On the Retrial and Redial Phenomena in GSM Networks

GSM operators work with call data that include retrials and redials as well. Based on these inated, virtual call attempt statistics, it appears that enormous demands are put on the available spectrum. In this paper, we develop simple models to estimate the expected number of retrials and redials per original call attempt, which is used to determine the eective load and the number of trac channels required to meet the grade of service. It is shown that signi cantly fewer channels are capable of handling high trac loads. I. Introduction A challenge often encountered by the GSM (Global System for Mobile Communications) operators is the gross errors in the theoretical predictions on the trac load and the corresponding number of required channels to meet a certain grade of service (GoS). This is particularly striking during rush hours, when the channel resources become inadequate and the blocking probability rapidly increases to levels that are unacceptable by the industry standards. D..