• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.6-13
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• 2011

Multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) with space-time coding (STC) is a promising technology for future wireless communication systems. However, MIMO-OFDM systems are greatly impaired by large cochannel interference (CCI) from the multiple transmitters. In this paper, we propose pre-fast Fourier transform (FFT) multibeamforming based on MMSE(minimizing the mean squared error) for a MIMO-OFDM system to preserves the STC diversity and to remove the CCI. The improvement in bit error rate is investigated through computer simulation of a MIMO-OFDM system in a multipath channel with CCI.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.185-190
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• 2008

Geophysical survey were investigated in the offshore around East Sea Research Institute, Korea Ocean Research and Development Institute (Jukbyeon-myun, Uljin-gu, Gyeongsangbuk-do, Korea). The surveys were conducted aboard the R/V Jangmok in 2008 using a hull-mounted EM 3002 multi-beam echosounder. Precise bathymetry and seabed images were obtained using multi-beam and thicknesses of sedimentary layer were found through seismic survey. Submarine topography deepens parallel to the coastline to -60 m and rock mass distributed in the southeast of study area. By finding the thickness of sedimentary layer through seismic survey, a sedimentary thickness on the study area was established. Futhermore, monitoring data of bathymetry, substructure and sedimentary environment will be secured through successive geophysical investigation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2C
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• pp.86-92
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• 2011

This paper details the downlink performance analysis of an multiple antennas system that combines adaptive beamforming and spatial multiplexing (SM) Multiple Input Multiple Output (MIMO). The combination of MIMO signal processing with adaptive beamforming is applied to WiBro, the South Korean Orthogonal Frequency Division Multiple Access (OFDMA) system that follows the IEEE 802.16e standard. Performance analysis is based on the results of experiments and simulations obtained from a fixed-point simulation testbed. Simulations demonstrate that the MIMO Beamforming OFDMA system improves the required signal to noise ratio (SNR) over the conventional MIMO OFDMA system by 3 dB (QPSK) / 2.5 dB (16-QAM) for the frame error rate (FER) of 1% in the WiBro signal environments. From the implementation of the fixed-point simulation testbed and its experimental results, we verify the feasibility of the MIMO Beamforming technology for realizing a practical WiBro base station.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1574-1580
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• 2021

This paper designs and presents the results of an air network simulation radio transmission link applied with a multi-beam active phase array antenna simulator in a testbed system for verifying an air network currently underway as a technology development task. Using the Ku band, the Radio transmission link was designed in consideration of the link budget to satisfy the requirements for the system being developed. Considering short-distance links and long-distance links, the required EIRP and G/T performance scales of multi-beam repeaters and mission planes were applied to confirm the minimum and maximum link margins based on Eb/No. In this Radio Transmission Link design, the application analysis results such as rainfall availability are used to effectively establish standards when selecting the operating radius of the multi-beam relay system and related system standards.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.130-138
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• 2008

In this paper, we propose a user selection method to maximize the sum-rate of downlink over opportunistic beamforming. The throughput of an opportunistic beamforming with non-uniformly distributed or a small number of users can decrease. In order to improve the throughput, we propose a scheduling method that does not use SINR or SNR but uses the effective channel gain of each user obtained from the SINR or SNR feedback. The proposed method makes it possible to select users flexibly according to the distribution of users. In numerical results, we show that the proposed methods improve the average sum-rate about 60% when users are distributed non uniformly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1058-1066
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• 2004

This paper proposes the acquisition system using the multiple antennas in DS-CDMA system. The conventional acquisition schemes using multiple antennas are the methods to utilize the multi-antenna combining and the fixed multi-beam forming of a serial acquisition. Then, this paper proposes the hybrid acquisition scheme using the fixed multi-beam forming. The numerical results show the performance comparison of two acquisition schemes in terms of the acquisition time ill the multipath Rayleigh fading channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.49-59
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• 2005

An adaptive hybrid beamformer is proposed to improve the reception performance of the advanced television system committee (ATSC) digital television (DTV) in a mobile environment. Dynamic multipaths and Doppler shifts severely degrade the reception performance of the ATSC DTV receiver. Accordingly, a hybrid beamformer, called a Capon and least mean square (CLMS) beamformer, is presented that uses direction of arrival (DOA) information and the least mean square (LMS) beamforming algorithm. The proposed CLMS algerian efficiently removes dynamic multipaths and compensates for the phase distortion caused by Doppler shifts in mobile receivers. After the CLMS beamformer is operated, the subsequent use of an equalizer removes any residual multipath effects, thereby significantly improving the performance of DTV receivers. The performances of the proposed CLMS, Capon, and LMS beamformersare compared based on computer simulations. In addition, the overall performance of the CLMS beamformer followed by an equalizer is also considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1A
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• pp.25-33
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• 2012

Random beamforming (RBF) uses the signal to interference plus noise ratio (SINR) feedback to select users in multiple-input multiple-output (MIMO) systems. A large number of users are required to obtain the gain of multi-user diversity for a downlink transmission. However, if the number is not large enough, it may be difficult to obtain multi-user diversity, leading to a rapid degradation in performance. To resolve this problem, we propose the beamforming matrix transformation and the user scheduling method. The beamforming matrix transformation scheme uses the SINRs of each users and have a better performance than conventional schemes over a small number of users. In addition, we propose the user scheduling scheme corresponding to the beamforming matrix transformation. In simulation results, we demonstrate that the sum-rate can be improved according to the number of users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.5
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• pp.220-228
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• 2014

ESPAR(Electronically Steerable Parasitic Array Radiator) antenna is the technique for overcoming the problems of space limitation and energy efficiency due to the multiple RF-chain. Conventional MIMO system with multiple antenna requires a large number of RF-chain for transmitting the multiple data because it transmits the data in proportion to the number of antenna. Beamspace MIMO system using the ESPAR antenna which has single RF-chain was proposed for solving the problems caused by using the multiple antenna and RF-chain. In this paper, therefore we propose 2x2 beamspace MIMO system using the 16, 64-QAM modulation and evaluate the performance of this system to reveal that it is possible that beamspace MIMO system can use not only PSK modulation but also QAM modulation. We confirm that QAM symbol can be generated by adjusting reactance of parasitic elements and making reactance set and also we confirm that performance of beamspace MIMO system is similar to the conventional MIMO system by transmitting the QAM symbol made by reactance set through the simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.3B
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• pp.280-287
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• 2001

본 논문에서는 기존의 LCD MW를 이용한 각 다중화 시스템에서 인접한 수직방향 MW 사이의 crosstalk를 제거하기 위하여 MW의 뒷단에 수직방향으로 주기적으로 서로 다른 초점 길이를 갖는 이중초점 렌즈를 삽입하여 인접한 MW의 기준빔이 서로 다른 공간에 기록되게 함으로써 기준빔의 전자적 제어뿐만 아니라 고밀도의 정보저장 및 복원이 가능한 새로운 공간-각 다중화 기법을 제안하고 이에 대한 광학 실험을 통해 구현가능성을 제시하였다.