The radio interface is composed of different layers in order to set up, reconfigure and release the radio bearer services.

The protocol layer is composed of physical layer (layer 1), data link layer (layer2), and the network layer (layer3).

In the E-UTRAN layer 2 is divided into two sub-layers: Medium Access Control
(MAC) and Radio Link Control (RLC) protocol. Layer 3 consists of two protocols, called Radio Resource Control (RRC) and Packet Data Convergence Protocol (PDCP).

The top to down arrows represent downlink (DL) channels from eNB to UE..
Down to top arrows are uplink channel (UL) from UE to eNB. Most of common and dedicated channels transmitted from RLC to the physical layer share the same transport channel. There are no dedicated channels in transport and physical layer.

Some physical channels are existing solely in the physical layer itself, such as
PHICH, PCFICH and PDCCH.