This chapter provides an overview of the GSM/UMTS core network, as specified by the 3GPP release 99 standards. There is still no strict formal definition of the core network, but the position of the core network for the purpose of this chapter and how it relates to other parts of the PLMN (Public Land Mobile Network) and co-operating networks.
Originally decided by
the ETSI SMG, the 3GPP release 99, the UMTS core network standard is
evolved from the earlier GSM standards releases. The core network forms
the central part of a PLMN and accommodates important functions for
intra and inter PLMN roaming, the provision of IP-connectivity and
The core network may be looked upon as consisting of two different parts :
Although logically very different the two parts share certain core network functionality, such as the HLR, Auc, EIR etc, and may also run over a common transport infrastructure.