blished operators in the area. This makes investments in new cables extremely risky, since you don't know exactly where your new subscribers will be located. This favours radio solutions, as an intruder. Among wireless solutions PLMN 2G, 2.5G and 3G, LMDS (local multipoint distribution system) and WLAN (hot spots) are wireless alternatives to cover subscribers which have not subscribed to wired systems. Length of possible waiting lists. 13.4 ACCESS SYSTEM FRAGMENTATION After proceeding with business cases based on appropriate parameters including state-of- the-art access solutions, the operators selected a large number of access solutions. This has led to a fragmentation in subscriber access networks. See Figure 13.9. Especially the three top alternatives show a sub-fragmentation, sometimes denoted with 'X'. xDSL includes ADSL, HDSL, SDSL, SHDSL, RADSL and VDSL to take some variants. WLAN systems exist in a number of 802.11 standards. Mobile systems grow with new standards, while the older ones are still in operation. An example is the analogue Nordic NMT system 450 MHz with an excellent coverage. The evolution looks like Figure 13.10. The fragmentation will be treated at an overview level later in this chapter. Understanding Changing Telecommunications - Building a Successful Telecom Business User segment 1 LAN, WLAN e.g. human private Cellular (mobile) User segment 2 fixed cellular e.g. human business PSTN/ISDN Cable TV User segment 3 e.g. appliances Satellite Power line Figure 13.9 Fragmentation in access GSM/GPRS GSM/GPRS/EDGE WCDMA/HSDPA cdmaOne CDMA2000 1X CDMA2000 1X CDMA2000 1XEV First step into 3G Evolved 3G 28.8 kb/s 64 -144 Kb/s 384 Kb/s - 2 Mb/s 384 Kb/s - 10 Mb/s+ 2001/2002 2002/2003 2004+ Figure 13.10 Mobile system evolution 13.5 UNIFICATION At the same time there is an opposite converging trend in the core network. This requires a kind of cross-connect between access systems and the core, with three interfaces to the access network: A signalling interface, developing towards SIP, or possibly H.323.