Mobile Packet Core

In brief, the User Equipment (UE) you are having should be able to make voice calls, in addition to data sessions.

The mobile  network contains, 

• The PS domain (Packet Switching domain), which handles the data sessions.
• And, the CS domain (Circuit Switching domain), which handles the voice calls.

The 'core network' is the combination of the CS domain, and the PS domain.

The UE connects to the core network through the 'access network', which controls the communication between the UE and the core network.

Mobile network technologies evolved over time to satisfy the increasing customer needs. Therefore, we are having different technologies (2G, 3G, and 4G).

2G mobile network 'GSM/GPRS'

2G core network is having a PS domain for data sessions, and a CS domain for voice calls.

The access network name in 2G is called the 'GERAN'.

3G mobile network 'UMTS'

 The core network in 3G is inherited from 2G network. Therefore, 3G network is also having  both a PS domain for data sessions, and a CS domain for voice calls in its core network.

The access network for the 3G network is the UTRAN. 

4G mobile network 'LTE'

Unlike previous generations, LTE network is having only a PS domain in its core network, while it doesn’t have a CS domain for voice calls.

In addition , the PS domain architecture enhanced and named the 'Evolved Packet Core', (EPC).

The UE can make voice calls by connecting to an external network, which is the 'IMS' network. The UE connects to the IMS network through the PS domain.

The access side of the LTE network is the E-UTRAN.