point Mobility management, charging, security (management Ex BSC subscriber data Requirements Access Access Backbone transport Access node 2 Revenue Expenses Capital employed Figure 13.2 A broader view of access architecture, environment and issues velocity, variations in business conditions such as ARPU, adaptation to geographical topology and subscriber density, distance to the edge node, cost development and new enabling technologies. The result is thousands of different possible access network designs. Therefore stress is put on the more generic aspects of access, complemented with overview information on some specific systems. In the long run access independence is more or less necessary, and the development is ongoing. A fairly generic access architecture with some hot issues is shown in Figure 13.2. The access network is continuously evolving and adapting to meet emerging needs. Some drivers of this evolution are business aspects (expressed as ROCE etc.), service development and the related need for bandwidth, the Internet protocol (IP), the regulatory development such as unbundling of the local loop, competition; emerging technologies; QoS and reliability; security requirements and the formation of a multi-service and all- access core network. A brief part on the access network as the bandwidth bottleneck is included in Chapter 3, Section 3.13.2. See also Chapter 4, Section 4.7.3, which deals with cost efficiency in the access network. Finally, Chapter 8, Section 8.3, Figure 8.12 and associated text gives more introductory input to the area of this chapter. 13.3 WHAT IS AN ACCESS NETWORK? In the reference model used, the access network extends between the subscriber premises and the point that corresponds to a mobile switching centre (MSC), local exchange (office), edge node or media gateway (MGW). In this book, the term access network (AN) is used to represent only the basic access connectivity service over various infrastructure technologies. Access Network What is called an ad hoc network is briefly co