Robust and reliable multimedia transmission over the Internet
Víctor Manuel Ramos Ramos · 2004
In this thesis, we propose models to evaluate the performance of real-time multimedia applications. Besides, we propose a model for AIMD protocols. The first subject we study is a simple error correction (FEC) mechanism. We first model the network as an M/M/1/K queuing system. We assume a linear utility function relating the audio quality and the amount of redundancy. The redundancy of packet i is carried by packet i+f. Our analysis shows that, even for the case f->inf, this simple FEC scheme always leads to a quality deterioration. Next, we model the bottleneck router as an M/G/1/K queue. We consider two cases that may contribute to a quality improvement: (a) multiplexing the audio flow with an exogenous flow, and (b) considering non-linear utility functions. Under these assumptions, we show that this FEC scheme can lead to a quality improvement. The second subject investigated is about playout delay algorithms. We propose a set of moving average algorithms allowing to control the average loss rate in an audio session. We study and compare the performance of our algorithms by simulation with real packet traces. The third subject we study is about the performance of AIMD protocols. We propose, at the best of our knowledge, the first analytical model for this kind of protocols accounting for delay variability. The model is based on stochastic difference equations. It provides a closed-form expression for the throughput and for the window size in steady state. We show by analysis and simulation that an increase in delay variability improves the performance of AIMD protocols.