一种改进的保证混合业务服务质量的跨层调度算法

提出一种改进的基于优先级的IEEE 802.16系统跨层调度算法,该算法综合考虑了媒体接入控制(MAC)层的业务服务质量(QoS)要求与无线信道的时变特性,通过动态调整实时轮询(rtPS)业务的优先级加权系数,在保证rtPS业务QoS要求的前提下,增加非实时轮询(nrtPS)业务和尽力而为(BE)业务的调度机会,提高nrtPS业务和BE业务的传输速率.每个连接分配的优先级根据信道和服务状态进行动态更新,每次调度优先级最高的连接.仿真结果表明,该算法能够为不同业务提供QoS保证,同时有效提高了频谱利用率和系统吞吐量.     

一种改进的空分交换型OPS节点结构及其性能分析

提出了一种改进的空分交换型光分组交换(OPS)节点结构--共享反馈和输出缓存(SFOB)结构.该结构不但结合了基本的OPS节点结构的优势(将反馈缓存与共享缓存组合配置),而且在缓存使用方面改进了每根光纤延迟线(FDL)独立使用的做法,增加了将反馈缓存和共享缓存中两根FDL串联使用的机制,并据此设计了相应的缓存调度算法.最后使用计算机仿真的方法对该结构在随机网络负载下的丢包率性能进行了研究.仿真结果表明在相同缓存容量条件下该结构比传统的共享存储光分组(SMOP)交换结构具有更好的交换性能.     

一种多源协作网络中轮询节点选择算法

针对放大转发(AF)的多源多中继两跳协作通信网络模型,提出了一种基于轮询分组调度算法的节点选择与用户调度策略.与之前所提出的中继选择选择算法相比,所提出的中继节点轮询分组调度算法,不需要额外的信令开销,复杂度低,并保证中继间的负载均衡.此外,为保证用户传输的公平性,提出一种结合多用户分集的轮询分组调度算法.最后在已选择的中继节点和所调度的源节点用户中引入分布式空时编码.仿真结果表明,该节点选择和用户调度算法能保证所有节点使用的公平性,并且结合分布式空时编码之后,可以提高频谱利用率,从而提高了系统性能.     

一种具有QoS保障能力的T比特路由器交换结构的实现

为了在能够通过较小的交换网络加速比就可以实现与OQ相比拟的时延和100％的吞吐率的CIOQ交换结构中支持DiffServ QoS模型,提出了一种在输入端口和输出端口采用两级调度和队列管理的具有QoS保障能力的交换结构。输入侧采用MTRED＋PDMCRR模式,输出侧采用WRED＋PQ混合调度模式,给出了详细的设计分析,并通过仿真实验验证了该结构可以良好地支持DiffServ中各种业务的QoS性能。     

一种分布式联合输入输出排队结构及其调度算法

分析论证了分布式联合输入输出排队(DCIOQ)结构模拟输出排队调度的充分条件,提出了一类满足这一条件的调度算法,并从工程实现的角度给出了这类算法的一种简易实现方案。与传统方案相比,该方案不仅具有高的带宽利用效率和良好的调度公平性,而且工程实现复杂度较低。     

基于多指标感知的命名数据网络自适应拥塞控制算法

为解决命名数据网络拥塞控制算法普遍存在的瓶颈链路缓存队列积压问题,提出一种基于多指标感知的命名数据网络自适应拥塞控制(MACC)算法。在网内节点,根据实时监测的接收端数据接收速率、数据包排队时延、链路带宽等多个指标估计链路负载程度,并通告终端节点。在终端节点,根据Data包携带的链路负载信息,自适应地调整发送窗口,以实现高吞吐、低时延目标。基于ndnSIM的仿真结果表明,该算法能有效实现终端高吞吐量、瓶颈链路低队列,并在实现流间公平性方面具有显著优势。     

基于低压电力线载波的轮询通信改进

针对制造和生产企业信息化改造过程中,信号线布线复杂、空间受限、维护升级困难等问题,设计了一种无需专用通信线路且抗干扰性强的电力线载波轮询通信方案.该方案的物理层使用了正交频分复用、自适应跳频传输等抗干扰技术,在应用层引入标记从机状态、超时重传、缓存队列、传输紧急帧等通信机制,通信可靠,轮询周期短.实际测试表明,该方案应用在MES条码信息采集上,与原有的RS485传输方案相比,具有无需布线、系统稳定性高、丢包率低的特点,为自动化提升改造提供了一种无需额外布线、快速可靠的信息传输方法.     

A reliability-cost and Makespan driven fault-tolerant scheduling algorithm for distributed systems

为解决异构分布式环境下采用主副版本策略的可靠性调度问题,提出一种基于优先级约束的可靠性代价和Makespan(调度时长)驱动的分布式容错调度算法DRCAMD.该算法可在满足系统可调度性的前提下,以异构分布式环境的节点、通信链路的可靠性与Makespan做为可调节局部目标函数,实现具有较高可靠性及较短执行时间的容错调度策略,避免将任务分配到失效率较高的节点上执行.另外,算法的副版本采用被动和主副重叠方式执行,使得容错调度算法具有较大的灵活性.仿真实验表明,该算法性能优于现有容错算法.     

基于MLAG的三层码分多粒度光交换系统的性能研究

在波长交换的基础上,引入光码交换,并基于光码分复用(OCDM)建立了一种三层多粒度光交叉联接(MG-OXC)系统,并给出了一种新的业务疏导算法。该体系结构能够很好地改善业务疏导,减少使用波长数量,节省消耗端口数目,因此它可以简化路由设置,优化节点业务疏导的灵活性,提高系统性能。简要介绍了三层多粒度光交换体系的结构,并在端口节省方面进行了比较。通过在多路分层辅助图表(MLAG)上对交换结构网络模型和业务疏导链路建立的分析,以及对阻塞率和吞吐量的仿真,展现了该体系的良好性能。     

基于SDN的四层多粒度光交叉连接体系研究

在波带交换的基础上加入光码粒度,构成包括光纤、波带、波长、光码粒度的四层多粒度光交叉连接(MG-OXC)结构,并应用码群路由(CGRE)技术使多个波长通道级联,构成波带交换和CGRE共存的混合捆绑体系,提出混合算法以缓解端口数目过多和波长利用率较低的问题,使业务在各个粒度灵活上下路。将基于通用多协议标签交换(GMPLS)的四层多粒度光交叉连接结构体系作为软件定义网络(SDN)体系中数据转发层的一部分,由软件定义网络控制器进行集中管理,可优化网络结构。通过对波长利用率、端口需求数目和系统丢包率3方面的仿真分析,验证了该网络体系的优秀性能。     

A pinwheel packet scheduling scheme for broadband wireless networks

Abstract

A frame‐based packet scheduling scheme, the pinwheel scheduling (PWS) scheme, is proposed and investigated at the medium access control (MAC) layer in broadband wireless networks. The objective of the proposed scheduling scheme is to provide low delay and low jitter for real‐time traffic. We have demonstrated in this paper that the proposed PWS scheme not only satisfies the packet‐level QoS requirements but also has low implementation cost. The PWS scheme gives the highest priority to CBR connections in a service cycle to minimize their delay and jitter. For ABR traffic, a number of slots are allocated to fit their MCR. The remaining time slots are then allocated to VBR traffic according to their PCR. Thus, the VBR traffic may suffer large delay and jitter when the number of CBR connections increases. The PWS with modular strategy (PWS/MS) is proposed to improve the performance of the VBR traffic. We also introduce three different slot‐reuse strategies named real‐time traffic first (RTF), non‐real‐time traffic first (NRTF) and longest queue first (LQF), respectively, to improve resource utilization. In order to demonstrate the performance of the PWS and PWS/MS schemes, comparisons are made with existing schemes such as the round‐robin (RR) and weighted‐round‐robin (WRR) by using OPNET software. Simulation results show that the proposed schemes are capable of maintaining the lowest delay and jitter for VBR and CBR traffic while not sacrificing the available bit rate (ABR) traffic.     

Hierarchical smoothed round robin scheduling in high-speed networks

The hierarchical smoothed round robin (HSRR) packet scheduler that improves the performance of the smoothed round robin (SRR) for real-world packet scheduling scenarios is presented. The SRR suffers from an inability to fairly distribute service in highly skewed weight distributions where such distributions often occur in practice. As a result, the transmission behaviour of the SRR can be bursty and non-smooth for the high weighted (or high priority) flows. A novel aggregation strategy is proposed to reshape the sessions' weight distribution that aims to minimise the variance of the high-priority flows' intra-session service times. The aggregation scheme also provides a new capability that supports the provisioning of high-priority service to an arbitrary set of selected flows. The reshaped weight distribution results in guaranteed lower bound in maximum packet delay for the high-priority flows. Furthermore, empirical analyses show that the cumulative average packet delay and jitter of the high-priority flows are significantly reduced from the original SRR and also overall lower for all flows. Along with the enhanced performance in packet delays, the HSRR scheduler attains a worst-case time complexity of O(1).     

基于AIS数据的航运物流港口调度优化研究

目的 针对宁波舟山港区的复杂航道水域与密集物流交通流,研究更加有效的调度方案,达成调度时间和等待时间最小化,即效率最大化。方法 分析宁波舟山港区航道的航行情况,提出交会处复杂航道水域存在的问题,以调度时间和等待时间最小为目标的多目标函数,建立复杂航道水域船舶调度模型。针对大量的船舶AIS数据,构建基于神经网络的航道水域调度模型,对不同类型、不同大小的船舶建立速度变化和船舶预测模型,实现对船舶调度状态的预测。设计以传统粒子群算法为基础的改良版船舶调度算法。结果 算法对模型求解表明,根据不同船长与间距可判别交通流拥挤程度进而对船舶进行调度。通过模型预测到可能产生拥挤,则应当选择小型船只走条帚门航道,大型船只走虾峙门航道,并且尽量避免产生拥堵。结论 使用该模型与算法可以有效地提升船舶调度效率,为复杂航运物流港口调度优化研究提供了一定理论基础。     

Analysis on D2D Heterogeneous Networks with State-Dependent PriorityTraffic

In this work, we consider the performance analysis of state dependent priority traffic and scheduling in device to device (D2D) heterogeneous networks. There are two priority transmission types of data in wireless communication, such as video or telephone, which always meet the requirements of high priority (HP) data transmission first. If there is a large amount of low priority (LP) data, there will be a large amount of LP data that cannot be sent. This situation will cause excessive delay of LP data and packet dropping probability. In order to solve this problem, the data transmission process of high priority queue and low priority queue is studied. Considering the priority jump strategy to the priority queuing model, the queuing process with two priority data is modeled as a two-dimensional Markov chain. A state dependent priority jump queuing strategy is proposed, which can improve the discarding performance of low priority data. The quasi birth and death process method (QBD) and fixed point iteration method are used to solve the causality, and the steady-state probability distribution is further obtained.Then, performance parameters such as average queue length, average throughput, average delay and packet dropping probability for both high and low priority data can be expressed. The simulation results verify the correctness of the theoretical derivation. Meanwhile, the proposed priority jump queuing strategy can significantly improve the drop performance of low-priority data.     

APON接入系统分布式分层调度算法

分析了APON中MAC子层的算法特点，按照不同的QoS需求把ATM的各类业务重新作了划分，提出了适合于APON系统的分布式分层调试方式。分布式分层调度方式对需调度的信息进行了聚合，并能十分容易地嵌入各种公平调度算法。通过仿真，证明了该调度方式能有效地保证服务质量。同时由于采用了分层调度，减少了各ONU与OLT之间的信息交互开销。     

Mixed Self-adapting GA Optimal Scheduling Algorithm for a Multiple Resource Job-shop

With an aim at the job-shop scheduling problem of multiple resource constraints, this paper presents mixed self-adapting Genetic Algorithm （ GA ） , and establishes a job-shop optimal scheduling model of multiple resource constraints based on the effect of priority scheduling rules in the heuristic algorithm upon the scheduling target. New coding regulations or rules are designed. The sinusoidal function is adopted as the self-adapting factor, thus making cross probability and variable probability automatically change with group adaptability in such a way as to overcome the shortcoming in the heuristic algorithm and common GA, so that the operation efficiency is improved. The results from real example simulation and comparison with other algorithms indicate that the mixed self-adapting GA algorithm can well solve the job-shop optimal scheduling problem under the constraints of various kinds of production resources such as machine-tools and cutting tools.     

面向印制电路板钻孔任务动态调度的短视策略

印制电路板钻孔任务因随机到达和工艺要求而难以调度。考虑该问题的NP难性质,提出基于优先规则和智能算法的短视策略。该策略采用事件驱动的再调度机制,在任务到达和任务完工时触发优化算法对当前未开工任务进行决策。为了高效求解每个决策时刻的优化问题,构建了嵌入局部优势定理的模拟退火和变邻域搜索算法,其初始解由优先规则获得。通过计算实验,在不同调度环境下对比两种智能算法与经典优先规则的表现。实验结果表明,智能算法在多数目标下的优化效果较优先规则可提升20%以上,变邻域搜索的优化效果略好于模拟退火,但是模拟退火的计算效率高一倍。     

Scheduling of flexible manufacturing systems based on Petri nets and hybrid heuristic search

This paper proposes and evaluates a hybrid search strategy and its application to flexible manufacturing system (FMS) scheduling in a Petri net framework. Petri nets can concisely model multiple lot sizes for each job, the strict precedence constraint, multiple kinds of resources, and concurrent activities. To cope with the complexities for FMS scheduling, this paper presents a hybrid heuristic search strategy, which combines the heuristic A* strategy with the DF strategy based on the execution of the Petri nets. The search scheme can invoke quicker termination conditions, and the quality of the search result is controllable. To demonstrate this, the scheduling results are derived and evaluated through a simple FMS with multiple lot sizes for each job. The algorithm is also applied to a set of randomly generated more complex FMSs with such characteristics as limited buffer sizes, multiple resources, and alternative routings.     

Scheduling with alternatives: a link between process planning and scheduling

The objective of this research is to develop and evaluate effective, computationally efficient procedures for scheduling jobs in a large-scale manufacturing system involving, for example, over 1000 jobs and over 100 machines. The main performance measure is maximum lateness; and a useful lower bound on maximum lateness is derived from a relaxed scheduling problem in which preemption of jobs is based on the latest finish time of each job at each machine. To construct a production schedule that minimizes maximum lateness, an iterative simulation-based scheduling algorithm operates as follows: (a) job queuing times observed at each machine in the previous simulation iteration are used to compute a refined estimate of the effective due date (slack) for each job at each machine; and (b) in the current simulation iteration, jobs are dispatched at each machine in order of increasing slack. Iterations of the scheduling algorithm terminate when the lower bound on maximum lateness is achieved or the iteration limit is reached. This scheduling algorithm is implemented in Virtual Factory, a Windows-based software package. The performance of Virtual Factory is demonstrated in a suite of randomly generated test problems as well as in a large furniture manufacturing facility. To further reduce maximum lateness, a second scheduling algorithm also incorporates a tabu search procedure that identifies process plans with alternative operations and routings for jobs. This enhancement yields improved schedules that minimize manufacturing costs while satisfying job due dates. An extensive experimental performance evaluation indicates that in a broad range of industrial settings, the second scheduling algorithm can rapidly identify optimal or nearly optimal schedules.