Virtual waiting time in the single-server queuing system with unreliable server

The unreliable queuing system was considered both in the stationary and nonstationary modes. A Poisson flow of customers arrives to the system. The flow of stable failures makes up the renewal process, and the inter-failure intervals are distributed hyper-exponentially. The times of customer servicing and renewal of the servicing system are distributed arbitrarily. The virtual waiting time was established.