It is the main controlling function in the AS responsible for establishing the radio bearers and configuring all lower layers using RRC signaling between the eNB and the UE. The radio resource control (RRC) protocol is known as layer 3 in the AS protocol stack and in 3GPP RAN terminology. The lower layers perform the same functions as for the user-plane with the exception that there is no header compression function for the control-plane. This includes both access stratum (AS) and NAS protocols. The protocol stack for the control plane between the UE and MME is shown in Figure 3.5. A 3GPP-specific tunneling protocol called GPRS tunneling protocol (GTP) is used over S1 and S5/S8 interfaces. Different tunneling protocols are used across different interfaces. An IP packet for a UE is encapsulated in an EPC-specific protocol and tunneled between the P-GW and the eNB for transmission to the UE. The main functions in each entity and their termination points in the network have been shown in the figure. The functional split between the EPC and E-UTRAN is shown in Figure 3.4.

Step enb not working