This tutorial is organized by the protocols and shows their usage in the interfaces. That means protocols will be described individually. Only the references to the interfaces are indicated. Interface specific explanations of the protocols are, however, not included. Before we review the individual interface protocols, we introduce the UMTS general protocol model.
Data streams contain the user data that is transparently transmitted between the network elements.
They react to the radio network layer s demands to set up, maintain, and release data bearers. The dedicated mode is shown in Figure 10 . This layer is responsible for in-sequence transfer and priority handling of messages. This provides connectionless and connection-oriented services. Because of the protocol layer specified in Q.2630.1, a converter is needed to correspond with underlying sublayers of the protocol stack.