通讯机构：
[Xie, Wenwu] H;Huazhong Normal Univ, Dept Elect & Informat Engn, Wuhan 430079, Peoples R China.
关键词：
antenna selection;correlation channels;MIMO
摘要：
In this work, a new antenna selection algorithm,is proposed for multiple-input multiple-output (MIMO) wireless communication systems. It is assumed that the channel state information (CSI) is exactly known at the receiver, and hence the antenna selection is considered only at the receiver. The goal of antenna selection is to find a tradeoff between the maximization of the channel capacity and the minimization of the pair-wise error probability (PEP). It turns out that the scheme of antenna selection plays an important part when dealing with high antenna correlation. It is shown that our proposed scheme for a system with two-transmit antennas and five-receive antennas offers better PEP performance than the algorithm based on the maximization capacity, but has little capacity loss., The simulation results indicate that our proposed scheme can jointly meet the capacity maximization and the PEP minimization.
摘要：
Recently, the antenna selection (AS) scheme is a hot topic in the region of multiple-input multiple-output (MIMO) systems, due to lower complexity. In the previous research, it is assumed that the channel state information (CSI) is available at the receiver, which, howerer, is impractical ill the wireless transmission environment. During the process of the channel estimation, there exists two-aspect impacts, namely Gaussian errors and Doppler spread, which are caused by Gaussian noise and the speed of mobile, respectively. In this paper, we analyze the performance of AS systems with the imperfect CS1, caused by Gaussian errors and Doppler spread, and derive the exact bit-error-ratio (BER) expression of AS systems in Rayleigh fading channel, using space-time coding transmission scheme. The corresponding simulations are carried out to illustrate the impacts of Gaussian errors and Doppler spread on the performance of AS systems and to prove the theoretical analysis. The results show that the length of pilot symbols needs a tradeoff under this environment with Doppler spread and Gaussian errors.
摘要：
We study the branching ratios, the direct CP asymmetries in B→K(*)K̄(*) decays and the polarization fractions of B→K*K̄* decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of B→K(*)K̄(*), and some of these constraints are stronger than the existing bounds. Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in B→K(*)K̄(*) decays which have not been measured yet. We find that the R-parity violating effects on the branching ratios and the direct CP asymmetries could be large; nevertheless their effects on the longitudinal polarizations of B→K*K̄* decays are small. Near future experiments can test these predictions and shrink the parameter spaces.
通讯机构：
[Hu, Xiangming] H;Huazhong Normal Univ, Dept Phys, Luoyu Rd 152, Wuhan 430079, Peoples R China.
摘要：
We reveal that for a realistic system, interference effects are obtained such as the suppression of central line and inner sidebands and the narrowing of the outer fluorescence sidebands. For this purpose, we consider a spontaneous decay from an excited state to a metastable state when the excited and metastable states are resonantly coupled to an auxiliary metastable state by a laser field and a microwave field, respectively. The fluorescence spectrum evolves from a five-peaked structure into a doublet of ultrasharp lines as the ratio of the laser field Rabi frequency to the microwave Rabi frequency is decreased. The physical origin is presented in terms of dressed states.
作者机构：
[Li, Gao-xiang; Li, GX] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
通讯机构：
[Li, Gao-xiang] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We propose schemes for the deterministic preparation of pure multipartite entangled vibrational states for N ions trapped in a single-mode cavity. Through sequentially sending lasers with appropriate phases and amplitudes to drive the ions, two kinds of pure multipartite entangled continuous variable entangled states respectively suggested by van Loock and Braunstein [Phys. Rev. Lett. 84, 3482 (2000)] and Pfister et al. [Phys. Rev. A 70, 020302(R) (2004)] can be unconditionally prepared with the help of cavity dissipation.
期刊：
Chemical Physics Letters,2006年426(4-6):469-473 ISSN：0009-2614
通讯作者：
Hou, X.-W.(xwhou@phy.ccnu.edu.cn)
作者机构：
Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;Wuhan Univ Technol, Sch Nat Sci, Wuhan 430079, Peoples R China.;Inst High Energy Phys, Beijing 100049, Peoples R China.;[Hou, Xi-Wen] Department of Physics, Huazhong Normal University, Wuhan, 430079, China;[Ma, Zhong-Qi] Institute of High Energy Physics, P.O. Box 918(4), Beijing, 100049, China
通讯机构：
[Hou, X.-W.] D;Department of Physics, Huazhong Normal University, China
作者机构：
Argonne National Laboratory, Argonne, Illinois 60439;[Adams, J.; Barnby, L.S.] University of Birmingham, Birmingham, United Kingdom;Brookhaven National Laboratory, Upton, New York 11973;California Institute of Technology, Pasadena, California 91125;University of California, Berkeley, California 94720
