LTE Radio Protocol Architecture (User plane & Control plane)

User plane
The figure below shows the protocol stack for the user-plane, where PDCP, RLC and MAC sublayers (terminated in eNB on the network side) perform the functions listed for the user plane, e.g. header compression, ciphering, scheduling, ARQ and HARQ;

 Control plane

 The figure below shows the protocol stack for the control-plane, where:

• -  PDCP sublayer (terminated in eNB on the network side) performs the functions like ciphering and integrity protection.
  
• -  RLC and MAC sublayers (terminated in eNB on the network side) perform the same functions as for the user plane.
  
• -  RRC (terminated in eNB on the network side) performs the functions listed below:
  
  • -  Broadcast;
    
  • -  Paging;
    
  • -  RRC connection management;
    
  • -  RB control;
    
  • -  Mobility functions;
    
  • -  UE measurement reporting and control.
    
• -  NAS control protocol (terminated in MME on the network side) performs among other things:
  
  • -  EPS bearer management;
    
  • -  Authentication;
    
  • -  ECM-IDLE mobility handling;
    
  • -  Paging origination in ECM-IDLE;
    
  • -  Security control. 
    
    
    
    
    
    Reference:3GPP TS 36.300