Sign in Subscribe

rrc lte

Last updated on 

The Radio Resource Control (RRC) is an essential component of the LTE (Long-Term Evolution) protocol stack. LTE is a standard for wireless broadband communication for mobile devices and data terminals. RRC plays a critical role in controlling the radio resources, managing radio bearers, and facilitating communication between the User Equipment (UE) and the Evolved Node B (eNodeB), which is the base station in LTE terminology.

RRC States:

RRC has multiple states to manage the connection between the UE and the eNodeB:

  1. Idle State: In this state, the UE does not have any active connection with the network. The UE listens to system information broadcasted by nearby cells to decide on cell selection or reselection.
  2. Connected State: When the UE establishes a connection with the network, it enters the connected state. This state further divides into:
    • RRC_CONNECTED: The UE is connected and can transmit and receive data.
    • RRC_INACTIVE: The UE can receive data but cannot transmit.

RRC Procedures:

  1. Connection Establishment: When a UE wants to initiate a connection, it goes through various procedures like random access, contention resolution, and RRC connection establishment with the eNodeB.
  2. Security Setup: Once the RRC connection is established, security procedures like key exchange and encryption setup take place to ensure a secure communication link.
  3. Bearer Setup: RRC is responsible for establishing, modifying, and releasing Radio Bearers (RBs). Radio Bearers are logical channels used for data transfer between the UE and the network.
  4. Mobility Management: RRC manages handovers, which involve transferring the UE connection from one eNodeB to another as the UE moves. RRC handles procedures like handover preparation, execution, and completion.
  5. System Information Handling: The eNodeB broadcasts system information using RRC messages. The UE reads this information to configure its parameters and make decisions like cell selection and handover.

RRC Messages:

RRC messages are used for signaling between the UE and the eNodeB. Some key RRC messages include:

  1. RRC Connection Request: Sent by the UE to request a connection with the eNodeB.
  2. RRC Connection Setup: Sent by the eNodeB to establish an RRC connection with the UE.
  3. RRC Reconfiguration: Used to modify the existing RRC configuration, such as adding or removing radio bearers.
  4. RRC Release: Sent to release the RRC connection between the UE and the eNodeB.