基于正交频分复用无源光网络的动态带宽分配算法研究

介绍了一种应用于未来大容量、多业务接入场景下的称为光正交频分复用无源光网络的下一代接入网技术,并提出了一种基于此结构的称为基于服务质量需求的固定周期流水线轮询动态带宽分配算法.该算法通过应用二级带宽分配机制、带宽预申请机制和最小带宽申请优先原则等方法,有效地保障了在大容量、多业务接入场景下各个业务不同的服务质量需求.为研究其性能,建立了该算法的仿真模型并进行了对比仿真.仿真结果显示该算法以低时延和低抖动有效地支持快速转发业务,同时平衡了确保转发业务和尽力而为业务之间的优先性和相对公平性,并且实现了不同光网络单元间的同优先级业务带宽分配的公平性.与传统的动态带宽分配算法算法相比,基于服务质量需求的固定周期流水线轮询动态带宽分配算法具有执行效率高、算法复杂度低、性能良好等优点,并且能够更好地适应光正交频分复用无源光网络的特性,发挥网络最大的性能.     

基于OFDM-PON的媒质接入控制协议设计

在以太网无源光网络帧结构的基础上,针对正交频分复用无源光网络的特点,提出了一种适用于正交频分复用无源光网络的媒质接入控制协议.对多点控制协议、控制消息的结构、业务优先级等进行了设计,提出了一种提供服务质量保障的特殊情况下区别用户服务等级的动态带宽分配算法.该算法引入两级调度的机制,将带宽资源的分配分为不同优先级业务的调度和同类型业务下不同等级的光网络单元调度.文章对提出协议的时延、丢包率、吞吐量等方面的性能进行了仿真,仿真结果显示提出的媒质接入控制协议很好地实现了对各业务的服务质量保障,符合多业务接入对服务质量等的需求.     

分组传送网中基于业务服务等级的带宽分配机制(英文)

分析了分组传送网络中现存几种带宽资源分配优化算法的优缺点,针对现有带宽资源分配机制无法很好地保证在不同等级业务带宽需求和实现不同业务公平性之间取得平衡的缺陷,提出了一种基于服务等级的带宽调整机制.通过分析基于MPLS-TP技术的分组传送网网络中存在的基本类型的流量,构建出不同类型业务流量所需带宽资源的数学模型.分析了在不同网络带宽资源情况下,基于不同类型流量的带宽资源分配问题,满足不同服务等级业务对带宽、时延、丢包等的不同要求;并着重分析了带宽实时调整机制下,新接入业务的带宽需求对网络中已有的不同服务等级业务占用带宽的影响.通过计算机仿真,表明该机制在保证高等级业务带宽需求的同时,实时调整低等级带宽业务的带宽,尽最大努力满足低等级业务的带宽需求,同时避免出现饿死现象,实现不同服务等级业务占用带宽的公平性.本机制可实现低丢包率,同时保证高等级业务的实时性.     

一种改进的EPON动态带宽分配算法

 在分析了现有带宽分配算法的基础上,结合已有算法的优缺点,提出一种新的区分业务等级的、保证服务质量的动态带宽分配算法。新算法动态确定轮询周期,分配给高优先级业务请求带宽,按权重对中、低优先级业务进行带宽分配,并考虑到了剩余带宽的再分配。经仿真验证：该方案充分保证了高优先级业务的带宽需求,考虑到了低等级业务可能分不到带宽的情况,体现了带宽分配的公平性,全面提高了上行带宽的利用率,提高了系统的服务质量保证。     

Mixed-Line-Rate IP over OTN网络中基于蚁群算法的路由和资源分配策略(英文)

混合线路速率场景下光传送网业务的路由和资源分配问题需要进行特定研究;根据网络的总代价更新蚁群的信息素表,对网络进行虚拓扑重构,由此实现基于蚁群算法的光网络路由和资源分配问题的启发式算法;并通过控制业务光路的时延来平衡网络的服务质量和成本.通过与k短路算法的仿真比较得出,对网络总代价而言,在不同的网络负载下,相对k短路算法,本算法拥有20%左右的性能优势;通过对不同线路速率及混合线路速率下的性能比较得出,本算法能很好地适应混合线路速率的场景并实现其优势,对解决混合线路速率场景下的光传送网业务路由和资源分配问题拥有良好的效果.     

IP/WDM网络的集成服务质量(QoS)控制方法

对IP/WDM网络的集成服务质量（QoS）控制技术问题做了研究, 给出了基于通用多协议标记交换（GMPLS）技术的业务差分处理模型, 设计了新的业务分类、光路分类以及层间映射/疏导/重构策略, 给出了具体的映射技术方案. 本方法具有三大特点：1）光电集成的差分服务模型; 2）多粒度多优先级业务的自适应资源管理机制; 3）支持电信级应用. 该模型较好地折中了多种类型业务的QoS控制复杂性和有效性, 具有较强的实用性和可扩展性, 能够解决光因特网络中支持多媒体业务传送的QoS问题.     

一维PSD瞬态响应特性的有限差分方法研究

基于有限差分方法,提出了一种新的PSD RC网络传输线模型模拟算法.利用该算法,得到了一维PSD在不同光信号激励下,从开始响应到进入稳态后的各个阶段的精确数值解.揭示了PSD电极对不同照射点的起始响应时间的差异正相关于光入射点与PSD几何中心之间的距离.在高速瞬态探测时,PSD器件参数限制了激励光脉冲信号的频率,其最高调制速率为1/(3.75Tc).模拟计算结果证明了PSD稳态位置响应结果与入射光类型和时间无关.     

基于FDLs的边缘汇聚节点的性能研究

随着全光接入网的不断发展,接入速率不断提高,对于边缘节点发送来的高速数据业务也必须进行流量梳理。为了适应未来全光高速网络接入的需求,基于光纤延迟线(Fiber delay lines,FDLs)结构,构造了一种简单高效的全光包交换网络边缘汇聚节点。并针对光线延迟线结构,提出一种新的主动缓存队列管理模型来分析节点性能,得到了与以往研究不同的结果。同时在对节点性能分析的基础上,提出一种新的FDLs的排列方式,在缓存深度相同的情况下,大大提高了FDLs的效率,实现了对到来的具有自相似性的数据业务的合理调配。     

基于高斯凸优化与光幕双约束的退化场景复原

针对雾霾和沙尘天气下的场景退化问题,提出一种基于高斯模型凸优化与光幕双约束的退化场景复原算法.首先根据景深与场景亮度和饱和度之间的相关关系,利用高斯模型和凸优化估计景深;其次通过对大气光幕与场景关系作深入分析,结合最小通道平滑和景深衰减双约束获得退化场景的大气光幕;然后通过亮通道先验以及局部大气光的改进求解获得大气光值;最后基于复原模型对退化场景进行复原处理,并对沙尘场景进行颜色修正,进而实现场景复原.实验结果表明,所提算法的复原场景亮度适宜,颜色自然,细节信息丰富,在定量指标中也可以取得理想的评分,有效解决退化场景出现的偏色和细节丢失等问题.     

基于马尔可夫决策模型的异构无线网络切换选择算法

针对异构环境下不同业务类型用户对于接入网络的不同服务质量(quality of service,Qo S)需求,该文提出了一种基于马尔可夫决策模型的切换选择算法.建立基于软件定义网络(software defined network,SDN)的异构无线网络架构,以实现对异构网络的通透控制.利用马尔可夫过程预测下一时刻的网络状态以得到采取动作后的一次回报,依据网络的不同状态属性针对实时用户和非实时用户分别构建立即回报函数,并采用层次分析法确定属性权重;基于状态动作对构建期望回报函数,采用逐次逼近的迭代方式得到使长期期望回报最大的切换策略.仿真结果表明,该方法针对不同业务类型用户均能选取最优切换策略,同时降低阻塞率,提高了用户的Qo S和无线网络的资源利用率.     

Cyclic polling-based dynamic wavelength and bandwidth allocation in wavelength division multiplexing passive optical networks

Cyclic polling-based dynamic wavelength and bandwidth allocation algorithm supporting differentiated classes of services in wavelength division multiplexing （WDM） passive optical networks （PONs） is proposed. In this algorithm, the optical line terminal （OLT） polls for optical network unit （ONU） requests to transmit data in a cyclic manner. Services are categorized into three classes： expedited forward （EF） priority, assured forwarding （AF） priority, and best effort （BE） priority. The OLT assigns bandwidth for different priorities with different strategies. Simulation results show that the proposed algorithm saves a lot of downstream bandwidth under low load and does not show the light-load penalty compared with the simultaneous and interleaved polling schemes.     

A Wavelength and Bandwidth Assignment Algorithm to Support Guaranteed Bandwidth Levels in Hybrid Time Division Multiplexing/Wavelength Division Multiplexing Ethernet Passive Optical Networks

Abstract

A novel bandwidth assignment algorithm in wavelength division multiplexing Ethernet passive optical networks, called a dynamic wavelength assignment service level agreement, is proposed to efficiently provide subscriber differentiation. Simulation results show that the dynamic wavelength assignment service level agreement outperforms other bandwidth allocation algorithms in wavelength division multiplexing Ethernet passive optical networks, as it makes a fairer bandwidth distribution than other methods and is able to overcome the non-allowed packet fragmentation of the Ethernet passive optical network standard. Consequently, it greatly increases the achieved throughput and always ensures a minimum guaranteed bandwidth to every priority subscriber. Furthermore, the new algorithm obtains lower mean packet delay and packet loss rate for the highest priority subscribers when compared with other bandwidth distribution schemes in wavelength division multiplexing Ethernet passive optical networks.     

OFDMA-based LAN emulation in long-reach hybrid PON system

A novel long-reach, hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) passive optical network (PON) architecture which supports local area network (LAN) emulation among customers is proposed. Orthogonal frequency division multiplexing access (OFDMA) technology is used in optical network units (ONUs) to transmit the LAN data. The optical LAN data from an ONU is converted into the electrical signal and combined with TDM downstream access data in the extended box for delivery to other ONUs. This scheme has many advantages on LAN emulation, such as dynamic allocation of LAN bandwidth, no bandwidth cost of TDM business, supporting multiple concurrent LAN services and so on. Simulations are performed to verify the scheme. Tolerance of dispersion and factors that influence the performance of various independent services are all investigated and analyzed.     

Four-dimensional scheduling for uplink dynamic bandwidth allocation in OFDM-PON

Orthogonal frequency division multiplexing passive optical network (OFDM-PON) has been considered a promising access solution to meet the variable bandwidth demand. In this paper, a novel scheduling for dynamic bandwidth allocation (DBA) at medium access control (MAC) layer is proposed for uplink transmission of OFDM-PON. In order to utilize the bandwidth efficiently, scheduling in four dimensions is adopted in the proposed DBA algorithm. Four dimensions stand for frequency domains, time domains, modulation formats and power allocations. The algorithm is quite flexible. Simulation results and analysis show that the proposed algorithm can efficiently utilize the OFDM bandwidth and make the system highly energy-efficient.     

Adaptive dynamic bandwidth allocation algorithm supporting multi-services over Ethernet passive optical networks

In order to ensure fairness of each optical networks unit (ONU) in access network and meet quality of service (QoS) requirements of differentiated service such as voice, video and data, Ethernet passive optical network (EPON) dynamic bandwidth allocation (DBA) algorithm should avoid light load penalty, choose different scheduling scheme according to light loading or heavy loading circumstances, adaptively adjust the order of ONUs at the case heavy loading in order to guarantee QoS. Aiming at this problem, an adaptive dynamic bandwidth allocation algorithm supporting multi-services is presented. The algorithm guarantees QoS through dividing service into voice, video and data putting them into different queues, optical line terminal (OLT) collects all requests of different services from different ONUs, divides the adopted scheduling scheme according to loading, adaptively adjusts the order of ONUs queue based on minimum delay at the case heavy load. Therefore, it can really guarantee QoS. Simulation results of the algorithm show that the algorithm not only can support multi-service and avoid light load penalty, but also can guarantee the fairness of each ONUs and QoS. It has a better performance than other algorithms particularly at the case of heavy loading.     

Enhanced performance for 10 Gb/s long reach RSOA based WDM-PON by using power pre-emphasized OFDM signal

An extended reach 10 Gb/s wavelength division multiplexing passive optical networks (WDM-PONs) system based on reflective semiconductor optical amplifier (RSOA) is proposed by using power pre-emphasized orthogonal frequency division multiplexing (OFDM) signal. Experimental results show that the proposed technique can effectively enhance the system performance against the limited bandwidth and chirp induced fading effect from direct modulation of RSOA. The receiver sensitivity is improved by 5 dB at the limit of BER for forward error correction (FEC) code over the 60 km and 85 km fiber transmission without any dispersion compensation module.     

A bandwidth-efficient channel allocation scheme for mitigating FWM in ultra-dense WDM-PON

In this paper, we investigate four-wave mixing (FWM) effects in the ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) system and propose an efficient channel allocation scheme to mitigate the FWM impact. This scheme is formed by grouping signal channels into several blocks with different channel spacing. Through numerical analysis and simulations, our proposed scheme is verified to be able to reduce the FWM effects and have higher bandwidth efficiency than the traditional unequal channel allocation scheme. The simulation results also demonstrate that our proposed scheme can achieve nearly 4 dB increases in optical power budget of the UDWDM-PON systems at the BER of 1e−3, in comparison with the equal spaced channel scheme.     

A Survivable Wavelength Division Multiplexing Passive Optical Network with Both Point-to-Point Service and Broadcast Service Delivery

Abstract

A survivable wavelength division multiplexing passive optical network enabling both point-to-point service and broadcast service is presented and demonstrated. This architecture provides an automatic traffic recovery against feeder and distribution fiber link failure, respectively. In addition, it also simplifies the protection design for multiple services transmission in wavelength division multiplexing passive optical networks.