 It carries user data and higher layer control information coming from the Dedicated Traffic Channels (DTCH) and Dedicated Control Channels (DCCH) as logical channels. Moreover it can carry the information from several DTCHs. For instance a user may have several connections for different services (e.g. voice and video call). Each service requires an individual DTCH, but all of them share the same DCH. It should be noticed that DCH is the dynamically allocated resource, it can be set up on demand for one user and then released, whereas common channels basically exist permanently. The traffic in the uplink direction is usually smaller, hence it requires less transport and physical resources. There are three Transport Channels available in uplink: Dedicated Channel (DCH) is a duplex channel. On the uplink it has the same function as a DCH in the downlink direction. Random Access Channel (RACH) is a common channel used to transmit control information from the mobile terminal to the network, e.g. a UE sends the initial access information via RACH to the network when it requests to set up a connection. RACH can also be used to send small amounts of packet data from the terminal to the network. For proper system operation the RACH must be heard from the entire cell coverage area, which also means that data rates have to be rather low [HT04]. Common Packet Channel (CPCH) is a shared channel which carries small amounts of user packets on the uplink. Similar to DSCH on the downlink, it is also optional for network operation and becomes obsolete with the emergence of HSPA. 3.3.3 Iub Interface This section gives a detailed introduction of the Rel99 lub interface, including the protocol stack used for the user plane, the underlying ATM transport technology and the involved protocols within the Transport Network Layer. At the end, the explicit transport requirements that the lub interface has to satisfy are described. 3.3.3.1 Protocol Stack for the Iub User Plane The major tasks of the lub interface are to provide the means fo