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Journal of Applied Mathematics and Stochastic Analysis
Volume 9 (1996), Issue 2, Pages 97-105

A non-regenerative model of a redundant repairable system: bounds for the unavailability and asymptotical insensitivity to the lifetime distribution

STORM Research Centre, University of North London, London N7 8DB, UK

Received 1 October 1995; Revised 1 February 1996

Copyright © 1996 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In this paper we investigate steady state reliability parameters of an F:r-out-of-N redundant repairable system with m(1mr1) repair channels in light traffic conditions. Such a system can also be treated as a closed queueing network of a simple kind. It includes two nodes, with infinite number of channels and m channels, respectively. Each of the N customers pass cyclically from one node to the other; the service time distributions are of a general form for both the nodes.

It is an N-component system with a general distribution A(t) of free-of-failure periods of the components is considered. Failed components are repaired by an m-channel queueing system with a general distribution B(t) of repair times. The system is assumed to be failed if and only if the number of failed components is at least r. (Only the rather difficult case rm+1 is considered.)

Let μ be the intensity of the stationary point process of the occurrences of (partial) busy periods within which systems failures happen at least once, and let Q be the steady-state unavailability of the system.

Two-sided bounds are established for Q and μ based on the behavior of the renewal rate of an auxiliary renewal process. The bounds are used for deriving some asymptotical insensitivity properties in light traffic conditions.