Loss of Point-to-Point Traffic in Three-Stage Circuit Switches
by M. Karnaugh
A theoretical study is made of simple analytical models for the point-to-point loss of telecommunication traffic caused by blocking in three-stage circuit switches. Two new models are compared with Jacobaeus' frequently used model and with some simulation results to determine regions of acceptable accuracy. The effects of random hunting and sequential hunting for routes are compared by simulation. The results apply to space-division link systems and also to some time-division switches of current interest. In the case of random hunting, the new models give improved agreement with simulation results. The overestimate of loss inherent in the Jacobaeus method, however, is found to be acceptably low when the numbers of primary and tertiary matrix switches are not small, e.g. > 10. We lack a good analytical model for the sequential hunting method, which is found to result in lower traffic loss for the switches being studied.