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Poisson Cluster process as a model for teletraffic arrivals and its ...

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How long is the length of each cluster?<br />

The answer to this question is of importance<br />

<strong>for</strong> various structural properties of the cluster<br />

<strong>process</strong>, in particular <strong>for</strong> <strong>its</strong> dependence structure.<br />

Obviously,<br />

S K =<br />

K�<br />

Xi .<br />

i=1<br />

Under what conditions is S K regularly varying?<br />

We start with the c<strong>as</strong>e when X h<strong>as</strong> heavier tail<br />

than K.<br />

Proposition 1. Assume that P(X > x) is<br />

regularly varying <strong>for</strong> some α > 0, EK < ∞ <strong>and</strong><br />

P(K > x) = o(P(X > x)). Then, <strong>as</strong> x → ∞,<br />

P(S K > x) ∼ EK P(X > x) .<br />

9

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