自适应技术在后3G中的应用

采用自适应的方法。根据信道、业务要求的变化改变系统中的某些参数，是无线通信系统中提高频谱利用率的重要手段，尤其适用于后3G系统。首先介绍了应用于移动通信的自适应技术，包括其基本思想和目前采用的主要技术，然后重点展望了自适应技术在未来后3G中的应用，包括自适应调制编码、混合ARQ、动态分组分配和层闻自适应等。最后指出自适应技术将是后3G中的关键技术。     

红外半实物仿真系统的关键技术

红外半实物仿真系统通过生成高逼真动态红外场景图像，为红外成像系统提供测试环境，在红外成像系统的开发、测试和评估中起着非常重要的作用。围绕红外半实物仿真系统中的关键技术，介绍了该系统中采用的动态红外图像生成技术和红外场景投影技术的原理及其优缺点和目前发展状况，以及红外场景仿真和投影器件的发展方向。     

认知无线电关键技术研究

认知无线电技术是一种崭新的提高频谱利用率的解决方法,而自适应OFDM技术则以其具有频谱利用率高、抗多径性能强、可自适应地改变传输参数等特点而非常适合于认知无线电系统的应用。文中在研究了认知无线电系统关键技术的基础上,将认知无线电系统分类为分布式系统以及集中式系统两种应用场景,然后着重对分布式场景中的功率控制和频谱资源管理问题进行了深入研究,并在假设的认知无线电网络环境中对系统性能进行了仿真分析。     

在线计费系统综合性能评估体系研究

在线计费系统(OCS)是一个业务复杂、应用场景多、对性能具有高要求的系统,传统的性能指标单项评估模式无法体现OCS综合性能的优势和瓶颈。为此,本文设计出一套OCS综合性能评估方案,针对各种测试场景,提出不同的性能指标评估算法,形成了一套完整的综合性能指标评估体系。该评估体系能够有效地指导在线计费系统的性能评估和选型对比,同时,能够初步定位OCS的性能瓶颈,为性能调优提供一定的参考价值。     

LTE-Hi关键技术研究

随着第四代移动通信技术（LTE）在世界范围的广泛部署,无线接入技术的关注重点从传统的语音业务转移到数据业务。本文将给出第三代合作伙伴计划（3GPP）12版本（R12）协议规定的LTE热点／室内（LTE-Hi）增强系统的协议进展和研究现状,分析更高阶调制、动态时分双工（TDD）时隙自适应配置等关键技术对系统性能的影响。     

反馈时延下LTE链路自适应算法性能研究

介绍了一种LTE系统的快速链路自适应算法,算法基于瞬时信道信息计算预编码矩阵指示、秩指示和信道质量指示3种反馈信息。当前对快速链路自适应算法的研究大部分都假设无反馈时延,因此研究了反馈时延对算法性能的影响,针对发射分集和闭环空间复用两种传输模式在低速和较高速场景下进行了算法性能评估。     

安恒信息发布AiTrust零信任解决方案

安恒信息基于零信任思想,结合多年在企业安全运营、安全大数据分析、数据安全等领域的实践与技术积累,推出了基于“以身份为基础、以资源为核心、持续信任评估、动态访问控制”的AiTrust零信任解决方案,在原有物理边界之上构建动态身份边界,从终端、用户、系统等资源访问主体的可信身份出发,向政企提供全新的业务安全视角,有效支撑应用开放、业务互通、数据共享等场景的安全、高效运转,助力政企网络安全体系逐步向自适应安全演进。     

基于IEEE802．16e的链路自适应技术研究

链路自适应是移动宽带系统的关键技术之一,它通过研究无线电信道的衰落程度、信道流量等参数动态改变调制编码方式、发送功率、帧长等,从而有效地改善误比特率性能和信息传输速率。主要介绍了链路自适应技术在IEEE802,16e系统中的应用。     

TD-LTE系统性能仿真评估研究

TD-LTE由于采用了OFDM和MIMO等技术,其性能相对于3G系统有了大幅度的提升。本文介绍了TD-LTE的最新性能评估结果,包括Release 8和Release 9的主要传输技术,如预编码技术、波束赋形技术、流自适应技术等在各种场景下所能得到的性能,仿真评估的具体指标包括基站平均频谱效率和5%边缘用户的频谱效率等。仿真结果充分展示了TD-LTE的优越性能,文章结合理论分析进一步阐释TD-LTE性能增益的技术根源。评估结果有助于对TD-LTE在各种场景和技术配置下系统性能的全面认识,对后续的网络规划、部署和产品规范的制定等都有很大的参考意义。     

三网融合下自适应编解码技术的研究和应用

本文介绍了自适应编解码技术在三网融合视频业务中的应用以及技术发展情况,并详细分析了各种自适应编解码技术的应用场景、实现方式以及影响视频质量的相关因素,并对部分关键技术进行了讨论,指出自适应编解码技术发展和商用过程中需要解决的一些关键问题。     

TD-LTE-Advanced系统SRS信道估计误差性能研究

在实际TD-LTE-Advanced系统中,针对非理想SRS信道,结合SRS信道估计误差的理论,建立SRS信道估计误差的模型,深入研究SRS误差对MIMO的性能影响。仿真分析显示,存在SRS误差的实际信道对协作多点传输（CoMP）有较大影响,但是相对其他基于波束赋形的MIMO模式仍能保证较高的增益。文章的研究工作分析非理想信道估计对系统性能的影响,并评估非理想SRS信道下多种MIMO模式的系统性能。     

波束成形在TD-LTE-A系统中的性能优化

TD-LTE系统中的波束成形(Beam Forming)会受到收、发天线不对称性的影响。TD-LTE-Advanced(TD-LTE-A)系统中使用上行多天线发送可以解决天线不对称性的问题,因此需要对其分析以优化Beam Forming的性能。通过对上行多天线的信道状态信息(CSI)做特征值(SVD)分解,指出了Beam Forming对下行信噪比(SNR)的改善。针对Beam Forming模式下SNR和链路质量指示(CQI)的差异,提出了一种优化链路自适应的方法。数值仿真验证了优化后的TD-LTE-A相比TD-LTE的Beam Forming吞吐率最大提高了24%,其结论对商用TD-LTE网升级到TD-LTE-A具有显著价值。     

TD-LTE-Advanced国际标准历程

2000年5月,中国提交的TD-SCDMA技术被国际电联接受为IMT-2000（3G）的国际标准;2010年10月,国际电联WP5D工作组确认中国提交的TD-LTE-Advanced技术成为IMT-Ad-vanced（4G）国际标准。从TD-SCDMA到TD-LTE-Advanced,10年时间里中国已经打造了比较完整地TD产业链,并在积极推动移动通信产业的发展。     

Runtime Support for Multicore Packet Processing Systems

Network processors promise a flexible, programmable packet processing infrastructure for network systems. To make full use of the capabilities of network processors, it is imperative to provide the ability to dynamically adapt to changing traffic patterns in the form of a network processor runtime system. The differences from existing operating systems and the main challenges lie in the multiprocessor nature of NPs, their on-chip resource constraints, and real-time processing requirements. In this article we explore the key design trade-offs that need to be considered when designing a network processor operating system. In particular, we explore the performance impact of application analysis on partitioning, traffic characterization, workload mapping, and runtime adaptation. We present and discuss qualitative and quantitative results in the context of a particular application analysis and mapping framework. The observations and conclusions are generally applicable to any runtime environment for network processors.     

TD-LTE-Advanced新技术研究及终端设计和测试挑战

TD—LTE—Advanced作为TD—LTE的增强版本,在TD-LTE基础上引入了一系列新技术特性,如载波聚合,增强型MIMO,中继等。本文介绍了这些技术的物理层、协议栈、高层关键过程及相应的增强内容．分析了技术增强所带来的终端设计和测试上的挑战。     

Performance evaluation of adaptation functions in the ATMenvironment

The paper models and evaluates key design issues for the adaptation layer in ATM networks. The role and efficient design of the adaptation layer is crucial for future B-ISDN based on ATM. We concentrate on packet-mode adaptation services analyzing and simulating relevant protocols employed for narrowband ISDN signaling and packet data. Processing and transmission resources are modeled. In particular we investigate the performance of software based solution resident in microprocessors and interfaces to the ATM world via a generic interface component. This set-up which is currently under development is found adequate to handle narrowband ISDN signaling and data traffic. It offers a cost effective and readily-available solution for the transition phase towards fully customized broadband components     

A teletraffic model for the Physical Downlink Control Channel in LTE

Recent advances in mobile handsets have led to new trends in mobile broadband data consumption, with a huge increase of signaling traffic generated by always-connected devices. Thus, a proper planning of control channels in mobile networks is necessary to avoid network capacity problems and provide an appropriate quality of service to the end user. A key issue in network planning is the availability of a complete and accurate system model. In this paper, an analytical performance model for the Long Term Evolution (LTE) Physical Downlink Control Channel (PDCCH) is constructed based on queuing theory. Unlike previous works, the proposed model considers important network features, such as link adaptation, and can be tuned with available network performance statistics. Model assessment is carried out by comparing performance estimates with request-level simulations and real performance measurements taken from a live LTE network. Results show that the proposed model can predict the PDCCH load distribution in a live network accurately.     

Designing and building SDN testbeds for energy-aware traffic engineering services

As experimenting with energy-aware techniques on large-scale production infrastructure is prohibitive, a large number of proposed traffic engineering strategies have been evaluated only using discrete-event simulations. The present work discusses (i) challenges towards building testbeds that allow researchers and practitioners to validate and evaluate the performance and quality of energy-aware traffic engineering strategies, (ii) requirements to fulfil when porting simulations to testbeds, and (iii) two proof-of-concept testbeds. One testbed uses and provides software-defined network (SDN) services created on the open-network operating system while the other is a composition of virtual Open vSwitches controlled by the Ryu SDN framework. The aim of the testbeds is to validate previously proposed energy-aware traffic engineering strategies in different environments. We detail the platforms and illustrate how they have been used for performance evaluation. Additionally, the paper compares results obtained in the testbeds with evaluations performed using discrete-event simulations and presents challenges faced while implementing energy-aware traffic engineering mechanisms as SDN services in testbed environments.     

TD-LTE／TD-LTE-Advanced技术

作为TD—SCDMA技术的演进。TD—LTE／TD—LTE-Advanced是下一代移动通信系统IMT-Advanced的主流候选技术之一。与第三代移动通信系统采用CDMA技术不同,TD—LTE采用OFDM和MIMO作为基本技术,大量采用了目前移动通信领域最先进的技术和设计理念。本文介绍了TD—LTE／TD—LTE—Advanced技术的标准化进程、技术特点以及系统性能评估情况。     

Virtual-topology adaptation for WDM mesh networks under dynamic traffic

We present a new approach to the virtual-topology reconfiguration problem for a wavelength-division-multiplexing- based optical wide-area mesh network under dynamic traffic demand. By utilizing the measured Internet backbone traffic characteristics, we propose an adaptation mechanism to follow the changes in traffic without a priori knowledge of the future traffic pattern. Our work differs from most previous studies on this subject which redesign the virtual topology according to an expected (or known) traffic pattern, and then modify the connectivity to reach the target topology. The key idea of our approach is to adapt the underlying optical connectivity by measuring the actual traffic load on lightpaths continuously (periodically based on a measurement period) and reacting promptly to the load imbalances caused by fluctuations on the traffic, by either adding or deleting one or more lightpath at a time. When a load imbalance is encountered, it is corrected either by tearing down a lightpath that is lightly loaded or by setting up a new lightpath when congestion occurs. We introduce high and low watermark parameters on lightpath loads to detect any over- or underutilized lightpath, and to trigger an adaptation step. We formulate an optimization problem which determines whether or not to add or delete lightpaths at the end of a measurement period, one lightpath at a time, as well as which lightpath to add or delete. This optimization problem turns out to be a mixed-integer linear program. Simulation experiments employing the adaptation algorithm on realistic network scenarios reveal interesting effects of the various system parameters (high and low watermarks, length of the measurement period, etc.). Specifically, we find that this method adapts very well to the changes in the offered traffic.