hort set-up times, being able to communicate with many others (having many film titles to select from), being able to find them (catalogue or enquiry services), mobility and clear billing information. 7.3.6 QOS CLASSES Service Classification In this part of the chapter a brief summary of the connection between services and QoS classes is presented. The real behaviour depends a lot on the traffic situation in the network. In calculating a traffic model, the end-user behaviour with regard to particular applications needs to Quality of Service Table 7.2 UMTS traffic classes and some related requirements QoS class Transfer Transfer Low bit Guaranteed Example delay delay error rate bit rate requirement variation Conversational Stringent Stringent VoIP, video conferencing, audio conferencing Streaming Constrained Constrained Broadcast services (audio, video), news, sport Interactive Looser Web browsing, interactive chat, games, m-commerce Background E-mail, SMS, database downloads, transfer of measurements be determined. The mix of applications and the daily traffic distributions must also be characterized in order to carry out analyses and calculations. All types of packet data traffic will not have the same requirements on delays, packet loss etc. As a result traffic may be divided into four different classes: streaming, conver- sational, background and interactive. See section 5.4. Real-Time Applications Streaming The fundamental characteristics for QoS are to preserve time variation between information entities of the stream, e.g. video streaming. Conversational Here the fundamental QoS characteristics are to preserve time variation between information entities of the stream and to have a low delay, e.g. voice. Non Real-Time Applications Background In the background class, the destination is not expecting the data within a certain time but is expecting a preserved payload content, e.g. e-mail. Interactive A request/response pattern is important in the interactive class and the payload content must be preserved. UMT