Call Blocking Probabilities in a Two-Link Loss Model with Restricted Accessibility

In this paper we study the impact of restricted accessibility in a system of two parallel links that accommodates Poisson arriving calls from a single service-class. In a restricted accessibility system, a new call may be blocked even if available bandwidth units do exist at the time of its arrival. In the two-link system, each particular link has a low and a high threshold. Both thresholds express the number of in-service calls in the link. The low threshold shows the point up to which the link can support offloaded calls from the other link. The high threshold shows the point where one link starts offloading calls to the other link. The two-link system with restricted accessibility is modelled as a loss model whose steady state probabilities do not have a product form solution. In order to determine the main teletraffic performance metric in this model which is call blocking probabilities, we propose an approximate method. The accuracy of this method is verified via simulation and found to be quite satisfactory.