MPLS网络多路径动态流量分配的研究

本文描述了MPLS(多协议标记交换)流量工程性能最优化方面的一种分析途径,首先对多路径系统模型进行了描述,然后在引入流量分配颗粒度g的概念的基础上,提出一种改进的多路径上的动态流量分配算法,利用此算法,可以实现LSPs(标记交换路径)上流量的动态调整,并降低运算量,本文通过数值分析验证了算法的性能和稳定性.     

MPLS流量内容检测框架研究

多协议标记交换(MPLS)是新一代的IP高速骨干网络交换标准.随着MPIS在流量工程、服务质量保证、VPN网络中的广泛应用,MPLS承载的应用也越来越多,因此迫切需要构建MPLS流量内容检测框架.讨论的核心就是以太网下MPLS流量内容检测框架.     

浅析ATM的MPLS流量工程

探讨了基于ATM的MPLS流量工程研究,重点分析了实现MPLS流量工程的ATM流控措施、使用约束路由的标记分发协议、路由协议等;同时研究了融合IP路由技术,ATM的QOS(Quality of Service)及交换技术,使得流量工程模式可以部署在基于IP的网络,MPLS多协议标记交换技术,其中包括ATM网上承载IP业...     

多协议标记交换中的流量工程

流量工程是网络运营商为提高网络运营利润和市场份额而进行的网络资源分配和优化利用,流量工程在传统电信商的网络中得到了比较广泛的应用。Ｉｎｔｅｒｎｅｔ本质上无连接的尽力传送网络,因此很难进行有效的流量测量和控制。ＩＥＴＦ提出的多协议标记交换（ＭＰＬＳ）以比较小的代价赋予互联网一种面向连接的控制能力,从而使互联网中的流量工程成为可能,流量工程反过来成为促进ＭＰＬＳ的主要功能之一。流量工程能力不仅能提高网     

基于ATM的MPLS流量工程研究

研究了基于ATM的MPLS,重点研究和分析了具体实现MPLS流量工程的ATM流控措施、使用约束路由的标记分发协议、路由协议,为MPLS流量工程的具体实施提供了参考。同时研究了MPLS多协议标记交换技术融合IP路由技术、ATM的QoS（Quality of Service）及交换技术,使得流量工程模式可以部署在基于IP的网络,其中包括ATM网上承载IP业务的模式。     

基于MPLS的流量工程仿真

多协议标签交换（MPLS）技术的成熟和扩展将推进基础网络的智能化和下一代光网络的实现。在对流量工程和MPLS体系结构分析的基础上,讨论了利用MPLS实现流量工程的优势。利用网络仿真器NS2设计了OSPF（开放最短路径优先）路由协议和MPLS流量工程的实例。通过对仿真结果的比较和分析,可以看出MPLS流量工程可以有效地实现网络负载均衡和恢复机制,提高网络服务质量。     

光电混合数据中心的流量分级分类调度研究

光电混合数据中心中的电分组交换可以灵活交换 突发小流量但不能有效传输持续时间 长的大流量,而光路交换正好相反。为此,在基于阵列波导光栅路由器(arrayed waveguide grating router,AWGR)的光电混合数 据中心网络中,提出一种采用主动队列检测的流量分级分类调度策略,由电交换和光路交换 共同实现大小流量的有效调度。根据数据中心的流量模型设计了仿真实验,分析了不同流量 模型下各架构的平均时延和吞吐量。结果表明,和带宽收敛比为1∶1 的树型、Fat-tree型 和C-Through型相比,随机流量模型下AWGR模型的吞吐量增幅达19.43%,时延 降幅达45.73%。点对点流量模型下,随 着K从1增大到4,相比于其它 3种模型,AWGR模型的 吞吐量降幅和时延增幅最低,分别为2.85%和46.98%。说明所提设计方案能有效地提高数据 中心吞吐量和降低时延。     

因特网上的MPLS流量工程

主要讨论因特网上多协议标记交换（MPLS）流量工程，首先简述了MPLS、约束路由技术以及增强链路状态内部网关协议，然后讨论了设计MPLS流量工程系统的主要问题，接着说明了配置MPLS流量工程系统的步骤，最后阐述了MPLS网络的QoS机制。     

基于LSP平衡的流量分配机制研究

对尽力而为（BE）网络流量工程中的自适应流量分配问题进行了深入研究,引入了一种平衡思想,提出一种基于LSP平衡的流量分配（LE-TD）机制,对网络中的流量进行网络平衡规划,利用需求和代价的平衡,使整个网络达到一种稳态,从而使网络中流量的分布模式是稳定的。仿真表明,该机制具有稳定性和收敛性,能有效地实现流量在多条并行LSP之间的合理分配,能有效提高网络端到端平均吞吐量,降低网络端到端平均时延,从而有效地实现了流量工程的优化目标。     

MPLS在Internet流量工程中的应用

首先回顾了IP网络流量工程的概念和所面临的挑战,然后讨论了MPLS(多协议标记交换)的基本概念和发展,指出了MPLS巨大的流量工程能力和主要功能,最后着重分析了MPLS在IP网络流量工程中的应用.     

基于分组并行最大似然检测的多用户信号检测器

根据矩阵的Ｃｈｏｌｅｓｋｙ分解原理和并行运算的思想，提出了基于分组并行最大似然检测的多用户信号检测器。这种检测器的特点是：１．“化整为零”，即将全体用户信号检测转化为多组部分用户信号检测；２．“相互并行”，即各组部分用户信号检测过程相互并行。计算机体育场结果表明：这种检测器的性能接近最佳多用户信号检测器的性能。     

Jointly multi‐user detection and channel estimation with genetic algorithm

This work aims at proposing the use of the evolutionary computation methodology in order to jointly solve the multi‐user channel estimation (MuChE) and detection problems at its maximum‐likelihood, both related to the direct sequence code division multiple access (DS/CDMA). The effectiveness of the proposed heuristic approach is proven by comparing performance and complexity merit figures with that obtained by traditional methods found in literature. Simulation results considering genetic algorithm (GA) applied to multipath, DS/CDMA and MuChE and multi‐user detection (MuD) show that the proposed genetic algorithm multi‐user channel estimation (GAMuChE) yields a normalized mean square error estimation (nMSE) inferior to 11%, under slowly varying multipath fading channels, large range of Doppler frequencies and medium system load, it exhibits lower complexity when compared to both maximum likelihood multi‐user channel estimation (MLMuChE) and gradient descent method (GrdDsc). A near‐optimum multi‐user detector (MuD) based on the genetic algorithm (GAMuD), also proposed in this work, provides a significant reduction in the computational complexity when compared to the optimum multi‐user detector (OMuD). In addition, the complexity of the GAMuChE and GAMuD algorithms were (jointly) analyzed in terms of number of operations necessary to reach the convergence, and compared to other jointly MuChE and MuD strategies. The joint GAMuChE–GAMuD scheme can be regarded as a promising alternative for implementing third‐generation (3G) and fourth‐generation (4G) wireless systems in the near future. Copyright © 2010 John Wiley & Sons, Ltd.     

Performance analysis of multi‐stage interference cancellation for ultra‐wide band multiple‐access communication systems

In this contribution, a novel particle swarm optimization (PSO)‐based multi‐user detector (MUD) aided time‐hopping ultra‐wide band (TH‐UWB) system has been investigated in the multi‐path channel model. In this approach, the PSO‐based MUD employs the output of the Rake receiver as its initial value to search for the best solution which results in a formulated optimization mechanism. By taking advantage of the heuristic values and the collective intelligence of PSO technique, the proposed detector offers almost the same bit error rate (BER) performance as the full‐search‐based optimum MUD does, while greatly reducing the potentially computational complexity. Simulation results have been provided to examine the evolutionary behavior and the detection performance of the proposed PSO‐based MUD in both the additive white Gaussian noise and the multi‐path fading channel. Copyright © 2011 John Wiley & Sons, Ltd.     

一种带预处理的多用户检测器

本文提出了一种带预处理的多用户检测器.其预处理器是通过二进制二次规划问题的全局最优性条件得到的.本文的预处理器只用很小的计算量就可以判断出大部分用户的信息码,而且可以保证通过预处理得到的部分用户的信息码与最佳多用户检测得到的结果相同.因为由预处理得到的用户的信息码已经是全局最优的,所以我们就可以将其从原多用户检测问题中剔除,进而得到一个相对小规模的多用户检测问题.与原问题相比,这个小规模的多用户检测问题的多址干扰减小了,然后可以用一些常用的多用户检测器来求解这个小规模的多用户检测问题.     

多用户检测CDMA系统的阻塞度量和控制

本文讨论了ＣＤＭＡ系统在多用户检测和单用户检测两种情况下系统的阻塞度量和控制问题,并给出了相应的用户功率平衡方程和小区干扰平衡方程。本文证明两种平衡方程有相同的阻塞因子,但干扰平衡方程和维数与系统内小区数相等,并远小于用户功率平衡方程的维数即系统用户数,因而降低了计算复杂度。理论和模拟结果表明多用户检测系统中平衡方程有更小的阻塞因子,因而相对应的迭代算法能很快收敛,并且系统的阻塞率得到降低。     

Near-ML multiuser detection with linear filters and reliability-based processing

The prohibitive - exponential in the number of users - computational complexity of the maximum-likelihood multiuser detector for direct-sequence code-division multiple-access communications has fueled an extensive research effort for the development of low-complexity multiuser detection alternatives. We show that we can efficiently and effectively approach the error rate performance of the optimum multiuser detector as follows. We utilize a multiuser zero-forcing or minimum mean-square error (MMSE) linear filter as a preprocessor and we establish that the output magnitudes, when properly scaled, provide a reliability measure for each user bit decision. Then, we prepare an ordered, reliability-based error search sequence of length linear in the number of users; it returns the most likely user bit vector among all visited options. Numerical and simulation studies for moderately loaded systems that permit exact implementation of the optimum detector indicate that the error rate performance of the optimum and the proposed detector are nearly indistinguishable over the whole predetection. signal-to-noise ratio range of practical interest. Similar studies for higher user loads (that prohibit comparisons with the optimum detector) demonstrate error rate performance gains of orders of magnitude in comparison with straight decorrelating or MMSE multiuser detection.     

Optimum multiuser noncoherent DPSK detection in generalized diversity Rayleigh-fading channels

The jointly optimum multiuser noncoherent detector for differential phase-shift keying (DPSK) modulation over the generalized diversity Rayleigh-fading (GDRF) channel is derived and analyzed. The GDRF channel includes time/frequency/receiver antenna diversity and allows fading correlations between the various diversity branches of each user. Noncoherent detection here refers to the case where the receiver has neither knowledge of the instantaneous phases nor of the envelopes of the users' channels. Upper and lower bounds on the bit-error probability of the optimum detector are derived for a given user. For fast fading, when the fading coefficients vary from one symbol interval to the next (but are still essentially constant over one symbol interval), the detector asymptotically (for high signal-to-noise ratios (SNRs)) reaches an error floor, which is bounded from below and above for different fast fading scenarios. For slow fading, when the channel is constant for at least two consecutive symbol intervals, the upper bound is shown to converge asymptotically to the lower bound. Thus, the asymptotic efficiency of optimum multiuser DPSK detection can be determined and is found to be positive. In contrast to coherent detection, however, it is smaller than unity in general. Since the asymptotic efficiency is independent of the interfering users' signal strengths, the optimum detector is near-far resistant. While optimum multiuser detection is exponentially complex in the number of users, its performance provides the benchmark for suboptimal detectors. In particular, it is seen that the previously suggested post-decorrelative detectors can be far from satisfactory.     

The Cholesky-iterative detector: a new multiuser detector forsynchronous CDMA systems

The decorrelating decision-feedback (DDF) multiuser detector based on Cholesky factorization has been shown to alleviate the performance degradation of the users in the detection process, especially for relatively low cross-correlation values between user signals. A new detection concept for multiple users described in this paper employs two triangular matrices (upper and lower) and soft output information to improve the data estimates. Simulation results show that significant performance gains can be achieved over the DDF. Also, the users tend to have their bit error probabilities clustered. Thus, the performance of a given user is less dependent on its position in the detection process than for the DDF detector     

CDMA multiuser detection: a nonlinear programming approach

The optimum receiver to detect the bits of multiple code-division multiple access (CDMA) users has an exponential complexity in the number of active users in the system. Consequently, many suboptimum receivers have been developed to achieve good performance with less complexity. We take the approach of approximating the solution of the optimum multiuser detection problem (OMUD) using nonlinear programming relaxations. First, we observe that some popular suboptimum receivers indeed correspond to relaxations of the optimal detection problem. In particular, one proposed approximation method yields to iterative solutions which correspond to previously proposed heuristic nonlinear detectors. Using a nonlinear programming approach, we identify the convergence properties of these iterative detectors. Secondly, we propose a relaxation that yields a receiver which we call the generalized minimum mean squared error detector. We give a simple iterative implementation of the detector. Its performance is evaluated and comparisons to other suboptimum detection schemes are given     

Minimum class variance support vector machines.

In this paper, a modified class of support vector machines (SVMs) inspired from the optimization of Fisher's discriminant ratio is presented, the so-called minimum class variance SVMs (MCVSVMs). The MCVSVMs optimization problem is solved in cases in which the training set contains less samples that the dimensionality of the training vectors using dimensionality reduction through principal component analysis (PCA). Afterward, the MCVSVMs are extended in order to find nonlinear decision surfaces by solving the optimization problem in arbitrary Hilbert spaces defined by Mercer's kernels. In that case, it is shown that, under kernel PCA, the nonlinear optimization problem is transformed into an equivalent linear MCVSVMs problem. The effectiveness of the proposed approach is demonstrated by comparing it with the standard SVMs and other classifiers, like kernel Fisher discriminant analysis in facial image characterization problems like gender determination, eyeglass, and neutral facial expression detection.