Traffic Classes

Traffic Classes are used to categorise the types of communication carried by a Universal Mobile Telephone System (UMTS).

When implementing QoS within a UMTS you can divide the types of traffic that can be carried into classes based on their characteristics. Also, with the bandwidth, latency, and reliability there are some characteristics that the network needs to adapt if it has to carry the traffic effectively. Two of these are whether the traffic comes intermittently and whether the upstream and downstream traffic characteristics are symmetric or asymmetric.

The traffic classes carried by a UMTS are divided into the following categories:

• Conversational Traffic Class (Voice telephony) - This is characterized by a fixed, and relatively small bandwidth with a small latency and comparatively less number of transmission errors. The upstream and downstream data rates are symmetrical.

• Streaming Traffic Class - This class of traffic is continuous data such as streaming video. Some errors can be tolerated for example, dropped lines in a single video frame. The data rates are high and generally asymmetrical.

• Interactive Traffic Class - This class of traffic handles user request or server response traffic such as web browsing. It is medium bandwidth, must be reliable and is intermittent asymmetric data. Unlike the other classes different priorities can be attached to interactive traffic.

• Background Traffic Class - This traffic is low volume occasional traffic such as an Email. A reasonable delay is acceptable to the user but reliability must be high.

The following table illustrates the characteristics of these classes: