• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11A
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• pp.1045-1050
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• 2010

This paper proposes a new $2{\times}2$ spatial-multiplexing(SM) scheme which is constructed by serially concatenating an orthogonal precoder with a conventional SM. Compared to the conventional SM, the proposed scheme achieves improved performance under erasure fading channels without any performance loss under non-erasure fading channels. Particularly the performance gain is more larger as a correlation value between two receive antennas increases.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.215-219
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• 2012

This paper applies transmit antenna selection algorithms to spatial-temporal combining-based spatial multiplexing (SM) ultra-wideband (UWB) systems. The employed criterion is based on the largest minimum output signal-to-noise ratio of the multiplexed streams. It is shown via simulations that the bit error rate (BER) performance of the SM UWB systems based on the two-dimensional Rake receiver is significantly improved by antenna diversity through transmit antenna selection on a log-normal multipath fading channel. When the transmit antenna diversity through antenna selection is exploited in the SM UWB systems, the BER performance of the spatial-temporal combining-based zero-forcing (ZF) receiver is also compared with that of the ZF detector followed by the Rake receiver.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.44-49
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• 2008

Recently, a so called orthogonal spatial multiplexing(OSM) scheme was presented which allows simple maximum likelihood decoding at the receiver with single phase feedback In this paper, by serially concatenating this scheme by a linear precoder, a new closed-loop SM scheme is proposed for two transmit arid two receive antennas. By computer simulation results, we show that the proposed scheme outperforms the conventional SM and OSM. For the proposed code, we also propose a new simple decoding algorithm which leads to a greatly reduced decoding complexity compared with the ML receiver without any loss of error performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.413-423
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• 2014

With the increasing demands on high data rate, there has been growing interests in multi-input multi-output (MIMO) technology based on spatial multiplexing (SM) since it can transmit independent information in each spatial stream. Recent standards such as 3GPP LTE-advanced and IEEE 802.11ac support up to eight spatial streams, and massive MIMO and mm-wave systems that are expected to be included in beyond 4G systems are considering employment of tens to hundreds of antennas. Since the complexity of the optimum maximum likelihood based detection method increases exponentially with the number of antennas, low-complexity SM MIMO detection becomes more critical as the number of antenna increases. In this paper, we first review the results on the detection schemes for SM MIMO systems. In addition, massive MIMO reception schemes based on simple linear filtering which does not require exponential increment of complexity will be explained, followed by brief description on receiver design for future high dimensional SM MIMO systems.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.471-480
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• 2013

The beating of two or more lasers that have the same or a finite difference in the central frequencies, is the main source of noise in spectral amplitude coding optical code division multiple access (SAC OCDMA) systems. In this paper we adopt a spatial multiplexing (SM) scheme for SAC OCDMA systems to mitigate this beat noise. The results show that for different code weights and different data rates SM SAC can support a larger number of users than the conventional SAC for all different laser source configurations. However, SM SAC requires a more complex system than the conventional SAC, and almost twice as much optical component.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.337-344
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• 2011

In this paper, a multiple-input and multiple-output (MIMO) spatial multiplexing (SM) relay system is studied in a bit error rate (BER) sense, where every node is deployed with multiple antennas. In order to efficiently use the limited power resource, it is essential to optimally allocate the power to nodes and antennas. In this context, the power allocation (PA) algorithm based on minimum BER (MBER) for a MIMO SM relay system is proposed, which is derived by direct minimization of the average BER, and divided into inter-node and inter-antenna PA algorithm. The proposed scheme outperforms the conventional equal power allocation (EPA) algorithm without extra power consumption.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.466-469
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• 2011

최근 무선전송에서 SISO(single input singe output) 시스템의 전송률이 샤논 한계(Shannon limit)에 근접함에 따라, 이것을 극복하여 더 높은 데이터 전송률을 얻기 위해 MIMO(multiple input multiple output) 시스템에 대한 연구가 활발하게 이루어지고 있다. 현재 진행 중인 DVB-NGH 시스템 표준화에도 전송률 개선을 위해 MIMO SM(Spatial Multiplexing) 기술에 대해 고려하고 있으며, 방송 시스템 내 송수신 안테나들 간 상관(correlation)이 발생하는 경우에 성능 개선을 위해 Precoding과 MIMO SM을 결합한 $2{\times}2$ 구조의 MIMO SM 방법이 제안되었다. 이 방법은 두 개의 송신안테나에 모두 16QAM 신호가 전송되는 경우와 두 송신안테나에 각각 16QAM, QPSK 신호가 전송되는 경우를 포함하고 있다. 이때 고출력 증폭기(high power amplifier) 전단에서 두 송신 안테나에 서로 다른 변조가 적용되는 경우에 PAPR(peak-to-average power ratio)이 달라서 고출력 증폭기 출력단의 송신전력 차이로 인해 각 신호의 방송권역(coverage)이 같지 않은 문제가 발생한다. 본 논문은 이러한 문제를 극복하기 위해 $2{\times}2$ MIMO SM 방식에서 송신 안테나별로 신호의 변조방식이 서로 다른 경우에 송신신호의 PAPR을 같게 하여 증폭기 출력단에서 각 송신신호의 전력이 동일하게 할 수 있는 방법을 제안한다. 제안한 방법은 수신기의 복잡도를 증가시키지 않으면서 두 송신 신호의 방송권역을 동일하게 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.322-331
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• 2010

This paper introduces a new efficient design scheme for spatial multiplexing (SM) systems over closed loop multiple-input multiple-output (MIMO) wireless channels. Extending the orthogonalized spatial multiplexing (OSM) scheme which was developed recently for transmitting two data streams, we propose a new SM scheme where a larger number of data streams can be supported. To achieve this goal, we partition the data streams into several subblocks and execute the block-diagonalization process at the receiver. The proposed scheme still guarantees single-symbol maximum likelihood (ML) detection with small feedback information. Simulation results verify that the proposed scheme achieves a huge performance gain at a bit error rate (BER) of $10^{-4}$ over conventional closed-loop schemes based on minimum mean-square error (MSE) or bit error rate (BER) criterion. We also show that an additional 2.5dB gain can be obtained by optimizing the group selection with extra feedback information.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.10
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• pp.75-82
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• 2008

In this paper, we propose an efficient symbol detection algorithm for multiple-input multiple-output spatial multiplexing (MIMO-SM) systems and present its design and implementation results. By enhancing the performance of the first detected symbol which causes error propagation, the proposed algorithm achieves a considerable performance gain as compared to the conventional sorted QR decomposition (SQRD) based detection and the ordered successive detection (OSD) algorithms. The bit error rate (BER) performance of the proposed detection algorithm is evaluated by the simulation. In case of 16QAM MIMO-SM system with 4 transmit and 4 receive ($4{\times}4$) antennas, at $BER=10^{-3}$ the proposed algorithm obtains the gai improvement of about 2.5-13.5 dB over the conventional algorithms. The proposed detection algorithm was designed in a hardware description language (HDL) and synthesized to gate-level circuits using 0.18um 1.8V CMOS standard cell library. The results show that the proposed algorithm can be implemented without increasing the hardware costs significantly.

• Journal of information and communication convergence engineering
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• v.9 no.4
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• pp.385-390
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• 2011

In this paper, various ultra-wideband (UWB) spatial multiplxing (SM) multiple input multiple output (MIMO) receivers based on a prerake diversity combining scheme are discussed and their performance is analyzed. Several UWB MIMO detection approaches such as zero forcing (ZF), minimum mean square error (MMSE), ordered successive interference cancellation (OSIC), sorted QR decomposition (SQRD), and maximum likelihood (ML) are considered in order to cope with inter-channel interference. The UWB SM systems based on transmitter-side multipath preprocessing and receiver-side MIMO detection can either boost the transmission data rate or offer significant diversity gain and improved BER performance. The error performance and complexity of linear and nonlinear detection algorithms are comparatively studied on a lognormal multipath fading channel.