23.1213GPPArchitectural requirements for Release 1999Release 1999TS
A UMTS network is divided into a radio access network and a core network, which are connected via an open interface over the Iu reference point. Furthermore, the core network is from a functional point of view divided into a Packet Switched Service Domain and a Circuit Switched Service Domain.
The following network configurations shall be allowed:
a) networks which provide the functionality of CS Service Domain and PS Service Domain;
b) networks which only provide the functionality of the CS Service Domain;
c) networks which only provide the functionality of the PS Service Domain.
The following terminal configurations shall be allowed:
a) terminals which are able to access both to the CS Domain and PS Domain;
b) terminals which are only able to access to the PS Domain;
c) terminals which are only able to access to the CS Domain.
It shall be noted that e.g. terminal which is only able to access to the PS Domain supports only mobility management, protocols etc. of that particular domain. The different configurations given above shall not prevent CS-type services from being delivered over the PS domain.