While analyzing the architecture of cellular networks it is noticeable that each of the networks in question is characterized by the radio access network and the backbone network. The core part of the mobile network is constructed through technologies used in telecommunications and computer wide area networks, and the most frequently used technology today is asynchronous transfer mode (ATM). This technology was a standard that was recommended for constructing the backbone network in early versions of the UMTS system (Section 2.2, Figure 2.4) and, in fact, it is still used by many operators. It is envisaged that newer versions of the UMTS system (Figures 2.5 and 2.6) as well as the backbone network in the LTE system (Section 3.2), will be constructed on the basis of the IP protocol (Internet Protocol).
Regardless of the technology used, the backbone network has been and will remain a network with virtual channel switching that services traffic generated by subscribers who use a number of different services (see, for example, Table 2.4). Traffic in such networks can be considered in three time scales (Figure 9.1): packet level, burst level and call level. From the perspective of designing and dimensioning of networks with virtual channel switching, the call level is the most important. It should be remembered, however, that traffic characteristics at the burst and the packet levels have a substantial influence upon characteristics at the call level. ...