适用于稀疏信道的MVA算法

主要介绍了一种适用于稀疏信道的复杂度可大大降低的Viterbi均衡算法。在本算法中,计算的复杂度并不依赖于信道冲激响应的长度,而是依赖于信道冲激响应中非零系数的数目。仿真结果表明,在稀疏信道下,此算法具有良好的性能,它不仅适用于最小相位系统,也适用于非最小相位系统。     

激光深熔焊接小孔效应的理论和试验研究

本文采用理论和试验相结合的方法系统研究了激光深熔焊接GG17玻璃时的小孔效应。首先采用高速摄影的方法清晰、完整地观测到了激光深熔焊接GG17玻璃时小孔的形状,并通过实验研究了聚焦光斑尺寸、离焦量、焊接速度等焊接工艺参数对小孔尺寸和形状的影响。然后,论文根据实验得到的小孔形状,通过曲线拟合的方法得到小孔前后沿孔壁的曲线方程,再按照几何光学原理,分析了激光在小孔孔壁上的多次反射吸收情况,并由此计算出了小孔孔壁通过多次反射吸收的激光功率密度分布情况。最后,建立了一个分层圆柱体面热源传热模型,在综合考虑热传导和熔池对流换热的基础上,计算了小孔周围的温度场和流场,求出了小孔孔壁上的热流密度分布,并与小孔孔壁吸收的激光功率密度进行了比较。     

Improving MANET performance by a hop‐aware and energy‐based buffer management scheme

A hop‐aware and energy‐based buffer management scheme (HEB) is proposed in this paper. HEB can provide better quality of service to packets with real‐time requirements and improve MANET power efficiency. In our algorithm, the buffer is divided into real‐time and non‐real‐time partitions. We consider the number of hops passed, the power levels of the transmitting node, the predicted number of remaining hops, and waiting time in the buffer to determine packet transmission priority. In addition, specialized queue management and a probabilistic scheduling algorithm are proposed to decrease retransmissions caused by packet losses. Mathematical derivations of loss rates and end‐to‐end delays are also proposed. Coincidence between mathematical and simulation results is also shown. Finally, the HEB is compared with first in first out, random early detection, and hop‐aware buffering scheme. Simulation results show that the proposed algorithm reduces loss rates, power consumption, and end‐to‐end delays for real‐time traffic, considerably improving the efficiency of queue management in MANET. Copyright © 2012 John Wiley & Sons, Ltd.     

InAIN薄膜MOCVD外延生长研究

为了研究不同压力和不同模板对InAlN薄膜外延生长的影响,分别选取以GaN为模板时生长压力为4.00、6.67和13.33 kPa,压力为4.00 kPa时模板为GaN和A1N这两组条件进行实验比较.研究发现,随着生长压力的增加,样品中In含量降低,样品的粗糙度则随压力的增加而增大;压力为4.00 kPa时,分别以摇摆曲线半高宽(FWHM)为86.97”的AIN和224.1”的GaN为模板,发现A1N模板上生长的InAIN样品(002)和(102)峰的FWHM值及表面粗糙度比上述GaN为模板生长的InAlN样品都要小很多.综合以上结果可初步得知:降低压力可以优化InAlN薄膜的表面形貌,增加In组分含量;采用高质量的AIN作模板能生长出晶体质量和表面形貌都比较好的InAlN薄膜.     

基于大数据分析的旅游管理服务系统

针对海量的基站存储数据,基于云计算技术的云平台进行部署,引入大数据分析,结合GIS地图,通过分析用户在景区的驻留等行为,精确建模,对用户主动提供旅游信息和服务,同时景区管理人员有效掌握景区人员流量情况,有的放矢进行管理。     

Downlink Performance Analysis of MIMO Relaying Networks

In recent years, there has been an upsurge of interest in relay-augmented infrastructure-based networks. On the other hand, multiple-input-multiple-output (MIMO) wireless system becomes a hot topic for it can achieve significant increases in overall system performance. This paper gives a detailed analysis of downlink performance of MIMO relaying networks, in which different channel models and classic MIMO cellular system model with fixed relay are considered. Our results in single cell scenario show that when meeting effective relay system efficiency of 100%, the required relay SNR gain of 2-antenna system can be reduced to less than half of that with only one transceiver antenna. We also observe that MIMO is more tolerant to interference compared with the one-transceiver antenna system. After that, multi-hop architecture is researched and statistics figures out the tolerable number of hops which is supported in wireless communication with a view to real application. In addition, multi-cell scenario is also studied. Statistics results show that there is more 8 dB average spectral efficiency gain in a two-hop fixed relay 4 × 4 MIMO system than that in a SISO system. These results present significant indications in deployment and optimization of relay-based MIMO networks.     

数字中频技术的研究及其FPGA实现

首先给出了软件无线电收/发信机的基本结构,分析了数字化中频技术在其中的关键作用,给出了一种有效的适合于FPGA实现的数字上/下变频方式,并讨论了高阶Fir滤波器在FPGA中采用分布式算法(Distributed Arithmetic)的实现.     

一种改进的多模数字下变频结构及其FPGA实现

针对目前多种通信模式的共存和发展趋势,对传统DDC结构进行改进,以适用于多模系统。提出了多模数字下变频改进结构与参数设计,完成了各模块Verilog代码编写和Modelsim仿真,并对Modelsim仿真结果进行分析和验证,验证了改进数字下变频的可行性;最后将代码移植到FPGA,并结合ETTUS射频板、自主设计的中频板以及友晶TR4 FPGA开发板多模硬件平台进行了板级调试,验证了多模功能的可行性,充分证明该结构能兼容WCDMA和TD-LTE两种模式,具有较高的实用性和通用性。     

半导体激光线阵弯曲矫正方法的理论分析与实验

半导体激光线阵(LDB)在制作和封装过程中会发生弯曲,从而引起发光弯曲,即"smile",这影响其在抽运固体激光和外腔半导体激光阵列线宽窄化中的使用.利用平凸柱面镜在一定程度上可矫正半导体激光线阵的"smile".通过几何光学方法对平凸柱面镜矫正半导体激光线阵的"smile"进行理论分析,利用不同焦距平凸柱面镜对不同半导体激光线阵的"smile"进行矫正,并通过ORIGIN软件对"smile"的矫正进行模拟,其结果与实验相吻合.结果显示,抛物线状"smile"矫正效果很好,相对矫正量高达90%,选择合适小焦距平凸柱面镜对"smile"矫正较明显且模拟误差小,修正透镜焦距参数可减小误差.     

基于模糊控制的路灯节能系统的设计

道路照明设施的规模越来越大,照明耗能在迅速上升.针对此问题,讨论了可行的照明节能新途径.设计出了一种模糊控制节能照明电路.他依据气体放电光源在工作电流适当减少时仍能正常运行的原理.在后半夜车稀人少时,自动降低光源电流,减少在路灯系统能耗中占主要比例的光源能耗,以达到路灯系统整体节能的目的,而且还避免了光源后半夜的过压运行,延长了路灯寿命.与传统照明电路相比,节电率在20%以上.该电路实施方便,运行可靠,可使照明工程既满足功能性的要求,又能实现最大限度的节能.