Optimal Number of Users in Zero-Forcing Based Multiuser MIMO Systems with Large Number of Antennas

Jung, Minchae,Kim, Younsun,Lee, Juho,Choi, Sooyong The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.4

The optimal number of users achieving the maximum sum throughput is analyzed in zero-forcing (ZF) based multiuser multiple-input multiple-output (MIMO) systems with a large number of base station (BS) antennas. By utilizing deterministic ergodic sum rates for the ZF-beam forming (ZF-BF) and ZF-receiver (ZF-R) with a large number of BS antennas [1], [2], we can obtain the ergodic sum throughputs for the ZF-BF and ZF-R for the uplink and downlink frame structures, respectively. Then, we can also formulate and solve the optimization problems maximizing the ergodic sum throughputs with respect to the number of users. This paper shows that the approximate downlink sum throughput for the ZF-BF is a concave function and the approximate uplink sum throughput for the ZF-R is also a concave function in a feasible range with respect to the number of users. The simulation results verify the analyses and show that the derived numbers of users provide the maximum sum throughputs for the ZF-BF as well as ZF-R in multiuser MIMO systems with a large number of BS antennas.

항공 통신 기술 분야 : 셀간 협력 통신을 위한 상향링크 환경에서의 ML 및 ZF/MMSE 를 결합한 검출 기술

김점수 ( Jum Su Kim ),김정곤 ( Jeong Gon Kim ),김석우 ( Seok Woo Kim ) 한국항행학회 2011 韓國航行學會論文誌 Vol.15 No.3

본 논문에서는 최근 4세대 이동통신에서 논의 되고 있는 기술인 셀 간 협력 통신이 가능한 다중 셀 환경에 서 상향링크에서의 다중 사용자 신호 검출기술에 대해서 다루었다. 먼저 기존 검출 기술로 ML, ZF, MMSE 그리고 SIC 등을 다루었고, 보통 ML은 최적의 성능을 보이지만, 복잡도가 지수적으로 증가하며, ZF 나 MMSE 는 간단하지만 성능이 떨어지며, SIC 는 복잡하고 오류전파 현상이 발행 할 수 있는 문제점을 가지고 있다. 이에 기존의 ZF/MMSE 에 비해서는 성능 개선이 이루어지면서, 복잡도를 유지 또는 감소시킬 수 있는 구조 제안을 위해서 ZF/MMSE 방식과 ML 의 적용구조를 단순화 시킨 부분 ML 복호 방식을 결합한 검출 방식을 제안하였다. 모의실험 결과, 제안방식은 ZF/MMSE 기반의 SIC 방식에 비해 BER 성능이 개선 또는 유지 되었으며, 복잡도 측면에서 감소하는 효과를 보였으며, 또한 복잡도 감소는 협력 기지국 및 안테나 수가 증가할수록 더 감소 효과가 커질 수 있음을 알 수 있었다. In this paper, we address the issue of joint detection schemes for uplink cellular system when base station cooperation is possible for multi-user detection in multi-cell scenario. The ZF, ML, MMSE and SIC detection are analyzed and evaluated as a conventional scheme. ML attains the optimal performance but the complexity increases exponentially, ZF/MMSE have simple structure but have poor detection performance and SIC has better performance but it has large complexity and potential of the error propagation. However, they need the increased decoder complexity as the number of iteration is increased. We propose a new joint ML and ZF/MMSE detection scheme, which combines the partial ML decoding and ZF/MMSE detection, in order to decrease the decoder complexity. Simulation results show that the proposed scheme attains same or a little bit better BER performance and expect reduced decoder complexity, specially in the case of large number of Base Station are cooperated each other.

Optimal Number of Users in Zero-Forcing Based Multiuser MIMO Systems with Large Number of Antennas

정민채,김윤선,이주호,최수용 한국통신학회 2013 Journal of communications and networks Vol.15 No.4

The optimal number of users achieving the maximum sum throughput is analyzed in zero-forcing (ZF) based multiuser multiple-inputmultiple-output (MIMO) systems with a large number of base station (BS) antennas. By utilizing deterministic ergodic sum rates for the ZF-beamforming (ZF-BF) and ZF-receiver (ZFR)with a large number of BS antennas [1], [2], we can obtain the ergodic sum throughputs for the ZF-BF and ZF-R for the uplink and downlink frame structures, respectively. Then, we can also formulate and solve the optimization problems maximizing the ergodic sum throughputs with respect to the number of users. This paper shows that the approximate downlink sum throughput for the ZF-BF is a concave function and the approximate uplink sum throughput for the ZF-R is also a concave function in a feasible range with respect to the number of users. The simulation results verify the analyses and show that the derived numbers of users provide the maximum sum throughputs for the ZF-BF as well as ZF-R in multiuser MIMO systems with a large number of BS antennas.

EGCG에 의한 간경화전사인자 zf9의 발현조절 연구

김용석 대한암예방학회 2007 Journal of cancer prevention Vol.12 No.2

Zf9/core promoter-binding protein, a Kruppel-like zinc finger transcription factor is induced early in hepatic stellate cell (HSC) activation and transactivates TGF-β1 and TGF-β receptors, types I and II in response to fibrogenic stimuli. To understand the role of Zf9 as the regulator of liver cirrhosis, 3kb sized zf9 promoter was cloned from human genomic DNA and generated 11 kinds of zf9 reporter constructs which were 3kb, 2.4kb, 2.2kb, 1.8kb, 1.6kb, 1.5kb, 1.1kb, 1.0kb, 0.9kb, 0.8kb, 0.5kb-sized respectively. When PGF2α was treated as the fibrogenic stimulus, zf9 promoter was activated in HSC-T6 cells (an SV40-immortalized rat HSC line). Also, zf9 promoter was characterized in LX2, the human hepatic stellate cell which was pretreated by EGCG before PGF2α treatment to investigate the preventive effect of EGCG for liver cirrhosis. EGCG inhibited zf9 promoter activity at ()979∼(+)155 region in LX2 cell. (Cancer Prev Res 12, 112-119, 2007)

Role of moss and Arabidopsis zinc-finger homeodomain transcription factors in regulating plant architecture

Lee Young Koung,김근화,Ware Doreen 한국식물생명공학회 2024 Plant biotechnology reports Vol.18 No.2

Zinc-finger homeodomain transcription factors (ZF-HD TFs) are relatively a small gene family in Arabidopsis involved in plant development and stress response. However, the biological functions of ZF-HD TFs remain largely undiscovered. Here, we aimed to elucidate the evolutionary history and functional role of ZF-HD TFs in other species, by performing phylogenic analysis and domain and motif identification studies in Arabidopsis, sorghum (Sorghum bicolor), and moss (Physcomitrella patens). Forty-two ZF-HD TF proteins were classified into two distinct subfamilies based on the conserved ZF Cys/His-rich dimerization and homeodomain (HD) domains. The phylogenetic tree of proteins was further divided into five groups based on the similarity of sequences, and three distinct motifs were defined in the amino acid sequences. Genetic analysis revealed that the moss PpZF-HD1, Pp3c1_15290, gene partially rescued the amiR zf-HD-79 mutant lines at phenotypic and molecular levels. Subcellular localization studies revealed that moss PpZF-HD1 was localized in the cytosol and nuclei. Phylogenetic analysis and genetic complementation revealed that ZF-HD TFs play functional roles in regulating plant architecture, which is conserved in Arabidopsis, sorghum, and moss. Although our study is only a preliminary exploration into ZF-HD TFs, it provides a novel perspective that will help future researchers better understand the biological role of ZF-HD proteins in plants.

상향링크 SIMO 시스템에서 공간 및 주파수 다이버시티 이득에 따른 SC-FDMA의 BER 성능 분석

이진희(Jin-Hui Lee),최권휴(Kwonhue Choi) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.9(통신이론)

상향링크 SIMO(Single Input Multiple Output) 시스템의 SC-FDMA 기법에서 공간 및 주파수 다이버시티 이득에 따른 BER(Bit Error Ratio) 성능 변화를 분석한다. 본 논문에서 분석한 주요내용은 다음과 같다. 첫째, 공간 다이버시티 컴바이닝과 주파수 다이버시티 컴바이닝을 동시에 수행할 수 있는 통합된 시스템과 공간 다이버시티 컴바이닝과 주파수 다이버시티 컴바이닝을 순서대로 수행하는 단계별 시스템이 동등한 성능을 가지는 것을 확인한다. 단계별 시스템의 주파수 다이버시티 컴바이닝 기법과 통합된 시스템의 다이버시티 컴바이닝 기법이 동일할 때, 단계별 시스템에서 주파수 다이버시티 컴바이닝보다 공간 다이버시티 컴바이닝을 선행하면서 공간 다이버시티 컴바이닝 기법을 MRC(Maximal Ratio Combining)로 하면 두 시스템의 성능이 동일함을 신호 모형화 결과를 통해 증명한다. 둘째, 신호 모형화 결과와 BER 실험 결과를 통해 공간 다이버시티 이득과 주파수 다이버시티 이득이 각각 성능에 어떤 영향을 미치는지 분석한다. 부반송파 개수가 증가함에 따라 주파수 다이버시티 이득이 증가함을 알 수 있고 이는 주파수 다이버시티 기법이 ZF(Zero Forcing)일 때의 성능과 MMSE(Minimum Mean Square Error)일 때의 성능 차이는 유지하면서 높은 SNR(Signal to Noise Ratio) 영역의 성능 향상에 영향을 미치는 것을 보인다. 그리고 수신안테나 개수의 증가는 공간 다이버시티 이득을 증가시키며 공간 다이버시티 이득의 증가는 모든 SNR 영역의 성능을 향상시키면서 주파수 다이버시티 컴바이닝이 ZF일 때와 MMSE일 때의 성능 차이를 줄이는데 영향을 미침을 보여준다. 마지막으로, 공간 다이버시티 이득이 신호 모형화 유도과정에서 어떤 영향을 미치는지 분석하여 수신안테나 개수가 6개 이상이면 주파수 다이버시티 컴바이닝을 ZF으로 했을 때의 성능이 MMSE로 했을 때의 성능을 대체할 수 있음을 확인할 수 있다. We investigate BER (Bit Error Ratio) performance according to the gain of spatial and frequency diversities in uplink SC-FDMA of SIMO (Single Input Multiple Output) systems. The main results of the analysis in this paper are as follows. First, we prove that performance of integrated system for considering spatial and frequency diversity combining in parallel is equivalent with the performance of sequential system for performing diversity combining in sequence. By signal modeling, it is demonstrated that the performances of both systems are the same when the frequency diversity combining technique of the sequential system is equal to diversity combining technique of the integrated system, and spatial diversity combining technique of the sequential system is performed as MRC in advance of frequency diversity combining. Secondly, it is found that effect on the BER performance is different according to the gain of spatial and frequency diversities, respectively. The frequency diversity gain increases by increasing the number of subcarrier. It might affect the performance improvement of high SNR(Signal to Noise Ratio) while it maintains gap between performances of ZF(Zero Forcing) and MMSE(Minimum Mean Square Error) in frequency diversity combining schemes. Also, spatial diversity gain increases as the number of receiving antennas increases. It means that it can reduce performance gap between ZF and MMSE in frequency diversity combining schemes by increasing the number of receiving antennas. In addition, it might affect the performance improvement of the whole SNR. Finally, through the analysis of performance according to the spatial diversity gain, the performance of ZF in frequency diversity combining is equal to the MMSE if the number of receiving antennas is 6 or more.

Performance analysis of precoding‐aided differential spatial modulation systems with transmit antenna selection

김상춘 한국전자통신연구원 2022 ETRI Journal Vol.44 No.1

In this paper, the performance of precoding-aided differential spatial modulation (PDSM) systems with optimal transmit antenna subset (TAS) selection is examined analytically. The average bit error rate (ABER) performance of the optimal TAS selection-based PDSM systems using a zero-forcing (ZF) precoder is evaluated using theoretical upper bound and Monte Carlo simulations. Simulation results validate the analysis and demonstrate a performance penalty < 2.6 dB compared with precoding-aided spatial modulation (PSM) with optimal TAS selection. The performance analysis reveals a transmit diversity gain of urn:x-wiley:12256463:media:etr212438:etr212438-math-0001 for the ZF-based PDSM (ZF-PDSM) systems that employ TAS selection with urn:x-wiley:12256463:media:etr212438:etr212438-math-0002 transmit antennas, urn:x-wiley:12256463:media:etr212438:etr212438-math-0003 selected transmit antennas, and urn:x-wiley:12256463:media:etr212438:etr212438-math-0004 receive antennas. It is also shown that reducing the number of activated transmit antennas via optimal TAS selection in the ZF-PDSM systems degrades ABER performance. In addition, the impacts of channel estimation errors on the performance of the ZF-PDSM system with TAS selection are evaluated, and the performance of this system is compared with that of ZF-based PSM with TAS selection.

A Novel Recursive Algorithm for Efficient ZF-OSIC Detection in a V-BLAST System

( Zuo-liang Yin ),( Xing-peng Mao ),( Qin-yu Zhang ),( Nai-tong Zhang ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.12

To reduce the implementation complexity of the Vertical Bell Labs layered space-time (V-BLAST) systems with respect to the zero-forcing (ZF) criterion, a computationally efficient recursive algorithm is proposed. A fast implementation of the proposed algorithm is developed and its complexity is analyzed in detail. The proposed algorithm matches the ZF-OSIC detection well, and its three significant advantages can be demonstrated by analyses and simulations. Firstly, its speedups over the conventional ZF-OSIC with norm-based ordering, the original fast recursive algorithm (FRA) and the fastest known algorithm (FKA) in the number of flops are 1.58, 2.33 and 1.22, respectively. Secondly, a much simpler implementation than FRA and FKA can be expected. Finally, the storage requirements are lower than those of FRA and FKA. These advantages make the proposed algorithm more efficient and practical.

Media Optimization for Laccase Production by Trichoderma harzianum ZF-2 Using Response Surface Methodology

( Hui Ju Ga ),( Xiang Chu ),( Yan Wen Wang ),( Fei Zhou ),( Kai Zhao ),( Zhi Mei Mu ),( Qing Xin Liu ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.12

Trichoderma harzianum ZF-2 producing laccase was isolated from decaying samples from Shandong, China, and showed dye decolorization activities. The objective of this study was to optimize its culture conditions using a statistical analysis of its laccase production. The interactions between different fermentation parameters for laccase production were characterized using a Plackett-Burman design and the response surface methodology. The different media components were initially optimized using the conventional one-factor-at-atime method and an orthogonal test design, and a Plackett-Burman experiment was then performed to evaluate the effects on laccase production. Wheat straw powder, soybean meal, and CuSO4 were all found to have a significant influence on laccase production, and the optimal concentrations of these three factors were then sequentially investigated using the response surface methodology with a central composite design. The resulting optimal medium components for laccase production were determined as follows: wheat straw powder 7.63 g/l, soybean meal 23.07 g/l, (NH4)2SO4 1 g/l, CuSO4 0.51 g/l, Tween-20 1 g/l, MgSO4 1 g/l, and KH2PO4 0.6 g/l. Using this optimized fermentation method, the yield of laccase was increased 59.68 times to 67.258 U/ml compared with the laccase production with an unoptimized medium. This is the first report on the statistical optimization of laccase production by Trichoderma harzianum ZF-2.

다중 안테나 시스템에서 Zero-Forcing(ZF)과 Sphere Decoding(SD)을 결합한 향상된 성능의 복호 방법

이홍주,배정민,김동우,Lee, Hong-Ju,Bae, Jeong-Min,Kim, Dong-Woo 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.10A

다중 안테나(MIMO) 시스템은 무선 통신에서 높은 전송용량을 제공하지만 사용하는 안테나의 숫자가 증가할수록 수신단의 복호 과정에서 높은 연산량이 요구된다. 높은 연산량은 고속 통신 시스템의 구현을 어렵게 만드는 요인이다. 본 논문에서는 MIMO 시스템의 복호 기법으로 널리 알려진 ZF(Zero-Forcing) 방법과 SD(Sphere decoding) 방법을 결합하는 알고리즘을 제안한다. 본 논문에서 제안하는 알고리즘을 통해 수신단의 복호 과정에서 필요한 연산량을 크게 줄이는 동시에 비트 에러 율(BER) 성능은 SD와 비슷한 결과를 얻을 수 있다 In this paper, we describe a hybrid ZF-SD method. The method is based on dimensionality reduction via predecoding and cancellation of those symbols that can be quickly and reliably detected by a linear decoder. The proposed method shows BER performance similar to SD but with much lower computational complexity than SD.