• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1827-1832
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• 2014

In this thesis, we use one by one each of the analog switch and a high-speed DAC instead of the DAC that two or more are used in transmitting and receiving antennas multiple systems, maintaining the advantages of the existing method, reducing design costs, physical to provide a method that can reduce the data converters from MIMO system can improve the economic efficiency and the size reduction of a basis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.436-444
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• 2005

Unitary matrix modulation (UMM) is investigated in multiple antennas system that is called unitary space-time modulation (USTM). In an OFDM, the diagonal components of UMM with splitting over the coherence bandwidth (UMM-S/OFDM) have been proposed. Recently LDPC code is strongly attended and studied due to simple decoding property with good error correction property. In this paper, we propose LDPC coded UMM-S/OFDM for increasing the system performance. Our proposed system can obtain frequency diversity using UMM-S/OFDM like USTM/OFDM, and large coding gain using LDPC code. The superior characteristics of the proposed UMM-S/OFDM are demonstrated by extensive computer simulations in multi-path Rayleigh fading channel.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1299-1305
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• 2017

In this paper, we consider a beamforming game between the transmitters in a two-user multiple-input single-output interference channel using limited feedback and investigate how each transmitter is able to find a modified strategy from the quantized channel state information (CSI). In the beamforming game, each of the transmitters (i.e., a player) tries to maximize the achievable rate (i.e., a payoff function) via a proper beamforming strategy. In our case, each transmitter's beamforming strategy is represented by a linear combining factor between the maximum ratio transmission (MRT) and the zero forcing (ZF) beamforming vectors, which is the Pareto optimal achieving strategy. With the quantized CSI, the transmitters' strategies may not be valid because of the quantization errors. We propose a modified solution, which takes into account the effects of the quantization errors.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.29-34
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• 2011

In this paper, we propose antenna and relay selection system by considering channel environment between nodes. Each node has multiple antennas in each hop. And, we analyze the performance of proposed system. A General MIMO system receives signals through multiple channels and obtains diversity gain. But MIMO system causes performance degradation due to poor received signals. The proposed system consider transmitters-relays channels, relays-receivers channels and select a best channel. This channel selection prevents performance degradation and increase total system's performance. Therefore, we must select best antennas and a best relay, simultaneously.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.130-132
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• 2011

본 논문은 지상파 방송망 내 전계강도가 낮은 지역에 최소한의 데이터 전송률을 보장하기 위한 계층변조와 다중경로 채널 극복 및 수신 성능 향상을 위한 다중 안테나 수신기법을 SFN에 적용하여 제안하였다. 계층변조는 기존의 데이터 스트림에 부가적인 데이터 스트림을 삽입함에 따라 지상파 3D HDTV 방송 서비스는 더 많은 유효 전송률을 확보하고 고품질 비디오 서비스를 제공할 수 있었다. 그러나 기본 서비스의 품질을 유지하면서 부가적인 서비스의 품질을 보장하기 위한 대책이 필요하다. 그래서 송, 수신 안테나의 이득을 올리기 위해 다중 안테나 사용 방식을 채용하고, 그 수신 성능을 다중 안테나 위치에 따라 비교해 보았다. 그 결과, 수신 안테나가 한 쪽의 송신 안테나에 가까워질수록 실질적인 SNR이 증가하여 BER 성능이 향상되는 것을 확인하였다.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.125-126
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• 2006

송수신 사이의 거리가 가까운 GPR 시스템들과 같이 신호가 빨리 감쇄되는 산란 측정시스템에서는 송신신호의 왜곡을 줄여 산란체의 신호를 정밀하게 찾아내는 것이 매우 중요하다. 여기에 주로 사용되는 광대역 안테나는 안테나의 급전점과 끝부분의 개방단 사이에서 다중 반사가 일어나서 입력신호의 왜곡으로 인한 떨림현상이 일어나게 되는데, 본 논문에서는 리액턴스 장하를 통해 안테나의 내부 반사를 줄인 초광대역 안테나를 설계하고 제작하여 특성을 측정하였다.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.115-116
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• 2008

본 논문에서는 다중입력 다중출력(Multiple Input Multiple Output: MIMO) 시스템에서 Maximum Likelihood (ML) 수신기와 같은 성능을 가지지만 복잡도가 낮은 Sphere Decoding (SD) 알고리즘에 대해 분석하고, 그 성능을 평가한다. 각각의 송신 안테나에서 채널로 전송되는 독립적인 신호는 QPSK 방식을 사용하여 변조되며, 채널은 산란이 활발하게 일어나는 레일리(Rayleigh) 평탄 페이딩 채널로 가정한다. 수신기에서 수신된 신호는 Fincke & Pohst SD 알고리즘에 의해 간 송신 안테나로부터의 독립적인 신호로 검파되며 그 성능이 ML수신기의 성능과 비교되었다. 추가적으로 복잡도를 줄이기 위해 개선된 형태인 Viterbo & Boutros SD 알고리즘을 이용하여 검파된 신호의 BER 성능과 부동 소수점 연산량 (Floating Point Operations: FLOPS)이 각각 비교 분석되었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1238-1243
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• 2007

The computational complexity for the zero-forcing (ZF)-based multiuser (MU) multiple-input multiple-output(MIMO) preprocessing matrices can be immoderately large as the number of transmit antennas or users increases. In this paper, we show that the span of singular vector space of a matrix can be obtained from the singular vectors of the parted rows of that matrix with computational saving and propose a computationally efficient recursive-algorithm for achieving the ZF-based preprocessing matrices. Analysis about the complexities shows that a new recursive-algorithm can lighten the computational load.

• Journal of Broadcast Engineering
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• v.20 no.6
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• pp.837-847
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• 2015

In this paper, the reception performance of spatial modulation multiple-output multiple-input (MIMO) is analyzed for high speed terrestrial broadcasting. The MIMO scheme is required to reduce the inter symbol interference (ISI) and spatial correlation. The spatial modulation scheme solves the problem of ISI, but the spatial correlation degrades the reception performance of SM scheme. The space-time block coded spatial modulation (STBC-SM) is combined the SM system with space-time block code (STBC) for reducing the effects of the spatial correlation. However, the STBC-SM scheme degrades the spectral efficiency by transmitting same data in the two symbol period. The double space-time transmit diversity with spatial modulation (DSTTD-SM) scheme transmits the data with full antenna combination. To adapt these SM MIMO systems into the terrestrial broadcasting system, the reception performance is analyzed using computer simulation in SUI channel environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.462-467
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• 2007

This paper proposes Minimum Distance Searching Algorithm (MDSA) which reduces the computational complexity (CC) of the ML, the kind of Spatial Multiplexing (SM) MIMO system. The MDSA searchs candidate symbols with a starting symbol, which is called reference bits. We used the linear receiver of MIMO techniques to find a starting symbol. The MDSA searchs the shortest path to a transmitted symbol using reference bits and Minimum Distance(MD) concept. The CC of MDSA is reduced to the 0.21% to the ML as the transmit antennas is 4 in 16QAM. The simulation result shows the BER of MDSA is nearly same to the BER of ML as the transmit antennas is 2 and the receive antennas is 3 in 16QAM and slightly degraded to the BER of ML as the transmit antennas is 4 and the receive antennas is 6 in QPSK.