Universal Mobile Telecommunication System (UMTS)
Services and QoS differentiation

The 2G mobile networks (GSM) enabled circuit-switched voice services with simple text messaging (SMS) and relatively expensive circuit-switched data capabilities (CSD, HSCSD). The 2.5G system evolution (GPRS) and 2.75G (EDGE) introduced packet-switched data services, such as web browsing, WAP or multimedia messaging service (MMS). These supported realistic data bit rates approximately up to 50 kbps for GRPS and up to 200 kbps for EDGE respectively. The achievable data bit rates were insufficient for more demanding multimedia services.

The 3G mobile technologies provide a wide range of new services since UMTS is supposed to support IP-based multimedia applications with high data bit rates up to several Mbps depending on current Release. Several services that 3G users can benefit from are summarized below:

- Streaming video on demand –Video content, such as movies, music, sport events, etc., can be streamed to UE.
- Real-time gaming – Games can be supported depending on UMTS version (i.e., which Release is implemented). Games requiring high data bit rates and low delays can be supported only by newer releases such as Release 5 and more recent ones.
- Downloading multimedia contents – User can easily download mp3 songs, photos, and other interactive content.
- Messaging services – While in 2G networks, only SMS or simple MMS messages (text together with picture) are available, 3G networks supports inclusion of short video, etc.
- Video telephony and conferencing – Simultaneous interaction of several mobile users who can communicate online using both voice and video.
- Location based services – Offering to users useful navigation services like navigation of users to final destination, notification of spot of interest (restaurant, sport centres, malls, sightseeing) or improved emergency services.
- Push to talk – By simple pressing a button on the handset, the user can immediately start talking to other users like in case of walkie-talkie.

In order to support above mentioned services in UMTS network, differentiation in QoS is defined. To put it simply, if the load of the system is high, some services needs to be prioritized in order to guarantee end-to-end application performance. To that end, UMTS introduces four QoS classes (see Table below) that are mainly distinguished by their packet delay susceptibility:

Service class | Description
Conversational class | High requirements on delay with symmetric or nearly symmetric traffic, and with dedicated amount of radio resources
Streaming class | Lower requirements on delay in comparison to conversational class, but still with dedicated amount of radio resources
Interactive class | High requirements on delay, no dedicated amount of radio resources
Background class | Low requirements both on delay and the amount of radio resources

The conversational class together with streaming class is used for supporting of real-time (RT) applications, such as voice (conversational class) or video streaming (streaming class). On the other hand, the interactive class and background class is designated to be used by non real-time (NRT) applications when so called Best Effort (BE) access is used. Consequently, these are designed for services such as online gaming, location based services (interactive class) or www browsing (background class).