• ETRI Journal
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• v.40 no.5
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• pp.570-581
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• 2018

This work analyzes the performance of implementable detectors for the multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) technique under specific and realistic operation system conditions, including antenna correlation and array configuration. A time-domain channel model was used to evaluate the system performance under realistic communication channel and system scenarios, including different channel correlation, modulation order, and antenna array configurations. Several MIMO-OFDM detectors were analyzed for the purpose of achieving high performance combined with high capacity systems and manageable computational complexity. Numerical Monte Carlo simulations demonstrate the channel selectivity effect, while the impact of the number of antennas, adoption of linear against heuristic-based detection schemes, and the spatial correlation effect under linear and planar antenna arrays are analyzed in the MIMO-OFDM context.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.241-244
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• 1997

A speckle pattern from an optical fiber is used for a reference beam in writing and reading a volume hologram. The photorefractive volume hologram with this scheme shows good spatial selectivity for spatial(shift) multiplexing because the speckle pattern in writing and reading a hologram looses correlation with a small spatial shift. This scheme has the insensitivity to axial movement. The data storage system with this scheme will have a high storage density and a good stability in operation. We theoretically analyze the diffracted beam from a volume hologram recorded with the speckle pattern from the optical fiber. Experimental results are presented and compared with numerical analysis.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.81-88
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• 2012

Space diversity and space multiplexing gain can be achieved with MIMO system. This paper proposes spatial coding method to MIMO system using data information and antenna selection technique. This technique provides coding gain as well as space diversity gain. For MIMO system with BPSK modulation, BER performance is analyzed and space diversity gains are compared through simulation in terms of data maldistribution degree.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.122-130
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• 2008

Improving the transmission rates of multi-media delivery, such as moving pictures and internet services, has become increasingly important in modern society. To satisfy such high data rate requirements, the MIMO technique, which has the capacity to transmit large amounts of data using limited frequency resources, was developed. The Space Division Multiplexing (SDM) system is one of the MIMO techniques to be able to improve the transmission capacity. However, it is unable to achieve diversity gain because of interference due to the use of multiple antennas. In this paper, an SDM system that utilizes a Multi-Block method as an advanced transmission technique in a wireless communication system to obtain diversity gain is proposed and discussed fur the performance of the proposed system.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.488-488
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• 2004

• Journal of KIISE:Information Networking
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• v.29 no.6
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• pp.749-754
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• 2002

In this paper, We propose a titrate allocation method in which the bitrates of the videos for the lower layer are restricted by constant titrate, but those of the higher layer are assigned to have the uniform picture quality, for the multiplexing system of multiple spatial scalable video sources. We first find an approximated model of distortion-bitrate for the MPEG-2 spatial scalable video coding system, then we obtain the bitrate for each source to have constant distortion ratio among the sources by using the approximated model parameters for real-time simple implementation. It is shown by simulation that the proposed bandwidth allocation can keep almost constant picture Quality ratio among the sources of higher layer.

• Journal of information and communication convergence engineering
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• v.13 no.1
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• pp.1-6
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• 2015

In this study, we consider visible light communication in an indoor line-of-sight environment. It has been proved that among the multiple input multiple output (MIMO) techniques, spatial modulation (SM) performs better than repetition coding (RC) and spatial multiplexing (SMP). On the basis of a combination of SM and pulse amplitude modulation (PAM), here, we propose an enhanced SM algorithm to improve the bit error rate. Traditional SM activates only one light-emitting diode (LED) at one time, and the proposed enhanced SM activates two LEDs at one time and reduces the intensity levels of PAM by half. Under the condition of a highly correlated channel, power imbalance is used to improve the algorithm performance. The comparison between the two schemes is implemented at the same signal-to-noise ratio. The simulation results illustrate that the enhanced SM outperforms the traditional SM in both highly correlated and lowly correlated channels. Furthermore, the proposed enhanced SM scheme can increase the transmission rate in most cases.

• ETRI Journal
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• v.39 no.5
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• pp.707-717
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• 2017

This paper presents a novel generalized quadrature spatial modulation (GQSM) transmission scheme using antenna grouping. The proposed GQSM scheme combines QSM and conventional spatial multiplexing (SMux) techniques in order to improve the spectral efficiency (SE) of the system. Analytical and simulation results show that the proposed transmission scheme has minimal losses in terms of the average bit error probability along with the advantage of an increased SE compared with previous SM and QSM schemes. For the case studies, this advantage represents a reduction of up to 81% in terms of the number of required transmit antennas compared with QSM. In addition, a detection architecture based on the ordered successive interference cancellation scheme and the QR decomposition is presented. The proposed QRD-M adaptive algorithm showed a near-maximum-likelihood performance with a complexity reduction of approximately 90%.

• ETRI Journal
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• v.26 no.6
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• pp.565-574
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• 2004

Differential unitary space-time modulation (DUSTM) has emerged as a promising technique to obtain spatial diversity without intractable channel estimation. This paper presents a study of the application of DUSTM on multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with frequency-selective fading channels. From the view of a correlation analysis between subcarriers of OFDM, we obtain the maximum achievable diversity of DUSTM on MIMO-OFDM systems. Moreover, an efficient implementation strategy based on subcarrier reconstruction is proposed, which transmits all the signals of one signal matrix in one OFDM transmission and performs differential processing between two adjacent OFDM blocks. The proposed method is capable of obtaining both spatial and multipath diversity while reducing the effect of time variation of channels to a minimum. The performance improvement is confirmed by simulation results.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.49-51
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• 2017

본 논문에서는 ATSC 3.0 시스템의 2x2 MIMO (multiple input multiple output) 방식을 적용한 송수신기 구조에 대해서 살펴본다. ATSC 3.0 시스템의 MIMO 에서 적용된 프리코더 (precoder)는 스트림 결합기(stream combining), IQ 편파 인터리빙 (I/Q polarization interleaving), 위상 홉핑부 (phase hopping)로 구성된다. 또한, ATSC 3.0 의 2x2 MIMO 방식을 사용함으로써 공간 다중화 (spatial multiplexing) 이득과 공간 다이버시티 (spatial diversity) 이득을 얻을 수 있다.