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Search Results: 1 - 10 of 4508 matches for " Shin Hyundong? "
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MIMO Diversity in the Presence of Double Scattering
Hyundong Shin,Moe Z. Win
Mathematics , 2005,
Abstract: The potential benefits of multiple-antenna systems may be limited by two types of channel degradations rank deficiency and spatial fading correlation of the channel. In this paper, we assess the effects of these degradations on the diversity performance of multiple-input multiple-output (MIMO) systems, with an emphasis on orthogonal space-time block codes, in terms of the symbol error probability, the effective fading figure (EFF), and the capacity at low signal-to-noise ratio (SNR). In particular, we consider a general family of MIMO channels known as double-scattering channels, which encompasses a variety of propagation environments from independent and identically distributed Rayleigh to degenerate keyhole or pinhole cases by embracing both rank-deficient and spatial correlation effects. It is shown that a MIMO system with $n_T$ transmit and $n_R$ receive antennas achieves the diversity of order $\frac{\n_T n_S n_R}{\max(n_T,n_S,n_R)}$ in a double-scattering channel with $n_S$ effective scatterers. We also quantify the combined effect of the spatial correlation and the lack of scattering richness on the EFF and the low-SNR capacity in terms of the correlation figures of transmit, receive, and scatterer correlation matrices. We further show the monotonicity properties of these performance measures with respect to the strength of spatial correlation, characterized by the eigenvalue majorization relations of the correlation matrices.
Gallager's Exponent for MIMO Channels: A Reliability-Rate Tradeoff
Hyundong Shin,Moe Z. Win
Mathematics , 2006,
Abstract: In this paper, we derive Gallager's random coding error exponent for multiple-input multiple-output (MIMO) channels, assuming no channel-state information (CSI) at the transmitter and perfect CSI at the receiver. This measure gives insight into a fundamental tradeoff between the communication reliability and information rate of MIMO channels, enabling to determine the required codeword length to achieve a prescribed error probability at a given rate below the channel capacity. We quantify the effects of the number of antennas, channel coherence time, and spatial fading correlation on the MIMO exponent. In addition, general formulae for the ergodic capacity and the cutoff rate in the presence of spatial correlation are deduced from the exponent expressions. These formulae are applicable to arbitrary structures of transmit and receive correlation, encompassing all the previously known results as special cases of our expressions.
MIMO Networks: the Effects of Interference
Marco Chiani,Moe Z. Win,Hyundong Shin
Mathematics , 2008, DOI: 10.1109/TIT.2009.2034810
Abstract: Multiple-input/multiple-output (MIMO) systems promise enormous capacity increase and are being considered as one of the key technologies for future wireless networks. However, the decrease in capacity due to the presence of interferers in MIMO networks is not well understood. In this paper, we develop an analytical framework to characterize the capacity of MIMO communication systems in the presence of multiple MIMO co-channel interferers and noise. We consider the situation in which transmitters have no information about the channel and all links undergo Rayleigh fading. We first generalize the known determinant representation of hypergeometric functions with matrix arguments to the case when the argument matrices have eigenvalues of arbitrary multiplicity. This enables the derivation of the distribution of the eigenvalues of Gaussian quadratic forms and Wishart matrices with arbitrary correlation, with application to both single user and multiuser MIMO systems. In particular, we derive the ergodic mutual information for MIMO systems in the presence of multiple MIMO interferers. Our analysis is valid for any number of interferers, each with arbitrary number of antennas having possibly unequal power levels. This framework, therefore, accommodates the study of distributed MIMO systems and accounts for different positions of the MIMO interferers.
Error Probability of Binary and -ary Signals with Spatial Diversity in Nakagami- (Hoyt) Fading Channels
Duong Trung Q,Shin Hyundong,Hong Een-Kee
EURASIP Journal on Wireless Communications and Networking , 2007,
Abstract: We analyze the exact average symbol error probability (SEP) of binary and -ary signals with spatial diversity in Nakagami- (Hoyt) fading channels. The maximal-ratio combining and orthogonal space-time block coding are considered as diversity techniques for single-input multiple-output and multiple-input multiple-output systems, respectively. We obtain the average SEP in terms of the Lauricella multivariate hypergeometric function . The analysis is verified by comparing with Monte Carlo simulations and we further show that our general SEP expressions particularize to the previously known results for Rayleigh ( = 1) and single-input single-output (SISO) Nakagami- cases.
Wireless Cooperative Networks
Andrea Conti,Jiangzhou Wang,Hyundong Shin,Ramesh Annavajjala
EURASIP Journal on Advances in Signal Processing , 2008, DOI: 10.1155/2008/810149
Abstract:
Error Probability of Binary and M-ary Signals with Spatial Diversity in Nakagami-q (Hoyt) Fading Channels
Trung Q. Duong,Hyundong Shin,Een-Kee Hong
EURASIP Journal on Wireless Communications and Networking , 2007, DOI: 10.1155/2007/53742
Abstract: We analyze the exact average symbol error probability (SEP) of binary and M-ary signals with spatial diversity in Nakagami-q (Hoyt) fading channels. The maximal-ratio combining and orthogonal space-time block coding are considered as diversity techniques for single-input multiple-output and multiple-input multiple-output systems, respectively. We obtain the average SEP in terms of the Lauricella multivariate hypergeometric function FD(n). The analysis is verified by comparing with Monte Carlo simulations and we further show that our general SEP expressions particularize to the previously known results for Rayleigh (q = 1) and single-input single-output (SISO) Nakagami-q cases.
Two-Way Relay Channels: Error Exponents and Resource Allocation
Hien Quoc Ngo,Tony Q. S. Quek,Hyundong Shin
Mathematics , 2009,
Abstract: In a two-way relay network, two terminals exchange information over a shared wireless half-duplex channel with the help of a relay. Due to its fundamental and practical importance, there has been an increasing interest in this channel. However, surprisingly, there has been little work that characterizes the fundamental tradeoff between the communication reliability and transmission rate across all signal-to-noise ratios. In this paper, we consider amplify-and-forward (AF) two-way relaying due to its simplicity. We first derive the random coding error exponent for the link in each direction. From the exponent expression, the capacity and cutoff rate for each link are also deduced. We then put forth the notion of the bottleneck error exponent, which is the worst exponent decay between the two links, to give us insight into the fundamental tradeoff between the rate pair and information-exchange reliability of the two terminals. As applications of the error exponent analysis, we present two optimal resource allocations to maximize the bottleneck error exponent: i) the optimal rate allocation under a sum-rate constraint and its closed-form quasi-optimal solution that requires only knowledge of the capacity and cutoff rate of each link; and ii) the optimal power allocation under a total power constraint, which is formulated as a quasi-convex optimization problem. Numerical results verify our analysis and the effectiveness of the optimal rate and power allocations in maximizing the bottleneck error exponent.
On the Capacity of Doubly Correlated MIMO Channels
Hyundong Shin,Moe Z. Win,Jae Hong Lee,Marco Chiani
Mathematics , 2005,
Abstract: In this paper, we analyze the capacity of multiple-input multiple-output (MIMO) Rayleigh-fading channels in the presence of spatial fading correlation at both the transmitter and the receiver, assuming that the channel is unknown at the transmitter and perfectly known at the receiver. We first derive the determinant representation for the exact characteristic function of the capacity, which is then used to determine the trace representations for the mean, variance, skewness, kurtosis, and other higher-order statistics (HOS). These results allow us to exactly evaluate two relevant information-theoretic capacity measures--ergodic capacity and outage capacity--and the HOS of the capacity for such a MIMO channel. The analytical framework presented in the paper is valid for arbitrary numbers of antennas and generalizes the previously known results for independent and identically distributed or one-sided correlated MIMO channels to the case when fading correlation exists on both sides. We verify our analytical results by comparing them with Monte Carlo simulations for a correlation model based on realistic channel measurements as well as a classical exponential correlation model.
MIMO Zero-Forcing Performance Evaluation Using the Holonomic Gradient Method
Constantin Siriteanu,Akimichi Takemura,Satoshi Kuriki,Hyundong Shin,Christoph Koutschan
Mathematics , 2014, DOI: 10.1109/TWC.2014.2385075
Abstract: For multiple-input multiple-output (MIMO) spatial-multiplexing transmission, zero-forcing detection (ZF) is appealing because of its low complexity. Our recent MIMO ZF performance analysis for Rician--Rayleigh fading, which is relevant in heterogeneous networks, has yielded for the ZF outage probability and ergodic capacity infinite-series expressions. Because they arose from expanding the confluent hypergeometric function $ {_1\! F_1} (\cdot, \cdot, \sigma) $ around 0, they do not converge numerically at realistically-high Rician $ K $-factor values. Therefore, herein, we seek to take advantage of the fact that $ {_1\! F_1} (\cdot, \cdot, \sigma) $ satisfies a differential equation, i.e., it is a \textit{holonomic} function. Holonomic functions can be computed by the \textit{holonomic gradient method} (HGM), i.e., by numerically solving the satisfied differential equation. Thus, we first reveal that the moment generating function (m.g.f.) and probability density function (p.d.f.) of the ZF signal-to-noise ratio (SNR) are holonomic. Then, from the differential equation for $ {_1\! F_1} (\cdot, \cdot, \sigma) $, we deduce those satisfied by the SNR m.g.f. and p.d.f., and demonstrate that the HGM helps compute the p.d.f. accurately at practically-relevant values of $ K $. Finally, numerical integration of the SNR p.d.f. produced by HGM yields accurate ZF outage probability and ergodic capacity results.
Expression and characterization of a xylosidase (Bxyl) from Bacillus halodurans C-125
嗜碱芽孢杆菌C-125木糖苷酶基因的表达与酶特征鉴定

Yanli Liang,Xingyu Li,Hyundong Shin,Rachel R Chen,Zichao Mao,
梁艳丽
,李兴玉,Shin Hyundong,Chen R. Rachel,毛自朝

生物工程学报 , 2009,
Abstract: 嗜碱芽孢杆菌(Bacillus halodurans)C-125菌株的基因组中,一个编码木糖苷酶的基因(BH1068)被克隆并在大肠杆菌中获得高效表达。通过全面分析纯化蛋白,确证了它的木糖苷酶功能。该酶在pH4~9的范围内保持稳定,最适pH值为中性,有较宽的最适温度(35°C~45°C),且能在45°C范围内保持稳定。这些特性使得该酶可在较为宽广的条件下对木聚糖进行酶促降解。该酶对人工合成底物对硝基苯-β-木糖苷(p-nitrophenyl-β-xylose,pNPX)的比活力为174mU/mg蛋白质,且木糖对其反馈抑制较弱(抑制常数Ki为300mmol/L)。结果显示该酶是活性较高且较耐木糖抑制的细菌源木糖苷酶。该酶与商品化的木聚糖酶一起水解山毛举木聚糖(Beechwood xylan)时显示了增效作用,且水解率可获40%。该酶最适pH为中性,对木糖耐受等特性与大多数来源于真菌、最适pH为酸性、对木糖敏感的木糖苷酶将有较好的互补。结果表明该酶在木聚糖或含木聚糖多糖的单糖化过程可能发挥重要作用。
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