r rate (BER). The UMTS network designer must fulfil QoS requests from the UMTS application or user. In addition to these four classes the global information infrastructure (GII) presented another two classes according to a taxonomy described in the Telecommunication Journal of Australia, 47(2), 1997. Understanding Changing Telecommunications - Building a Successful Telecom Business GII considers transactional and messaging services as separate from other conventional groups. A particular advantage is that both these service types were represented among the list for mobile Internet. See Sections 5.3.2 (Transactional services) and 5.3.6 (Mes- saging services). Messaging is in addition a very important service type, today it is the biggest non-voice service used over mobile networks. Some analysts expect transactional mobile services to successively become one of the biggest non-voice services. In addition, transactional services represent the important security area. This book thus uses a set of six service classes as an input to service implementation. See Figure 5.7. All the services are covered, but some services need one or more service enablers, such as positioning services. 5.4.1 CONVERSATIONAL CLASS 1. Video telephony - Video telephony is a real-time service, which is the most demand- ing type. Due to the nature of video compression, the BER requirement for video is even more stringent than that of speech. It is indeed very important to distin- guish between conversational real-time services and other services, because of the development towards multimedia paired with the original basic mismatch between the conversational services and the packet-based technologies. 2. Voice telephony - The integrity of the existing telephony service is a key concern for service providers. The following distinction is useful, recognizing that classical telephony and IP telephony are really two different services: Classical telephony, i.e. the existing PSTN telephony service with its characteristics and service features, irres