Delay Analysis of a Queue with Reservation-Based Scheduling and Class-Dependent Service Times

In this paper, we study the delay characteristics of a discrete-time queue with a reservation-based scheduling mechanism. The objective is to provide a better quality of service to delay-sensitive packets at the cost of allowing higher delays for the best-effort packets. We consider a single-server infinite-capacity queue with general independent packet arrivals of class 1 (delay-sensitive) and class 2 (best-effort). The service times of the packets are independent and have a general distribution that depends on the class of the packet. The scheduling mechanism makes use of an in-queue reserved place for future class-1 packet arrivals. A class-1 arrival takes the place of the reservation in the queue, after which a new reservation is created at the tail of the queue. Class-2 arrivals always take place at the tail of the queue. Closed-form expressions are obtained for the probability generating functions and the mean values of the packet delays of both classes.