E-UTRA - EUTRAN Protocol Stack

EUTRAN Protocol Stack

The EUTRAN protocol stack consist of:

• Physical layer: Carries all information from the MAC transport channels over the air interface. Takes care of the link adaptation (AMC), power control, cell search (for initial synchronization and handover purposes) and other measurements (inside the LTE system and between systems) for the RRC layer.
• MAC: The MAC sublayer offers a set of logical channels to the RLC sublayer that it multiplexes into the physical layer transport channels. It also manages the HARQ error correction, handles the prioritization of the logical channels for the same UE and the dynamic scheduling between UEs, etc..
• RLC: It transports the PDCP's PDUs. It can work in 3 different modes depending on the reliability provided. Depending on this mode it can provide: ARQ error correction, segmentation/concatenation of PDUs, reordering for in-sequence delivery, duplicate detection, etc...
• PDCP: For the RRC layer it provides transport of its data with ciphering and integrity protection. And for the IP layer transport of the IP packets, with ROHC header compression, ciphering, and depending on the RLC mode in-sequence delivery, duplicate detection and retransmission of its own SDUs during handover.
• RRC: Between others it takes care of: the broadcasted system information related to the access stratum and transport of the non-access stratum (NAS) messages, paging, establishment and release of the RRC connection, security key management, handover, UE measurements related to inter-system (inter-RAT) mobibility, QoS, etc..

Interfacing layers to the EUTRAN protocol stack:

• NAS: Protocol between the UE and the MME on the network side (outside of EUTRAN). Between others performs authentication of the UE, security control and generates part of the paging messages.
• IP