지TC
• /
• 제48권6호
• /
• pp.6-13
• /
• 2011

시공간 부호화기법을 가진 MIMO(Multiple-input multiple-output)-OFDM(Orthogonal frequency division multiplexing)은 미래의 무선통신 시스템에서 성능향상을 위한 약속된 기술이다. 그러나 다중 송신기를 가진 다른 사용자에 따른 간섭과 다중경로의 지연신호에 따른 영향으로 성능이 크게 감소된다. 이 논문에서는 MIMO-OFDM 시스템에서 시공간 다이버스티를 유지하면서 이와 같은 간섭신호와 다중경로 지연신호를 효율적으로 제거하기 위하여 MMSE(minimizing the mean squared error) 기반의 pre-FFT 다중 빔형성기법을 제안한다. MIMO-OFDM 시스템에 제안된 다중 빔형성기법을 적용할 경우 성능 개선 효과를 CCI(Cochannel interference)를 가진 다중경로 채널환경에서 모의실험을 통하여 확인한다.

• Journal of Communications and Networks
• /
• 제13권2호
• /
• pp.167-174
• /
• 2011

In this paper, we propose and simulate an efficient interference cancellation scheme with an optimal ordering successive interference cancellation (SIC) algorithm for ultra wideband (UWB)/multiple-input-multiple-output (MIMO) systems in a wireless body area network (WBAN). When there are several wireless communication devices on a human body, multiple access interference (MAI) usually occurs. To mitigate the effect of MAI and achieve additional diversity gain, we utilize SIC with an optimal ordering algorithm. A zero correlation duration (ZCD) code with robust MAI capability is employed as a spread code for UWB systems in a multi-device WBAN environment. The performance of the proposed scheme is evaluated in terms of the bit error rate (BER). Simulation results confirm that the BER performance can be improved significantly if the proposed interference cancellation scheme and the ZCD code are jointly employed.

• Journal of Communications and Networks
• /
• 제15권4호
• /
• pp.352-361
• /
• 2013

Combining multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) with a massive number of transmit antennas (massive MIMO-OFDM) is an attractive way of increasing the spectrum efficiency or reducing the transmission energy per bit. The effectiveness of Massive MIMO-OFDM is strongly affected by the channel state information (CSI) estimation method used. The overheads of training frame transmission and CSI feedback decrease multiple access channel (MAC) efficiency and increase the CSI estimation cost at a user station (STA). This paper proposes a CSI estimation scheme that reduces the training frame length by using a novel pilot design and a novel unitary matrix feedback method. The proposed pilot design and unitary matrix feedback enable the access point (AP) to estimate the CSI of the signal space of all transmit antennas using a small number of training frames. Simulations in an IEEE 802.11n channel verify the attractive transmission performance of the proposed methods.

• Earthquakes and Structures
• /
• 제17권5호
• /
• pp.463-475
• /
• 2019

In this paper, a procedure to develop fragility curves of structures equipped with semi-active tuned mass dampers (SATMDs) considering multiple failure criteria has been presented while accounting for the uncertainties of the input excitation, structure and control device parameters. In this procedure, Latin hypercube sampling (LHS) method has been employed to generate 30 random SATMD-structure systems and nonlinear incremental dynamic analysis (IDA) has been conducted under 20 earthquakes to determine the structural responses, where failure probabilities in each intensity level have been evaluated using Monte Carlo simulation (MCS) method. For numerical analysis, an eight-story nonlinear shear building frame with bilinear hysteresis material behavior has been used. Fragility curves for the structure equipped with optimal SATMDs have been developed considering single and multiple failure criteria for different performance levels and compared with that of uncontrolled structure as well as structure controlled using passive tuned mass damper (TMD). Numerical analysis has shown the capability of SATMDs in significant enhancement of the seismic fragility of the nonlinear structure. Also, considering multiple failure criteria has led to increasing the fragility of the structure. Moreover, it is observed that the influence of the uncertainty of input excitation with respect to the other uncertainties is considerable.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권3호
• /
• pp.1140-1155
• /
• 2021

Up to now, many state-of-arts have been proposed for two-way relaying system with linear modulations. The performances of antenna selection (AS) at both transmit and relay nodes need to be investigated in some two-way relaying multiple-input multiple-output (TWRM) systems. In this paper, the goal is focused on the study of nonlinear modulations, i.e., continuous phase modulation (CPM) in TWRM systems. Firstly, the joint phase trellis are simplified by reversed Rimoldi processing so as to reduce the systems' complexity. Then the performances of joint transmit and receive antenna selection (JTRAS) with CPM modulations in two-way relaying MIMO systems are analyzed. More exactly, the pair wise probability (PEP) is used to evaluate the error performance based on the CPM signal matrix, which is calculated in terms of Laurent expression. Since the channels subject to two terminal nodes share common antennas at relay node R in multiple-access scheme, we revise the JTRAS algorithm and compare it to existing algorithm via simulation. Finally, the error performances for various schemes of antenna selection are simulated and compared to the analysis in this paper.

• 한국전자파학회논문지
• /
• 제29권11호
• /
• pp.878-883
• /
• 2018

본 논문은 분산 배치된 다수의 전자전 센서를 통하여 수신된 바이스태틱 multiple-input multiple-output(MIMO) 레이다 시스템의 신호를 조합하여 레이다 시스템의 위치탐지 기능을 무력화 혹은 기만하는 재밍 설계기법을 제안한다. 제안된 기법은 하나의 전자전 센서에서 수집된 신호를 특정주기로 지연시킨 신호들의 합을 송신하거나, 다수의 센서에서 수집된 신호들의 가중치 합을 송신하여, 표적을 탐지 못하게 하거나 허위표적을 발생시킨다. 시뮬레이션 결과를 통해서 제안한 기법의 재밍 성능을 확인한다.

• 한국태양에너지학회 논문집
• /
• 제34권4호
• /
• pp.23-29
• /
• 2014

Recently, in power system studies, Multiple Energy Carriers (MECs) such as Energy Hub has been broadly utilized in power system planners and operators. Particularly, Energy Hub performs one of the most important role as the intermediate in implementing the MECs. However, it still needs to be put under examination in both modeling and operating concerns. For instance, a probabilistic optimization model is treated by a robust global optimization technique such as multi-agent genetic algorithm (MAGA) which can support the online economic dispatch of MECs. MAGA also reduces the inevitable uncertainty caused by the integration of selected input energy carriers. However, MAGA only considers current state of the integration of selected input energy carriers in conjunctive with the condition of smart grid environments for decision making in Energy Hub. Thus, in this paper, we propose an immune algorithm based Multiple Energy Carriers System which can adopt the learning process in order to make a self decision making in Energy Hub. In particular, the proposed immune algorithm considers the previous state, the current state, and the future state of the selected input energy carriers in order to predict the next decision making of Energy Hub based on the probabilistic optimization model. The below figure shows the proposed immune algorithm based Multiple Energy Carriers System. Finally, we will compare the online economic dispatch of MECs of two algorithms such as MAGA and immune algorithm based MECs by using Real Time Digital Simulator (RTDS).

• 한국군사과학기술학회지
• /
• 제17권5호
• /
• pp.643-653
• /
• 2014

High-capacity video, control and situation awareness data should be transmitted efficiently to control robots properly in the ground unmanned system, which requires the technology maximizing the communication range and the data transmission throughput. This technology is connected to the OFDMA(Orthogonal Frequency Division Multiple Access)-MIMO(Multiple Input Multiple Output) transmission technology under the limited bandwidth and transmission power. In this paper, we design MIMO communication system for ground unmanned systems, and investigate the data reception performance experimentally, comparing with SISO(Single Input Single Output) system. Experiment results show that the data reception performance of MIMO is significantly improved compared to that of SISO, e.g. 4dB gain of sensitivity and 5dB of SNR at the value MPR = 1, for the mobile stations with $2{\times}2$ STBC diversity.