For wireless networks QoS method shouid be robust .UMTS supports four QoS classes (Depending on delay sensitivity of traffic ) as follows:
A. Conventional class
B. Streaming class
C. Interactive class
D. Background class

• Conventional class is most delay sensitive followed by streaming, interactive and background class with lowest delay sensitivity.
• The conventional and steaming class are both used for carrying real – time traffic flows. For service like video telephony, voice conferencing that are very sensitive to delay are examples of conversational class .Streaming class is only less less delay sensitive in comparision to the conventional class.
• For applications like news, FTP,Email, www, Telnet that are less sensitive to delay interactive and background classes are used. With the help of proper channel coding and retransmission the interactive and background classes provide a good error rate.
• For web browsing interactive class is preferred to be used and for background downloading of emails, data the background class is used. The priority of traffic in the interactive class has a higher scheduling priority than that in background class.
• When interactive resources do not use transmission resources, the background applications use them for loading the data.