Heavy-traffic extreme-value limits for queues

  • Authors:
  • Peter W. Glynn;Ward Whitt

  • Affiliations:
  • Department of Operations Research, Stanford University, Stanford, CA 94305-4022, USA;AT&T Bell Laboratories, Murray Hill, NJ 07974-0636, USA

  • Venue:
  • Operations Research Letters
  • Year:
  • 1995

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Abstract

We consider the maximum waiting time along the first n customers in the G1/G/1 queue. We use strong approximations to prove, under regularity conditions, convergence of the normalized maximum wait to the Gumbel extreme-value distribution when the traffic intensity @r approaches 1 from below and n approaches infinity at a suitable rate. The normalization depends on the interarrival-time and service-time distributions only through their first two moments, corresponding to the iterated limit in which first @r approaches 1 and then n approaches infinity. We need n to approach infinity sufficiently fast so that n(1 - @r)^2 - ~. We also need n to approach infinity sufficiently slowly: If the service time has a pth moment for @r 2, then it suffices for (1 - @r)n^1^p to remain bounded; if the service time has a finite moment generating function, then it suffices to have (1 - @r)log n - 0. This limit can hold even when the normalized maximum waiting time fails to converge to the Gumbel distribution as n - ~ for each fixed @r. Similar limits hold for the queue-length process.