• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2365-2382
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• 2014

While single-user spatial multiplexing multiple-input multiple-output (SU-MIMO) allows spatially multiplexed data streams to be transmitted to one node at a time, multi-user spatial multiplexing MIMO (MU-MIMO) enables the simultaneous transmission to multiple nodes. However, if the transmission time required to send packets to each node varies considerably, MU-MIMO may fail to utilize the available MIMO capacity to its full potential. The transmission time typically depends upon two factors: the link quality of the selected channel and the data length (packet size). To utilize the cumulative capacity of multiple channels in MIMO applications, the assignment of channels to each node should be controlled according to the measured channel quality or the transmission queue status of the node.A MAC protocol design that can switch between MU-MIMO and multiple SU-MIMO transmissions by considering the channel quality and queue status information prior to the actual data transmission (i.e., by exchanging control packets between transmitter and receiver pairs) could address such issues in a simple but in attractive way. In this study, we propose a new MAC protocol that is capable of performing such switching and thereby improve the system performance of very high throughput WLANs. The detailed performance analysis demonstrates that greater benefits can be obtained using the proposed scheme, as compared to conventional MU-MIMO transmission schemes.

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2003년도 제2회 정기총회 및 추계학술대회
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• pp.153-158
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• 2003

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3887-3907
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• 2015

This paper introduces a full duplex single secondary user multiple-input multiple-output (FD-SSU-MIMO) cognitive radio network, where secondary user (SU) opportunistically accesses the authorized spectrum unoccupied by primary user (PU) and transmits data based on FD-MIMO mode. Then we study the network achievable average sum-rate maximization problem under sum transmit power budget constraint at SU communication nodes. In order to solve the trade-off problem between SU's sensing time and data transmission time based on opportunistic spectrum access (OSA) and the power allocation problem based on FD-MIMO transmit mode, we propose a simple trisection algorithm to obtain the optimal sensing time and apply an alternating optimization (AO) algorithm to tackle the FD-MIMO based network achievable sum-rate maximization problem. Simulation results show that our proposed sensing time optimization and AO-based optimal power allocation strategies obtain a higher achievable average sum-rate than sequential convex approximations for matrix-variable programming (SCAMP)-based power allocation for the FD transmission mode, as well as equal power allocation for the half duplex (HD) transmission mode.

• 디지털콘텐츠학회 논문지
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• 제5권4호
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• pp.264-268
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• 2004

최근 대용량 고속데이터 전송을 위해 여러 개의 송,수신 안테나를 이용하여 전송용량을 증가시킬 수 있는 MIMO(Multi-Input Multi-Output) 시스템에 대한 연구가 활발히 진행되고 있다. 본 논문에서는 먼저 MIMO 채널을 모델링하고, MIMO 채널에서 OSUC 복호알고리즘을 이용한 ZF수신기와 MMSE 수신기를 각각 적용하여 V-BLAST 시스템의 성능을 비교분석하였다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.12-16
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• 2008

In this paper, we study precoding techniques for co-channel interference suppression in multiuser MIMO systems. DPC is optimal techniques to achieve the system capacity of multiuser MIMO downlink channels. DPC is not proper in practical wireless systems because complexity is very high. So block diagonal precoding for multiuser MIMO downlink channel is studied. The block diagonal precoding is used to suppress co-channel interference between multiuser. Block diagonal precoding method, whose complexity is reduced by modified null space operation, change multiuser MIMO channel to multiple single-user MIMO channel. We also use V-BLAST decoder in receiver. V-BLAST decoder can achieve increased system capacity in proportion to the number of users. We show improved system performance by using computer simulation.

• 대한전자공학회논문지TC
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• 제44권7호통권361호
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• pp.88-95
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• 2007

본 논문에서는 다양한 방식의 MIMO 기법에 쉽게 적용이 가능한 송수신 시스템 모델을 제안하고 이들의 성능 분석 시 필요한 채널간의 상관 특성 획득이 가능한 MIMO 채널 모델을 제시한다. 실내 환경에서의 채널 모델링을 통하여 MIMO 채널 형성에 따른 안테나 사이의 간섭을 시뮬레이션을 통하여 획득하고 주파수 선택적 채널 하에서 MIMO-UWB 시스템의 성능을 분석한다. 특히 채널 전달함수의 역행렬 계산시 과다한 연산량을 줄이기 위하여, 임의의 한 수신안테나에서 각각의 송신 안테나 신호를 복원하며, 각 수신안테나에서 추정된 송신 신호를 결합하는 방법을 채택하였다.

• 디지털산업정보학회논문지
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• 제14권3호
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• pp.77-85
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• 2018

Multi-User Multiple-Input Multiple-Output (MU-MIMO) is the core technology for improving the channel capacity compared to Single-User MIMO (SU-MIMO) by using multiuser gain and spatial diversity. Key problem for the MU-MIMO is the user selection which is the grouping the users optimally. To solve this problem, we adopt Extreme Value Theory (EVT) at the beginning of the proposed algorithm, which defines a primary user set instead of a single user that has maximum channel power according to a predetermined threshold. Each user in the primary set is then paired with all of the users in the system to define user groups. By comparing these user groups, the group that produces a maximum sum rate can be determined. Through computer simulations, we have found that the proposed method outperforms the conventional technique yielding a sum rate that is 0.81 bps/Hz higher when the transmit signal to noise ratio (SNR) is 30 dB and the total number of users is 100.

• 한국정보통신학회논문지
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• 제12권6호
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• pp.1082-1086
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• 2008

MIMO기술은 대역폭과 전력에 의해 제한을 받는 무선네트워크의 데이터 전송률을 증대시켜주는 효과적인 기술이다. 송수신단사이의 데이터 전송률은 채널용량에 의해 결정되며, MIMO기술은 이 채널용량을 적절히 이용함으로써 무선채널에서의 통신신뢰도를 높이는 이점을 가지고 있다. 본 논문은 Confluent Hypergeometric Function를 이용하여 새로운 공식 인 closed form capacity formula를 유도한다.

• Journal of information and communication convergence engineering
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• 제17권1호
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• pp.1-7
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• 2019

In this paper, we present the block diagonalization (BD) algorithm for the multiple-user multiple input multiple output (MU-MIMO) $4{\times}4$ system using specific purpose processor (SPP) hardware. Our objective is to improve the single-user MIMO (SU-MIMO) system using the MU-MIMO technology, which is remarkably fast and allows more users to connect simultaneously. To that end, our MU-MIMO precoder uses the BD algorithm to ensure signal integrity when connecting multiple users; but remains accurate and stable. However, a precoder that uses the BD algorithm is computationally complex; therefore, we use an SPP with special functions designed to compute the BD algorithm. The implementation test results show that our SPP computes the BD algorithm faster than the software solution.

• 한국정보통신학회논문지
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• 제19권5호
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• pp.1157-1162
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• 2015

본 논문에서는 OFDM 기반의 4x4 MIMO 알고리즘을 설계 및 구현을 하였으며, 구현된 결과를 검증하기 위한 방법을 제시한다. 알고리즘은 MRVD와 QRM-MLD을 적용했다. Matlab과 Simulink를 이용하여 채널 추정 및 MIMO 알고리즘을 Floating-point와 Fixed-point 모델로 설계하였다. 그 다음 Modelsim을 이용하여 VHDL로 구현한다. 구현된 알고리즘의 성능 검증을 위해 설계한 Simulink 모델과 Modelsim 시뮬레이션, ISE ChipScope, 그리고 오실로스 코프로 측정한 결과를 비교하는 방법을 사용하였다. 이 방법은 시스템이 완성되지 않은 상태에서 구현된 알고리즘을 검증하는 방법이다. 검증 결과 ChipScope의 결과와 오실로스코프의 결과가 동일함을 확인하였고, 백홀 시스템에 적용이 가능함을 확인하였다.