WDM疏导网络中基于光路的动态恢复

针对波分复用(WDM)网络中单链路出错的生存性流量疏导问题,文章提出了一种基于光路的动态恢复机制(DRAL).DRAL不预留任何资源,当链路出错时,通过在网络中动态地发现资源来对错误链路进行恢复,将一个出错的光路转发到一条新建立的光路或其他可用的光路上.仿真结果显示,DRAL拥有很高的恢复概率.     

WDM光网络中基于链路的动态组播共享保护算法

针对WDM光网络中单链路失效的情况,提出了一种基于链路的保护动态组播业务的优化共享保护算法(Link-based optimized shared-protection algorithm for multicast sessions,LB-OSPM).该算法在对工作树任意光纤链路失效情况寻找保护路径时,允许组播内不同保护路径共享预留波长资源,同时通过引入预留波长使用情况矩阵和波长预留矩阵记录预留波长资源的使用情况,实现了不发生冲突的不同组播的保护链路间共享预留波长资源.研究采用欧洲光网络(European Optical Network,EON)的拓扑对不同波长资源配置和网络负载情况下LB-OSPM算法的网络连接阻塞率做了仿真.结果表明,通过引入共享机制,LB-OSPM算法在对单链路失效保证100％恢复率的同时可以获得更低的连接阻塞率,提高了波长资源利用效率.     

一种用於空间光通信系统的FSOP及应用

提出一种可用于空间光通信系统的通信协议(FSOP)。该协议在光路的物理连接之上建立一种可进行数据传输的逻辑链路,该链路具有数据实时备份、出错即时恢复等机制以保证传输数据的安全与可靠。本文提供的通信协议可以弥补空间光通信系统的通信质量易受外部环境影响而容易出错的不足,使光通信系统真正具有和光纤可相比较的传输稳定性和可靠性。同时可用於具有移动平台之光通信系统上。     

一种高效的无线Ad-Hoc网络自适应资源管理技术研究

本文针对无线Ad Hoc网络的高度动态性、网络拓扑动态变化、链路不稳定等问题,提出了一种无线网络资源管理技术.该技术通过探测邻居节点,然后无线资源进行动态划分设置请求优先级从而建立动态划分资源优先级机制.实验表明,提出的方法能够快速进行查询,有效提高了Ad-Hoc网络中资源发现的性能和系统的稳定性,在时延方面也有一定的提高.     

业务量疏导WDM网状网中的动态子通路保护算法

该文研究了业务量疏导WDM网状网中的生存性问题,提出一种自适应子通路保护(ASPP)算法。该算法根据网络当前状态以及到达业务连接请求的带宽要求动态调整链路权值;在此基础上选择一条最短路作为工作通路,然后将该通路分为互不重叠的n段子通路(每段经过的链路数为m),并分别找出各自的保护通路。仿真结果表明:ASPP既可以保证业务连接的可靠性要求,同时又允许网络管理者根据一定优化策略调整m值,从而可以在资源利用率和恢复时间之间进行折中。     

一种基于动态规划的间断连接 无线互联网络选路算法

 在无线互联网络中,由于自然干扰或网络规划的需要,节点之间无线链路通常在时间上具有间断特性.我们将链路具有间断特性的无线互联网络称为间断连接无线互联网络.间断连接无线网络的路由优化问题需要联合考虑无线链路的时间和空间特性,这就为间断连接无线互联网络的选路问题提出了新的挑战.本文为这种网络提出了一种全新的选路算法——DPRA算法,该算法在链路统计特性的基础上,采用动态规划的方法,以转发时延为选路标准进行路由的选择.仿真结果表明,本文提出的算法可以有效得到间断连接无线互联网络中时延最短的路径.     

网状WDM网中多播业务的共享保护设计

研究网状波分复用(WDM)光网络中动态多播业务的保护方案,提出一种共享保护和重配置(SPR)算法.该算法根据网络状态动态调整链路代价,为每个多播业务请求建立最小代价工作树,并为光树上互不重叠的工作段提供链路分离的保护段.当网络中发生链路失效时,进行业务段保护切换和局部资源重配置.仿真表明,该算法可以合理共享波长资源、平衡网络负载,有效保护WDM网中任意单链路失效,并在多链路失效情况下大大提高业务恢复能力.     

基于DRAC的分组业务传输策略

简单介绍一种用于上行FDD的分组业务传输机制———动态资源分配控制策略(DRAC),主要讨论DRAC的原理、相关信令和数据传输过程。仿真表明,该策略有助于改善系统性能。     

城域光网络生存性的研究

从分析目前常用的网络保护和恢复方法出发,提出将路由算法引入到光网络保护中去:通过动态路由算法,网络动态计算源、宿节点间最佳工作路径.通过将虚连接引入面向连接的光网络,建立保护路径.在消除为工作路径预留独享资源的同时,简化了保护倒换流程,缩短了故障恢复时间,提高了网络资源利用率.     

WDM光网络中单链路失效的混合生存性算法研究

提出了一种新的动态混合生存性(Dynamic Hybrid Survivability,DHS)算法.在DHS算法中,不同优先级的连接请求采取了不同的抗毁策略.DHS算法对到来的连接请求,能够根据网络当前的状态动态调整链路权值,计算相应的工作路径/保护路径,从而在整个网络中起到平衡负载的作用.计算机仿真表明DHS算法具有较优的网络性能.     

一种基于ASON的新型动态恢复路径建链协议

讨论了动态波长路由光网络的恢复路径提供问题，在联合可变权重路由选择(JVWR)算法的基础上重点对恢复路径建立时延进行了分析，通过对恢复路径建立过程中的非物理资源相关因素的考虑，基于ASON控制平面的分布式信令协议提出了前向并行建链协议(FPLSP)。理论分析和仿真实验表明，该建链协议对于减少恢复路径链路建立时延具有明显的效果。     

Dynamic resource allocation schemes during handoff for mobilemultimedia wireless networks

User mobility management is one of the important components of mobile multimedia systems. In a cell-based network, a mobile should be able to seamlessly obtain transmission resources after handoff to a new base station. This is essential for both service continuity and quality of service assurance. In this paper, we present strategies for accommodating continuous service to mobile users through estimating resource requirements of potential handoff connections. A diverse mix of heterogeneous traffic with diverse resource requirements is considered. The investigate static and dynamic resource allocation schemes. The dynamic scheme probabilistically estimates the potential number of connections that will be handed off from neighboring cells, for each class of traffic. The performance of these strategies in terms of connection blocking probabilities for handoff and local new connection requests are evaluated. The performance is also compared to a scheme previously proposed by Yu and Leung (see IEEE J. Select. Areas Commun., vol.15, p.1208-25, 1997). The results indicate that using dynamic estimation and allocation, we can significantly reduce the dropping probability for handoff connections     

Shared Sub-Path Protection Algorithm in Traffic-Grooming WDM Mesh Networks

In this paper, we investigate the problem of dynamically establishing dependable connections in wavelength division multiplexing (WDM) mesh networks with traffic-grooming capabilities. We first develop a new wavelength-plane graph (WPG) to represent the current state of the network. We then propose a dynamic shared sub-path protection (SSPP) scheme based on this WPG. To establish a dependable connection, SSPP first searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. If two sub-paths in SSPP are fiber-disjoint then their backup paths can share backup resources to obtain optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between resource utilization and restoration time.     

WDM疏导网络的共享子通路保护算法

研究了WDM疏导网络中的生存性问题,提出一种支持多粒度业务的共享子通路保护算法(GSSP)。GSSP首先根据网络当前状态动态调整链路权值,在此基础上选择一条最短路作为工作通路;然后将该通路分为互不重叠的等长子通路,分别找出它们的保护通路,并且允许共享保护资源。GSSP可以保证业务连接的可靠性,又允许网络管理者根据不同的优化策略调整子通路长度,可以在恢复时间和资源利用率之间进行折中。最后对GSSP进行了仿真研究,给出了仿真结果。     

A Novel Probability-Based Handoff Strategy for Multimedia LEO Satellite Communications

A novel bandwidth allocation strategy and a connection admission control technique arc proposed to improve the utilization of network resource and provide the network with better quality of service （QoS） guarantees in multimedia low earth orbit （LEO） satellite networks. Our connection admission control scheme, we call the probability based dynamic channel reservation strategy （PDR）, dynamically reserves bandwidth for real-time services based on their handoff probability. And the reserved bandwidth for real-time handoff connection can also be used by new connections under a certain probability determined by the mobility characteristics and bandwidth usage of the system. Simulation results show that our scheme not only lowers the call dropping probability （CDP） for Class I real-time service but also maintains the call blocking probability （CBP） to certain degree. Consequently, the scheme can offer very low CDP for rcal-time connections while keeping resource utilization high.     

Hybrid survivability approaches for optical WDM mesh networks

This paper studies the problem of providing recovery from link failures in optical wavelength division multiplexing (WDM) networks. One of the widely studied mechanisms is dynamic link restoration, which provides recovery by determining restoration paths around a link after a failure occurs. This mechanism leads to a lower backup resource utilization, fast failure signaling rate, and a scalable operation. However, one of the main drawbacks of uncoordinated dynamic restoration is the inability to provide a 100% recovery for all connections, especially at high network loads. An alternate solution is proactive protection, where backup capacity is reserved during connection setup that can guarantee recovery under certain conditions (e.g., single link failures) but requires higher backup capacity and has low spare capacity utilization when failures do not occur. This paper presents two hybrid survivability approaches that combine the positive effects of restoration and protection. The proposed algorithms make use of available or collected network state information, such as link load, to identify critical links or segments in the network that are then proactively protected. The overall goal of the proposed approaches is to improve the restoration efficiency by providing a tradeoff between proactive protection and dynamic restoration. This paper presents a detailed performance analysis of the proposed algorithms. Experimental results show that under high loads, both the proposed approaches maintain a consistent restoration efficiency of at least 10%, or higher, when compared to the basic restoration scheme.     

Dynamic connection rerouting and wired‐resource reservation scheme on ATM‐based PCN

In this paper, we propose a connection rerouting and dynamic resource reservation scheme for fast inter-switch handoffs on ATM-based personal communications networks. The proposed rerouting and reservation scheme can reduce the delay in connection rerouting by reserving VPI/VCIs for possible inter-switch handoff calls in advance. It also improves the utilization of wired resources by reserving statistically the wired resources in separate ways according to the classes (i.e., real-time vs. non-real-time traffic) of possible inter-switch handoff calls. Our simulation results show that the proposed scheme can decrease the dropping rate of inter-switch handoff calls without the sacrifice of the blocking probability of new calls and, moreover, can flexibly cope with the time-variant environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

A generalized protection framework using a new link-State availability model for reliable optical networks

This paper investigates a generalized protection framework for availability-guaranteed connection provisioning in an optical wavelength-division-multiplexed (WDM) network. Reliability is a crucial concern in high-speed optical networks. A service level agreement (SLA), which mandates high service availability even in the face of network failures must be met in provisioning a reliable connection. In this study, a new link-state-modeling mechanism is developed to form a dynamic link-state parameter called link and resource availability (LRA), which represents physical-layer availability and resource status for an optical link. Such up-to-date link-state information can be used by a standard link-state routing protocol to efficiently provision reliable connections. Based on the link-state availability model, LRA, a connection-provisioning algorithm is then proposed which can guarantee customers' availability requirements. A new generalized protection model is developed through dynamic LRA-based provisioning. Numerical results demonstrate the performance of the proposed provisioning approach to be promising.     

Survivable traffic grooming with non‐service‐interruptive wavelength retuning in a WDM mesh network

This paper proposes a new survivable traffic grooming wavelength retuning (STGWR) scheme in an all‐optical wavelength division multiplexing (WDM) network. In a dynamic WDM network, a connection may require a bandwidth less than a wavelength capacity. In addition, a connection should be protected against any network failures. Survivable traffic grooming (STG) can protect connections at subwavelength granularities. Wavelength retuning is a promising approach in an all‐optical WDM network, where a signal must remain on the same wavelength from its source to the destination, to alleviate the wavelength continuity constraint and reduce the connection blocking probability. Although both STG and wavelength retuning have attracted extensive research attentions nowadays, no effort has been made to combine these two promising approaches in one network. In this paper, we propose a wavelength retuning scheme with no service interruption in an all‐optical network with STG capability. The scheme allocates two routes, one for the active path and other for the backup path, in a shared mesh restoration manner to each incoming connection request and conducts wavelength retuning only on the backup path. Both wavelength retuning and mesh protection are done at the connection level instead of at the lightpath level. The simulation results of the proposed schemes are also presented. Copyright © 2008 John Wiley & Sons, Ltd.     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.