A. Architecture
The whole system is divided in two parts: Evolved Packet
Core (EPC) in figure 1 and Evolved UMTS Terrestrial Radio
Access Network (E-UTRAN) in figure 2. Compatibility with
old network infrastructures is provided, based on 3GPP or
non-3GPP technologies, being them classified as trusted
or non-trusted accessing networks [2]. This classification
describes the way to authenticate the users, defines how to
migrate their security contexts during a handover process and
establishes the behaviour of the core network towards the user.