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LTE Protocol Stack

LTE Protocol stack is divided into Three Layers.

Layer 1 (Physical Layer)

Layer 2 (PDCP,MAC,RLC Layers)

Layer 3 (NAS and RRC Layers)

Protocol Stack

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.