This paper presents the stochastic approach to congestion that is unknown to some users or designers of telecommunication networks. Its purpose is to help designers predict network behavior, characterize load, determine number and size of components, these elements are important for those who want to optimize the network in terms of its architecture, so as to meet the required quality of service standards by taking the most economical route possible. This approach will be based on the modelizations of the arrival and the waiting calls on the network following some hypotheses. A key element of call reception to consider is the base transmission station (BTS) in the GSM network or the NODE B in the 3G to 4G + networks.