• International Journal of Internet, Broadcasting and Communication
• /
• 제15권4호
• /
• pp.44-50
• /
• 2023

For Wi-Fi and IoT wireless systems, high-capacity wireless communication technology is being applied using MIMO OFDM. Because of virtu0al subcarriers in the practical MIMO OFDM system, the pilot subcarriers cannot be spaced equally. Thus, it is difficult to obtain a good mean square error (MSE) performance of the channel estimate. This paper proposes applicable methods and the newly discovered locations of pilot subcarriers in four transmitted antennas resulting in a good MSE performance with proposed optimization algorithms.

• Journal of Electrical Engineering and Technology
• /
• 제12권2호
• /
• pp.601-611
• /
• 2017

This paper proposes a simultaneous control of frequency deviation and electric vehicles (EVs) battery state of charge (SOC) using load frequency control (LFC) and EV controllers. In order to provide both frequency stabilization and SOC schedule near optimal performance within the whole operating regions, a multiple-input multiple-output model predictive control (MIMO-MPC) is employed for the coordination of LFC and EV controllers. The MIMO-MPC is an effective model-based prediction which calculates future control signals by an optimization of quadratic programming based on the plant model, past manipulate, measured disturbance, and control signals. By optimizing the input and output weights of the MIMO-MPC using particle swarm optimization (PSO), the optimal MIMO-MPC for simultaneous control of the LFC and EVs, is able to stabilize the frequency fluctuation and maintain the desired battery SOC at the certain time, effectively. Simulation study in a two-area interconnected power system with wind farms shows the effectiveness of the proposed MIMO-MPC over the proportional integral (PI) controller and the decentralized vehicle to grid control (DVC) controller.

• 한국정보전자통신기술학회논문지
• /
• 제6권4호
• /
• pp.255-261
• /
• 2013

본 논문에서는 공간다중화 방식을 사용하는 다중 안테나 시스템의 수신부에서 연판정 값의 신뢰도 향상 기법 두 가지를 비교분석한다. 공간 다중화 MIMO 시스템의 수신기술 복잡도는 일반적으로 생성하는 후보 벡터의 수 에 비례하여 증가한다. 적은 수의 후보벡터를 발생하여 낮은 복잡도를 갖는 검출기법은 연판정 값의 신뢰도가 저하되는 단점을 갖는다. 이렇게 저하된 신뢰도를 향상시키는 방법으로써 절삭임계치를 사용하는 방법과 squared Euclidian 거리대신 Euclidian 거리를 사용하는 방법이 있다. 본 논문에서는 이 두가지 방법의 이론적 인 유사성을 보이고 하드웨어 구현관점에서의 장단점들을 분석한다.

• 한국정보전자통신기술학회논문지
• /
• 제1권1호
• /
• pp.53-59
• /
• 2008

본 논문에서는 공간다중화 방식을 사용하는 다중 안테나 시스템의 수신부에서 연판정 값의 신뢰도 향상기법 두 가지를 비교분석한다. 공간 다중화 MIMO 시스템의 수신기술 복잡도는 일반적으로 생성하는 후보벡터의 수에 비례하여 증가한다. 적은 수의 후보벡터를 발생하여 낮은 복잡도를 갖는 검출기법은 연판정 값의 신뢰도가 저하되는 단점을 갖는다. 이렇게 저하된 신뢰도를 향상시키는 방법으로써 절삭임계치를 사용하는 방법과 squared Euclidian 거리대신 Euclidian 거리를 사용하는 방법이 있다. 본 논문에서는 이 두 가지 방법의 이론적인 유사성을 보이고 하드웨어 구현관점에서의 장단점들을 분석한다.

• Journal of electromagnetic engineering and science
• /
• 제19권1호
• /
• pp.20-30
• /
• 2019

A wide-band multiple-input multiple-output (MIMO) antenna with dual-band (2.4 and 5 GHz) operation is proposed for premium indoor access points (IAPs). Typically, an omni-directional pattern is used for dipole antennas and a directional radiation pattern is used for patch antennas. In this paper, both antenna types were used to compare their performance with that of the proposed $2{\times}2$ MIMO antenna. We simulated and measured the performance of the MIMO antenna, including the isolation, envelope correlation coefficient (ECC), mean effective gain (MEG) for the IAPs, and the throughput, in order to determine its communication quality. The performance of the antennas was analyzed according to the ECC and MEG. The proposed antenna has sufficient performance and excellent characteristics, making it suitable for IAPs. We analyzed the communication performance of wireless networks using the throughput data of a typical office environment. The network throughput of an 802.11n device was used for the comparison and was conducted according to the antenna type. The results showed that the values of the ECC, MEG, and the throughput have unique characteristics in terms of their directivity, antenna gains, isolation, etc. This paper also discusses the communication performance of various aspects of MIMO in multipath situations.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권4호
• /
• pp.1373-1391
• /
• 2022

We investigate mobile multiple-input multiple-output (MIMO) molecular communication via diffusion (MCvD) system which is consisted of two source nodes, two destination nodes and one relay node in the mobile three-dimensional channel. First, the combinations of decode-and-forward (DF) relaying protocol and network coding (NC) scheme are implemented at relay node. The adaptive thresholds at relay node and destination nodes can be obtained by maximum a posteriori (MAP) probability detection method. Then the mathematical expressions of the average bit error probability (BEP) of this mobile MIMO MCvD system based on DF and NC scheme are derived. Furthermore, in order to minimize the average BEP, we establish the optimization problem with optimization variables which include the ratio of the number of emitted molecules at two source nodes and the initial position of relay node. We put forward an iterative scheme based on block coordinate descent algorithm which can be used to solve the optimization problem and get optimal values of the optimization variables simultaneously. Finally, the numerical results reveal that the proposed iterative method has good convergence behavior. The average BEP performance of this system can be improved by performing the joint optimizations.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제3권6호
• /
• pp.647-666
• /
• 2009

Multiple-input multiple-output (MIMO) multiplexing is an attractive technology that increases the channel capacity without requiring additional spectral resources. The design of low complexity and high performance detection algorithms capable of accurately demultiplexing the transmitted signals is challenging. In this technical survey, we introduce the state-of-the-art MIMO detection techniques. These techniques are divided into three categories, viz. linear detection (LD), decision-feedback detection (DFD), and tree-search detection (TSD). Also, we introduce the lattice basis reduction techniques that obtain a more orthogonal channel matrix over which the detection is done. Detailed discussions on the advantages and drawbacks of each detection algorithm are also introduced. Furthermore, several recent author contributions related to MIMO detection are revisited throughout this survey.

• 융합정보논문지
• /
• 제10권11호
• /
• pp.23-29
• /
• 2020

IoT 장치가 기하급수적으로 증가하면서 다중 안테나를 통해 IoT 정보를 송·수신하기 위한 MIMO 간섭 최소화 및 전송 용량 증대는 가장 큰 이슈로 남아있는 상황이다. 본 논문에서는 MIMO 기반의 IoT 통신 잡음을 최소화하기 위해서 딥러닝을 활용한 비밀키 차원 분배 메커니즘을 제안한다. 제안 메커니즘은 다중의 안테나를 통해 송·수신되는 IoT 정보를 딥러닝을 사용하여 일괄적으로 분산 처리함으로써 송·수신 과정 중에 발생하는 자원 손실을 최소화하고 있다. 또한, 제안 메커니즘은 AP들간의 직접적인 간섭이 없는 기지국의 다중 안테나 다중 스트림 전송을 통해 용량을 최대로 증대시킬 수 있도록 다차원 키 분배 처리 과정을 적용하였다. 또한, 제안 메커니즘은 다중 안테나 기술을 최대한 활용하기 위해서 IoT 정보의 주파수 채널 수에 따라 비밀키를 차원 분배하는 방식을 적용함으로써 IoT 정보수에 따른 비밀키 사용 빈도수를 딥러닝하여 IoT 정보를 서로 동기화하고 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권4호
• /
• pp.1330-1350
• /
• 2022

As a preprocessing operation of transmitter antennas, the hybrid precoding is restricted by the limited computing resources of the transmitter. Therefore, this paper proposes a novel hybrid precoding that guarantees the communication efficiency with low complexity and a fast computational speed. First, the analog and digital precoding matrix is derived from the maximum eigenvectors of the channel matrix in the sub-connected architecture to maximize the communication rate. Second, the extended power iteration (EPI) is utilized to obtain the maximum eigenvalues and their eigenvectors of the channel matrix, which reduces the computational complexity caused by the singular value decomposition (SVD). Third, the Aitken acceleration method is utilized to further improve the convergence rate of the EPI algorithm. Finally, the hybrid precoding based on the EPI method and the Aitken acceleration algorithm is evaluated in millimeter-wave (mmWave) massive multiple-input and multiple-output (MIMO) systems. The experimental results show that the proposed method can reduce the computational complexity with the high performance in mmWave massive MIMO systems. The method has the wide application prospect in future wireless communication systems.

• 한국통신학회논문지
• /
• 제39A권10호
• /
• pp.579-584
• /
• 2014

본 논문에서는 패치형 ESPAR(Electronically Steerable Parasitic Array Radiator) 안테나를 이용한 빔 공간 MIMO(beamsapce mulitple input multiple output) 시스템을 제안한다. 기존의 모노폴 ESPAR 안테나의 경우 단일 RF 체인을 갖기 때문에 하드웨어의 비용과 RF회로의 전력 소모를 절감할 수 있는 장점을 가진다. 하지만 공간적 제약이 큰 휴대용 이동기기에 적용하기 문제점이 있다. 따라서 부피를 간소화 시키는 방법으로써 패치형 ESPAR 안테나를 설계하고 단일 RF 체인으로 MIMO 기술이 가능한 빔 공간 MIMO 시스템에서의 성능을 분석한다. 본 논문에서 설계한 패치형 ESPAR 안테나를 통해 빔패턴이 ${\pm}15$도의 앙각의 변화를 가지는 것을 확인하였고, 또한 이 ESPAR 안테나를 사용하여 빔 공간 MIMO 시스템을 구현하고 이 시스템의 BER 성능을 확인하였다.