A vacation queueing model with service breakdowns

In this paper we analyze a multiple-vacation queueing model, where the serv ice station is subject to breakdown while in operation. Service resumes imm ediately after a repair process, and a vacation starts at the end of each b usy period. Arrivals follow a Poisson process with rates depending upon the system state, namely, vacation, service, or breakdown state. The repair ti mes, times to breakdown following a repair or vacation, uninterrrupted serv ice times, and length of each vacation follow exponential distributions. So me results are also obtained when vacation, service, and repair times follo w phase-type distributons. (C) 2000 Elsevier Science Inc. All rights reserv ed.