The RRC protocol covers a number of functional areas:
• System information handles the broadcasting of SI, which includes NAS common information. Some of the system information is applicable only for UEs in RRC_IDLE while other SI is also applicable for UEs in RRC_CONNECTED.
• RRC connection control covers all procedures related to the establishment, modification and release of an RRC connection, including paging, initial security activation, establishment of Signalling Radio Bearers (SRBs) and of radio bearers carrying user data (Data Radio Bearers, DRBs), handover within LTE (including transfer of UE RRC context information4), configuration of the lower protocol layers,5 access class barring and radio link failure.
• Network controlled inter-RAT mobility includes handover, cell change orders and redirection upon connection release, security activation and transfer of UE RRC context information.
• Measurement configuration and reporting for intra-frequency, inter-frequency and inter-RAT mobility, includes configuration and activation of measurement gaps.
• Miscellaneous functions including, for example, transfer of dedicated NAS information and transfer of UE radio access capability information.