  The interest to retrial queueing systems is due to their application to
telephone systems. The paper studies multiserver retrial queueing systems with
$n$ servers. Arrival process is a quite general point process. An arriving
customer occupies one of free servers. If upon arrival all servers are busy,
then the customer waits for his service in orbit, and after random time retries
more and more to occupy a server. The orbit has one waiting space only, and
arriving customer, who finds all servers busy and the waiting space occupied,
losses from the system. Time intervals between possible retrials are assumed to
have arbitrary distribution (the retrial scheme is exactly explained in the
paper). The paper provides analysis of this system. Specifically the paper
studies optimal number of servers to decrease the loss proportion to a given
value. The representation obtained for loss proportion enables us to solve the
problem numerically. The algorithm for numerical solution includes effective
simulation, which meets the challenge of rare events problem in simulation.

Probability