面向2G、3G、4G融合接入应用的光载无线分布式天线系统

近年来,信息技术以日新月异的速度飞快发展,对人们工作及生活产生了极大的影响,而2G、3G、4G等网络的变更,促使天线网络应用过程中功能提升.新时期,为了不断降低天线网络成本,相关机构提出了光载无线分布式天线系统,该系统当中需要将2G、3G、4G进行有效融合.本文首先分析了该系统当中的传输性能影响因素,并对SCM-CWDM这一分布式传输技术进行了充分地研究.     

面向三网融合的光载无线系统

光载无线技术是三网融合关键技术的极具前景的解决方案.本文介绍了面向三网融合的光载无线系统的架构,对光载无线系统的调制、传输、放大等关键技术进行了系统的阐述,并基于此搭建了光载无线系统实验平台,指出了三网融合快速发展的趋势.     

全双工光载无线隧道通信系统

鉴于长距离隧道内复杂的无线传输环境,传统通信技术不能满足旅客高质量的通信需求,提出了一种基于波分复用无源光网络的光载无线（RoF）分布式隧道通信系统。采用波分复用技术实现不同业务在光域的物理隔离,协同分布式天线技术,在隧道内部提供高频无线接入,提升系统带宽的同时解决了隧道内部信号急剧衰减的问题。通过实验搭建了全双工的光载无线试验平台,实现了用光学的方法产生和传输载频为24 GHz的16/64QAM矢量信号,并且通过测量上下行链路的EVM值验证了方案的可行性。     

动态可重构的智能光载无线接入技术

文章认为动态可重构的智能光载无线网络可以融合光纤和无线接入系统,通过引入新的网络架构、媒体访问控制(MAC)协议、系统链路以及关键器件等系列新技术,满足通信网对高效、宽带以及灵活等特性的需求。基于动态可重构的智能光载无线技术,文章在网络层提出适合智能光载无线技术的网络架构;在MAC层提出使光载无线MAC层的性能得到提升、保障联合资源的动态可管控的专用设计;在系统层提出在光域对射频信号进行处理、传输与控制的相关技术。文章还在器件方面提出利用特殊结构改善滤波、天线等性能的新技术。     

光载无线通信系统的传输限制与抑制方法

针对光载无线通信（RoF）系统的传输限制因素,文章提出并实验证明两种传输距离长性能高的RoF系统。一种是采用抑制奇数边带的基于外部调制的40GHz的RoF系统;另一种是采用载波抑制（OCS）的外部调制的40GHz光正交频分复用（OFDM）RoF系统。理论与实验证明这两个系统不仅抗色散能力强,而且可以实现远距离传输。     

面向5G光载通信系统的数字预失真线性化技术应用

随着5G通信技术的迅猛发展,光载无线(Radio-over-Fiber, RoF)通信系统在实现高数据传输率和低延迟方面日益发挥出重要作用。然而,该系统在处理高频宽带5G信号时,常受到射频功率放大器和光电组件非线性特性的影响,导致信号产生失真问题。为解决这一问题,文章深入探讨了数字预失真(Digital Predistortion, DPD)技术在5G RoF通信系统中的应用及其效果。     

一种多波段信号输出的全双工光载无线系统

为了提升通信系统的灵活性,扩大应用范围,同时降低建设成本,提出一种多波段信号输出的全双工光载无线系统。在单光源条件下,通过灵活控制偏振控制器、线性偏振器的角度,实现3路不同频段的下行矢量信号传输;利用载波重用和相干检测技术,实现上行基带信号输出。仿真结果表明：6 Gb/s四进制正交幅度调制（16QAM）信号经30 km光纤传输后,下行链路中5 GHz、45 GHz和25 GHz频段输出信号的最小误差矢量幅度（EVM）分别为5.66%、4.03%和2.67%,上行链路输出信号的最小EVM为4.01%。     

粗波分复用(CWDM)系统及其测试

对粗波分复用技术的产生、发展和应用进行描述，并与密集波分复用技术进行比较，最后介绍了粗波分复用系统的测试及其注意事项。     

面向5G前传的新型CWDM承载方案

随着5G网络流量快速增长,6通道25 Gbit/s前传承载需求日趋明显。介绍了移动前传在现网部署的主要方案和标准化情况,针对6通道25 Gbit/s前传低成本承载需求,提出了一种基于CWDM/光环行器的承载方案,分析了该方案的优势与面临的挑战,介绍了该方案在实验室测试和现网试点的情况。     

Models,Complexity and Algorithms for the Design of Multi-fiber WDM Networks

In this paper, we study multi-fiber optical networks with wavelength division multiplexing (WDM). We extend the definition of the well-known Wavelength Assignment Problem (WAP) to the case of k fibers per link and w wavelengths per fiber, generalization that we will call (k,w)-WAP. We develop a new model for the (k,w)-WAP based on conflict hypergraphs. Furthermore, we consider two natural optimization problems that arise from the (k,w)-WAP: minimizing the number of fibers k given a number of wavelengths w, on one hand, and minimizing w given k, on the other. We develop and analyze the practical performance of two methodologies based on hypergraph coloring.     

TD-SCDMA网络2/3G共LAC区及精确LAC区边界划分

在现阶段TD-SCDMA网络与GSM网络共同组网的情况下,2/3G互操作作为两代网络互惠互补的有效手段得到了广泛应用和发展。要提升网络指标和用户感知,需要提高2/3G互操作成功率、缩短2/3G互操作时延。目前很多地市开展网络优化的过程中已开始进行缩短2/3G互操作时延的尝试,2/3G共LAC区便是其中较为成功的一例。在此基础上,进行精确LAC区边界划分的专项优化,可以在2/3G共LAC区的效果之下,达到进一步提升和完善网络性能的效果。     

A new family of 2D variable-weight optical orthogonal codes for OCDMA systems supporting multiple QoS and analysis of its performance

A new family of two-dimensional variable-weight and constant-length optical orthogonal codes (2D VWOOCs) is proposed, and the code cardinality and BER performance for the corresponding OCDMA system are analyzed in this article. It is shown that the cardinality of 2D VWOOC is larger than that of constant-weight 2D OOC and close to the upper bound in theory. In an OCDMA network, the users employing 2D VWOOC codewords with larger Hamming weight outperform the users using 2D VWOOC codewords with smaller Hamming weight in bit-error-rate performance. Therefore, the OCDMA network employing 2D VWOOC can support diverse quality-of-services (QoS) classes and multimedia services, and make the better use of bandwidth resources in optical networks.

A Family of High‐Performance Cathode Materials for Na‐ion Batteries,Na3(VO1−xPO4)2 F1+2x (0 ≤ x ≤ 1): Combined First‐Principles and Experimental Study

Room‐temperature Na‐ion batteries (NIBs) have recently attracted attention as potential alternatives to current Li‐ion batteries (LIBs). The natural abundance of sodium and the similarity between the electrochemical properties of NIBs and LIBs make NIBs well suited for applications requiring low cost and long‐term reliability. Here, the first successful synthesis of a series of Na₃(VO_1?x PO₄)₂F_1+2x (0 ≤ x ≤ 1) compounds as a new family of high‐performance cathode materials for NIBs is reported. The Na₃(VO_1?x PO₄)₂F_1+2x series can function as high‐performance cathodes for NIBs with high energy density and good cycle life, although the redox mechanism varies depending on the composition. The combined first‐principles calculations and experimental analysis reveal the detailed structural and electrochemical mechanisms of the various compositions in solid solutions of Na₃(VOPO₄)₂F and Na₃V₂(PO₄)₂F₃. The comparative data for the Na _y (VO_1?x PO₄)₂F_1+2x electrodes show a clear relationship among V³⁺/V⁴⁺/V⁵⁺ redox reactions, Na⁺?Na⁺ interactions, and Na⁺ intercalation mechanisms in NIBs. The new family of high‐energy cathode materials reported here is expected to spur the development of low‐cost, high‐performance NIBs.