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 covered 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', a