软件定义卫星光网络蚁群优化波长路由技术

针对卫星光网络中网络拓扑动态时变和业务类型多样化的问题,研究了在软件定义网络架构下保障服务质量的路由技术,提出了一种基于多业务的卫星光网络蚁群优化波长路由算法。通过改进蚁群算法的启发函数,将波长空闲率、时延、时延抖动、丢包率作为蚂蚁选路的重要依据,为业务选择了满足多种服务质量的最优路径;采用分组波长分配方法对不同等级的业务进行了区分服务,为不同业务分配了不同的波长集。仿真结果表明:与CL-ACRWA算法和Dijkstra算法相比,降低了卫星光网络的平均时延、平均时延抖动、平均丢包率,提高了波长利用率,同时也降低了高优先级业务的网络拥塞概率。     

优先级调度在交换式工业以太网中的应用研究

针对交换式以太网用于工业实时通信时不能确保数据按时送达问题,在通信站点和交换机端引入IEEE802.1p优先级服务机制,通过设置实时优先级字段来区分其不同的紧急程度的实时数据帧,并采用非抢占式固定优先级调度算法改善实时数据帧的传输时延.通过将调度分析法和网络演算法相结合,提出了一种混合的实时数据帧传输时延上界计算方法.比较研究表明该方法得到的结果比网络演算法更准确.     

ASON网络环境下面向业务的RWA问题研究

从下一代光网络的业务需求出发,研究了在自动交换光网络(ASON)架构下面向业务的路由与波长分配(RWA)问题,提出了适应光网络向业务网络演进环境下面向业务的RWA概念,并分别就选路和波长分配问题进行了初步的探讨;面向业务的网络环境要求能为业务提供区分服务,以提供区分服务为目的对基于优先级的RWA算法进行了研究,并提出了面向区分业务的RWA实现框图.     

自适应混合光交换

当前的混合光交换只是简单地把光电路交换和光突发交换叠加在一起,其复杂度高.并且不能有效支持突发性强的业务.针对这种缺陷,本文提出了一种自适应混合光交换方式.自适应混合光交换的入口边缘节点监测一对入口边缘节点和出口边缘节点之间的业务流量的大小,自适应地调整光交换方式.在最小突发长度最大汇聚时间算法的基础上,提出了自适应混合光交换的汇聚算法,以提高光路的利用率和有效支持突发性强的业务.同时提出了数据信道调度算法,它能统一为光路和数据突发预留资源,并降低了混合光交换的复杂度,提高了网络性能.仿真结果表明,与光突发交换相比,自适应光交换能有效降低IP包丢失率和端对端时延.     

提供区分服务的可抢占信道调度算法

在OBS网络LAUC-VF信道调度算法的基础上,提出了一种新的能够提供区分服务的可抢占武信道调度算法,它既保证了高优先级业务的低延迟传输,也使低优先级的业务能与高优先级业务共享信道资源,从而改善了OBS网络的QoS特性.     

基于并行排队策略的天基光网络接入选择算法

针对卫星光网络接入选择算法不够灵活高效的问 题,研究了天基光网络中基于并行排队策略(PQS,parallel queuing strategy)的 动态在线式接入选择算法。分析接入选择问题的约束条件并建立数学模型,在 排队模型的基础上增加动 态优先级策略dps(dynamic priority strategy),实现不同优先级任务的区分服务;通过引 入时间敏感因子实现对不同优先级任务等待 时延区分度的调节,避免低优先级任务一直被高优先级任务抢占的问题;通过增加PQS使调 度 方案得到全局优化,缩短任务等待时延。仿真结果表明,本文算法将等待时延降低 30%左右,有效提升了接入调度的灵活和高效性。     

一种光交换核心节点调度算法研究

光交换核心节点是光交换网络的核心设备,其性能的优劣直接影响网络的吞吐量、时延等重要指标。文章提出一种SWC-MSD(基于波长变换器的多播空分交换)模块的严格无阻塞光交换核心节点,在此基础上提出了三种调度算法,通过数学分析和实验仿真验证了算法的正确性。考察了这种核心节点在有无波长变换以及业务优先级不同的场景下阻塞率的变化情况,结果表明所提出的严格无阻塞光交换核心节点具有较低的阻塞率。     

两种新型的OBS网络数据信道调度算法

光突发交换(OBS)是实现IP/DWDM网络的一种极有前途的方案。该文提出了两种新型的OBS网络数据信道调度算法:最少波长转换(MWCT)调度算法和区分服务(SD)调度算法。通过仿真,证明了这两种算法在减少OBS网络中的光信号的波长转换和保证高优先级数据可靠传输方面比已有的FF和LAUC调度算法具有更好的性能。     

基于优先级的OBS核心节点性能研究

设计了基于业务优先级的光突发交换核心节点模型,采用多级光纤延迟线的光缓存来提高交换网络的性能.交换节点在4个端口8条波长(4×8核心交换结构)的情况下,当光纤延迟线基本延迟单元为50μs、级数为8,负载为0.8时,丢包率小于0.01;为了满足不同业务服务质量的要求,将数据包按优先级划分,采用基于优先级的插空算法(VFPP),在相同缓存配置条件下使高优先级数据的丢包率降低到以下,在高负载下平均时延小于不区分优先级的情况.     

光突发交换网络中信道调度的PBR-VF算法

光突发交换网络中,数据信道的调度是一个关键问题.文章基于现有的信道资源调度算法,提出了基于优先级的可插空重新调度-PBR-VF(Priority-based Burst Rescheduling with Void Filling)算法,该算法采用LAUC-VF Plus作为子算法,并结合重新调度和优先级选择丢弃机制,能够充分利用信道空隙,对信道资源进行高效调度.仿真结果表明,该算法有效地提高了光突发交换网络的信道资源利用率,同时较好地提供了网络的QoS保证.     

Traffic scheduling in hybrid WDM–TDM PON with wavelength-reuse ONUs

Hybrid WDM?CTDM PON (wavelength division multiplexing?Ctime division multiplexing passive optical network) that applies wavelength-independent or colorless ONU (optical network unit) technologies will further reduce implementation and maintenance expenses. The ??wavelength-reuse?? colorless ONU technology imposes a physical constraint in the hybrid WDM?CTDM PON that the same wavelength is used for both upstream and downstream traffic transmission of an ONU. This physical constraint brings a new challenge to developing traffic scheduling algorithms in the network, as upstream traffic scheduling is no longer independent of downstream traffic scheduling and the existing traffic scheduling algorithms that treated the upstream and downstream traffic independently cannot be applied in this case. We propose a new traffic scheduling algorithm that takes both directions?? traffic scheduling into account at the same time. A logical PON concept is defined, and wavelength resource sharing is performed based on reconfiguring logical PONs. Simulation study on this algorithm is conducted, and results show that it achieves efficient wavelength and bandwidth resource sharing in the network.     

A Modified Dynamic Weighted Round Robin Cell Scheduling Algorithm

In this paper, we propose the modified dynamic weighted round robin (MDWRR) cell scheduling algorithm, which guarantees the delay property of real‐time traffic and also efficiently transmits non‐real‐time traffic. The proposed scheduling algorithm is a variation of the dynamic weighted round robin (DWRR) algorithm and guarantees the delay property of real‐time traffic by adding a cell transmission procedure based on delay priority. It also uses a threshold to prevent the cell loss of non‐real‐time traffic that is due to the cell transmission procedure based on delay priority. Though the MDWRR scheduling algorithm may be more complex than the conventional DWRR scheme, considering delay priority minimizes cell delay and decreases the required size of the temporary buffer. The results of our performance study show that the proposed scheduling algorithm has better performance than the conventional DWRR scheme because of the delay guarantee of real‐time traffic.     

The traveling miser problem

Various monitoring and performance evaluation tools generate considerable amount of low priority traffic. This information is not always needed in real time and often can be delayed by the network without hurting functionality. This paper proposes a new framework to handle this low priority, but resource consuming traffic in such a way that it incurs a minimal interference with the higher priority traffic. Consequently, this improves the network goodput. The key idea is allowing the network nodes to delay data by locally storing it. This can be done, for example, in the Active Network paradigm. In this paper we show that such a model can improve the network's goodput dramatically even if a very simple scheduling algorithm for intermediate parking is used. The parking imposes additional load on the intermediate nodes. To obtain minimal cost schedules we define an optimization problem called the traveling miser problem. We concentrate on the on-line version of the problem for a predefined route, and develop a number of enhanced scheduling strategies. We study their characteristics under different assumptions on the environment through a rigorous simulation study. We prove that if only one link can be congested, then our scheduling algorithm is O(log/sub 2/B) competitive, where B is congestion time, and is 3-competitive, if additional signaling is allowed.     

Dynamic Bandwidth Allocation Algorithms for Ethernet Passive Optical Networks with Threshold Reporting

In this paper we present a dynamic bandwidth allocation algorithm for Ethernet Passive Optical Networks (EPON), which makes use of the Multipoint Control Protocol (MPCP) with threshold reporting and with inter- and intra-ONU priority scheduling. Three varieties of this algorithm are compared under both symmetric and asymmetric traffic conditions, by means of a detailed simulation program, regarding average packet delay for several priorities, delay variation for constant bit rate (CBR) traffic and bandwidth utilization. Two types of intra-ONU priority scheduling algorithms are considered, being full and interval priority scheduling, called FPS and IPS, respectively. It is shown that by combining IPS with the threshold reporting mechanism one can achieve a nearly optimal bandwidth utilization (by avoiding nearly all fragmentation losses). IPS, however, causes an increased packet delay and delay variation for CBR traffic in comparison with FPS. In order to eliminate this drawback, we combine the IPS scheduling algorithm with a rate-based scheme for the highest priority (CBR) traffic. The combined IPSA algorithm provides an interesting trade-off between the efficiency, which is still near to the optimal, and the delay characteristics of time critical applications. Finally, we also demonstrate that unfairness arises with FPS under asymmetric traffic conditions, that is, ONUs with more best effort traffic are favored by FPS. Whereas asymmetric traffic conditions only slightly affect the fairness of IPS under low load conditions.     

Network queue scheduling algorithm based on self-similar traffic level grading prediction

Self-similarity characteristic of network traffic will lead to the continuous burstness of data in the network.In order to effectively reduce the queue delay and packet loss rate caused by network traffic burst,improve the transmission capacity of different priority services,and guarantee the service quality requirements,a queue scheduling algorithm P-DWRR based on the self-similarity of network traffic was proposed.A dynamic weight allocation method and a service quantum update method based on the self-similar traffic level grading prediction results were designed,and the service order of the queue according was determined to the service priority and queue waiting time,so as to reduce the queuing delay and packet loss rate.The simulation results show that the P-DWRR algorithm can reduce the queueing delay,delay jitter and packet loss rate on the basis of satisfying the different service priority requirements of the network,and its performance is better than that of DWRR and VDWRR.     

Adaptive envelope process and minimum service curve applied to resource block allocation in the LTE downlink

In this work, we propose a resource allocation algorithm for the LTE downlink that makes use of an adaptive multifractal envelope process and a minimum service curve. The proposed scheduling algorithm aims to improve some network parameters while guaranteeing a maximum delay to the user by considering the following information: backlog, channel condition and user traffic behavior. In order to estimate the maximum network delay, we propose an adaptive minimum service curve for the LTE network that can be used for admission control purposes in the resource allocation algorithm. The performance of the proposed scheduling algorithm is compared to those of several scheduling schemes known in the literature through computational simulations of the LTE downlink. In order to develop a new adaptive envelope process and to precisely describe network flows, we propose an adaptive algorithm to estimate the parameters of the Multifractal Wavelet Model (MWM). The proposed envelope process is compared to the main traffic model based envelope processes known in the literature. Simulations of the LTE downlink considering AMC (Adaptive Modulation and Coding) are carried out showing the efficiency of the proposed resource allocation approach that considers adaptive estimation of network traffic parameters.     

基于智能网络的租户服务质量保证技术

在多租户虚拟网络环境中,用户对于网络服务的多样性以及性能的稳定性需求并不会随着网络架构和运营模式的升级而削弱,用户需求之间的差异性和动态性对于不同切片间资源的分配和调度效率提出了新的挑战。针对多租户虚拟网络的特殊环境,首先提出了QVR(QoS-Virtual Routing)流量调度算法,同时将用户流量调度与网络虚拟资源分配看做一个联合优化问题,提出了面向多租户的流量调度算法以及适用于共享链路的动态带宽分配算法。该算法能够释放更多的物理网络资源,明显降低了租户网络的延时和拥塞。     

一种适用于W-CDMA系统的多业务无线资源调度算法

3G系统将以分组交换方式提供语音、数据、视频等具有不同QoS要求的多种业务，资源调度对保证系统服务质量和提高资源利用效率起关键作用．本文提出了一种基于业务类型、当前待发送负荷以及剩余延时限的时间调度策略和基于资源优化的资源调度策略，并使无线链路的传输质量与业务的优先级水平一致．通过系统仿真评价了算法的性能．     

基于模糊流感知的动态优先公平调度算法

为适应网络的动态性,提高调度公平性和资源效率,流感知优先公平调度机制需要动态的多业务区分转发。与链路负载状态相关的模糊流感知能够实现路径上的一致性业务区分,而基于模糊流感知的动态优先公平调度算法通过调整优先队列负载门限在流式流和弹性流之间实现转发优先权的动态交替,在链路轻载时实现不同流间的相对公平调度,在链路重载时则强调实时业务的绝对优先权以保证其时延要求。算法公平性分析和仿真计算显示提出算法的动态区分转发通过适度增加优先业务队长能够大幅度提高弹性流的接纳率,具有较高的链路平均吞吐量和资源效率。     

软件定义时分波分复用无源光网络中基于带宽预测的资源分配策略

针对时分波分复用无源光网络(TWDM-PON)多个光线路终端(OLT)间资源缺乏协同集中调度问题,该文提出一种带有软件定义的基于带宽预测的资源分配策略(RABP)。在光线路终端间,设计粒子群优化的BP神经网络模型预测各光线路终端所需带宽,避免了控制器与光线路终端信息交互时延对资源分配实时性的影响;其次,在光线路终端内,动态设定滑动周期并基于光网络单元授权信息实时统计资源池共享带宽,同时,设计负载均衡的波长调度机制实现多波长的高效利用。仿真结果表明,该策略提高了信道资源利用率,降低了平均包时延。