Editing My 3GPP 38.300 Notes (section)

== Section 7 Radio Resource Controller (RRC) ==

=== 7.1 Services and Functions ===

The main services and functions of the RRC sublayer over the Uu interface include:
* <span style="color:red">Broadcast of System Information related to AS and NAS;</span>
* Paging initiated by 5GC or NG-RAN;
* Establishment, maintenance and release of an RRC connection between the UE and NG-RAN including:
** Addition, modification and release of carrier aggregation;
** Addition, modification and release of Dual Connectivity in NR or between E-UTRA and NR.
* Security functions including key management;
* Establishment, configuration, maintenance and release of Signalling Radio Bearers (SRBs) and Data Radio Bearers (DRBs);
* Mobility functions including:
** <span style="color:red">Handover and context transfer;</span>
** <span style="color:red">UE cell selection and reselection and control of cell selection and reselection;</span>
** Inter-RAT mobility.
* QoS management functions;
* UE measurement reporting and control of the reporting;
* Detection of and recovery from radio link failure;
* <span style="color:red">NAS message transfer to/from NAS from/to UE.</span>

The sidelink specific services and functions of the RRC sublayer over the Uu interface include:
* Configuration of sidelink resource allocation via system information or dedicated signalling;
* Reporting of UE sidelink information;
* Measurement configuration and reporting related to sidelink;
* Reporting of UE assistance information for SL traffic pattern(s).

=== 7.2 Protocol States ===

RRC supports the following states which can be characterized as follows:
* '''RRC_IDLE:'''
** <span style="color:red">PLMN selection;</span>
** Broadcast of system information;
** <span style="color:red">Cell re-selection mobility;</span>
** Paging for mobile terminated data is initiated by 5GC;
** DRX for CN paging configured by NAS.
* '''RRC_INACTIVE:'''
** <span style="color:red">PLMN selection;</span>
** Broadcast of system information;
** <span style="color:red">Cell re-selection mobility;</span>
** Paging is initiated by NG-RAN (RAN paging);
** RAN-based notification area (RNA) is managed by NG- RAN;
** DRX for RAN paging configured by NG-RAN;
** 5GC - NG-RAN connection (both C/U-planes) is established for UE;
** The UE Inactive AS context is stored in NG-RAN and the UE;
** NG-RAN knows the RNA which the UE belongs to;
** Transfer of unicast data and/or signalling to/from the UE over radio bearers configured for SDT.
* '''RRC_CONNECTED:'''
** 5GC - NG-RAN connection (both C/U-planes) is established for UE;
** The UE AS context is stored in NG-RAN and the UE;
** NG-RAN knows the cell which the UE belongs to;
** Transfer of unicast data to/from the UE;
** Network controlled mobility including measurements.

=== 7.3 System Information Handling ===

=== 7.3.1 Overview ===

System Information (SI) consists of a MIB and a number of SIBs, which are divided into Minimum SI and Other SI:
* '''Minimum SI''' comprises basic information required for initial access and information for acquiring any other SI. Minimum SI consists of:
** ''MIB'' contains cell barred status information and essential physical layer information of the cell required to receive further system information, e.g. CORESET#0 configuration. MIB is periodically broadcast on BCH.
** ''SIB1'' defines the scheduling of other system information blocks and contains information required for initial access. SIB1 is also referred to as Remaining Minimum SI (RMSI) and is periodically broadcast on DL-SCH or sent in a dedicated manner on DL-SCH to UEs in RRC_CONNECTED.
* '''Other SI''' encompasses all SIBs not broadcast in the Minimum SI. Those SIBs can either be periodically broadcast on DL-SCH, broadcast on-demand on DL-SCH (i.e. upon request from UEs in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED), or sent in a dedicated manner on DL-SCH to UEs in RRC_CONNECTED (i.e., upon request, if configured by the network, from UEs in RRC_CONNECTED or when the UE has an active BWP with no common search space configured or when the UE configured with inter cell beam management is receiving DL-SCH from a TRP with PCI different from serving cell's PCI). See spec for details what SIBx are within ''Other SI''.

=== 7.6 Transport of NAS Messages ===

<span style="color:red">New Radio (NR) provides reliable in-sequence delivery of Non-Access Stratum (NAS) messages over Signalling Radio Bearers (SRBs) in Radio Resource Controller (RRC), except at handover where losses or duplication can occur when Packet Data Convergence Protocol (PDCP) is re-established.</span> In RRC, NAS messages are sent in transparent containers. Piggybacking of NAS messages can occur in the following scenarios:
* At bearer establishment/modification/release in the Downlink (DL);
* For transferring the initial NAS message during connection setup and connection resume in the Uplink (UL).

:NOTE:	In addition to the integrity protection and ciphering performed by NAS, NAS messages can also be integrity protected and ciphered by PDCP.

Multiple NAS messages can be sent in a single downlink RRC message during Protocol Data Unit (PDU) Session Resource establishment or modification. In this case, the order of the NAS messages contained in the RRC message shall be in the same order as that in the corresponding Next Generation Application Protocol (NGAP) message in order to ensure the in-sequence delivery of NAS messages.

NG-RAN node may trigger the NAS Non Delivery Indication procedure to report the non-delivery of the non PDU Session related NAS PDU received from the AMF as specified in TS 38.413.