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:
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).