UMTS Networks : Architecture, Mobility and Services

The UMTS Terminal 197
Figure 7.1 User Equipment (UE) reference architecture
standardised telecommunication services on behalf of user applications. It also terminates
the telecommunication service platform.
The Mobile Termination (MT), on the other hand, is the part of the ME that terminates
radio transmission to and from the network and adapts TE capabilities to those
necessary for radio transmission. From the mobile system’s point of view, the MT is
basically the actual terminal device itself. The MT has the ability to change its location
within the access network or move to a coverage area of another access network
implementing the same access technology. The MT also terminates the services of
UMTS network systems.
The Network Termination (NT) functional group of the MT is the CN-dependent
part of the MT. The NT uses non-access stratum protocols for Mobility Management/
GPRS Mobility Management (MM/GMM) and Communication Management/Session
Management (MM/SM). Therefore, the NT may be seen as the terminal from the pure
CN point of view. Non-access stratum protocols are presented in Chapter 10.
The Radio Termination (RT) functional group of the MT is related to the RAN only.
It contains functions common to all services using the same RT-specific radio access
technology, and uses such access stratum protocols as Medium Access Control (MAC),
Radio Link Control (RLC) and Radio Resource Control (RRC) on top of the physical
radio connection. Therefore, the RT is seen as a terminal from the UMTS Terrestrial
Access Network (UTRAN) point of view. MAC, RLC and RRC are also discussed in
Chapter 10.
In this book, terminal architecture is described by using the functional groups described
above. A summary of their dependence on network end services and subsystems
can be found in Table 7.1. Allocation of main functional entities to the above functional
groups clarifies the nature of the functional groups in Figure 7.2.