基于波束空间的DBF协方差矩阵估计方法

该文对波束空间数字波束合成(Digital Beamforming,DBF)的前后向平滑协方差矩阵估计算法进行了改进,利用对称阵列特殊结构,把复数运算转化为实数运算,从而减少了运算量。文章介绍了算法的原理和实现过程,并分析了运算量。而仿真表明,改进算法在减少运算量的同时,保持了阵列抑制干扰性能。     

一种基于加权处理的无线传感器网络平均跳距离估计算法

定位技术是无线传感器网络的关键技术之一,传统DV-Hop定位算法只考虑了最近一个锚节点估计的平均跳距离值,而单个锚节点估计的平均跳距离值无法准确地反映网络的实际平均跳距离。本文提出了一种基于加权处理的平均跳距离估计算法,考虑多个锚节点估计的平均跳距离值,根据距离未知节点的跳数进行加权,使网络平均跳距离的估计更加准确,从而提高定位精度。仿真结果表明,与DV-Hop算法的平均跳距离估计算法相比,本文算法更准确地估计平均跳距离,降低了均方根误差,并提高了定位精度。     

基于边界查找车牌定位算法的研究

车辆牌照识别是实现现代交通管理智能化的一个关键环节,其中车辆牌照定位是实现这个环节中的核心技术。车辆牌照的定位是车辆牌照识别的前提和基础,因此车辆牌照的定位有着重要的意义,本文提出了一种基于边界查找的车牌定位算法,实验证明该算法不仅实时性强、稳定性高、鲁棒性好,而且计算量小,从而车辆牌照识别系统的整体性能在很大程度上得到了提高。     

一种用于900MHz射频识别（RFID）读写器芯片的1.8V CMOS直接变频接收机

设计了针对解决900MHz RFID读写器收发机芯片中本地载波干扰问题而优化的直接变频接收机,并在0.18μm 1P6M 混合信号CMOS工艺上实现验证. 设计中使用了一种串联反馈结构的基带放大器以达到同时实现无源混频器输出缓冲,直流消除以及信号放大的功能. 实际测量显示,该接收机的输入1dB压缩点为-4dBm,当中频信号解调信噪比要求为10dB时,可达到的灵敏度为-70dBm. 该接收机与整个收发机集成在同一块芯片中,使用1.8V电源电压,工作时静态电流为90mA.     

基于级联光纤的拉曼光纤放大器的研究

文章利用光子转换理论给出了两种光纤的任意信道间隔、N信道单向受激拉曼散射(SRS)的稳态分析结果,提出了一种新型的具有平坦增益的宽带拉曼光纤放大器(FRA).对64信道的波分复用(WDM)系统进行了仿真,为FRA增益平坦化提供了一种新的实现方法.     

TD—HSDPA中联合检测因子的新型检测方法以及映射方法

介绍了在TD-SCDMA快速下行分组接入技术(TD-HSDPA)系统中链路级仿真与系统级仿真之间的映射方法,主要探讨了联合检测增益在链路级获取和系统级应用的两个方面.重点阐述了如何根据链路级仿真得到联合检测的干扰消除因子的统计特性,并将其映射到系统级仿真的SINR模型中的策略.对比于传统仿真方法论中所采用的固定干扰消除因子的策略,文章所设计的映射策略具有更高的准确性和可靠性,并能够更好地适应实时的信道环境.     

认知中继网络中的鲁棒传输

In cognitive relay networks, the transmission of Secondary Users (SUs) suffers from the activity of Primary Users (PUs) and wireless channel fading. Therefore, how to achieve robust transmission for cognitive relay networks is a challenging task. In this paper, we propose a relaying transmission scheme which exploits robust beamforming at the physical layer and rateless codes at higher layers. We derive the optimal beamforming weight vector and analyze the performance of the proposed scheme when the channel estimation is not accurate between two SU nodes. We also study how the amount of channel information between SU and PU impacts the system performance. Simulation results validate our theoretical analysis and demonstrate that the proposed scheme can significantly enhance the system throughput.     

Yolk–Shell Hybrid Materials with a Periodic Mesoporous Organosilica Shell: Ideal Nanoreactors for Selective Alcohol Oxidation

This contribution describes the preparation of multifunctional yolk–shell nanoparticles (YSNs) consisting of a core of silica spheres and an outer shell based on periodic mesoporous organosilica (PMO) with perpendicularly aligned mesoporous channels. The new yolk–shell hybrid materials were synthesised through a dual mesophase and vesicle soft templating method. The mesostructure of the shell, the dimension of the hollow space (4～52 nm), and the shell thickness (16～34 nm) could be adjusted by precise tuning of the synthesis parameters, as evidenced by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption investigations. Various metal nanoparticles (e.g., Au, Pt, and Pd) were encapsulated and confined in the void space between the core and the shell using impregnation and reduction of adequate metal precursors. The selective oxidation of various alcohol substrates was then carried out to illustrate the benefits of such an architecture in catalysis. High conversion (～100%) and excellent selectivity (～99%) were obtained over Pd nanoparticles encapsulated in the hybrid PMO yolk–shell structures.     

Network‐coded multiple‐source cooperation aided relaying for free‐space optical transmission

A network‐coded cooperative relaying aided free‐space optical (FSO) transmission scheme is designed. The resultant multiple‐source cooperation diversity is exploited by the relay to mitigate the strong turbulence‐induced fading experienced in FSO channels. At the destination, an iterative multiple source detection algorithm is proposed in conjunction with a chip‐level soft network decoding method. Our performance evaluation results using simulation analysis demonstrate that the proposed FSO multiple source detection is capable of approaching the single‐user‐bound for transmission over Gamma–Gamma turbulence channels. Also, the network‐coded cooperative FSO scheme can achieve a significant BER improvement in comparison with conventional noncooperation schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

路基设备辅助下的高速公路车辆信息方向性传输协议

针对现有VANET网络广播传输协议信道利用率低,易造成信道拥塞等问题,提出在路基设备辅助下的改进协议。利用路基设备进行车辆分簇,将簇内车辆编号加入到发送数据帧头,每个车辆节点有选择地进行数据包接收与发送。仿真结果表明,改进协议可以有效地改善传输过程中的信道使用情况,有效信息传输率可提高20%。