Considered are bulk systems of GI/M/1 type in which the server stands by
when it is idle, waits for the first group to arrive if the queue is empty, takes customers up to its capacity and is not available when busy. Distributions of arrival
group size and server's capacity are not restricted. The queueing process is analyzed via an augmented imbedded Markov chain. In the general case, the generating function of the steady-state probabilities of the chain is found as a solution of
a Riemann boundary value problem. This function is proven to be rational when
the generating function of the arrival group size is rational, in which case the solution is given in terms of roots of a characteristic equation. A necessary and sufficient condition of ergodicity is proven in the general case. Several special cases
are studied in detail: single arrivals, geometric arrivals, bounded arrivals, and an
arrival group with a geometric tail.
