共查询到18条相似文献,搜索用时 625 毫秒
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本文对现有的几种主动队列管理算法:自适应虚拟队列(AVQ)算法、动态阈值(DT)算法以及队列长度阈值(QLT)分组调度算法等进行了介绍,并对其进行了简单的分析和比较。最后针对AVQ算法进行了改进,使其在原性能的基础上增加了区分服务的功能。 相似文献
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本文针对AVQ算法存在的不足,在PD-AVQ算法基础上,为进一步提高系统的稳定性,引入积分选项,构成PID-AVQ算法,运用控制理论推导出了满足系统稳定条件的取值范围.利用PID-AVQ算法更新虚拟带宽,综合考虑平均队列长度和包到达速率,提出了一种新的基于队列的PID控制自适应虚拟队列管理算法QPID-AVQ,可根据网络实际情况调节参数,保持队列长度稳定.仿真结果表明,当控制参数在稳定范围内取值时,QPID-AVQ算法能较好地适应网络状态变化,使队列长度始终维持在期望值附近,而不受用户数量的影响,具有较好的稳定性、抗干扰能力和较高的带宽利用率,综合性能优于PD-AVQ和RED算法. 相似文献
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PDAVQ:一种基于PD控制的自适应虚拟队列管理算法 总被引:3,自引:0,他引:3
提出了一种新的基于比例差分控制的自适应虚拟队列管理(AVQ)算法—PDAVQ,用于对网络链路中产生的拥塞进行控制,以达到有效利用网络带宽,使整个网络系统达到稳定,缓解网络拥塞的目的。而且本文对所提算法运用控制理论对系统的稳定性进行了证明,给出了满足系统稳定性条件的参数选择方法和 PDAVQ 算法的具体描述。最后,通过 ns2 仿真实验与现有的 AVQ 算法比较,结果表明,所提 PDAVQ 算法具有较高的吞吐率、较低的链路延迟和数据丢失率,并能更快的使整个网络系统达到稳定,具有较好的网络性能。 相似文献
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针对BLUE算法缺少早期拥塞检测机制,导致队列溢出或空闲现象频繁发生的问题,通过引进基于动态阈值算法的控制机制,借鉴RED算法所采用的早期拥塞检测机制,提出了DT-BLUE算法。仿真实验表明本文算法能保持队列长度的稳定性,有效降低队列空闲或溢出现象的发生,提高链路的利用率。 相似文献
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基于对网络服务质量中队列调度算法的介绍和分析,从队列的优先级角度出发,对经典的二进制堆Heap调度排序算法进行了改进,提出了一种新的Heap+算法,该算法充分利用原算法出队、入队操作数固定的特点,使其在保证硬件实现复杂度低的情况下能够做到出队、入队操作的流水化,从而达到高度的并行性。且具备很高的资源利用率和可扩展性,可用于高速链路上高精度虚拟时间的排序操作。 相似文献
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主动队列管理算法性能评价:比较研究 总被引:3,自引:0,他引:3
对当前的主动队列管理算法进行了分类,然后基于NS2网络仿真器比较了它们在不同流量和网络拓扑条件下的多种性能指标。主要结论包括:ARED综合表现最好;PI和REM的瞬态性能较差,对动态流量响应较慢:REM和没有ECN支持的AVQ可以得到较小的时延,但同时牺牲了链路的带宽利用率并造成大量分组丢失;在多瓶颈网络拓扑中,大部分算法的性能有所提高。 相似文献
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本文提出一个获取连通网络是小生成树的算法。该算法采用一个优先队列组织各顶点集合,每次根据边的权值对队列头集合进行增长。由于对每个顶点的相关联边进行了按权值分级排序的预处理,算法获取具有。个预示e条边的无向连通网络的最小生成树的期望时间是O(e*loglogn)。 相似文献
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根据无线网状网的包调度特点,结合已有的差分队列服务算法和分布式贝尔曼-福特算
法,将有线网络中的差分队列服务算法改进为分布式队列服务算法(DQS),使之实用于无
线网状网中多任务条件下实现系统的吞吐量最大化。仿真实验证明了DQS算法能有效地避免
传统多径传输中的按“类”或 “流”来进行调度的缺陷,有效地减少了数据包的端到端
延时和缓冲区需求,尤其是DQS算法的实际平均吞吐量性能有了很大的提高。 相似文献
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This paper focuses on the local stability of a classical congestion control model in the Internet,namely adaptive virtual queue(AVQ) algorithm with feedback delay.Firstly,necessary and sufficient stability conditions in terms of key tuning parameters are given,which can provide exact guidelines for setting system parameters.Furthermore,by computing the rightmost characteristic root,the optimal parameter configuration for AVQ is derived,which can guarantee superior stability performance.Finally,some simulation examples are given to illustrate the correctness of the theoretical analysis. 相似文献
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In this paper, we describe a new adaptive-vector-quantization (AVQ) algorithm designed for the coding of non-stationary sources. This new algorithm, generalized threshold replenishment (GTR), differs from prior AVQ algorithms in that it features an explicit, online consideration of both rate and distortion. Because of its online nature, GTR is more amenable to real-time hardware and software implementation than are many prior AVQ algorithms that rely on traditional batch training methods. Additionally, as rate-distortion cost criteria are used in both the determination of nearest-neighbor codewords and the decision to update the codebook, GTR achieves rate-distortion performance superior to that of other AVQ algorithms, particularly for low-rate coding. Results are presented that illustrate low-rate performance surpassing that of other AVQ algorithms for the coding of both an image sequence and an artificial non-stationary random process. For the image sequence, it is shown that (1) most AVQ algorithms achieve distortion much lower than that of nonadaptive VQ for the same rate (about 1.5 b/pixel), and (2) GTR achieves performance substantially superior to that of the other AVQ algorithms for low-rate coding, being the only algorithm to achieve a rate below 1.0 b/pixel. 相似文献
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AVQ(Adaptive Vector Quantizer)overcomes some shortcomings of traditional vectorquantizer with a fixed codebook trained and generated by the LBG or other algorithms by applyinga variab|e codebook.In this paper,we describe an effective and efficient implementation of AVQby modifying the CCN(Carpenter/Grossberg Net).The encoding process of AVQ is very similarto the learning process of the CGN.We study several different encoding schemes,includingwaveform AVQ,analysed parameter AVQ and so on,implemented by the CGN.And we simulatethe encoding performance of each scheme for encoding Gaussian process source,first order Gauss-Markov process source and practical speech signal.Our simulation results show that good qualityboth in subjective and objective tests can be obtained in a low or middle bit rate range. 相似文献
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针对非平稳信号进行小波阈值消噪方法,提出了一种将广义交叉确认(GCV)规则和遗传算法结合的新方法,利用这种方法,可以求得近似最佳阈值。接着,将方法应用到倾角传感器信号消噪中,取得到了很好的效果。 相似文献
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Adaptive vector quantization (AVQ) is a recently proposed approach for electrocardiogram (ECG) compression. The adaptability of the approach can be used to control the quality of reconstructed signals. However, like most of other ECG compression methods, AVQ only deals with the single-channel ECG, and for the multichannel (MC) ECG, coding ECG signals on a channel by channel basis is not efficient, because the correlation across channels is not exploited. To exploit this correlation, an MC version of AVQ is proposed. In the proposed approach, the AVQ index from each channel is collected to form a new input vector. The vector is then vector quantized adaptively using one additional codebook called index codebook. Both the MIT/BIH database and a clinical Holter database are tested. The experimental results show that, for exactly the same quality of reconstructed signals, the MC-AVQ performs better than single-channel AVQ in terms of bit rate. A theoretical analysis supporting this result is also demonstrated in this paper. For the same and relatively good visual quality, the average compressed data rate/channel is reduced from 293.5 b/s using the single-channel AVQ to 238.2 b/s using the MC-AVQ in the MIT/BIH case. 相似文献
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为了提高基于身份的加密签名(IBES)系统中密钥生成中心(PKG)的可信性,采用门限密码学中的(t,n)秘密共享方法,对Xavier IBES算法进行了改进,将主密钥s共享于n个对等的可信第三方PKG之间,并且将改进后的新的基于门限与身份的加密签名一体化方法(ITBES)应用于无线传感器网络,从方法的复杂性、存储需求、安全性方面进行了分析,结果表明我们的方法能够提高PKG可信性,加强无线传感器网络的安全。 相似文献
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We propose two techniques that are applicable to any adaptive vector quantization (AVQ) systems. The first one is called the locality-based codebook updating: when performing a codebook updating, we update the operational codebook using not only the current input vector but also the codewords at all positions within a selected neighboring area (called the locality), while the operational codebook is organized in a "cache" manner. This technique is rationalized by the high correlation cross neighboring vectors that facilitates a more efficient coding of the indices of the codewords chosen from the codebook. The second technique is called the history aid, which makes use of the information of previously coded vectors to quantize the current input vector if it is used to update the operational codebook. A more effective AVQ system is obtained by combining together the history aid and the locality-based updating. Extensive simulations are carried out to demonstrate the improved results achieved by our AVQ systems. Particularly, when the operational codebook size is relatively small, the improvement over a benchmark AVQ system - the generalized threshold replenishment (GTR) - is drastic. For example, when the size is 32, testing on a nonstationary signal (containing frames from different video sequences, ordered in the concatenating or interleaving format) shows that the combination of history aid and locality-based updating offers more than 4 dB gain over GTR at 0.5 bpp. 相似文献