A cross-layer analysis of TCP/link adaptation technologies over free-space optical links with Markov error model

This paper presents a comprehensive cross-layer framework on the performance of transmission control protocol (TCP) over a free-space optical (FSO) link, which employs automatic repeat request (ARQ) and adaptive modulation and coding (AMC) schemes. Not similar to conventional works in the literature of FSO, we conduct a Markov error model to accurately capture effects of burst errors caused by atmospheric turbulence on cross-layer operations. From the framework, we quantify the impacts of different parameters/settings of ARQ, AMC, and the FSO link on TCP throughput performance. We also discuss several optimization aspects for TCP performance.     

Design of the QoS framework for the IEEE 802.16 mesh networks

IEEE 802.16 (WiMax) technology is designed to support broadband speeds over wireless networks for the coming era of broadband wireless access (BWA). IEEE 802.16 is expected to provide transmission of high‐rate and high‐volume multimedia data streams for fixed and mobile applications. As an extension of point‐to‐multipoint (PMP) configuration, the IEEE 802.16 mesh mode provides a quicker and more flexible approach for network deployment. Multimedia networking requires quality‐of‐service (QoS) support, which demands elaborate mechanisms in addition to the four service types defined in the specification. By examining standard centralized and distributed scheduling/routing schemes in the mesh mode from QoS aspect, a BS‐controlled and delay‐sensitive scheduling/routing scheme is proposed in the paper. Associate mechanisms including admission control, flow setup and link state monitoring are also proposed. Integration of the proposed mechanisms is presented as a complete QoS framework. Simulation study has demonstrated that the average delay as well as the delay jitters per hop in the proposed scheme is smaller than that of the distributed scheme and much smaller than that of the centralized scheme. Furthermore, proposed mechanisms can also achieve higher throughput than the contrasts and generate much smaller signaling overhead, making the proposed framework a promising scheme for multimedia support in the IEEE 802.16 mesh network. Copyright © 2009 John Wiley & Sons, Ltd.     

通信机房用精确下送风空调系统

介绍了精确下送风空调系统的原理和系统组成,并对某采用精确下送风空调系统的通信机房的能源利用效率进行测试分析,实测结果表明：该通信机房的能源利用效率达到1．54,比某大型通信集团广东公司通信机楼的平均值优23．0％,节能效果明显。     

Cloud Based Software Computing as a Service in Hybrid Evolution Algorithm with Feedback Assistance

This paper develops cloud based software computing as a service (SCaaS) in the hybrid evolution algorithm with feedback assistance to solve the data optimal NP-complete problems such as travel salesman problems and job shop scheduling problems. Suitable steps, methods, or procedures of the genetic algorithm can be adopted from various evolution procedures or methods of the genetic algorithms based on the fitness evaluation results and survival ratio of different crossover methods in the current generation. The proposed system can dynamically emphasize the corresponding methods or procedures for the better performance in optimal solution searching. In addition, according to the proposed XML format, system users can upload only the coding of chromosomes without implementing the genetic algorithm program. Furthermore, by using the feedback assistance, the convergence time of the optimal solution can be enhanced.     

多层防御反坦克阵地效能建模与仿真

现代反坦克防御作战中,陆军多采用武装直升机、车载式反坦克导弹与便携式反坦克导弹相结合的立体、多层部署的方法对重点区域进行防御。敌方常通过施放红外热源、烟幕等电子干扰方式来提高其生存能力和突防效率。基于排队论和反坦克作战理论,建立了电光干扰对抗环境下的多层防御反坦克阵地的排队服务模型,并对作战想定进行了仿真应用。仿真结果表明了模型的可信性和实用性。     

不同变形下梯形脊波导传输特性研究

脊波导器件在使用中会产生各种变形,本文采用有限元方法研究错位和受力变形对梯形脊波导传输特性的影响.数值分析结果表明错位变形使脊波导截止波长变长,单模带宽增大程度小于1%,对于脊波导传输特性影响较大的是双边受力变形,当变形达到10%时,其特性交化超过10%以上,在使用中应引起重视.     

Transmission Characteristics of Ridge Waveguide Loaded with Left-Handed Materials

This paper presents a numerical study of the electromagnetic wave propagation in a double ridge waveguide, loaded with left-handed materials (LHM). The LHM is defined phenomenologically by assigning to it a negative permittivity and negative permeability simultaneously. Transmission characteristics such as cutoff wavelength, single-mode bandwidth, dispersion and field patterns have been investigated by edge-based finite element method. The results are compared to those with air- and dielectric-loaded ridge waveguide. It was found that the LHM-loaded ridge waveguide can greatly increase the cutoff wavelength with the disadvantage of a dramatic reduction in the single-mode bandwidth. The behavior of the dispersion curve of LHM-loaded ridge waveguide is similar to the cases of waveguide loaded with air or dielectric, except for a significant improvement of the propagation constant. The boundary conditions at the interface between the air and the LHM have been well illustrated and the antiparallel wave vector in LHM were obtained by considering the field patterns. The unusual behaviors of the LHM-loaded ridge waveguide provides the potential opportunities to design novel microwave and millimeter devices.     

On the Cutoff Wavelength of Rectangular-Shaped Microshield Line by Edge Element Method

In this paper, the cutoff characteristic of rectangular-shaped microshield transmission line has been analysed by edge element method. Dependence of cutoff wavelengths on the thickness of metallic signal strip, dielectric constant of dielectric substrate and the width of the rectangular-shaped ground conductor are presented in tabular form. Numerical results in this paper have important values in design of rectangular-shaped microshield lines in microwave and millimeter wave integrated circuits.     

广播电视台播控中心整备系统的构建与实现

2020年上半年广东广播电视台新播控中心建设完成,并在下半年投入使用,实现了全台网架构下的制作、新闻与播出一体化,以及全台频道高清化播出、网络化送播和频道一体化编播管理的流程改革。本文主要阐述了全台网架构下,播出整备系统在广东广播电视台的构成与运用。     

智能动态网络资源分配系统

通过对解决GSM移动通信网络热点区域话务拥塞问题的研究，提出了利用可控功分器实现智能动态网络资源的分配，解决不同种类的话务拥塞问题，并着重讨论了该系统目前的成功运用及前景。