X2 layer 1

The main functions of X2 interface layer 1 are as following:

X2 Application Protocol (X2AP)

The X2AP protocol is used to handle the UE mobility within E-UTRAN and provides the following functions:

X2 Signalling Transport

X2 signalling bearer provides the following functions:

GPRS Tunnelling Protocol User Plane (GTP-U)

GTP-U protocol is used over S1-U, X2, S4, S5 and S8 interfaces of the Evolved Packet System (EPS).

GTP-U Transport

The transport layer for data streams over S1, X2, S4, S5 and S8  is an IP based Transport.

S1 Application Protocol (S1AP)

S1AP provides the signalling service between E-UTRAN and the evolved packet core (EPC) and has following functions:

S1 Signalling Transport

S1 signalling bearer provides the following functions:

S1 layer 1

The main functions of S1 interface layer 1 are as following:

Non-Access-Stratum (NAS) Protocol

The non-access stratum (NAS) is highest stratum of the control plane between UE and MME at the radio interface.

Air Interface Physical Layer

The LTE air interface physical layer offers data transport services to higher layers. The access to these services is through the use of a transport channel via the MAC sub-layer.

Medium Access Control (MAC)

MAC protocol layer exists in UE & eNodeb, It is part of LTE air interface control and user planes.

The main services and functions of the MAC sublayer include:

Radio Link Control (RLC)

RLC protocol layer exists in UE & eNodeb, It is part of LTE air interface control and user planes.

The main services and functions of the RLC sublayer include:

Packet Data Convergence Protocol (PDCP)

PDCP protocol layer exists in UE & eNodeb, It is part of LTE air interface control and user planes.

The main services and functions of the PDCP sublayer for the user plane include:

Radio Resource Control (RRC)

RRC protocol layer exists in UE & eNodeb, It is part of LTE air interface control plane. The main services and functions of the RRC sublayer include: