Effects of Day-to-Day Load Variation on Trunk Group Blocking

1.1 Background An important class of trunk groups in the Public Switched Network consists of those groups that provide the last-choice route for a call trying to reach its destination. The performance of such a "final trunk group" is defined to be the 20-day average blocking during the chosen busy hour of the busy season. In the Bell System, the final groups are sized for an objective of one percent average blocking (£.01) in the busy season. Figure 1 shows the history of the measured busy-hour loads offered to a trunk group over consecutive days. The degree of variability of the load measurements is not consistent with the hypothesis that the 123 60 50 - 40 - O o > Q 30 - 20 - 10 - 0 1 2 3