  In this paper, we present a new queueing model providing the accurate average
system time for packets transmitted over a cognitive radio (CR) link for
multiple traffic classes with the preemptive and non-preemptive priority
service disciplines. The analysis considers general packet service time,
general distributions for the channel availability periods and service
interruption periods, and a service-resume transmission. We further introduce
and analyze two novel priority service disciplines for opportunistic spectrum
access (OSA) networks which take advantage of interruptions to preempt low
priority traffic at a low cost. Analytical results, in addition to simulation
results to validate their accuracy, are also provided and illustrate the impact
of different OSA network parameters on the average system time. We particularly
show that, for the same average CR transmission link availability, the packet
system time significantly increases in a semi-static network with long
operating and interruption periods compared to an OSA network with fast
alternating operating and interruption periods. We also present results
indicating that, due to the presence of interruptions, priority queueing
service disciplines provide a greater differentiated service in OSA networks
than in traditional networks. The analytical tools presented in this paper are
general and can be used to analyze the traffic metrics of most OSA networks
carrying multiple classes of traffic with priority queueing service
differentiation.
