@article{Wong2007generalizations,
author = {E. W. M. Wong and A. Zalesky and M. Zukerman},
title = {On generalizations of the Engset model},
journal = {IEEE Communications Letters},
volume = {11},
number = {4},
pages = {360-362},
month = {Apr.},
year = {2007},
abstract = {The Engset model has been extensively studied and
widely used for blocking probability evaluation in telecommunications networks.
In 1957, J.W. Cohen considered two generalizations of the Engset model: 1)
permitting the distributions of the holding time and interarrival time to differ
from source to source; 2) permitting the idle time distribution to depend on
whether or not the previous call was successful. He derived the call and time
congestions for the first generalization, however, he simply posed the second
generalization as a problem. In a leading teletraffic text by Syski, the call
and time congestions are approximated for the second generalization, though it
appears that Syski has overlooked that his results are in fact an approximation.
In this paper, we point out Syski's apparent oversight, we improve the accuracy
of his approximation, and we provide an efficient algorithm for its numerical
computation and prove its convergence.}
}