Measurement Based Optimal Source Shaping with a Shaping+Multiplexing Delay Constraint

Modani, Natwar and Dube, Parijat and Kumar, Anurag (2000) Measurement Based Optimal Source Shaping with a Shaping+Multiplexing Delay Constraint. In: IEEE INFOCOM 2000. Nineteenth Annual Joint Conference of the IEEE Computer and Communications Societies, 26-30 March, Tel Aviv,Israel, Vol.3, 1807-1816.

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Most on-line (i.e., not stored) variable bit rate sources would find it difficult to a priori declare the traffic parameters required by a connection admission control strategy. There is thus the problem of measurement-based on-line estimation of source parameters. In this paper we address the problem of selection of source parameters based on minimising a buffer-bandwidth cost function in the network, for a specified delay QoS violation probability. We consider the shaping delay plus first-hop multiplexing delay; this is adequate, for example, for n statistically identical packet voice sources being multiplexed at a PBX, or in approaches where the end-to-end delay bound is broken into per-hop delay bounds. Our approach yields a leaky bucket rate parameter $P^{*}$, and the sum of the shaper buffer and leaky bucket depth $(B_s+\sigma)$. We show that, for a fluid source model, for a linear buffer-bandwidth cost function, and for lossless multiplexing, a sustainable rate parameter of $P^{*}$ and burst parameter of 0 yields the minimum cost. We propose and study a stochastic approximation algorithm for on-line estimation of $P^{*}$. We then use buffer-bandwidth cost considerations to arrive at an optimal leaky bucket depth $\sigma^{*}>0$ for lossy multiplexing of several statistically identical sources. The computation of $\sigma^{*}$ must be done at the network node. We show, by an example, the improvement in cost that is possible by lossy multiplexing and a positive $\sigma^{*}$.