The estimation of signaling delay in ATM networks

In multimedia applications over ATM networks, more stringent quality of services are required, because these applications are especially sensitive to the time delay. In this letter, a simple estimation of signaling delay is presented using Erlang service models according to ITU-T “Q.2931”. Additionally, the call blocking probability of a realistic network is considered. The simulation results show that the proposed model can be an effective tool to estimate the setup delay. If the connection setup delay can be effectively estimated according to the network load, then the users may decide whether or not to join this congested network, and thus contributes to the load balance of ATM networks     

Medium-term centralized virtual-path bandwidth control based ontraffic measurements

The paper presents a centralized virtual path bandwidth (VPB) control scheme for ATM networks which satisfies mainly three specifications: a) optimality during a medium-term control interval, b) fast time response so as to absorb the medium-term traffic fluctuations, and c) easy implementation. The paper mainly points at the impact of direct, on-line traffic measurements on bandwidth control. The control objective is to rearrange the installed bandwidth of the virtual paths according to the offered traffic so as to minimize the maximum call blocking probability of the whole network. Network simulation shows that a sophisticated VPB controller which relies on simple measurements of the offered traffic can substantially improve the performance of an ATM network. The necessary bandwidth rearrangement time is also examined by simulation     

Design of a generalized priority queue manager for ATM switches

Meeting quality of service (QoS) requirements for various services in ATM networks has been very challenging to network designers. Various control techniques at either the call or cell level have been proposed. In this paper, we deal with cell transmission scheduling and discarding at the output buffers of an ATM switch. We propose a generalized priority queue manager (GPQM) that uses per-virtual-connection queueing to support multiple QoS requirements and achieve fairness in both cell transmission and discarding. It achieves the ultimate goal of guaranteeing the QoS requirement for each connection. The GPQM adopts the earliest due date (EDD) and self-clocked fair queueing (SCFQ) schemes for scheduling cell transmission and a new self-calibrating pushout (SCP) scheme for discarding cells. The GPQM's performance in cell loss rate and delay is presented. An implementation architecture for the GPQM is also proposed, which is facilitated by a new VLSI chip called the priority content-addressable memory (PCAM) chip     

ATM网络异种复用业务信元丢失率快速估计的新算法

ＡＴＭ网络信元丢失率（ＣＬＲ）的估计是呼叫接入和流量控制的关键技术,基于信元丢失机制的分析,本文了一种改进的简单业务模型,并进而得到一种新的算法,能够对异种混合业务复用的ＡＴＭ网络进行快速的ＣＬＲ估计,该算法处理速度快,能够做到呼叫的实时响应,模型采用国际规范的标准参数构造,可以直接应用于实际操作,仿真结果表明,算法的精度,运算复杂度和算法鲁棒性都比较理想,具有较高的实用价值。     

Survey of switching techniques in high-speed networks and their performance

One of the most promising approaches for high speed networks for integrated service applications is fast packet switching, or ATM (asynchronous transfer mode). ATM can be characterized by very high speed transmission links and simple, hard-wired protocols within a network. To match the transmission speed of the network links, and to minimize the overhead due to the processing of network protocols, the switching of cells is done in hardware switching fabrics in ATM networks. A number of designs have been proposed for implementing ATM switches. Although many differences exist among the proposals, the vast majority of them are based on self-routeing multistage interconnection networks. This is because of the desirable features of multi-stage interconnection networks such as self-routeing capability and suitability for VLSI implementation. Existing ATM switch architectures can be classified into two major classes: blocking switches, where blockings of cells may occur within a switch when more than one cell contends for the same internal link, and non-blocking switches, where no internal blocking occurs. A large number of techniques have also been proposed to improve the performance of blocking and non-blocking switches. In this paper, we present an extensive survey of the existing proposals for ATM switch architectures, focusing on their performance issues.     

Performance Benefits of Virtual Path Tunneling for Control and Management Flows in the Broadband ATM Networks

In this paper, we analyze the performance benefits of broadband ATM networks when the call control and management flows are separated from user data flows. The virtual path tunneling concept for control and management flows are applied to the same physical ATM networks. The behaviors of channel throughput and transfer delay are analyzed. It results that the proposed virtual short-cut paths can maintain the network being stable with acceptable bandwidth. They are very useful to provide the stable control and management capabilities for Internet and mobile applications in the broadband ATM networks. In our numerical results, the effective throughputs of the proposed virtual short-cut channel are about three times than those of end-to-end user data channels with hop distances of 10, and about two times than those with hop distance of 5 when the link blocking probability increases to 0.1. It concludes that the effective channel bandwidth are greatly reduced down while physical links are not stable and user traffic flows are occasionally overflowed.     

An ATM queue manager handling multiple delay and loss priorities

The asynchronous transfer mode (ATM) technique has been widely accepted as a flexible and effective scheme to transport various traffic over the future broadband network. To fully utilize network resources while still providing satisfactory quality of service (QOS) to all network users, prioritizing the user's traffic according to their service requirements becomes necessary. During call setup or service provisioning, each service can be assigned a service class determined by a delay priority and a loss priority. A queue manager in ATM network nodes will schedule ATM cells departing and discarding sequence based on their delay and loss priorities. Most queue management schemes proposed so far only consider either one of these two priority types. The queue manager handles multiple delay and loss priorities simultaneously. Moreover, a cell discarding strategy, called push-out, that allows the buffer to be completely shared by all service classes, has been adopted in the queue manager. We propose a practical architecture to implement the queue manager by using available VLSI sequencer chips     

Performance Evaluation and Resource Management of Hierarchical MACRO-/MICRO Cellular Networks using MOSEL-2

The paper presents a performance evaluation and resource management of hierarchical MACRO-/MICRO cellular networks using the new Modeling and Evaluation Language (MOSEL-2). MOSEL-2 with new constructs has the ability to find the performance and reliability modeling and evaluation of systems with exponential and non-exponential distributions. A MACRO/MICRO cell structure is solved numerically and mathematically in this paper to handle the handoff calls. Additionally, a simulation program is written to validate these results. In order to reduce the loss probability, a guard channels are introduced at the MICRO cell and channel reservation at the MACRO cell. Additionally, the concept of queuing is introduced where there is a possibility for the handoff calls from both MACRO and MICRO layers to be queued when all the resources are occupied. MOSEL-2 is used to find the numerical solution for this problem with both exponential and general exponential (GE) distribution. The performance analysis show the efficiency of the proposed scheme to manage the handoff calls and the ability of the suggested scheme to reduce the blocking probability of handover calls and the loss probability as the main objective is to block the new connection rather than terminating the ongoing connection as well as balancing the load all over the whole network. It is shown in this paper that there are a set of important factors that affect the performance, such as: reservation policy, channel allocation, handover ratio, capacity of the queue and the variation of the inter-arrival times. These factors are discussed via some important performance measures, such as: new call blocking probability, blocking probability of handover calls, loss probability, utilization and the average delay of the queue.     

Performance evaluation — Test configurations and results

In this paper experimental designs for investigating performance parameters and their corresponding experimental results on the EXPLOIT testbed facilities are given. In an exemplary way the performance evaluation of a switch and an ATM network is described. These designs and results can be used in two ways: firstly in determining the network performance of already existing equipment and networks and secondly in designing new equipment by modelling the described scenarios within simulations. As important network performance parameters under study have been identified cell delay, cell loss and cell delay variation. These will be investigated together with some techniques for assessing those. Initially the question, whether the occurring delays in successive switches are independent, is tackled. If the independence assumption holds true or the correlation can be quantified, then out of measurements at a single switch the delay behaviour after having passed a number of switches can be determined, thus extrapolation from a small network to a larger one becomes possible. Afterwards the fairness of the switch design with respect to multiplexing traffic sources while being in an overload state are discussed. For being able to predict delays in the future the suitability of traditional queueing models will be checked. Out of this, forecasts on cell losses can be gained as well. For this investigation specific traffic mixes have been chosen, which are representative of the predicted traffic for future ATM networks. Also some results on the end-to-end cell delay variation are given.     

Performance modeling of partial packet discarding using theend-of-packet indicator in AAL type 5

The ATM adaptation layer type 5 (AAL5) is an adaptation layer protocol for the ATM layer of broadband integrated services digital networks (BISDNs), which targets connection-oriented services. Among several features, it is unique in the sense that it includes an end-of-packet (EOP) indicator in the header of the ATM cell (the ATM-layer-user-to-ATM-layer-user (AUU) parameter in the payload type (PT) field). It was suggested that the use of this indicator may be used to provide a means by which buffer occupancy can be reduced by selectively dropping cells from already incomplete packets [Armitage and Adams, 1993]. The objective of this paper is to study the performance of this layer and the effectiveness of the EOP indicator. The performance measures of interest are the probability of packet loss and the mean packet delay. An approximate analytical model is constructed in which the blocking of a tagged source is kept track of in an exact manner. The rest of the sources are modeled approximately. The accuracy of the model is enhanced through an iterative approach. A simulation model is also constructed to assess the accuracy of the approximate model     

Traffic analysis for multiparty videoconferencing in virtual path‐based ATM networks

With effective bandwidth concept encapsulating cell‐level behaviour, asynchronous transfer mode (ATM) network design and analysis at the call‐level may be formulated in the framework of circuit‐switched loss networks. In this paper, we develop an analytical framework for a kind of multiparty videoconferencing in the VP‐based ATM network at call‐level. For this kind of conference, only the video of the current speaker is broadcast to other conferees. We first address several conference management issues in the VP‐based ATM network, including the bandwidth allocation strategies, routing rule, call admission policy and speaker change management. Next, we formulate a traffic model for the conferences. Since an exact analysis of such a multiparty conference network is mathematically intractable, an approximate analysis for such conferences in a fully connected VP network is performed. The key of our method is to make use of the reduced‐load approximation and open Jackson network model to derive the traffic loads from new conferences as well as that from the speaker change of the on‐going conferences. Our study shows that the proposed analysis can give accurate predictions of the blocking probabilities for the new conference calls as well as video freeze probabilities for the on‐going conferences. Copyright © 2000 John Wiley & Sons, Ltd.     

Call admission control in an ATM network using upper bound of cellloss probability

Call admission control in ATM networks without monitoring network load is proposed. Traffic parameters specified by users are employed to obtain the upper bound of cell loss probability, thereby determining call admission. A cell loss probability standard is guaranteed to be satisfied under this control without assumptions of a cell arrival process. Implementation of this control to quickly evaluate cell loss probability after acceptance of a new call is discussed. The result is also applicable to ATM network dimensioning based on traffic parameters     

具有质量控制功能的ATM交换节点的性能分析

本文提出一种用于ＡＴＭ网的质量控制方法－动态到达控制（ＤＡＣ），分析了采用ＤＡＣ的ＡＴＭ交换节点中，各类业务信元的丢失概率和平均时延，分析结果表明，ＤＡＣ是一种有效的质量控制方式，它能够提供多种服务等级以满足不同的需要，减小所有信元的平均时延，提高系统的有效吞吐量。     

Adaptive resource allocation for prioritized call admission over anATM-based wireless PCN

In future personal communications networks (PCNs) supporting network-wide handoffs, new and handoff requests will compete for connection resources in both the mobile and backbone networks. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The previously proposed guard channel scheme for radio channel allocation in cellular networks reduces handoff call blocking probability substantially at the expense of slight increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. While the effectiveness of a fixed number of guard channels has been demonstrated under stationary traffic conditions, with nonstationary call arrival rates in a practical system, the achieved handoff call blocking probability may deviate significantly from the desired objective. We propose a novel dynamic guard channel scheme which adapts the number of guard channels in each cell according to the current estimate of the handoff call arrival rate derived from the current number of ongoing calls in neighboring cells and the mobility pattern, so as to keep the handoff call blocking probability close to the targeted objective while constraining the new call blocking probability to be below a given level. The proposed scheme is applicable to channel allocation over cellular mobile networks, and is extended to bandwidth allocation over the backbone network to enable a unified approach to prioritized call admission control over the ATM-based PCN     

The Effects of Management Traffic on the Local Call Processing Performance of ATM Switches Using Queue Network Models and Jackson's Theorem

This paper considers a TMN‐based management system for the management of public ATM switching networks using a four‐level hierarchical structure consisting of one network management system, several element management systems, and several agent‐ATM switch pairs. Using Jackson's queuing model, we analyze the effects of one TMN command on the performance of the component ATM switch in processing local calls. The TMN command considered is the permanent virtual call connection. We analyze four performance measures of ATM switches—utilization, mean queue length and mean waiting time for the processor directly interfacing with the subscriber lines and trunks, and the call setup delay of the ATM switch—and compare the results with those from Jackson's queuing model.     

Performance evaluation of packet data services over cellular voice networks

In this paper we develop a Markov chain modeling framework for throughput/delay analysis of data services over cellular voice networks, using the dynamic channel stealing method. Effective approximation techniques are also proposed and verified for simplification of modeling analysis. Our study identifies the average voice call holding time as the dominant factor to affect data delay performance. Especially in heavy load conditions, namely when the number of free voice channels becomes momentarily less, the data users will experience large network access delay in the range of several minutes or longer on average. The study also reveals that the data delay performance deteriorates as the number of voice channels increases at a fixed voice call blocking probability, due to increased voice trunking efficiency. We also examine the data performance improvement by using the priority data access scheme and speech silence detection technique.     

A lossless handover method for video transmission in mobile ATMnetworks and its subjective quality assessment

Cell loss is one of the major causes of degradation in quality of service in ATM mobile communication systems. It can be suppressed by employing buffer memories in the network; however, cell delay occurs as a consequence. This article proposes a lossless handover method for mobile ATM communication networks that both prevents cell loss and can suppress cell delay variation. The method was simulated on an experimental system to subjectively evaluate MPEG2 images relative to buffer memory size and the results obtained are presented     

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     

Common packet data channel (CPDC) for integrated wireless DS-CDMAnetworks

A common packet data channel (CPDC) architecture is proposed to support bursty, packet-based services in direct sequence code-division multiple-access (DS-CDMA) integrated wireless access networks. The architecture employs an asynchronous transfer mode (ATM) strategy in the forward CPDC link and a spread ALOHA-type random access strategy in the reverse CPDC link. A congestion control algorithm using base station broadcast and portable terminal random delay call reattempt is described. A performance analysis of the CPDC architecture and algorithms is carried out, and formulas for the bit error rate, blocking probability, system delay time, transmission time, and waiting time for packet data calls are derived. The interference caused by a CPDC to stream services in the network is determined, and the capacity of a CPDC is evaluated in terms of the number of packet data subscribers that can be served with a specified grade of service (GOS)     

Contention-free distributed dynamic reservation MAC protocol withdeterministic scheduling (C-FD3R MAC) for wireless ATMnetworks

This paper proposes a novel MAC protocol for wireless ATM networks, which is characterized by a contention-free mechanism of the reservation request and a deterministic nature of mobile-assisted (distributed) uplink scheduling under a framework of the dynamic reservation TDMA, as discussed in the current standardization activities of ETSI Project BRAN (broadband radio access network) and the wireless ATM working group in the ATM Forum. The design objective of the proposed MAC protocol is to guarantee the real-time constraint of the real-time VBR (rt-VBR) traffic class while maximizing the multiplexing gain among all ATM traffic classes, especially with a fixed length frame. The proposed deterministic scheduling scheme for the rt-VBR traffic class lends itself to implementing the minimal configuration of control data units for reservation request as desired under the limited wireless resources. Simulation experiments using statistically multiplexed MPEG-2 video streams are performed for a 25 Mbits/s wireless ATM access link scenario. It has been shown that the proposed framework guarantees the delay constraint of rt-VBR sessions along with its cell loss rate significantly reduced, while improving the average delay performance of the nrt-VBR in the range of 10%-30% without compromising the channel utilization as compared to the DSA++ system