On Little’s Formula in Multiphase Queues

The structure of this work in the field of queuing theory consists of two stages. The first stage presents Little’s Law in Multiphase Systems (MSs). To obtain this result, the Strong Law of Large Numbers (SLLN)-type theorems for the most important MS probability characteristics (i.e., queue length of jobs and virtual waiting time of a job) are proven. The next stage of the work is to verify the result obtained in the first stage.

Diffusion Approximation for Efficiency-Driven Queues When Customers Are Patient

The analysis of queues with multiple servers is typically challenging when the service time distribution is general. Such analysis usually involves an infinite-dimensional process for tracking service ages or residual service times. In “Diffusion Approximation for Efficiency-Driven Queues When Customers Are Patient,” He demonstrates from a macroscopic perspective that, if customers are relatively patient and the system is overloaded, the dynamics of a many-server queue could be as simple as the dynamics of a single-server queue. In particular, the virtual waiting time process can be captured by a one-dimensional diffusion process, which enables us to obtain simple formulas for performance measures, such as service levels and effective abandonment fractions. To justify this diffusion model, a functional central limit theorem is established for the superposition of stationary renewal processes.

A note on the virtual waiting time in the stationary PH/M/c+D queue

In this paper we consider the stationary PH/M/c queue with deterministic impatience times (PH/M/c+D). We show that the probability density function of the virtual waiting time takes the form of a matrix exponential whose exponent is given explicitly by system parameters.

A note on the virtual waiting time in the stationary PH/M/c+D queue

In this paper we consider the stationary PH/M/c queue with deterministic impatience times (PH/M/c+D). We show that the probability density function of the virtual waiting time takes the form of a matrix exponential whose exponent is given explicitly by system parameters.

WAITING TIME ANALYSIS OF MULTI-CLASS QUEUES WITH IMPATIENT CUSTOMERS

In this paper, we study three delay systems where different classes of impatient customers arrive according to independent Poisson processes. In the first system, a single server receives two classes of customers with general service time requirements, and follows a non-preemptive priority policy in serving them. Both classes of customers abandon the system when their exponentially distributed patience limits expire. The second system comprises parallel and identical servers providing the same type of service for both classes of impatient customers under the non-preemptive priority policy. We assume exponential service times and consider two cases depending on the time-to-abandon distribution being exponentially distributed or deterministic. In either case, we permit different reneging rates or patience limits for each class. Finally, we consider the first-come-first-served policy in single- and multi-server settings. In all models, we obtain the Laplace transform of the virtual waiting time for each class by exploiting the level-crossing method. This enables us to compute the steady-state system performance measures.

Laws of Little in an open queueing network

The object of this research in the queueing theory is theorems about the functional strong laws of large numbers (FSLLN) under the conditions of heavy traffic in an open queueing network (OQN). The FSLLN is known as a fluid limit or fluid approximation. In this paper, FSLLN are proved for the values of important probabilistic characteristics of the OQN investigated as well as the virtual waiting time of a customer and the queue length of customers. As applications of the proved theorems laws of Little in OQN are presented.