Group-based spectrum assignment in dynamic flex-grid optical networks

Traditional wavelength switched optical network employing wavelength-division-multiplexing (WDM) technology, allocates constant spectrum band to different kinds of services, which lacks flexibility in spectrum provisioning and thus reduces the resource utilization efficiency. Flex-grid technology, which introduces a finer spectrum granularity and allocates spectrum to different services flexibly according to their required bandwidth, is considered a promising candidate solution to improve the resource utilization efficiency of an optical network. However, since multiple contiguous spectrum granularities are usually assigned to a single service in such flex-grid optical network, the spectrum continuity and contiguity constraints should always be guaranteed, which may induce spectrum fragmentation. With the accumulation of spectrum fragmentation, available spectrum resources decrease, and this will greatly worsen the performance of the whole network, especially in networking. Therefore, spectrum fragmentation is considered a serious problem in flex-grid optical networks and many schemes have been proposed to solve it. These existing schemes, known as defragmentation, can reduce spectrum fragmentation either by rerouting the lightpath or by reallocating the spectrum for a service, which re-optimizes the spectrum resources. However, in the rerouting or reallocation procedure, existing traffic may be disrupted or extra resources, such as alternative spectrum or expensive spectrum convertors, are needed. None of these schemes can solve spectrum fragmentation with both no disrupted traffic and extra resources. It is because all these schemes utilize remedial methods to solve fragmentation problem and either disrupted traffic or extra resources are the cost when they cope with the defragmented spectrum. Different from all the above schemes, we propose a precautionary method to solve fragmentation problem in this paper. By introducing group-based spectrum assignment algorithm into flex-grid optical networks, spectrum resources are sorted into groups and each spectrum group only accommodates one specific kind of services. Since released spectrum can always be reused by the services of the same kind, spectrum fragmentation is prevented from its generation. Simulation results demonstrate that the proposed algorithm induces no spectrum fragmentations and is suitable to accommodate high-speed services.     

PCE-based routing and spectrum assignment in OFDM-based bandwidth-variable optical networks

Bandwidth-variable optical networks can not only provide bandwidth-flexible lightpaths,but also complete high capacity all-optical switching,and improve the spectrum efficiency.However,for the spectrum...     

Spectrum defragmentation in flexgrid optical networks using a genetic algorithm

Flexgrid optical networking is an attractive solution for efficiently matching allocated bandwidth with link demand but suffers from inevitable spectrum fragmentation. Spectrum fragmentation impairs network performance and results in high blocking rate and low spectrum utilization efficiency. Therefore, an optimization mechanism handling spectrum fragmentation is of vital importance in flexgrid optical networks. In this paper, we propose a genetic algorithm for solving the spectrum fragmentation problem with the objective of compacting occupation of the spectrum in flexgrid optical networks. A string of lightpaths are coded as the chromosome. The spectrum fusion degree and fragment fusion degree are introduced as the fitness functions to conduct the evolution in genetic algorithm, which can also be used to assess the degree of spectrum fragmentation in the network. As a result, the genetic algorithm provides a lightpath reconfiguration map, which identifies the candidate lightpaths to be reallocated, their reconfiguration sequence, and new locations. The proposed algorithm is compared with commonly used approaches under different network conditions. Simulation results demonstrate the ability of the proposed algorithm to efficiently solve the problem of spectrum defragmentation in flexgrid optical networks. Copyright © 2013 John Wiley & Sons, Ltd.     

Joint optimization method of failure probability and fiber-link load balancing in flexible bandwidth optical network

In order to gain insight into the relationship between the failure probability and the spectrum efficiency,both failure probability (FP) and load balancing (LB) were attempted to minimize in flexible bandwidth optical networks.An optimized FP-LB algorithm was developed to reduce failure probability and to improve the spectrum efficiency,and a traditional algorithm was further introduced for comparison in flexible bandwidth optical networks.Simulation results show that the optimized FP-LB algorithm reduces 69.8% blocking probability,45.3% spectrum occupancy rate,and 41.9% average failure probability compared to the traditional algorithm.Obviously,the optimized FP-LB algorithm achieves the joint optimization of both failure probability and load balancing.     

Time-sensitive software-defined networking (Ts-SDN) control architecture for flexi-grid optical networks with data center application

Data center interconnected by flexi-grid optical networks is a promising scenario to meet the high burstiness and high bandwidth requirement of data center application, because flexi-grid optical networks can allocate spectral resources for applications in a dynamic, tunable and efficient control manner. Meanwhile, as centralized control architecture, the software-defined networking (SDN) enabled by OpenFlow protocol can provide maximum flexibility for the networks and make a unified control over various resources for the joint optimization of data center and network resources. Time factor is firstly introduced into SDN-based control architecture for flexi-grid optical networks supporting data center application. A traffic model considering time factor is proposed, and a requirement parameter, i.e., bandwidth-period product is adopted for the service requirement measurement. Then, time-sensitive software-defined networking (Ts-SDN)-based control architecture is designed with OpenFlow protocol extension. A novel deadline-driven PCE algorithm is proposed for the deadline-driven service under Ts-SDN-based control architecture, which can complete data center selection, path computation and bandwidth resource allocation. Finally, simulation results shows that our proposed Ts-SDN control architecture and deadline-driven PCE algorithm can improve the application and network performance to a large extent in blocking probability.     

LTE和LTE-Advanced系统中CPRI压缩算法研究

移动互联网新业务促使原有多层分级式通信网络向更扁平化的方向发展,互联互通的网络架构需要增加巨大光纤资源投入。为减少和控制光纤资源消耗,文章提出一种适用于LTE系统的低延时基带信号压缩算法,算法首先通过冗余频谱消除,减少了信号传输占用带宽,然后利用自适应动态范围控制以及分块非线性量化降低单位采样点比特位宽。该算法降低了总传输数据量,从而降低光纤资源的消耗。文中给出了该算法性能仿真分析和实验室系统验证结果。     

弹性光网络中结合预测的多维感知RSA算法

弹性光网络(EON)中的传统路由频谱分配(RSA)算法多考虑路由跳数或频谱资源占用情况,缺乏时域与相邻链路的信息有效利用.提出一种结合预测的多维感知RSA算法,对持续时间已知业务的历史时间信息通过后向传播神经网络预测未来业务的时间信息,在路由时综合考虑时间、频谱和相邻链路资源占用程度.仿真结果表明:与传统RSA算法相比...     

Hop distance–based bandwidth allocation technique for elastic optical networks

Elastic optical networks (EON) have emerged as a solution to the growing needs of the future internet, by allowing for greater flexibility, spectrum efficiency, and scalability, when compared to WDM solutions. EONs achieve those improvements through finer spectrum allocation granularity. However, due to the continuity and contiguity constrains, distant connections that are routed through multiple hops suffer from increased bandwidth blocking probability (BBP), while more direct connections are easier to form. This paper proposes HopWindows, a novel method that strategically allocates bandwidth to connections based on their hop distance. This new algorithm applies masks that control the range of frequency slots (FSs) allocated to each n‐hop connection. Furthermore, a new network metric is introduced, the normalized bandwidth blocking probability (normalized BBP). Utilization of this metric ensures increased fairness to distant connections. Extended simulation results are presented which indicate that the proposed HopWindows method achieves a superior performance over the well‐known FirstFit algorithm. The proposed algorithm may achieve a decrease in bandwidth blocking probability of up to 50%.     

混合复用无源光网络中带有灰色预测的高效动态资源分配策略

针对混合复用无源光网络的用户接入距离增大,使得往返时延增加,造成网络中闲置时间增多,进而引起带宽浪费的问题,该文提出一种带有灰色预测的高效动态混合资源分配策略。通过对闲置时间内到达的数据进行灰色预测,动态确立光网络单元的带宽分配策略,以减小网络时延;利用波长结束时间的差异性,周期性地实时调整各波长的数据传输顺序,实现波长的高效利用和负载均衡。仿真结果表明,该动态资源分配策略有效地消除闲置时间的影响,且波长得到高效地利用,提高了带宽利用率的同时减少网络时延。     

Multicast service protection algorithm based on elastic optical network

With the rapid growth of the network traffic,the elastic optical network (EON) has been proposed as a promising solution due to its high spectrum efficiency and flexible bandwidth provision.Meanwhile,multicast routing and spectrum allocation,and the survivability of the network become more challenging than that in the conventional optical network.The routing for multicast traffic and its protection algorithm in EON was investigated.An integer linear programming (ILP) formulation with the objective to minimize total spectrum consumption was presented.In addition,a heuristic algorithm called multicast sub-tree protection algorithm (MSPA) to achieve sufficient protection and satisfy resources savings was designed.The simulation results demonstrate that comparing with the traditional multicast routing and protection algorithm,MSPA performs well in improving the blocking probability and the spectrum utilization of the network.     

An adaptive inter-domain PCE framework to improve resource utilization and reduce inter-domain signaling

Upcoming broadband commercial and scientific applications are now demanding high bandwidth pipes across multiple domains with guaranteed Quality of Service (QoS). Recent research initiatives such as the Path Computation Element (PCE) framework are focusing on the development of scalable multi-domain QoS provisioning frameworks, especially within the emerging carrier grade transport technologies based on layer-2 tunnels. QoS provisioning across multiple domains requires that QoS parameters for available transit paths inside a domain be advertised in the inter-domain routing algorithms, while the dynamic inter- and intra-domain connections vary the available resource, and hence require frequent inter-domain updates. The signaling load on the other hand hampers the scalability of the inter-domain routing mechanisms. We propose the use of an adaptive partitioning framework, which can effectively use network resources and at the same time stabilize the advertised domain topologies and thus path advertisements. Our method partitions network resources by pre-reserving resources for inter-domain transit traffic, and uses policies to modify the resource partitioning in order to maintain the available transit capacity between specified bounds. We show by simulations that the proposed mechanism can reduce inter-domain signaling load by 10%-20% and reduce overall blocking inside a domain by creating a trade-off between available resources for intra-domain connections and inter-domain transit connections. The reduction in inter-domain signaling and blocking can be used as a building block to design scalable QoS routing systems for carrier grade transport networks.     

Optical resources provisioning: multipoint‐to‐point lightpaths mapping in all‐optical networks

In wavelength‐division multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming low‐speed connections onto high‐capacity lightpaths will improve the network throughput and reduce the network cost. In this paper, we propose and evaluate a new concept of traffic aggregation in WDM mesh networks that aims to eliminate both the bandwidth under‐utilization and scalability concerns that are typical in all‐optical wavelength routed networks. This approach relies on the multipoint‐to‐point lightpath concept. In order to assess the efficiency of our proposal, all underlying network costs are compared. To achieve this aim, we devise a new provisioning algorithm to map the multipoint‐to‐point lightpaths in the network. Our results show that the proposed aggregation technique can significantly improve the network throughput while reducing its cost. Copyright © 2005 John Wiley & Sons, Ltd.     

A spectrum-efficient algorithm based on traffic splitting and merging transmission for anycast in inter-datacenter elastic optical networks

Anycast is attracting much attention due to the need of scalable and cost-effective data delivery in inter-datacenter elastic optical networks. However, spectrum fragmentation degrades network’s performance and decreases probability of successful anycast delivery significantly. When the idle spectrum block in elastic optical network is not enough to transmit the anycast request, spectrum splitting with multi-path transmitting the anycast is an effective approach to improve the spectrum fragmentation utilization. For improving spectrum utilization and reducing time delay between multiple paths, we propose a spectrum-efficient algorithm based on traffic splitting and merging (Anycast_SA_TSM) transmission to avoid spectrum fragmentation and delay between multiple paths. In order to minimize the time delay between multiple paths, we design a modified scheme to select the multiple paths with minimal time delay to transmit the anycast. During the spectrum allocation phase, a new spectrum block allocation scheme, the exact fit or fragmentation minimal, is put forward. Moreover, when an appropriate size of spectrum block is found for the split anycast request, merging split sub-requests to a single path is activated for minimizing the additional guard bands and improving the spectrum efficiency. Comparing with other two anycast algorithms, simulation results show that the proposed algorithm can get minimal time delay between split multiple paths, the minimal bandwidth blocking probability and the highest spectrum utilization.     

Power-aware virtual optical network provisioning in flexible bandwidth optical networks [Invited]

Considering the virtual network infrastructure as a service, optical network virtualization can facilitate the physical infrastructure sharing among different clients and applications that require optical network resources. Obviously, mapping multiple virtual network infrastructures onto the same physical network infrastructure is one of the greatest challenges related to optical network virtualization in flexible bandwidth optical networks. In order to efficiently address the virtual optical network (VON) provisioning problem, we can first obtain the virtual links’ order and the virtual nodes’ order based on their characteristics, such as the bandwidth requirement on virtual links and computing resources on virtual nodes. We then preconfigure the primary and backup paths for all node-pairs in the physical optical network, and the auxiliary graph is constructed by preconfiguring primary and backup paths. Two VON mapping approaches that include the power-aware virtual-links mapping (PVLM) approach and the power-aware virtual-nodes mapping (PVNM) approach are developed to reduce power consumption for a given set of VONs in flexible bandwidth optical networks with the distributed data centers. Simulation results show that our proposed PVLM approach can greatly reduce power consumption and save spectrum resources compared to the PVNM approach for the single-line rate and the mixed-line rate in flexible bandwidth optical networks with the distributed data centers.     

基于无色无向无冲突可重构光分插复用器节点的全光IP组播能效调度

为了提高无色无向无冲突灵活的可重构光分插复用器(CDC-F ROADM)节点的弹性光网络IP组播频谱-能耗效率,该文提出一种全光组播能效调度算法(AMEESA)。在算法路由阶段,考虑能耗和链路频谱资源使用情况设计链路代价函数,构建最小代价光树算法组播光树。在频谱分配阶段,设计基于高效光谱分辨率(HSR)光树中间节点频谱转换方法,选择节能频谱转换方案为组播光树分配频谱块资源。仿真分析表明,所提算法能有效提升网络能效,降低IP组播带宽阻塞率。     

Survivable routing,spectrum and waveband assignment strategy in cloud Optical and Data Center Network

These years, data centers are developing quickly and cloud Optical and Data Center Network (ODCN) has been shown to be the most viable solution for inter-data-center network implementation with less energy consumption and higher transmit rate. At the same time, elastic optical networks and waveband switching can address the problems caused by dramatic increase in network scale. In cloud hierarchical ODCN with flexible spectrum and waveband switching, survivability is an important and complex issue which is needed to be researched. So, we study the survivable routing, spectrum and waveband assignment strategy in cloud hierarchical ODCN, and in this paper, a novel hierarchical shared-protection (HSP) strategy is proposed. We consider spectrum fragmentation, waveband and shared-protection simultaneously. By quantifying the influence of spectrum assignment and the emergence of fragmentation, slots are assigned to the optimal paths. In order to share protection resource or wavebands, a heuristics algorithm named HSPGA is proposed for optimally picking out the two protection paths. Simulation results show that the proposed HSP strategy decreased the amount of employed ports significantly. In addition, the spectrum efficiency is improved.     

AOTF-NIR宽带功率超声换能器阻抗匹配网络的设计与优化

随着近红外声光可调滤波器（Near Infrared Acousto-Optic Tunable Filter,AOTF-NIR）光谱成像技术在深空探测的广泛应用,超声换能器作为AOTF-NIR核心部件,对其工作带宽、光谱衍射效率及功率效率提出了更高的要求.超声换能器在不同频率下具有不同的输入阻抗,当驱动信号源输出阻抗与换能器输入阻抗失配时将会产生能量损耗,导致无法把功率最大限度的传递给换能器,从而使AOTF-NIR光谱衍射效率降低,影响光谱灵敏度.该文通过射频电路先进设计系统（Advanced Design System,ADS）仿真及实验测试,运用滤波器网络理论,采用LC无耗储能元件设计了一种带通型宽带匹配网络.最终在60-120MHz带宽范围内阻抗匹配网络的回波损耗S₁₁>-29.8dB,阻抗匹配网络功率效率达到90%以上.通过不断地微调优化匹配阻抗值及LC参数值,以此来提高光谱衍射效率,使光谱衍射效率最高达90%以上,提高了在620-1150nm波段内的光谱灵敏度及光谱成像清晰度.     

弹性光网络中面向任播业务的节能路由算法

为提高数据中心间光互联网络的能效,面向任播业务提出一种具有业务持续时间感知的混合路径传输节能路由算法.为了减少新建光路和工作元器件数量,优先采用单路径传输;若业务阻塞则以传输能耗最小化为目标进行多路径传输.除此之外,引入基于频谱预留的业务疏导策略来降低保护带宽和光收发器的开销.仿真结果表明:与传统节能路由算法相比,所提算法在显著降低网络能耗的同时,有效避免了业务阻塞率的过度增加,实现了网络能耗与性能的平衡.     

弹性光网络双重故障下的自适应保护级别算法

为了降低弹性光网络中双链路故障保护下的业务及带宽阻塞率、均衡带宽资源分配,提出了一种双重故障下的自适应保护级别算法。该算法综合考虑传输距离、调制格式等因素,根据链路频谱资源使用状态动态地更新链路惩罚系数,选取最佳路径进行传输,同时根据请求类型及网络空闲资源状态自适应地选择保护方法,为业务提供最大限度的保护。仿真结果表明,在双链路故障下,算法在阻塞率方面取得了较好的性能,同时均衡了网络中各链路上的资源使用。     

Survivable spectrum-shared ability in flexible bandwidth optical networks with distributed data centers

The survivable spectrum-shared ability problems are addressed by considering the shared-path protection in flexible bandwidth optical networks with distributed data centers. The overall objective of this paper is to investigate the effect of the spectrum-shared ability on the spectrum efficiency and the blocking probability of cloud service requests. We propose a survivable algorithm with the spectrum-shared ability (SA_SSA) to minimize blocking probability of cloud service requests and to improve the spectrum efficiency in shared-path protection. For comparison, an existing shared-path protection algorithm named Aggressive algorithm with spectrum-shared ability is also introduced. Simulation results show that, considering the different spectrum-shared abilities, our proposed SA_SSA has a better performance in terms of blocking probability, number of frequency slots/Erlang, spectrum occupation ratio, and spectrum redundancy ratio compared to Aggressive algorithm in flexible bandwidth optical networks with distributed data centers. Meanwhile, the spectrum efficiencies of the SA_SSA and Aggressive algorithms improve as the spectrum-shared abilities are strengthened.