own fundamental plans with some exceptions: PSTN and ISDN are strongly related, and the transmission facilities are often shared between different networks. To a more limited extent an IN (intelligent network) network service layer is also common for a number of networks. An obvious difference between them is the user service-oriented top layers, which are much more developed in the IP networks. See Figure 3.6. The new network has to interwork with the networks already present. Therefore a good knowledge of current 'vertical' networks, in particular their network properties, benefits and drawbacks, is an excellent starting point (Figure 3.7). The various network types were originally dedicated to various media type services according to Table 3.1. GPRS is considered a step between GSM and UMTS but is no doubt supporting mobile access to the information society media sources. The telephony and data service domains are still more or less kept separate. Historically, most functionality was located on telephone exchanges with vertical inter- faces offering a number of signalling interfaces for adaptation to the existing network environment. Taking Sweden as an example, hundreds of signalling systems and vari- ants have been used. Apart from signalling the interfaces were fairly homogeneous. The carried voice traffic mainly had only two shapes: either analogue with a bandwidth of 300-3400 Hz or digital with 64 kbit/s bandwidth. It should be borne in mind that both Networks and Technologies Multi-network operator Multiple charging User segments FAB = Actor-user interface, with fulfilment, Roles Life-stage dimension assurance and Value/attitude dimension billing ROCE etc. Services, QoS, Security perception SM = Service Stable economic Services management (Fulfilment) e-mail NM = Network management e-mail Internet Internet (excl. (GSM, (excl. (GSM, PSTN/ Fundamental PSTN/ TDMA, content) content) TDMA, technical plans etc.) etc.) Investments Transmission Transmission Staff split on networks Figure 3.6 The vertical 'monoli