On the time to reach a certain orbit level in multi-server retrial queues

Multi-server retrial queues are widely used to model stochastically many telephone systems and computer networks. This paper studies the distribution of the time needed to reach a certain level of congestion, i.e., a given number of customers in the retrial group. We present a detailed algorithmic analysis which includes the computation of the time to reach a critical number of customers (continuous descriptor), the number of customers served during such a time (discrete descriptor) and the corresponding moments for both queueing performance measures.