What is RRC reestablishment?

The purpose of RRC CONNECTION RE-ESTABLISHMENT procedure is to re-establish the RRC connection, which involves the resumption of SRB1 operation and the re-activation of security (without changing algorithms).

The RRC CONNECTION SETUP message is used to establish SRB1 . It contains configuration information for SRB1. This allows subsequent signaling to use the DCCH logical channel. The configuration for SRB1 can be a specific configuration or the default configuration.

The Radio Resource Control (RRC) protocol is used in UMTS, LTE and 5G on the Air interface. It is a layer 3 (Network Layer) protocol used between UE and Base Station.

RRC Connected State LTE UE monitors control channels associated with shared data channel to determine if the data is scheduled for it or not . The Channel quality feedback information is also provided by the UE after measurements. It also performs neighbor cell measurements of UTRAN,EUTRAN and GSM cells.