Serial concatenation of Hermitian codes with ring‐TCM codes

Hermitian codes are a class of very long algebraic‐geometric (AG) codes constructed from Hermitian curves, which outperform Reed–Solomon codes defined over the same finite fields and with the same code rates, as recently demonstrated by the authors. However, since there are no soft‐decision decoding algorithms for AG codes in the literature, the performance of Hermitian codes is limited and their potential is yet to be realized. An alternative method for achieving more significant coding gains is presented in this paper by serially concatenating long Hermitian codes with ring‐trellis‐coded modulation codes over the ring of integers ?₄ and evaluating their performance through simulation results on the AWGN and Rayleigh fading channels. The scheme achieves large coding gains over single Hermitian and Reed–Solomon codes with no increase in bandwidth use and a performance comparable with the well‐known capacity‐approaching codes. Copyright © 2007 John Wiley & Sons, Ltd.     

Cross-virtual concatenation for Ethernet-over-SONET/SDH networks

Ethernet-over-SONET/SDH (EoS) is a popular approach for interconnecting geographically distant Ethernet segments using a SONET/SDH transport infrastructure. It typically uses virtual concatenation (VC) for dynamic bandwidth management. The aggregate SONET/SDH bandwidth for a given EoS connection is obtained by “concatenating” a number of equal-capacity virtual channels. Together, these virtual channels form a virtually concatenated group (VCG). In this article, we introduce a new concatenation technique, referred to as cross-virtual concatenation (CVC), which involves the concatenation of virtual channels of heterogeneous capacities. We show that CVC can be implemented through a simple upgrade at the end node, thus utilizing the existing legacy SDH infrastructure. By employing CVC for EoS systems, we show that the SDH bandwidth can be harvested more efficiently than in conventional VC. We consider two problems associated with routing CVC connections: the connection establishment problem and the connection upgrade problem. The goal of the first problem is to compute a set of paths between two EoS end systems such that a total bandwidth demand and a constraint on the differential delay between the paths are satisfied. Among all feasible sets, the one that consumes the least amount of network bandwidth is selected. For this problem, we develop an integer linear program (ILP) and an efficient algorithm based on the sliding-window approach. For the connection upgrade problem, the goal is to augment an existing set of paths so as to increase the aggregate bandwidth, while continue to meet the differential-delay constraint. We model this problem as a flow-maximization problem with a constraint on the delay of the virtual channels with positive flow. We then consider the problem of path selection under imprecise network state information. Simulations are conducted to demonstrate the advantages of employing CVC and to evaluate the performance of the proposed algorithms.

Coding‐theoretic constructions for (t,m,s)‐nets and ordered orthogonal arrays

(t,m,s)‐nets are point sets in Euclidean s‐space satisfying certain uniformity conditions, for use in numerical integration. They can be equivalently described in terms of ordered orthogonal arrays, a class of finite geometrical structures generalizing orthogonal arrays. This establishes a link between quasi‐Monte Carlo methods and coding theory. The ambient space is a metric space generalizing the Hamming space of coding theory. We denote it by NRT space (named after Niederreiter, Rosenbloom and Tsfasman). Our main results are generalizations of coding‐theoretic constructions from Hamming space to NRT space. These comprise a version of the Gilbert‐Varshamov bound, the (u,u+υ)‐construction and concatenation. We present a table of the best known parameters of q‐ary (t,m,s)‐nets for qε{2,3,4,5} and dimension m≤50. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 403–418, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10015     

基于虚级联的链路容量调整方案

智能化是当前光网络研究的一个热点问题,在同步数字系列(SDH)网络中使用基于虚级联的链路容量调整方案(LCAS)能有效地增强SDH的智能性,减少带宽的浪费,并能增加SDH网络的健壮性。文章讨论了链路容量调整方案的原理及带宽动态调整过程,分析了宿端回送成员状态的产生及传送方式。     

一种新的Ethernet over SDH映射方式

介绍一种新的Ｅｔｈｅｒｎｅｔ ｏｖｅｒ ＳＤＨ的映射方式,以及相应的使用实例,并和ＨＤＬＣ映射方式作了比较。     

Novel node upgradation strategy for migration to elastic optical networks

For migration from dense wavelength division multiplexing (DWDM) networks to elastic optical networks (EON),it is required to upgrade the traditional reconfigurable optical add-drop multiplexer (ROADM) to the new-generation ROADM that supports flexible grids.However,for a large-scale optical network,it is generally impossible to upgrade the ROADM nodes all in once; rather,they would be upgraded gradually.For this,it is critical to study different strategies for selecting the ROADM nodes to be upgraded.Also,for the interconnection between different generations of ROADM,the sub-band virtual concatenation (VCAT) technique was employed to enable an optical channel to be established via traversing different types of nodes.An integer liner programming (ILP) model and an efficient heuristic algorithm were developed to jointly select the ROADM nodes to upgraded and assign spectrum resources.Simulation studies show that the proposed strategy for the upgraded node selection is efficient to perform close to the ILP model in terms of the maximum number of FS used in the whole network.     

On the impact of filter dispersion slope on the performance of 40 Gbps DWDM systems and networks

A technique to separate the phase-induced penalty of a cascade of optical filters into dispersion, dispersion slope, and higher-order terms is introduced and its impact on the proper design and engineering of high-speed Dense Wavelength Division Multiplexed (WDM) optical systems and networks is demonstrated. As the currently deployed fiber optic systems and networks strive for higher speeds to respond to the growing global needs for more bandwidth, the impact of physical layer impairments (such as optical filter dispersion slope) which were not significant at lower speeds are now becoming increasingly important and worth looking at. In this article we demonstrate that at speeds of 40 Gbps and beyond, where the next generation systems will be operating, optical filter dispersion slope is at least as important as filter dispersion. As a result, separating the above contributions and accounting for each using the described modeling technique proves to be an effective way for designing and engineering such systems.     

Twisted BCH-codes

We develop the theory of a generalization of the notion ofBCH-code to additive codes, which are not necessarily linear. The usefulness of this notion is demonstrated by constructing a large number of record-breaking linear codes via concatenation. © 1997 John Wiley & Sons, Inc. J Combin Designs 5: 377–389, 1997     

虚级联在数字包封技术中的应用

介绍了光传送网数字包封技术中虚级联概念、所用的虚级联容器，详细分析了常用的客户信号的虚级联映射方法。     

以太网交换机集群管理的设计与实现

随着以太网交换机在网络中应用规模的不断扩大,对以太网交换机的有效管理成为一个重要的研究课题。交换机集群管理技术的出现为这一问题提出了一个较好的解决方案。文章在国内起草的《以太网交换机集群管理技术规范》的基础上,重点介绍集群管理的设计与实现,结合实际工作中遇到的问题探讨了集群管理策略。