Queueing Systems 32 (1999) 5±40 5 A heavy traf®c limit theorem for a class of open queueing networks with ®nite buffers ∗ J.G. Dai a and W. Dai b,∗∗ a School of Industrial and Systems Engineering, and School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332-0205, USA E-mail:
[email protected] b School of Mathematics, Georgia Institute of Technology, Atlanta, GA 30332-0160, USA Submitted 1 February 1998; accepted 1 December 1998 We consider a queueing network of d single server stations. Each station has a ®nite capacity waiting buffer, and all customers served at a station are homogeneous in terms of service requirements and routing. The routing is assumed to be deterministic and hence feedforward. A server stops working when the downstream buffer is full. We show that a properly normalized d-dimensional queue length process converges in distribution to a d-dimensional semimartingale re¯ecting Brownian motion (RBM) in a d-dimensional box under a heavy traf®c condition. The conventional continuous mapping approach does not apply here because the solution to our Skorohod problem may not be unique. Our proof relies heavily on a uniform oscillation result for solutions to a family of Skorohod problems. The oscillation result is proved in a general form that may be of independent interest. It has the potential to be used as an important ingredient in establishing heavy traf®c limit theorems for general ®nite buffer networks. Keywords: ®nite capacity network, blocking probabilities, loss network, semimartingale re¯ecting Brownian motion, RBM, heavy traf®c, limit theorems, oscillation estimates 1.