 from around 64 kbit/s to more than 1 Mbit/s. Interactive browsing/downloads around say 100 kbit/s with a broad spectrum up and down. WAP browsing contains significantly fewer bytes and can therefore use a nar- rower bandwidth. Understanding Changing Telecommunications - Building a Successful Telecom Business Interactive multimedia browsing around say 300 kbit/s with a broad spectrum up and down. Interactive gaming around say 300 kbit/s with a broad spectrum up and down. Streaming music around 50-200 kbit/s. Streaming in general according to Figure 5.15. Background 'any' speeds. Background accepts what is offered. Messaging e-mail text about 30 kbit/s but down to 9.6 kbit/s is possible. With multi- media the requirements are much higher. Transactional services 'any' speeds, since focus is not speed, but security and accuracy. Many services are possible at quite a low bit rate around 10 kbit/s. One reason is WAP, another one is the Japanese I-mode system. The maximum speed for I-mode download is 28.8 kbit/s for top range models, and 9.6 kbit/s for standard handset models for 2G I-mode services and in the order of 200 kbit/s for 3G services. 9.6 kbit/s is sufficient for simple I-mode data. Of course this speed makes it impossible to download live movies through I-mode. I-mode on 3G is much quicker: it permits 384 kbit/s download (typically 200 kbit/s) and 64 kbit/s upload in best conditions and therefore allows video telephony. 5.9 SECURITY Security has developed to become a vast area. A lot of security improvement measures can be done outside the network, for example in the operating system of the terminals Authorities for encryption key handling and authorization certificates reside outside the network. Still there are a lot of measures that can be taken inside the networks. See Chapter 6. 5.10 FUTURE SERVICE DEVELOPMENT Initially it should be pointed out that WLAN systems can already cope with broader bands than 3G, as indicated in Figure 3.45. The evolution of application areas in mobile systems after 3G can be