Analysis of multiserver queues with constant retrial rate

We consider multiserver retrial queues in which the time between two successive repeated attempts is independent of the number of customers applying for service. We study a Markovian model where each arriving customer finding any free server either enters service or leaves the service area and joins a pool of unsatisfied customers called `orbit'. This system is analyzed as a quasi-birth-and-death (QBD) process and its main performance characteristics are efficiently computed.