“…Of course, the stationary waiting time distribution of a GI/N/1 queue is matrix exponential [13,14], but the class of queueing models defined by QBD processes includes not only MAP/PH/1 queues but also Markovian queueing models in which arrival and service processes are mutually dependent. One example of those Markovian queueing models is a MAP/MSP/1 queue [11], where MSP is the abbreviation of Markovian service process; the MSP is a model similar to a Markovian arrival process (MAP) [7,8], where arrivals are replaced with service completions. The MSP can represent various queueing models such as vacation models, N -policy models, and exceptional service models.…”