一种基于随机散射簇的非平稳3D空间信道模型

针对大规模MIMO信道的近场效应和非平稳特性,该文提出适用大规模MIMO信道的一种基于随机散射簇的非平稳3D空间信道模型。采用抛物波前代替球面波前建模近场效应,并分析抛物波前条件下该模型的信道容量。对于大规模MIMO信道的非平稳特性,提出基于散射簇的有效概率确定收发天线阵元的有效散射簇集合,从而建模散射簇沿天线阵列轴的随机演变来合理描述散射簇的出现和消失。仿真结果表明,用抛物波前和有效散射簇的随机演变来建模大规模MIMO信道特征是很好的候选方法。     

5 GHz无线局域网信道特征与信道模型

本文介绍了5GHz典型无线局域网场景下的信道的一些特征和测量结果,然后结合信道特征,说明信道建模的原理和方法,并给出了有关的信道模型.     

The COST 259 Directional Channel Model?Part II: Macrocells

This paper describes the attributes of the COST 259 directional channel model that are applicable for use in the design and implementation of macrocellular mobile and portable radio systems and associated technology. Special care has been taken to model all propagation mechanisms that are currently understood to contribute to the characteristics of practical macrocellular channels and confirm that large scale, small scale, and directional characteristics of implemented models are realistic through their comparison with available measured data. The model that is described makes full use of previously published work, as well as incorporating some new results. It is considered that its implementation should contribute to a too) that can be used for simulations and comparison of different aspects of a large variety of wireless communication systems, including those that exploit the spatial aspects of radio channels, as, for example, through the use of adaptive antenna systems     

超宽带室内LOS环境信道模型研究

分析了室内LOS环境下信号传播规律,多径分量成簇到达。针对该特定环境,在S-V模型的基础上,提出将模型中簇的个数定义为2个,并对其进行了仿真。仿真结果表明,该模型与IEEE802.15.3 a信道模型相比,能较好地反应UWB室内LOS环境信道的特征参数。在其他参数不变的情况下,能减少平均超量延时和均方根时延扩展,对提高系统的数据传输速率有帮助。     

高速铁路无线信道测量与信道模型探讨

我国高速铁路(简称"高铁")建设取得了举世瞩目的成就,高铁车地通信问题也成为学术界、产业界研究的热点,本文分析了高铁信道模型的特点,回顾了高铁信道测量和研究的已有成果,归纳了现阶段标准化组织高铁信道提案和模型,研究了高铁无线信道测量和建模的特殊问题,如不同覆盖方式信道模型的差异,小区重叠时无线信道特征,高铁信道互易性问题,非平稳相关散射特征,基于马尔科夫链生灭过程时变信道等问题。     

The COST259 Directional Channel Model?Part I: Overview and Methodology

This paper describes a model for mobile radio channels that includes consideration of directions of arrival and is thus suitable for simulations of the performance of wireless systems that use smart antennas. The model is specified for 13 different types of environments, covering macro- micro- and picocells. In this paper, a hierarchy of modeling concepts is described, as well as implementation aspects that are valid for all environments. The model is based on the specification of directional channel impulse response functions, from which the impulse response functions at all antenna elements can be obtained. A layered approach, which distinguishes between external (fixed), large-scale-, and small-scale- parameters allows an efficient parameterization. Different implementation methods, based on either a tapped-delay line or a geometrical model, are described. The paper also derives the transformation between those two approaches. Finally, the concepts of clusters and visibility regions are used to account for large delay and angular spreads that have been measured. In two companion papers, the environment-specific values of the model parameters are explained and justified     

云环境下基于迁移的虚拟机集群优化算法

针对云环境中虚拟机集群负载不均衡问题,提出一种基于虚拟机迁移的集群优化算法。通过对节点负载的实时监测,动态调整各种资源的权重,根据资源权重选择可最大程度降低主机负载的虚拟机进行迁移。该算法利用预测机制,消除主机资源利用率的临时越界引起的不必要的虚拟机迁移。在选择目标节点时,采用多目标决策法,兼顾多资源匹配率,服务级目标违背率(SLA)等多种管理目标。实验结果表明,与同类型的负载均衡算法相比,该算法能减少迁移次数,降低SLA违背率。     

基于ITS信道模型的HF信道模拟器的实现

提出了一种基于ITS短波信道模型的HF信道模拟器的实现方法,并给出了线性调频信号通过HF信道模拟器后频域的MATLAB仿真结果。信号通过信道后产生的时延展宽、多普勒频移和多普勒展宽都是利用现场可编程逻辑门阵列来实现。电离层参数是利用三维射线追踪技术根据选定的电离层模型得到。这种HF信道模拟器适用于高达500kHz带宽的信号。利用这种HF信道模拟器,实现了在实验室研究探测信号经过HF信道传输的特性的可能。     

基于荫罩式PDP新型十字扫描电极放大单元的研究

新型荫罩式等离子体显示板利用制造工艺成熟的金属荫罩替代复杂的介质障壁,不仅降低了成本、而且改善了性能.为了进一步提高其亮度和效率,针对42 inch荫罩式等离子显示器提出了一种新型十字形扫描电极结构,采用放大单元实验方法,研究了该电极结构的放电过程,给出了高速ICCD拍摄的光分布图.测量了相应的功耗、红外辐射强度、以及放电效率,并与传统条状电极结构进行了比较.结果表明,新型十字形扫描电极结构使放电区域沿扫描电极的主电极部分大大扩展,放电更剧烈,亮度也有显著提高,效率得到了改善,放电速度也更快.     

基于定向天线的无线传感网络环境自适应定位算法

在无线传感网络的各类应用中,传感器节点位置信息有着重要价值,在现有基于锚节点的各类定位算法设计中,锚节点大多采用全向天线技术,这虽然增加了算法设计的便利性,但是因其固有的物理缺陷,定位效果不理想。在充分分析现有各类天线技术的基础上,提出了一种基于定向天线测距的环境自适应分布式定位算法,并利用实验室现有设备搭建实验环境,对所设计的算法进行实验验证,结果表明其具有较高的定位精度和应用价值。     

Adaptive Echo Cancellation Based on a Multipath Model of Acoustic Channel

Usually Acoustic Echo Cancellers (AECs) are realized by adaptive Finite duration Impulse Response (FIR) filter having large number of coefficients and Least Mean Square (LMS) as an adaptive algorithm resulting in slow convergence speed and poor tracking performance of these adaptive filters. In this paper, we have proposed a Multiple Sub-filter (MSF) parallel structure based on multipath acoustic echo model using the basis that each sub-filter will compensate the echo contributed by each path of multipath acoustic channel. To realize the MSF, modified Generalized Autocorrelation-based Estimator (MAE) has been used to estimate time delay associated with each path while the order of each sub-filter has been estimated using Power Spectral Density (PSD) method. Accuracy Percentage (AP) performance measure has been used to characterize the performance of the estimator. Simulation results show that the performance of the MAE improves with the increase in SNR and/or decrease in number of multipath. Using these estimates MSF based AEC is constructed. The convergence performance of MSF-based AEC has been studied, via computer simulation, and compared with the conventional Single Long length adaptive Filter (SLF)-based canceller for different SNRs and number of multipath. The results of MSF have been found to be very encouraging in almost all of the various situations considered. Subsequently, the tracking behavior has also been studied with variation in the channel parameters of the multipath model. The proposed MSF can track variations in the channel parameters of the multipath model faster as compared to the conventional echo canceller.     

超宽带室内双簇信道模型的仿真与分析

提出一种基于随机波动模型（S-V模型）的改进室内模型,即修正的泊松超宽带（Ultrawideband,UWB）室内视距（Line of sight,LOS）信道模型,即两簇模型。模型的信道冲激响应具有两个确定的簇,每个簇内具有随机到达的多径射线。模型将多径增益分为能量较强和能量较弱两部分,在UWB室内LOS环境的小尺度多径特性上比S-V模型更好地拟合了UWB室内LOS环境测量数据,从而弥补了S-V模型和IEEE802．15．3a标准模型对室内LOS信道环境性能的不足。     

Two Novel Channel Estimation for OFDM Systems by Time-Domain Cluster Discriminant Analysis Based on Parametric Channel Modeling

In this paper, we describe two novel channel estimation technologies for orthogonal frequency-division multiplexing mobile communication systems using cluster discriminant analysis for sparse multipath channels. The least-squares estimator has a merit of low complexity and simple structure; however one of its drawbacks is that it does not take into consideration the effect of noise. Conventional DFT-based channel estimator improved its performance by suppressing time domain noise, but it does not completely suppress the noise. In order to overcome this disadvantage, we propose two novel channel estimation algorithms for Orthogonal frequency division multiplexing systems based on cluster analysis and discriminant analysis. The cluster analysis can be used to cluster residual noise. Discriminant analysis can distinguish the noise and channel taps in time domain. Computer simulation demonstrates the performance of the proposed algorithms in terms of bit error rate and mean square error performance.     

高铁场景下宽带无线信道模型的探讨

随着高铁的迅速发展,高铁宽带无线通信问题也成为学术界研究的热点。高铁场景下信道特性的测量与建模是高铁无线通信系统研究的基础工作之一。本文介绍了高铁无线通信发展现状、高铁环境下信道模型的发展现状及高铁无线信道测量和建模所面临的挑战。     

Performance Evaluation of a Bluetooth-Based WLAN Adopting a Polling Protocol Under Realistic Channel Conditions

Even if Bluetooth has not been specifically designated for WLANs (Wireless Local Area Networks) and the interconnection of computers, the possibility of establishing low-cost wireless connections makes this technology attractive for this kind of context also. In this paper we assess, by means of a simulative approach that takes the complete physical and MAC level aspects into account, the performance of a Bluetooth-based WLAN adopting a roll-call polling protocol under realistic channel conditions, that is, in the presence of the typical impairments of indoor wireless communications (fading, etc); moreover, we propose an analytical formulation to derive the maximum throughput offered by a Bluetooth link and we suggest a call admission control technique based on the previous analytical considerations.     

基于有限阶最优模型的时变信道均衡

本文分析了时变信道的最优基信道模型,通过对信道统计相关函数的离散K-L(Karhunen-Loeve)变换得到了多径信道的特征向量基模型,该信道模型可以精确地拟合时变信道的变化,并在中国数字电视地面传输标准(DTTB)系统上使用该方法进行仿真。仿真表明,在高速移动的情况下,该方法仍具有相当好的均衡性能。同时,在SNR较高时,可以得到很好的误码性能。该模型是统计意义上的有限阶数最优信道模型。     

基于动态规划(DP)的信道模型变化检测

本文提出一种适用于快衰落信道结构的模型变化检测算法.针对信号包络幅值寻找信道模型发生突变的采样时间点,运用动态规划(DP)方法推导了快衰落信道的模型变化检测的理论表达式,构造了信道的变结构模型切换准则.理论分析和仿真实验表明结合幅值变化检测,可有效地找出模型变化采样时间点,并在这些时间点对信道进行模型切换,使估计器达到...     

基于导频和多项式模型的信道估计

本文提出一种基于导频辅助、多项式近似和信号重建的信道估计通用方法,适用于高速移动环境.假定无线信道响应具有多项式特性,用两个或多个时隙的导频符号,估计出该时间段内任意符号时刻上的信道响应值.用仿真方法研究了WCDMA上行链路性能与移动台速度的关系、最佳多项式阶数和最佳时隙数,并与WMSA方法进行了比较.     

基于随机游动的宽带MIMO 信道模型研究

针对现有信道仿真模型要求支路数目多且仿真时间长的问题,提出了一种基于随机游动的谐波叠加改进方法,详细推导了该模型输出信道衰落幅值分布及空时相关系数的理论表达式。针对3GPP 空间信道模型（Spatial Channel Model,SCM）标准参数的仿真结果表明,新方法输出衰落幅值分布和各子信道衰落空时相关特性均与理论值非常吻合,优于传统精确多普勒频率扩展的仿真方法,可用于未来大规模多支路的多输入多输出（Multiple-Input Multiple-Output,MIMO）信道或多节点网络信道的实时仿真场合。     

一个基于集群的并行计算模型——NHCBL

当前,集群是流行的并行计算平台,既具有所有并行计算都具备的一般特性,又具有自己独有的特性———节点计算资源的异构性、节点计算资源的非独占性、对节点间通信的敏感性。针对基于集群环境的并行计算,对非独占、异构、同步LogGP模型NHBL(Nondedicated Heterogeneous Barrier Log GP model)进行改进,提出了一种更实用的计算模型,即考虑网络拥塞的非独占、异构、同步LogGP模型NHCBL(Nondedicated Heterogeneous Barrier Log GP model considering Conges-tion)。NHCBL模型既比较准确地描述了并行计算的一般特性,又比较准确地描述了基于集群的并行计算独有的节点计算资源的异构性、节点计算资源的非独占性、对节点间通信的敏感性,其描述比NHBL模型更全面也更准确。