共查询到18条相似文献,搜索用时 140 毫秒
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介绍和分析EPON的特点,侧重分析动态带宽分配算法的原理和相应类别的优缺点。主要分析3种DBA算法——间插轮询(IPACT)带宽分配算法算法、BGP算法和基于比例分配的支持服务等级区分带宽分配算法,分析其原理、上行通道的利用率及对不同业务等级之间公平性的影响,得出各自优缺点的结论。 相似文献
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当前以太无源光网络中动态带宽分配算法主要是基于轮询机制.其中限制带宽分配算法根据各个ONU发送的队列长度能够动态分配带宽,但是这种算法不能实时获得各个ONU的队列长度.因此,利用维纳滤波的方法对自相似业务流量进行预测,预测的结果应用于限制动态带宽分配,得出一种改进的动态带宽分配算法.这种改进算法通过预测ONU的队列长度,更确切地反映了其状态信息,有利于OLT进行准确地带宽分配.对这种算法进行了仿真分析,在业务负载介于0.1~0.5的情况下,平均包时延比较接近0.1ms,达到了改进目的. 相似文献
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动态带宽分配是EPON系统的关键技术之一。由于多个ONU共享同一上行信道,对上行数据流的控制显得尤为重要。EPON系统使用请求/应答机制对ONU进行带宽分配。在ETRI算法的基础上,提出了一种改进的算法,它支持队列优先级和ONU之间的公平性。通过仿真结果可以看出,改进的算法与ETRI相比,大大减少了平均队列长度。 相似文献
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根据业务流的自相似性提出了一种新颖的信道分配算法。该算法首先根据流的自相似性,估计网络中的节点的业务量。然后,根据业务量多少确定占用信道的优先级。业务量大的节点可以优先占用信道。这样,解决了“热点”信道资源紧张的问题。同时,算法对“非热点”的吞吐量影响很小。理论分析证明,这种算法可以有效提高网络吞吐量。仿真结果表明,运用这种算法,网络的吞吐量比最小干扰固定信道分配算法和最小干扰混合信道分配算法可分别提高70%和40%。 相似文献
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针对以往以太网无源光网络(EPON)动态带宽算法中存在的带宽分配不公平性问题,提出了基于带宽借贷机制的动态带宽算法LLR和LWR,其基本思想为当某光网络单元(ONU)有空余带宽时,光线路终端(OLT)将此ONU多余带宽借贷给重负载ONU,当债权ONU遇到带宽不足的情况时,OLT将会安排负债ONU偿还其未满足请求部分带宽.通过在正常使用和存在"贪婪"用户的两种情况下的仿真,分析了这两种算法的平均时延和丢包率特性.仿真结果表明这两种算法能为正常使用用户提供有保障的公平性服务,消除了以往算法在若干用户过量使用的情况下所有用户都受影响的问题,使动态带宽分配更加公平. 相似文献
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基于带缓存crossbar的交换结构提出了一种支持多优先级的调度方案.该方案在带缓存crossbar交换结构的输入端口提出了一种基于端口与优先级标识的层次化排队机制,并结合该排队机制提出了一种加权双轮询(DWRR)的调度算法,在crossbar内部交叉节点处的缓存队列提出了一种易于实现的补偿优先轮询(CPRR)调度算法.这种DWRR-CPRR优先级调度方案不需要在crossbar交叉节点设置多个优先级缓存队列,避免了在带缓存crossbar内部进行复杂的调度,实现简单.时延特性与带宽分配特性的仿真结果表明,该方案可以获得接近于采用加权公平排队(WFQ)调度策略的OQ交换结构的性能. 相似文献
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针对以太无源光网络(EPON),为各类业务提供服务质量支持,特别是保障时延敏感型业务的服务质量,提出一种调度算法,应用到EPON的光网络单元(ONU)中.我们设法让这个单级调度算法具备多级调度功能.通过理论分析和仿真测试,证明本算法具有灵活的优先级机制和公平调度功能. 相似文献
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《Communications, IET》2009,3(1):1-9
The IEEE 802.15.3 medium access control (MAC) protocol is an emerging standard for high-rate wireless personal area networks (WPANs), especially for supporting high-quality real-time multimedia applications. Despite defining quality of service (QoS) signalling mechanisms for interoperability between devices, IEEE 802.15.3 does not specify resource allocation algorithms that are left to manufacturers. To guarantee the QoS of real-time variable bit rate (VBR) videos and utilise the radio resource efficiently, the authors propose a dynamic resource allocation algorithm. The proposed bandwidth allocation algorithm is based on a novel traffic predictor. Recently, the variable step-size normalised least mean square (VSSNLMS) algorithm was employed for on-line traffic prediction of VBR videos. However, the performance of the VSSNLMS algorithm significantly degrades due to the abrupt traffic variation occurring at the scene boundary. To tackle this problem, the authors design a novel traffic predictor based on a simple scene detection algorithm and the VSSNLMS algorithm. Analyses using real-life MPEG video traces indicate that the proposed traffic predictor significantly outperforms the VSSNLMS algorithm with respect to the prediction error. The performance of the proposed bandwidth allocation algorithm is also investigated by comparing several existing algorithms. Simulation results demonstrate that the proposed bandwidth allocation algorithm surpasses other mechanisms in terms of channel utilisation, buffer usage and packet loss rate. 相似文献
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Boivin LP 《Applied optics》2002,41(10):1929-1935
The errors caused by monochromator bandwidth in spectral responsivity measurements with a monochromator-based apparatus are discussed. Bandwidth effects are not negligible in high-accuracy cryogenic radiometer-based calibrations. A simple numerical method is used to calculate bandwidth effects for different types of detectors, monochromator slit scattering functions, and monochromator output spectral distributions. The method uses low-order Lagrange polynomials fitted segmentwise to measured spectral responsivity and monochromator spectral distribution data in order to make the calculations. It is shown that the shape of the slit function has only a small influence on the bandwidth errors, whereas the output spectral distribution of the monochromator can strongly affect bandwidth errors. It is also shown that in most cases the magnitude of bandwidth effects will vary as the square of the bandwidth. Bandwidth error calculations are presented for various types of detectors (silicon, silicon trap, germanium, InGaAs), for a V(X) detector, and for a typical filter radiometer. A comparison is made between calculated and measured bandwidth effects to validate the method used. In general, calculations of bandwidth effects will be mostly useful for determining uncertainties associated with monochromator bandwidth in spectral responsivity measurements; however, in certain cases the calculations can be used to apply corrections for such effects. 相似文献
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Adaptive wavelet-based multifractal model applied to the effective bandwidth estimation of network traffic flows 总被引:1,自引:0,他引:1
The authors investigate effective bandwidth estimation and Quality of Service (QoS) aware bandwidth provisioning for multifractal network traffic flows. They develop a novel adaptive wavelet-based multifractal model (AWMM) by using properties of the wavelet coefficients of multifractal cascade processes. The proposed AWMM has real-time updating capability and proves to be efficient in capturing multifractal network traffic characteristics. In addition, the authors derive an analytical expression for the effective bandwidth estimation of AWMM traffic flows, capable of being used to meet desired byte loss probabilities. Finally, they present an online effective bandwidth estimation algorithm that is incorporated into an adaptive bandwidth provisioning scheme and comparatively evaluated against some other bandwidth allocation methods. 相似文献
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The paper proposes a new approximate calculation method of occupancy distribution and blocking probability in the full-availability group (FAG) with multi-rate traffic streams and bandwidth reservation. The algorithm involves calculation of system state probabilities by a convolution operation. In the paper, an effective method of calculating state probabilities in a reservation space of the system is derived. The analytical results of blocking probabilities in the FAG with bandwidth reservation, obtained on the basis of the proposed analytical method, are compared with the data obtained on the basis of other known analytical methods and with the simulation results. The accuracy of the proposed method is evaluated for different multi-rate Bernoulli (Erlang), Poisson (Engset), Pascal traffic streams. The method proposed is characterised by lower complexity than the convolution algorithm for the FAG with bandwidth reservation devised earlier. 相似文献
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Performances of differentiated services in the upstream transmission of Ethernet passive optical network (E-PON) are affected by bandwidth reservation algorithm of an optical network unit, since data packets can be transmitted to an optical line termination only during the reserved transmission window. The effects of time-slot reservation on differentiated services are analysed and an adaptive class-based excess bandwidth reservation algorithm, called service quality pre-engagement (SQP), which reserves a time-slot based on the backlog queue and traffic arrival pattern of class is proposed. SQP applies the prediction-based bandwidth reservation to selected forward reservation classes (FRCs) which are determined by the introduced dynamic FRC selection. The proposed short-term service work-based time-slot reservation and long-term adaptive FRC selection optimise time-slot reservation according to traffic load of class. Analytic and simulation results show that this approach improves the performance of differentiated services, especially in terms of system buffer size, light-load penalty and service fairness, while guaranteeing high link utilisation and throughput 相似文献
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研究了干扰链路流量大小对IEEE802.16Mesh网络传输性能的影响,提出了一种通过计算用户站(SS)和基站(BS)的通信路径干扰的总流量来寻找总干扰流量最小的路由算法,并结合路由树给出了一种冲突避免调度的方法。该算法既考虑了干扰链路的数量,又考虑了干扰链路的实际通信强度,在建立路由树的过程中能够更快地使系统达到更佳的负载均衡状态,最大强度地避免调度中可能出现的带宽冲突。由于干扰流量的影响可以得到有效的控制,系统的吞吐量可以明显提高。仿真结果验证了该算法的有效性。 相似文献