On-line measurement of QoS for call admission control

Online measurement of traffic can improve the quality of network monitoring and call admission control algorithms by providing reliable estimates of QoS parameters. We propose to estimate QoS by fitting an appropriate function to the buffer occupancy distribution of a single-server first-come/first-served queue. We collect samples of the buffer occupancy distribution just after packet arrivals in the queue. Then we fit an approximating function, a sum of exponentials, using minimum chi-squared estimation techniques. The QoS parameters can then be inferred from the fitted distribution function. We consider three types of minimum chi-squared estimators: the first uses the sample covariance matrix, while the last two use biased approximations that are considerably easier to compute. Furthermore, we extend these algorithms to virtual queuing systems to estimate the impact of additional connections being admitted to the queue. We provide algorithms and criteria for all three estimators, along with simulation results. These simulations show that we can quickly obtain reliable estimates of QoS parameters.