ven in the above table (although not 3.3 UMTS Release 99 triggered), then the upgrade is performed. But the downgrade on one link direction should not automatically affect the RAB rate on the other link direction. Channel Type Switching (CTS) Channel Type Switching (CTS) is to switch the user data transfer between DCH channel and the common channels, i.e. to FACH on the downlink and RACH on the uplink. The CTS mechanism is used to efficiently utilize the transport bandwidth for the packet switched data services. When one user is transmitting data over the common channels, it competes for the transmission resources with some other common channel users in the cell and only obtains a share of the bandwidth dynamically according to its demand. If the user does not transfer any data for an amount of time, it is assumed that this connection is inactive and does not need dedicated transport bandwidth anymore. Therefore, the system releases the DCH for this user and the corresponding transport connection, and switches it to the common channel. Then the reserved transport bandwidth for this user is released and given for other users to use. In this way, one user will not always occupy the available bandwidth even though it has no data to transfer. The released bandwidth can be reallocated for new user connections or shared by other existing user connections. On the other hand, the user in the common channel can be moved back to the DCH when the system detects this user is active again with increased traffic demand. Then this user will request to set up a DCH and a new transport channel in the transport network. The TNL CAC determines whether there are enough transport resources to allow the user to switch back to DCH. If not, the user has to remain in the common channel until there are enough transport resources again for setting up the transport connection for the requested DCH. With the use of the CTS function, the network resources can be allocated dynamically according to the user traffic demand. This can significantl