vered at the end of this chapter. An ad hoc network means units that occasionally are close to other units and establish a connection and relationship between them. An example would be to utilize an (idle) near-by TV screen as a display for a mobile service, by attaching it to a mobile device. Bluetooth is a main enabler for ad hoc networks. Most of what happens in the telecom world has a business-oriented explanation, often service-oriented. The access area is no exception. Let us therefore take a brief look at access as a serving network segment to the driving services. Figure 13.3 shows four main steps from voice over voice optimized systems to multimedia over IP systems. The trend is a development from 'all services over circuit mode' to 'all services over IP', although there is a pronounced uncertainty, for example for QoS reasons. At the same time the narrowband bandwidth is successively complemented by broadband accesses to fixed and mobile subscribers. The development towards IP is shown in Figure 13.4. 1. Voice over voice optimized system (fixed PSTN developing towards cellular PLMN) 2. Modem, dialled up over voice optimized system 3. Broadband data/ Internet 'Always on' etc. over data optimized system 4. Voice and data over compromise system (cells) 5. Voice and data over IP with QoS Figure 13.3 Access network service drivers Advanced multi- Important part media of profitable service offering Basic multi- media Voice Telephony over IP Carrier Leased line solution services Internet High speed Internet/intranet Figure 13.4 Two main applications of IP today are Internet access and IP-VPN, with VoIP and MMoIP (multimedia over IP) in the pipeline or being implemented Understanding Changing Telecommunications - Building a Successful Telecom Business As seen from previous chapters, VoIP (as a replacement for PSTN/GSM etc.) requires new signalling in the network (SIP or H.323) and the multimedia may require support from the IMS in for example UMTS (see Chapter 14). 13.3.1 HISTORY AND FUTURE The access area incl