高速网络自适应带宽预留模型及其分析方法的研究

介绍并提出了基于集成信源速率和基于缓冲区门限的两种自适应带宽预留方案,给出了各方案的流体分析方法,由此导出了系统信元丢失概率和延时等参数的表达式。文中还给出了实验结果和性能分析,对工程应用有一定的指导意义。     

基于统计网络演算的双漏桶模型带宽需求研究北大核心

为满足双漏桶模型的业务流量需求,提出一种基于统计网络演算理论的带宽需求研究方案。该方案利用统计网络演算在分析业务时延性能方面的优势,由时延与带宽的关系建立出双漏桶模型业务流带宽需求的统计模型,对业务带宽需求进行了研究分析。数值分析结果表明了该方案的有效性和优越性,对网络合理分配带宽资源有一定的参考意义。     

ATM网络中CBR业务排队性能分析

分析了ATM网络中CBR业务排队性能,给出了一种简单的计算信元丢失率和信元平均时延的表达式.分析结果表明,一方面在较小的缓冲区容量下,即使CBR业务被分配的带宽大于等于其峰值速率,也还存在着较大的信元丢失;另一方面,当复用的CBR业务源数目很大时,只需要分配相对较小的缓冲区容量就可以满足十分低的信元丢失率要求.该结果对于ATM设备中相应的缓冲区设计、带宽分配以及连接允许控制机制的研究具有重要的意义.     

输入为多媒体信源的ATM业务流警管方案

文章提出了一种输入为多媒体信源的利用模糊控制技术的ＡＴＭ网络业务流警管方案。文章以ＡＴＭ复用器为例，用ＭＭＢＰ模型讨论了了该方案的可能性，给出了模糊控制规则及其调整过程与实现步骤。仿真表明，该方案能满足多个不同语语音，图像，数据信源的分别或同时接入，其信元时延，丢失，抖动等服务质量 优于常规漏桶算法。     

一种APON上行带宽分配方案

文中介绍了APOW（ATM无源光网络）,在此基础上提出了APON上行带宽动态分配的一种方案--“最小分配”方案：即光线路终端（OLT）在分配上行带宽时,首先满足各光网络单元（ONU）的基本带宽需求,以保证电话等实时业务的传输;同时又以特定的算法使ONU中的上行发送缓冲队列最短。最后,使用仿真手段对本方案与“平均分配”方案进行了性能比较。“最小分配”方案的平均信元接入时延、ONU上发缓冲区尺寸、上行带宽使用效率和信元丢失率等性能指标均优于“平均分配”方案。     

话音ATM交换——一种现现的网络过渡方案

首先介绍了几种基于ＡＴＭ的语音交换方案，重点提出一种６４ｋｂ／ｓ的话音ＡＴＭ的实现模型。该系统包含了ＳＴＭ交换与ＡＴＭ交换间的相互转换，并能有效地解决诸如信元打包时延，信元时延抖动，以及系统带宽利用率等关键环节，最后还介绍了有关话音ＡＴＭ交换交换技术的其它热点。     

多级门限服务轮询系统MAC离散时间控制协议模型分析

 本文提出了一种新的多级门限服务轮询系统MAC控制协议的分析模型.采用嵌入马尔可夫链理论,对离散时间的多级门限服务轮询系统进行了分析,获得了轮询时刻系统队长的概率母函数,精确解析了系统的平均排队队长、平均循环周期、信息分组的平均等待时延.通过对多级门限服务轮询系统的控制机理研究,分析获得了m控制参数的有效控制取值大小和系统的相关特性.多级门限服务轮询系统综合了基本门限服务轮询系统和完全服务轮询系统,在轮询系统的MAC控制协议的应用方面更为有效.     

与多媒体信源模型弱相关的ATM复接器监管方案

本文提出一种与信源模型弱相关的复接器监管方案－－采用模糊漏桶控制方法改变令牌产生速率,对多媒体信源接入实施动态带宽分配。用ＭＭＢＰ模型及其合成讨论了该方案的可能性给出了模糊控制方案和规则,计算机仿真表明,在多个不同速率不同特性的语音、图像、数据信源接入时延该方法能很好地满足低时延低丢失的要求,提高带宽利用率,傅诉异步和编者复用特性被有效、充分地利用。     

模糊漏桶在ATM网络UPC中的应用

本文提出了模糊漏桶模型，研究了它与普通漏桶在用户量参数控制（ＵＰＣ）中的作用。由于ＣＡＣ初步协议的不完全合理性，在实际应用中动态调节是必要的；仿真结果表明在降低信元丢失率、时延和时延抖动方面，及在动态利用网络资源方面，模糊漏桶算法要比普通的优越。我们还给出了合适的模糊控制规则。     

话音ATM交换——一种现实的网络过渡方案

首先介绍了几种基于ＡＴＭ的话音交换方案，重点提出一种６４ｋｂｓ的话音ＡＴＭ交换（ＶＯＡ）的实现模型．该系统包含了传统ＳＴＭ交换与ＡＴＭ交换间的相互转换，并能有效地解决诸如信元打包时延、信元时延抖动，以及系统带宽利用率等关键环节．最后还介绍了有关话音ＡＴＭ交换（ＶＯＡ）技术的其它热点     

Policing mechanism and cell loss priority control on voice cells in ATM networks using fuzzy logic

The authors present a fuzzy logic-based implementation of the policing mechanism (PM) and cell loss priority control (CLPC) functions on voice cells in asynchronous transfer mode (ATM) networks. Specifically, a redesigned model of fuzzy leaky bucket (FLB) is presented which serves as an alternative PM on the voice sources in an ATM network. As a continuation of the implementation of the FLB in the ATM network, three models of ATM switches with different algorithms are constructed, to perform CLPC on the voice cells, as well as to enhance the network throughput. Simulation results show that FLB is a better PM than the conventional leaky bucket (LB) in terms of cell loss probability and throughput while the mean transfer delay remains unchanged. It is also shown that the model of ATM switch with fuzzy token generator is the most balanced CLPC scheme as compared with the other two models.     

Efficient Transmission of MPEG-2 Coded Video Traffic over ATM Networks

Video traffic is expected to account for a significant share of the traffic volume in the future asynchronous transfer mode (ATM) networks. MPEG-2 proposed by Moving Picture Expert Group is one of the most promising compression techniques for such applications. One of the critical issues in MPEG-2 is to realize effective variable bit rate (VBR) video transfer thorough ATM networks. The Leaky Bucket (LB) scheme has been widely accepted as the usage parameter control (UPC) mechanism to police the VBR sources. We proposed a new Adaptive Dynamic Leaky Bucket (ADLB) congestion control mechanism, which is based on the LB scheme. Unlike the conventional LB, the leak rate of the ADLB is controlled using delayed feedback information of available bandwidth sent by the network. This scheme allows sources to get varying amounts of bandwidth over time, while reserving a minimum guaranteed bandwidth (MCR) for the entire duration of the connection. At the time of congestion, the leak rate of the ADLB is adjusted according to the feedback indicating the currently available bandwidth to the connection. The simulation results show that the end-to-end cell transfer delay and cell loss of each source has been improved significantly.     

Optimal bandwidth and buffer allocation method for heterogeneoustraffic with multiple QoS in ATM networks

An optimal bandwidth and buffer allocation scheme is proposed which maximises network utilisation and satisfies both cell loss rate (CLR) and delay requirements for heterogeneous traffic with multiple quality of service. Simulation results show that the proposed scheme satisfies CLR and delay requirements and also utilises network resources efficiently     

基于标值更新通信量模型的ATM缓冲区信元丢失率分析方法

提出了一种不同于传统分析方法（如ＭＭＰＰ／Ｄ／１）的直接基于输入通信量带宽分布和自相关特性的信元丢失率分析方法,应用标值更新模型近似实际输入通信量的低阶统计特性,给出了一个基于马尔柯夫链极限概率的信元丢失率估计公式。该方法可以估计突发级的信元丢失率,而且具有算法简单,计算量小,数值稳定性好等特点。     

Rate regulation with feedback controller in ATM networks-a neuralnetwork approach

We propose the use of an artificial neural network (ANN) technique for a rate-based feedback controller in asynchronous transfer mode (ATM) networks. A leaky bucket (LB) mechanism is used for cell discarding, when the traffic violates a predefined threshold. Since the network cannot rely on the user's compliance with its declared parameters, it is extremely difficult to select the best threshold value and depletion rate for the LB. We propose an ANN model which monitors the status of the LB and predicts the possible cell discarding at the LB in the near future. The source rate is regulated to a certain amount depending on the feedback signal “strength” when possible cell discarding is detected. The lower the value carried in the feedback cell, the higher the possibility of cell discarding and, subsequently, the higher the probability that the traffic is regulated to a lower rate. Our model considers the propagation delay time of the feedback signal making our approach more realistic. This mechanism is transparent to the source if the LB is correctly set up and the traffic follows its declared parameters. We use the same trained ANN for different MPEG traces and the results of a simulation study suggest that our mechanisms provide simple and effective traffic management for ATM networks. Cell loss rate due to the congestion shows a two to five times improvement compared with the static approach, while transmission delays introduced by our ANN controller are also smaller than in the static approach. Channel utilization is also improved, showing that our mechanisms provides a better alternative to static feedback controllers     

Queuing analysis of the selective repeat automatic repeat requestprotocol wireless packet networks

This paper presents an analytical approach for analyzing the mean packet delay and mean queue length at the transmitting terminal in wireless packet networks using the selective repeat (SR) automatic repeat request (ARQ) scheme to control the errors introduced by the nonstationary transmission channel. Each transmitting terminal is modeled as a discrete time queue with an infinite buffer. The nonstationary transmission channel is modeled as a two-state Markov chain. Comparisons of numerical predictions and simulation results are presented to highlight the accuracy of the proposed analytical approach     

Efficient channel utilization for real-time video in OVSF-CDMA systems with QoS assurance

In this paper, the utilization of real-time video service in the downlink of an orthogonal variable spreading factor code division multiple access (OVSF-CDMA) system is studied. By modeling the video traffic and wireless channel as a joint Markov modulated process, and properly partitioning the states of the Markov process, an adaptive rate allocation scheme is proposed for real-time video transmission with quality of service provisioning while achieving high channel utilization. The scheme is applicable for packet switching and frame-by-frame real-time video transmission, and incorporates both the physical layer and network layer characteristics. For QoS provisions, the closed form expressions of packet delay and loss probability are derived based on the Markov model. Analytical and simulation results demonstrate that the proposed scheme can significantly improve the channel utilization over the commonly used effective bandwidth approach.     

NN based ATM cell scheduling with queue length-based priorityscheme

The asynchronous transfer mode (ATM) is the choice of transport mode for broadband integrated service digital networks (B-ISDNs). We propose a window-based contention resolution algorithm to achieve higher throughput for nonblocking switches in ATM environments. In a nonblocking switch with input queues, significant loss of throughput can occur due to head-of-line (HOL) blocking when first-in first-out (FIFO) queueing is employed. To resolve this problem, we employ bypass queueing and present a cell scheduling algorithm which maximizes the switch throughput. We also employ a queue length based priority scheme to reduce the cell delay variations and cell loss probabilities. With the employed priority scheme, the variance of cell delay is also significantly reduced under nonuniform traffic, resulting in lower cell loss rates (CLRs) at a given buffer size. As the cell scheduling controller, we propose a neural network (NN) model which uses a high degree of parallelism. Due to higher switch throughput achieved with our cell scheduling, the cell loss probabilities and the buffer sizes necessary to guarantee a given CLR become smaller than those of other approaches based on sequential input window scheduling or output queueing