Here I write some small notes on connection Re-Establishment procedure in LTE.

Re-Establishment

In a number of cases of failure (eg failure of radio link failure of teaching RLC unrecoverable error, failure of compliance reconfiguration), the procedure for restoring EU RRC connection, provided that security is active. If security is not enabled, when one of the failures listed appears RRC_IDLE EU moves instead.

Trying to restore the RRC connection, known as the EU starts a timer T311 and performs cell selection. EU should prioritize looking LTE frequencies.

However, not specified in terms of the EU while abstaining from research to other RATs. On finding a suitable cell on a frequency LTE EU stops timer T311, start timer T301 and initiate dispute proceedings based random access to enable message RRC connection re required to be sent. The RRC connection re request message, the EU includes the identity used in the cell where the failure occurred, the identity of that cell, a message authentication code and a cause.

The E-UTRAN uses the re-establishment procedure to continue SRB1 security and to reactivate without Changing algorithms. A Subsequent RRC Connection Reconfiguration procedure is used to resume operation on Radio Bearers other than SRB1 and to re-enable measurements. If the cell in Which the EU initiates the re-establishment is not Prepared (ie does not have a context for That EU), the E-UTRAN Will reject the procedure, Causing the EU to move to RRC_IDLE.