LTE Protocol stack is divided into Three Layers.

Layer 1 (Physical Layer)

Layer 2 (PDCP,MAC,RLC Layers)

Layer 3 (NAS and RRC Layers)

Functions of each Layer.

NAS: 3GPP TS 24.301

• EPS bearer management
• Authentication
• Paging origination
• EPC connection management-IDLE mobility handling
• Security mode control
• Tracking area update
• PDN connectivity and dysconnectivity procedure.

RRC:  3GPP TS 36.331

• RRC protocol layer exists in UE & eNodeb.
• It is part of LTE air interface control plane.
• Broadcast of System Information related to the non-access stratum (NAS) and access stratum (AS)
• Paging
• Establishment, maintenance and release of an RRC connection between the UE and E-UTRAN
• Mobility functions
• QoS management functions.
• UE measurement reporting and control of the reporting.
• Recovery from radio link failure

PDCP: 3GPP TS  36.323

• PDCP protocol layer exists in UE & eNodeb
• Header compression and decompression of IP data packet.
• Transfer of user data.
• Maintenance the PDCP sequence number.
• Security of data.
• Ciphering and Integrity Protection.
• Transfer of control plane data.

RLC: 3GPP TS 36.322

• Concatenation, Segmentation and reassembly of RLC SDUs.
• Retransmission of RLC PDUs (Only for AM data transfer)
• Reordering of RLC data PDUs (Only for UM and AM data transfer.
• Protocol error detection and recovery.

MAC: 3GPP TS  36.323

• Prioritization among various data streams for a given UE.
• Error Correction trough HARQ.
• Mapping between logical channels and transport channels.
• Transport format selection.
• Padding.

Physical layer

• Encode raw data before modulation.
• Measure the air interface to know the channel quality.
• Link adaptation.
• Power control.

Categories: techlteworld

Tags: LTE, MAC, NAS, PDCP, PHY, PROTOCOL STACK, RLC, RRC