We analyze 20 large sets of actual variable-bit-rate (VBR) video data, generated by a variety of different codecs and representing a wide range of different scenes. Performing extensive statistical and graphical tests, our main conclusion is that long-range dependence is an inherent feature of VBR video traffic, i.e., a feature that is independent of scene (e.g., video phone, video conference, motion picture video) and codec. In particular, we show that the long-range dependence property allows us to clearly distinguish between our measured data and traffic generated by VBR source models currently used in the literature. These findings give rise to novel and challenging problems in traffic engineering for high-speed networks and open up new areas of research in queueing and performance analysis involving long-range dependent traffic models. A small number of analytic queueing results already exist, and we discuss their implications for network design and network control strategies in the presence of long-range dependent traffic. >

Long-range dependence in variable-bit-rate video traffic

Traffic models are at the heart of any performance evaluation of telecommunications networks An accurate estimation of network performance is critical for the success of broadband networks Such networks need to guarantee an acceptable quality of service (QoS) level to the users Therefore, traffic models need to be accurate and able to capture the statistical characteristics of the actual traffic We survey and examine traffic models that are currently used in the literature Traditional short-range and non-traditional long-range dependent traffic models are presented The number of parameters needed, parameter estimation, analytical tractability, and ability of traffic models to capture marginal distribution and auto-correlation structure of the actual traffic are discussed

Traffic models in broadband networks

Over the last few years, a substantial number of call admission control (CAC) schemes have been proposed for ATM networks. We review the salient features of some of these algorithms. Also, we quantitatively compare the performance of three of these schemes.

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Call admission control schemes: a review

The authors explore a new concept of spectral characterization of wide-band input process in high speed networks. It helps them to localize wide-band sources in a subspace, especially in the low-frequency band, which has a dominant impact on queueing performance. They choose simple periodic-chains for the input rate process construction. Analogous to input functions in signal processing, they use elements of DC, sinusoidal, rectangular pulse, triangle pulse, and their superpositions, to represent various input correlation properties. The corresponding input power spectrum is defined in the discrete-frequency domain. In principle, a continuous spectral function of stationary random input process can be asymptotically approached by its discrete version as one sufficiently reduces the discrete-frequency intervals. An understanding of the queue response to the input spectrum will provide a great deal of knowledge to develop advanced network traffic measurement theory, and help to introduce effective network resource allocation policies. The new relation between queue length and input spectrum is a fruitful starting point for further research. >

Queue response to input correlation functions: discrete spectral analysis

Queueing performance in a richer, heterogeneous input environment is studied. A unique way to understand the effect of second- and higher-order input statistics on queues is offered, and new concepts of traffic measurement, network control, and resource allocation are developed for high-speed networks in the frequency domain. The technique applies to the analysis of queue response to the individual effects of input power spectrum, bispectrum, trispectrum, and input-rate steady-state distribution. The study provides clear evidence that of the four input statistics, the input power spectrum is most essential to queueing analysis. Furthermore, input power in the low-frequency band has a dominant impact on queueing performance, whereas high-frequency power to a large extent can be neglected. >

Queue response to input correlation functions: continuous spectral analysis

A method of characterizing video codec sources in asynchronous transfer mode (ATM) networks as an autoregressive moving average (ARMA) process is described. Measurements of long-term mean and the autocorrelation function of cell interarrival times allow the parameter estimation of the ARMA model. The video source is then described by ARMA model. Furthermore, it is shown that the multiplexed stream of video cells is also an ARMA process. Such a cell stream is then applied to a model of a queuing system to obtain performance measures of the system. Perturbation analysis is then performed on the functional behavior of the queuing system by appropriate perturbation of the model parameters to determine cell waiting time sensitivity due to slight variations of the input process. >

Characterization of video codecs as autoregressive moving average processes and related queueing system performance

Presents methods of measurements and a procedure for characterising a conditional replenishment (CR) video codec, as described by Chin (see IEEE SAC, SAC-7, p.826, 1989), as an autoregressive moving average process (ARMA). The ARMA process has been adopted because it has been shown by Ramaswami (1988) that the quality of service (cell congestion, cell waiting time in buffer) performance measures of a queueing system are most sensitive to the autocorrelation function of the arrival process. Also the estimated autocorrelation function of the video codec gives a good indication of its functional behaviour. The long term mean, variance and autocovariance function are measured from the cell output of the simulated video codec. These are then used to estimate the parameters of a mathematical model of an ARMA process. The mathematical model consists of a transverse filter of finite order and a recursive filter with a cell interarrival sequence which is assumed to be wide sense stationary (WSS).<
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S. Manthorpe

Papers

Characterization of video codecs as autoregressive moving average processes and related queueing system performance

Characterisation of variable rate video codecs as autoregressive moving average processes for ATM networks