LTE Architecture :
LTE network can be considered of two main components: RAN and EPC
RAN: Ran includes LTE radio protocol stacks ( RLC, PDCP, RLC, MAC, Physical) when they are connected to EPC core.
LTE Radio Protocol stacks new ( SDAP, PDCP, RLC, MAC, Physical, RRC) when they are connected to 5G Core Network.
EPC Core Network : Interface, Protocol & entity.