ABSTRACT :  In this paper, we investigate the bulk service queue with Bernoulli vacation schedule and restricted admissibility introduced and studied by Madan and Abu-Dayyeh, [Revista Investigacion Operacional, Vol.24, No.2, pp.113- 123, 2003]. Madan and Abu-Dayyeh assume exponentially distributed service times while we allow these times to be generally distributed. We obtain various performance measures that we use to derive the optimal values of the quorum size and maximum server capacity. The effect of the admission control parameter is further shown in a numerical example.

ABSTRACT : We present an iterative scheme based on the fixed-point approximation method, for the numerical calculation of the time-dependent mean number of customers and blocking probability functions in a nonstationary queueing network with multi-rate loss queues. We first show how the proposed method can be used to analyze a single-class, multi-class, and multi-rate nonstationary loss queue. Subsequently, the proposed method is extended to the analysis of a nonstationary queueing network of multi-rate loss queues.

ABSTRACT : The nonstationary Erlang loss model is a queueing system consisting of a finite number of servers and no waiting room with a nonstationary arrival process or a time-dependent service rate. The Erlang loss model is commonly used to model and evaluate many communication systems. Often, these types of service systems encounter a change in the arrival rate over time while the service rate remains either constant or changes very little over time.

ABSTRACT : Circuit-switched communication networks have been analyzed extensively in the stationary case, i.e. where the arrival and/or service rates are independent of time. In this paper, we study a circuit-switched network where the rates of external arrivals at the network are time-dependent functions. The circuit-switched network is modelled as a nonstationary queueing network with population constraints, which is analyzed approximately in order to obtain the blocking probability functions.

ABSTRACT : We present a survey of the main results and methods of the theory of retrial queues, concentrating on Markovian single and multi-channel systems. For the single channel case we consider the main model as well as models with batch arrivals, multiclasses, customer impatience, double connection, control devices, two-way communication and buffer. The stochastic processes arising from these models are considered in the stationary as well as the nonstationary regime.