基于FTT-CAN的电动汽车动态调度算法研究

针对在控制器局域网(CAN)总线中存在低优先级信息会因为高优先级信息频繁占用总线而出现的死锁问题,在车辆控制系统中引入柔性时间触发机制组建柔性事件触发控制器局域网(FTT-CAN),针对周期信息和随机信息,分别在FTT-CAN的同步相和异步相中采用最早截止期优先(EDF)调度和动态提升优先级(DPP)调度,介绍了FTT-CAN触发原理,提出基于EDF和DPP的动态调度算法,将该调度算法应用于典型电动汽车控制系统模型的调度,验证了该调度算法的优越性。     

设备级OS中任务调度的IO抖动优化策略

 为了减小任务调度产生的抖动对设备级操作系统的稳定性和可靠性的影响,提出了一种带有抢占阈值的任务分割模型RJPS.根据抢占阈值对任务调度的抖动与延迟的影响及该模型下任务可调度性的分析,分别设计了基于固定优先级调度和动态优先级调度策略的最小阈值分配算法.仿真结果表明,该模型可以在保证任务集可调度的前提下明显减少任务的IO抖动.     

TTE网络混合业务调度器设计和实现

分析了AS6802标准中支持的多种业务消息的传输特性,设计了一种时间触发以太网多种业务消息发送的混合业务调度器。采用发送计划表和允许发送帧长控制,实现了时间触发数据的按时发送。基于允许发送帧长控制和非抢占优先级调度的非时间触发业务发送,保证了带宽利用率,实现了PCF业务的事件触发特性、RC业务的速率限制特性和BE业务的尽力而为特性。混合业务调度器满足了时间触发以太网多业务传输要求。     

一种工业无线网络中受时间约束的消息调度方法

为了优化工业无线网络通信链路上的传输性能,降低消息队列排队延迟的发生。在考虑消息的发布时间、截止时间及端到端的截止时间约束下,通过计算消息的处理时延及传输时延,得到调度任务的开始时间矢量图,完成消息的调度。仿真结果表明,受时间约束的消息调度算法,降低了消息队列的排队延迟时间及调度的完成时间。     

支持优先级与公平策略的队列规程

首先介绍了队列调度算法在流量控制中的关键地位,然后讨论了现有队列调度算法,如基于优先级的调度算法、轮询调度算法与公平队列调度算法,最后提出了一种新的队列规程,该队列规程融合了优先级调度算法与DRR调度算法。在网络正常情况下,不同业务流公平地共享网络带宽,在网络出现拥塞的情况下,高优先级业务流能够抢占带宽,保证其较低的丢包率,并能够实现两种调度算法的快速切换。     

CAN网络实时性分析及改进

随着CAN总线控制网络的复杂化,单段网络上的控制节点数目增多而且网络带宽利用率要求日益提高,这使得总线上优先级属性低的数据传输延时增加.提出"取模增加"法动态改变站点优先级,使优先级较低的站点可以动态地提高优先级,通过动态改变各站点优先级,保证各站点有均等机会获得总线控制权,实现数据实时传输.与TTCAN(时间触发CAN)协议方式进行实验比较,得出了网络延时特征.在较大网络负载的情况下,对于事件型消息,采用动态优先级调度算法可以比CAN方式的网络传输延时降低10%,对于周期型消息,TTCAN方式比采用CAN方式降低网络传输延时20%.     

OBS网络中基于优先级抢占的恢复机制

提出一种新的支持光突发交换网络中优先级抢占的快速恢复机制.该机制对不同优先级的业务采取不同的恢复策略,实现故障的快速恢复.同时采用阈值检测方式支持优先级抢占,减少受影响链路中较高优先级业务的丢包.仿真结果表明,基于优先级抢占的恢复机制具有较低的丢包率,对高优先级业务丢包率性能改善更为明显.     

时间敏感网络流量调度算法研究综述

时间敏感网络（Time-sensitive Networking,TSN）是一种新型确定性网络,具有低时延、低抖动等特点,能够满足现代网络传输控制的要求。流量调度是TSN标准中关键技术之一,用于确保流量传输的服务质量。首先对时间敏感网络的发展背景、重要机制、应用场景进行阐述,着重研究5种时间敏感网络流量调度机制,包括基于时间的整形机制、基于信用值的整形机制、循环队列转发机制、帧抢占机制以及异步流量整形机制;然后,分析了流量调度算法的研究现状,归纳和总结了时间触发（Time-triggered,TT）流和事件触发（Event-triggered,ET）流的调度算法,分析了目前流量调度算法存在的问题;最后,指出了TSN流量调度算法的发展方向和趋势。     

E-OBS网络中一种基于优先级的抢占窗口机制

为了有效地降低突发包的丢失率和保证网络的服务质量,提出了模拟光突发交换网络中一种基于优先级的抢占窗口机制.该机制在模拟光突发交换核心路由器的控制信道上设置抢占窗口,以此来决定是否允许高优先级突发包抢占低优先级突发包.冲突发生时,系统判断高优先级突发包对应的控制包的到达时间是否满足抢占条件,如果满足抢占条件,则允许高优先...     

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.     

A Novel Method of Feedback Reducing and Cross-layer Scheduling Based on Traffic Rates for Relay System

This paper studies the scheduling schemes in multiuser downlink relay systems with orthogonal frequency division multiple access (OFDMA) where base station (BS) supports different traffic rates for different users. We formulate the problem as a cross-layer design of joint feedback reducing and OFDMA scheduling to support traffic rates and minimize packet loss rate. In most previous scheduling mechanisms with feedback, the parameters of traffic arrival process were not taken into account, consequently, the requirement of user traffic can not be guaranteed. In this paper, a dynamic threshold feedback mechanism (DTFM) based on traffic rates is proposed, of which the user with channel gain being larger than the dynamic threshold is only allowed to send its channel state information, thereby reducing the number of required feedback users and the computational burden of exhaustive search for best users at the BS. A cross-layer scheduling algorithm of traffic and queue proportional fairness (TQPF) taking into consideration the traffic fairness, the user queue length and the user transmission rate (related to its channel quality) is then proposed. Finally, a method of feedback reducing and cross-layer scheduling, i.e., TQPF based on DTFM (TQPF-DTFM), is proposed. Theoretical and simulation results show that DTFM reduces feedback by more than 90%, and TQPF-DTFM successfully meets user traffic rates that is, the user with high traffic rate can obtain more transmission rate than the user with low traffic rate and deceases packet loss rate of the system by almost 50% than the conventional methods.     

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。     

基于复用的自适应随机预约多址协议

为解决多业务环境下VSAT ATM中多址协议的信道分配效率及QoS问题,提出了基于复用的自适应随机预约多址协议(MRRAA)。在MRRAA中,由于rt-VBR业务所需带宽变化,其预约的时隙常有剩余,能被其他业务复用。复用rt-VBR业务剩余时隙时,按优先级顺序,首先是nrt-VBR,其次ABR,最后是UBR业务。用流体流方法表明,MR RAA在信源突发性比较高时,能大幅度提高信道的利用率,而又不违反业务的QoS要求。     

Analysis of DQLT scheduling policy for an ATM multiplexer

This letter suggests a modified priority scheduling policy for the asynchronous transfer mode (ATM) multiplexer, which is called DQLT. In the dual queue length threshold (DQLT) method, there exist two queues: (1) Q₁ is for nonreal-time traffic and (2) Q₂ is for real-time traffic and each queue has its own threshold to adaptively control the buffer congestion. If Q₁ is congested over the threshold T₁ one cell at the head of Q₁ moves into Q₂ in a slot time. It is shown that the DQLT method gives intermediate performance between those of minimum laxity threshold (MLT) and queue length threshold (QLT) policy, but its control method is quite simpler     

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 scheduling mechanism for IPTV over WiMAX IEEE 802.16j networks

A WiMAX technology is a very promising Broadband Wireless Access technology that is able to transmit different service types. This latter can have different constraints such as traffic rate, maximum latency, and tolerated jitter. The IEEE 802.16 Medium Access Control specifies five types of QoS classes: UGS, rtPS, ertPS, nrtPS, and BE. However, the IEEE 802.16 standard does not specify the scheduling algorithm to be used. Operators have the choice among many existing scheduling techniques. Also, they can propose their own scheduling algorithms. In this paper, we propose a scheduling strategy (Adaptive Weighted Round Robin, AWRR) for various Internet Protocol Television (IPTV) services traffic over 802.16j networks. Our scheme adapts dynamically the scheduler operation to according queue load and quality of service constraints. In particular, the proposed mechanism gives more priority to high definition television and standard definition television traffic by using two schedulers. The proposed scheduling algorithm has been simulated using the QualNet network simulator. The experimental results show that our scheduler schemes AWRR have a better performance than the traditional scheduling techniques for rtPS traffic, which allows ensuring QoS requirements for IPTV application. Copyright © 2012 John Wiley & Sons, Ltd.     

Explicit TCP window adaptation in a shared memory architecture

A multiple (priority) queueing system allows a network node to manage the queueing of packets in such a way that higher priority packets will always be served first, low priority packets will be discarded when the queue is full, and for same‐priority packets any interference between them will be prevented. This paper describes a TCP window control scheme for a shared memory device that has buffer memory logically organized into multiple queues. To handle changing queue traffic loads, the shared memory device uses a dynamic buffer threshold mechanism to allocate buffer space to the queues. The TCP window control scheme allows the receiver's advertised window size in ACK packets to be modified at the network queue in order to maintain the queue size at a computed dynamic threshold. Copyright © 2003 John Wiley & Sons, Ltd.     

Dynamic buffer management using per‐queue thresholds

Shared buffer switches consist of a memory pool completely shared among output ports of a switch. Shared buffer switches achieve low packet loss performance as buffer space is allocated in a flexible manner. However, this type of buffered switches suffers from high packet losses when the input traffic is imbalanced and bursty. Heavily loaded output ports dominate the usage of shared memory and lightly loaded ports cannot have access to these buffers. To regulate the lengths of very active queues and avoid performance degradations, threshold‐based dynamic buffer management policy, decay function threshold, is proposed in this paper. Decay function threshold is a per‐queue threshold scheme that uses a tailored threshold for each output port queue. This scheme suggests that buffer space occupied by an output port decays as the queue size of this port increases and/or empty buffer space decreases. Results have shown that decay function threshold policy is as good as well‐known dynamic thresholds scheme, and more robust when multicast traffic is used. The main advantage of using this policy is that besides best‐effort traffic it provides support to quality of service (QoS) traffic by using an integrated buffer management and scheduling framework. Copyright © 2006 John Wiley & Sons, Ltd.     

Dynamic queue length thresholds for multiple loss priorities

Buffer management schemes are needed in shared-memory packet switches to regulate the sharing of memory among different output port queues and among traffic classes with different loss priorities. Earlier, we proposed a single-priority scheme called dynamic threshold (DT), in which the maximum permissible queue length is proportional to the unused buffering in the switch. A queue whose length equals or exceeds the current threshold value may accept no new arrivals. We propose, analyze and simulate several ways of incorporating loss priorities into the DT scheme. The analysis models sources as deterministic fluids. We determine how each scheme allocates buffers among the competing ports and loss priority classes under overload conditions. We also note how this buffer allocation induces an allocation of bandwidth among the loss priority classes at each port. We find that minor variations in the DT control law can produce dramatically different resource allocations. Based on this study, we recommend the scheme we call OWA, which gives some buffers and bandwidth to every priority class at every port. Scheme OWA has tunable parameters, which we give rules of thumb for setting. Another scheme, called AWA, is also a good choice. It has an allocation philosophy more akin to strict priority and hence is not tunable     

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.