ing to Figure 3.18. The control layer is further dealt with in Chapter 14. 3.11 THE SERVICE LAYER From the convergence point of view the service network has the most central position. See Figure 3.34. An obvious task becomes integrating contents with users, their terminal capabilities and the network capabilities. Another task is to successively support new sets of applications. The service layer role for service implementation is further dealt with in Chapter 8, and the service network itself is dealt with in Chapter 9. The service layer responds to a number of needs: Contents Needless to say, multimedia is an important requirement for content. The final receivers are the eye, the ear and the computer, which could be a mobile device. For mobile devices it should be possible to update the content according to posi- tion. Other changes of content may be synchronization of content with other terminals employed by the user. It might/should be possible to download applications to the terminal, in order to offer new content. (Java, .NET). It should be possible to receive real-time, streamed or stored content. Client terminal Server Application control Applications Applications Service layer Positioning, MMS, WAP, kJava Service enablers Adaptations & session control GPRS, UMTS (and other) networks Figure 3.34 The position of service enablers - they also extend to the terminals Networks and Technologies Terminal capabilities and requirements The content can be coded in different ways, such as AMR, MPEG-4, XML and VML. The receiver must be able to decode the received standard. The small presentation format of mobile terminals must be considered. Security and QoS protocols might be necessary (tunnels, RTP, RTSP, RTCP). Header compression protocols are an advantage, especially for IP calls. New signalling protocols may be required in the terminal (SIP, SDP, possibly H.323 type of protocols.) Configuration over the air is important, as well as device management. Network capabilities It should be possible to select capabilit