透明光网络中多损伤约束物理层模型

从透明光网络物理损伤的多样性和复杂性出发,分析了目前物理损伤感知光网络中物理层损伤因素考虑比较单一的问题.在此基础上提出了一种将多种物理损伤量化为沿光信号传播方向的OSNR衰减的物理层模型,该模型考虑了多种物理层损伤,因此可以更加精确的评估光路损伤情况,以帮助在选路时有效规避物理层损伤的影响.     

基于物理并适用于电路仿真的多晶硅薄膜晶体管薄层电荷模型

本文利用薄层电荷理论,建立了一个基于表面势的、物理的多晶硅薄膜晶体管(Polysilicon Thin-Film Transistors,poly-Si TFTs)的电流模型,且该模型适用于电路仿真.推导了 poly-Si TFTs 表面势的近似解法,该求解法非迭代的计算大大地提高了计算效率,且精确度高并得到实验验证.基于物理的迁移率方程考虑了晶界势垒高度,和由于声子散射与表面粗糙散射引起的迁移率退化.基于 Brews 的薄层电荷模型和上述非迭代计算表面势,本电流模型同时考虑了漏致势垒降低(DIBL)效应、kink 效应和沟道长度调制效应.对不同沟长的器件实验数据比较发现,提出的模型在很广的工作电压内与实验数据符合得非常好.同时本模型的所有方程都具有解析形式,电流方程光滑连续,适用于电路仿真器如 SPICE.     

4H-SiC MESFET直流Ⅰ-Ⅴ特性解析模型

提出了一种改进的4H-SiC MESFET非线性直流解析模型,基于栅下电荷的二维分布,对该模型进行了分析,采用多参数迁移率模型描述速场关系.在分析了电流速度饱和的基础上,考虑沟道长度调制效应对饱和区漏电流的影响,建立了基于物理的沟道长度调制效应模型,模拟结果符合高场下漏极的MC(蒙特卡罗)计算的结果.与以前的研究模型相比较,结果说明了该研究的有效性,饱和电流的结果与实测的Ⅰ-Ⅴ特性更加吻合.     

4H-SiC MESFET直流I-V特性解析模型

提出了一种改进的4H-SiC MESFET非线性直流解析模型,基于栅下电荷的二维分布,对该模型进行了分析,采用多参数迁移率模型描述速场关系.在分析了电流速度饱和的基础上,考虑沟道长度调制效应对饱和区漏电流的影响,建立了基于物理的沟道长度调制效应模型,模拟结果符合高场下漏极的MC(蒙特卡罗)计算的结果.与以前的研究模型相比较,结果说明了该研究的有效性,饱和电流的结果与实测的Ⅰ-Ⅴ特性更加吻合.     

TIGBT的稳态和瞬态模型

从沟槽绝缘栅双极晶体管(TIGBT)的物理结构出发,提出了TIGBT的稳态模型和瞬态模型.该模型不仅考虑了槽底电子积累层引起的基区电导调制作用增强效应,而且还考虑到缓冲层对器件性能的影响.通过与器件模拟结果的比较,表明该模型能准确地描述TIGBT稳态和瞬态时的物理特性.     

TIGBT的稳态和瞬态模型

从沟槽绝缘栅双极晶体管(TIGBT)的物理结构出发,提出了TIGBT的稳态模型和瞬态模型.该模型不仅考虑了槽底电子积累层引起的基区电导调制作用增强效应,而且还考虑到缓冲层对器件性能的影响.通过与器件模拟结果的比较,表明该模型能准确地描述TIGBT稳态和瞬态时的物理特性.     

InP/InGaAs HBT的频率特性分析

频率特性是异质结双极型晶体管(HBT)设计中应首先考虑的因素,而fT,fmax则是HBT最主要的频率性能指标.首先基于InP/InGaAs HBT器件的物理结构构建了小信号等效电路模型,对该模型进行了理论分析,随后基于提取的有效参数结果,对该等效电路模型的频率特性进行了详细的计算和仿真,分析了影响fT,fmax的一些主要因素,得出的结论对于InP/InGaAs HBT的设计制作和性能优化具有一定的指导作用.     

考虑气化温度动态变化的选择性光热解模型

提出了考虑组织气化温度动态变化的选择性光热解(SP)光热作用新模型,模型包括模拟激光能量在组织内分布规律的基于网格的三维Monte Carlo模拟方法,计算组织内温度分布的考虑组织热物性参数和气化温度动态变化的三维Pennes生物传热方程,以及计算组织热损伤程度的Arrhenius方程3个部分.研究表明,滞留水蒸气系数k对结果有很大影响.k=0,0.022,0.18和1时的动态气化温度SP模型的数值结果分别接近于恒定100℃气化温度SP模型、恒定110℃气化温度SP模型、恒定130℃气化温度SP模型和不考虑气化影响的SP模型.     

SiGe HBT传输电流模型研究

基于SiGe异质结双极晶体管(HBT)大信号等效电路模型,建立了SiGe HBT传输电流模型.重点考虑发射结能带的不连续对载流子输运产生的影响,通过求解流过发射结界面的载流子密度,建立了SiGe HBT传输电流模型.该模型物理意义清晰,拓扑结构简单.对该模型进行了模拟,模拟结果与文献报道的结果符合得较好.将该模型嵌入PSPICE软件中,实现了对SiGe HBT器件与电路的模拟分析,并对器件进行了直流分析,分析结果与文献报道的结果符合得较好.     

损伤感知的光网络连接指配的关键问题研究

在透明网络中,光信号由于受到物理损伤的影响而质量降低,这使得损伤感知的连接指配日益成为人们研究的热点.文章从架构、损伤模型和损伤感知的路由波长分配(IRWA)算法3方面研究了损伤感知的光网络连接指配的     

Benefits of the use of impairment constraint routing in optical networks

In transparent optical networks, the optical signal accumulates the effects of all physical impairments present along the path it traverses. The conventional selection of signal paths based on e.g. shortest path routing without considering the signal quality and its association with the physical impairments does not always provide the optimum solution in terms of network performance such as blocking and resource utilization. This paper proposes an impairment constraint based routing algorithm to achieve an optimal combination of physical and networking performance taking into account all physical linear impairments including noise, chromatic and polarization mode dispersion, crosstalk and filter concatenation effects in an integrated approach. The performance of a typical metropolitan area network is examined and the improvement achieved when using the proposed approach compared to the conventional shortest path routing is demonstrated.     

Multiple-Constraint-Aware RWA Algorithms Based on a Comprehensive Evaluation Model： Use in Wavelength-Switched Optical Networks

Because of explosive growth in Internet traffic and high complexity of heterogeneous networks,improving the routing and wavelength assignment (RWA) algorithm in underlying optical networks has become very important.Where there are multiple links between different the node pairs,a traditional wavelength-assignment algorithm may be invalid for a wavelength-switched optical networks (WSON) that has directional blocking constraints.Also,impairments in network nodes and subsequent degradation of optical signals may cause modulation failure in the optical network.In this paper,we propose an RWA algorithm based on a novel evaluation model for a WSON that has multiple constraints.The algorithm includes comprehensive evaluation model (CEM) and directional blocking constraint RWA based on CEM (DB-RWA).Diverse constraints are abstracted into various constraint conditions in order to better assign routing and wavelength.We propose using the novel CEM to optimize routing according to an assessed value of constraints on transmission performance.This eliminates the effects of physical transmission impairments in a WSON.DB-RWA based on CEM abstracts directional blocking conditions in multiple links between network nodes into directional blocking constraints.It also satisfies rigorous network specifications and provides flexibility,scalability,and first-fit rate for the backbone,especially in multiple links between WSON nodes.     

基于损伤感知的动态RWA算法性能比较研究

从光网络向透明架构的演进和面向业务的发展趋势出发,介绍了损伤感知的RWA问题的相关研究,通过给经典RWA算法增加对损伤效果的考虑,提出了具有损伤感知能力的动态RWA算法(IBest,IFF,IPack)并进行了仿真验证,结果表明在有损伤的环境下具有损伤感知能力的动态RWA算法既能保持经典算法的优势又在阻塞率上具有优于经典算法的性能。     

A distributed ant-based algorithm for routing and wavelength assignment in an optical burst switching flexible spectrum network with transmission impairments

This work describes a distributed algorithm inspired by ant colony optimisation for a solution to the problem of dynamic routing and wavelength assignment with wavelength continuity constraint in optical burst switched networks. The evaluation was conducted in a wavelength division multiplexed network environment with limited number of wavelength channels and in a flexible spectrum network environment undergoing transmission impairments. The simulations in the flexible spectrum network environment aim to replicate the effects of both linear and nonlinear physical layer impairments. Under these effects, an optical burst control packet could be lost during traversal of the network with no measure in place to notify the network of the loss or to free up optical resource reservations. The optical burst switching acknowledgement protocol has been modified in this work to account for a burst control packet failure by implementing a traversal acknowledgement to cater for its loss. The performance of the distributed ant-based algorithm has been extensively evaluated on several network topologies and compared with that obtained by shortest path routing and ant colony routing and wavelength assignment. The results show that the distributed ant-based algorithm significantly improves the burst transmission success probability in the wavelength division multiplexed network environment and provides a good solution in the flexible spectrum network environment undergoing transmission impairments.     

Adaptive Routing Strategies in IEEE 802.16 Multi-Hop Wireless Backhaul Networks Based On Evolutionary Game Theory

The high frequency segment (10-66GHz) of the IEEE 802.16 standard seems promising for the implementation of wireless backhaul networks carrying large volumes of Internet traffic. In contrast to wireline backbone networks, where channel errors seldom occur, routing decisions in IEEE 802.16 networks are conditioned by wireless channel impairments rather than by congestion, exclusively. This renders a cross-layer routing approach between the routing and the physical layers more appropriate during fading periods. In this paper, an adaptive cross-layer routing scheme is presented based on the selection of the most reliable path in terms of packet error ratio (unipath routing). The paper argues that routing Internet traffic through wireless backhaul networks is modeled more realistically employing evolutionary rather than conventional game theory. The stability of the proposed routing algorithm is proven and the dependence of the speed of convergence on various physical layer parameters is investigated. Is is also shown that convergence may be further accelerated by increasing the amount of information from the physical layer, specifically the physical separation between the alternative paths provided to the routing layer.     

基于超图模型的多域ASON损伤感知组播路由算法

如何在缺乏全局信息的条件下构建安全可靠的组 播树,是智能光网络分域管理后引入的一个新问 题。针对此问题,通过建立新型的多域智能光网络超图模型,在考虑物理或攻击损伤的约束 条件下,利用 基于超路径的域间超树构建方法,结合K最短路径策略,提出了 一种基于超图模型的多域ASON损伤感知 组播路由算法,并进行了实例分析。本文算法在完成多域组播路由建立与波长分配的同时, 具有较低的时间复杂度。通过测量K值、组播规 模、波长数量及分配策略、域数量对网络平均连接阻塞率的影响,实验结果表明,本文算法 是有效的且取得了较好的阻塞性能,同时建议多域ASON组播规模大小应与域的数量保持一 定的比例均衡。     

Path selection methods with multiple constraints in service-guaranteed WDM networks

We propose a new approach to constraint-based path selection for dynamic routing and wavelength allocation in optical networks based on WDM. Our approach considers service-specific path quality attributes, such as physical layer impairments, reliability, policy, and traffic conditions, and uses a flooding-based transfer of path information messages from source to destination to find multiple feasible paths. It is fully decentralized, as it uses local network state information. To better understand how multiple constraints impact the efficiency of wavelength routing, and consequently provision the service guarantees, we specifically focus on electronic regenerators that, while being widely considered as the basic building blocks for optical switching nodes, are likely to impose conflicting constraints on routing. For example, electronic regenerators extend the optical reach and could perform wavelength shifting, but also induce impairments, such as delays and operational costs. The question for constraint-based routing is how to account for these conflicting effects. To validate the network modeling, a wide range of networking scenarios are simulated, such as ring, mesh and interconnections of all-optical networks with electronic gateways. For all these scenarios, our approach is shown to efficiently accommodate multiple, conflicting routing metrics related to different services and network architectures.     

OSNR model to consider physical layer impairments in transparent optical networks

We propose a model that considers several physical impairments in all-optical networks based on optical signal-to-noise degradation. Our model considers the gain saturation effect and amplified spontaneous emission depletion in optical amplifiers, coherent crosstalk in optical switches, and four-wave mixing in transmission fibers. We apply our model to investigate the impact of different physical impairments on the performance of all-optical networks. The simulation results show the impact of each impairment on network performance in terms of blocking probability as a function of device parameters. We also apply the model as a metric for impairment-constraint routing in all-optical networks. We show that our proposed routing and wavelength assignment algorithm outperforms two common approaches.

WDM网络中基于分层图模型的ICBR路由算法

考虑到物理损伤导致光信号质量下降的严重性,提出了一种新的损伤感知路由和波长分配算法。该算法同时考虑多种线性和非线性损伤,从光信噪比(OSNR,Optical Signal Noise Ratio)和Q因子两方面来评估光信号的整体质量,严格保证了业务的服务质量。最后将损伤感知路由算法(ICBR,Impairment Constraint Based Routing algorithm)和分层图模型相结合,与传统ICBR算法相比,避免了不必要的连接阻塞,显著改善了网络性能。     

Dynamic routing in translucent WDM optical networks: the intradomain case

Translucent wavelength-division multiplexing optical networks use sparse placement of regenerators to overcome physical impairments and wavelength contention introduced by fully transparent networks, and achieve a performance close to fully opaque networks at a much less cost. In previous studies, we addressed the placement of regenerators based on static schemes, allowing for only a limited number of regenerators at fixed locations. This paper furthers those studies by proposing a dynamic resource allocation and dynamic routing scheme to operate translucent networks. This scheme is realized through dynamically sharing regeneration resources, including transmitters, receivers, and electronic interfaces, between regeneration and access functions under a multidomain hierarchical translucent network model. An intradomain routing algorithm, which takes into consideration optical-layer constraints as well as dynamic allocation of regeneration resources, is developed to address the problem of translucent dynamic routing in a single routing domain. Network performance in terms of blocking probability, resource utilization, and running times under different resource allocation and routing schemes is measured through simulation experiments.