Statistical Multiplexing Gain Research Articles

Equivalent bandwidth and related admission criteria for ATM systems—a performance study

AbstractThe concept of the equivalent bandwidth of a source seems highly attractive for characterizing ATM traffic sources as it can be used to treat constant as well as variable bit rate sources within a common framework. In this paper we review the concept of equivalent bandwidth based on asymptotic results and study the performance of a few admission criteria which use this concept in one way or another. A major finding is that with appropriate refinements to account for the possible statistical multiplexing gain at small to moderate buffer sizes, the well‐known conservatism of the asymptotic equivalent bandwidth based criteria can be overcome. We also discuss how these criteria would perform in practical situations where the traffic sources are incompletely characterized, or where they are specified in terms of leaky‐bucket based traffic descriptors.

A self-healing ATM network based on multilink principles

Self-healing is the ability of a network to reconfigure itself around failures such that calls in progress are not dropped and suffer of no or almost no degradation in quality of service. Providing self-healing capabilities in all parts of the future ATM network in a cost effective way is therefore a key challenge. A new self-healing method based on the multilink concept is presented for dedicated parts of the ATM network, such as, for instance, feeder networks. In the multilink concept that is proposed, the cells of an ATM connection carried by a multilink are distributed over several physical links. If a physical link supporting the multilink fails, the cells will be distributed among the remaining physical links thus providing a self-healing capacity. In this way the quality of service can be maintained at the expense of a higher load on the remaining physical links. The speed of restoration only relies on the detection and signaling of the failure since spare capacity is available on the very multilink. The sharing of spare capacity in addition to the statistical multiplexing gain provides a cost effective self-healing method and leads to a simplified network resource management. The proposed multilink concept is based on an extension of the multipath self-routing concept, which is currently applied by Alcatel in its ATM switching fabric. >

Shared time division duplexing: an approach to low-delay high-quality wireless digital speech communications

Various strategies to provide low-delay high-quality digital speech communications in a high-capacity wireless network are examined. Various multiple access schemes based on time-division and packet reservation are compared in terms of their statistical multiplexing capabilities, sensitivity to speech packet dropping, delay, robustness to lossy packet environments, and overhead efficiency. In particular, a low-delay multiple access scheme, called shared time-division duplexing (STDD) is proposed. This scheme allows both the uplink and downlink traffic to share a common channel, thereby achieving high statistical multiplexing gain even with a low population of simultaneous conversations. The authors also propose a choice of low delay, high quality speech coding and digital modulation systems based on adaptive DPCM, with QDPSK or pseudo-analog transmission (skewed DPSK), for use in conjunction with the STDD multiple access protocol. The choice of the alternative systems depends on required end-to-end delay, recovered speech quality and bandwidth efficiency. Typically, with a total capacity of 1 MBaud, 2 ms frame and 8 kBaud speech coding rate, low delay STDD is able to support 48 pairs of users compared to 38, 35, and 16 for TDMA with speech activity detection, basic TDMA and PRMA respectively. This corresponds to respective gains of 26%, 37% and 200%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simulation analysis of a communication link with statistically multiplexed bursty noise sources

Variable bit rate (VBR) coding techniques have received great research interest as very promising tools for transmitting bursty multimedia traffic with low bandwidth requirements over a communication link. Statistically multiplexing the multimedia bursty traffic is a very efficient method of maximizing the utilization of the link capacity. The application of computer simulation techniques in analyzing a rate-based access control scheme for multimedia traffic such as voice traffic is discussed. The control scheme regulates the packetized bursty traffic at the user network interface of the link. Using a suitable congestion measure, namely, the multiplexer buffer length, the scheme dynamically controls the arrival rate by switching the coder to a different compression ratio (i.e., changing the coding rate). VBR coding methods can be adaptively adjusted to transmit at a lower rate with very little degradation in the voice quality. Reported results prove that the scheme greatly improves the link performance, in terms of reducing the probability of call blocking and enhancing the statistical multiplexing gain.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis on statistical multiplexing characteristics of atm cells with voice and video inputs

AbstractIn ATM networks, it is necessary to control the quality of service because a large number of traffic classes with different statistical characteristics and required quality of service is handled uniformly in these networks.This paper evaluates the characteristics of the statistical multiplexing gain among the heterogeneous cell streams from voice and video media. It is considered that the information of picture elements that change between adjacent video frames are packetized and then transmitted into ATM networks. Therefore, when one scene finishes, all the information for the new scene appears as a sudden burst at the first frame of the next scene. This is an important characteristic of video traffic which is called scene change here.By considering scene change, the superposed arrival process is modeled on the heterogeneous cell stream from voice and video media using the phase‐type Markov renewal process. By analyzing the queueing model with this process, the characteristics of the statistical multiplexing gain are obtained. In particular, by using numerical computation, the effect of scene change on the statistical multiplexing gain is evaluated.

Usage parameter control and bandwidth allocation methods for ATM-based B-ISDN

This paper proposes a ATM traffic management scheme that utilizes a deterministic source traffic descriptor, a deterministic Usage Parameter Control (UPC) algorithm and a conservative statistical bandwidth allocation method. The scheme not only guarantees the QOS of all connections but also allows for large statistical multiplexing gain. The proposed method, therefore, creates an effective B-ISDN that offers cost-effective broadband variable bit-rate services.

Precise UPC scheme and bandwidth allocation methods for ATM-based bisdn characterized by wide-ranging traffic parameter values

This paper proposes an ATM traffic management method that combines a deterministic source traffic descriptor, a deterministic usage parameter control (UPC) algorithm, and a conservative statistical bandwidth allocation method. The source traffic descriptor is based on sliding time interval-type descriptors for both the peak-rate and the average-rate. A UPC method which combines a sliding-window-type circuit and a two-phase credit-window-type circuit for widely-ranging traffic parameter values is proposed. The method is precise and accurate, and requires only a small amount of hardware. The bandwidth allocation method uses the worst pattern that can be transmitted through the proposed UPC circuit. The proposed traffic management method not only guarantees the QOS of all connections, but also allows for large statistical multiplexing gain. The proposed method, therefore, makes it possible to create a more effective BISDN, one that can offer cost-effective broadband VBR services.

Statistical multiplexing gain for variable bit rate video codecs in ATM networks

AbstractAsynchronous transfer mode (ATM) broadband networks will support variable bit rate video codecs, which are capable of maintaining a constant picture quality. To demonstrate this capability, a prototype hardware video coder has been developed in the Siemens Central Communications Laboratories. The prototype uses interframe coding, combined with a discrete cosine transform, and is able to reproduce the original picture quality, independent of signal sources or picture material used.A gain in transmission efficiency is expected when several video sources share a common ATM channel (‘statistical multiplexing’). This paper reports on a series of measurements that have been performed using this coder for a large variety of video sources to determine the possible gain in transmission efficiency.The main results are: for realistic video phone scenes, up to about three times the number of signals can be transmitted compared to transmision with constant rate and the same picture quality, if the output signal of the coder has been smoothed over a period of one frame. Smoothing over shorter periods reduces the potential gain substantially. The statistical multiplexing gain increases with the duration of the picture sequences due to the criterion of constant picture quality. It varies very little with the acceptable packet loss rate.

Statistical multiplexing in ATM networks

In this paper we evaluate the statistical multiplexing gain in ATM networks for bursty as well as variable bit rate (VBR) traffic using a fluid-flow approximate model. We obtain the required bandwidth per source in a finite buffer multiplexer in order to achieve a given Grade of Service (GOS), expressed by the cell loss probability. For both bursty and VBR traffic sources, we perform a sensitivity analysis of significant parameters in the homogeneous case (all traffic sources are of the same type). The required bandwidth for bursty sources is shown to depend on burst and buffer length through their ratio. Finally, the mixing of bursty traffic and variable bit rate is considered. We compare the results obtained through simulation with approximations proposed in the literature.

Toward a broadband congestion control strategy

The congestion control problem in asynchronous transfer mode (ATM) based broadband networks is defined. In general, a suitable set of congestion controls will include features for admission control, buffer and queue management, traffic enforcement, and reactive control. The leading alternatives for each of these congestion control features are summarized. An approach for choosing the best of these alternatives is presented, and a reasonable set of such alternatives that captures the increased utilization due to statistical multiplexing is suggested. It uses separate and static bandwidth pools for each service category; a statistical multiplexing gain determined for each bandwidth pool that supports a variable-bit-rate (VBR) service category; traffic enforcement on a virtual circuit basis using a leaky bucket algorithm with parameters set to accommodate anticipated levels of cell transfer delay variation; and multilevel loss priorities as well as a reactive control for appropriate VBR service categories based on multithreshold traffic enforcement and explicity congestion notification.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The impact of the ATM concept on video coding

The induction of the asynchronous transfer mode (ATM) concept may significantly influence the coding of video services for broadband networks. The authors show how the absence of a physical channel structure and the ability to switch bursty traffic can be used to enhance video coding. Packetization defects and their impact on picture quality, coding algorithms, and synchronization schemes are studied. The authors describe variable-bit-rate coding and report on the results obtained with a hardware implementation of a variable-bit-rate video codec. Statistical multiplexing gain figures are given. The influence of cell loss on image quality is discussed and simulation results are given. A layered coding model offering good cell loss concealment properties and high flexibility is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>