Base station location in a cellular CDMA system

We consider a cellular CDMA system in which blocking is enforced when the relative interference exceeds a certain threshold level. This paper addresses a radio network design problem in such a CDMA system. Given the data of call‐traffic distributed over the service area and potential sites of base stations, the objective of the problem is to locate base stations so as to minimize the associated cost for establishing base stations while keeping the probability of blocking under control. We develop an efficient algorithm for solving the design problem. Computational experiments with real‐world data are conducted to show both the efficiency and the practicality of the proposed design method. This revised version was published online in August 2006 with corrections to the Cover Date.     

基于仿射模型的重叠块运动估计补偿方法

本文对 Ｈ．２６３中基于平移模型的重叠块运动估计补偿方法进行改进,提出了一种基于仿射模型的重叠块运动补偿方法,该方法对复杂运动图像质量有明显改善。     

MOTOROLA的全面生产维护管理

本文主要通过对MOTOROLA全面生产维护管理知识介绍和研究,理解全面生产维护的内涵,明确如何通过TPM来提高设备使用效率,以及如何正确评估设备运行水平和全面生产维护的效果。     

关于提高变频器调频速度的研究

本文介绍了作者的一项专利技术。对于需要比较快速、比较频繁地调整变频器频率应用场合,目前的通用变频器就很难满足这个需要,尤其是在大惯性负载上使用变频器时,须将升、降频（特别是降频）速度设置的比较慢,以适应由于惯性造成的电机转速的滞后。本专利技术克服上述传统变频器目前存在的缺陷,在传统变频器上增加比较简单并业已成熟的换相技术,为变频器的制造提供了一种新的附加技术。     

Sidelobe Suppression for Robust Beamformer Via the Mixed Norm Constraint

Applying a sparse constraint on the beam pattern has been suggested to suppress the sidelobe of the minimum variance distortionless response (MVDR) beamformer recently. To further improve the performance, we add a mixed norm constraint on the beam pattern. It matches the beam pattern better and encourages dense distribution in mainlobe and sparse distribution in sidelobe. The obtained beamformer has a lower sidelobe level and deeper nulls for interference avoidance than the standard sparse constraint based beamformer. Simulation demonstrates that the SINR gain is considerable for its lower sidelobe level and deeper nulling for interference, while the robustness against the mismatch between the steering angle and the direction of arrival (DOA) of the desired signal, caused by imperfect estimation of DOA, is maintained too.     

A New Secure Authenticated Group Key Transfer Protocol

Group key transfer protocols depend on a mutually trusted key generation center (KGC) to generate group keys and transport group keys to all group members secretly. Generally, KGC encrypts group keys under another secret key shared with each user during registration. In this paper, we propose a novel secure authenticated group key transfer protocol using a linear secret sharing scheme (LSSS) and ElGamal cryptosystem, where KGC broadcasts group key information to all group members. The confidentiality of this transformation is guaranteed by this LSSS and ElGamal cryptosystem. We also provide authentication for transporting this group key. Goals and security threats of our protocol are analyzed in detail.     

Opportunistic Space-Division Multiple Access With Beam Selection

In this paper, a novel transmission technique for the multiple-input multiple-output (MIMO) broadcast channel is proposed that allows simultaneous transmission to multiple users with limited feedback from each user. During a training phase, the base station modulates a training sequence on multiple sets of randomly chosen orthogonal beamforming vectors. Each user sends the index of the best beamforming vector and the corresponding signal-to-interference-plus-noise ratio for that set of orthogonal vectors back to the base station. The base station opportunistically determines the users and corresponding orthogonal vectors that maximize the sum capacity. Based on the capacity expressions, the optimal amount of training to maximize the sum capacity is derived as a function of the system parameters. The main advantage of the proposed system is that it provides throughput gains for the MIMO broadcast channel with a small feedback overhead, and provides these gains even with a small number of active users. Numerical simulations show that a 20% gain in sum capacity is achieved (for a small number of users) over conventional opportunistic space division multiple access, and a 100% gain (for a large number of users) over conventional opportunistic beamforming when the number of transmit antennas is four.     

First-principles investigation of the optical properties of CuIn(SxSe1–x)2

We optimized the lattice structure of sulfur-doped CuInSe₂ using first principles. The lattice constants for CuIn(S_xSe_1–x)₂ vary linearly with x according to a(x)=–0.02828x+0.58786 nm and c(x)=–0.05692x+1.1834 nm, which agree well with experimental data. The optical properties of CuIn(S_xSe_1–x)₂ were then systematically investigated using first-principles calculations with the HSE06 functional. We present data for the complex dielectric function, refractive index, extinction coefficient, reflectivity index, absorption coefficient, and optical bandgap for CuIn(S_xSe_1–x)₂. The optical bandgap E_g obtained from the absorption coefficient is 1.07 eV for CuInSe₂ and 1.384 eV for CuInS₂. These values are very close to experimental results, indicating that first-principles calculations can yield accurate bandgap values. The optical bandgap of CuIn(S_xSe_1–x)₂ increases linearly with the sulfur concentration according to E_g=0.3139x+1.0825 eV.     

A Novel Metal-Rich Anneal for In Vacuo Passivation of High-Aspect-Ratio Mercury Cadmium Telluride Surfaces

A new method for Cd-rich annealing of mercury cadmium telluride (MCT) was developed based on the observation that the deposition of Cd onto MCT by vacuum evaporation became self-limiting whenever the substrate temperature was above 70°C regardless of the Cd evaporation rate. Preliminary results indicated that this new method may be suitable for passivation of high-aspect-ratio MCT surfaces, for passivation at low temperatures, for in vacuo operation, and/or for vacancy annihilation in MCT. Furthermore, the process can be carried out in the conventional open-tube reactors used for molecular beam epitaxy, metalorganic chemical vapor deposition, and physical vapor deposition.