Stability analysis of two-class preemptive priority retrial queuing model with constant retrial rate

We deal with retrial model under constant retrial rate policy. The system involves two nonequivalent classes of customers. One class have so called preemptive or high priority, while the other has low priority. Namely if high priority new arrival enters the system and finds the server busy by the other class, the low priority customer interrupts its service and joins the corresponding orbit. Relying on Markov Chain method for two-component processes, we obtain necessary and sufficient stability conditions for this model. The presented analysis is applicable for the general models with nonexponential distribution of service times.