ity handling such as key or algorithm change, specification of RRC context information transferred between network nodes; establishment/modification/suspension/resumption/release of radio bearers carrying user data (DRBs); radio configuration control including assignment/modification of ARQ configuration, HARQ configuration, and DRX configuration. In case of dual connectivity, the RRC sublayer provides cell management functions includ- ing change of primary second cell (PSCell), addition/modification/release of SCG cell(s). In case of carrier aggregation, RRC sublayer provides cell management functions including addition/modification/release of SCell(s). The RRC sublayer further provides QoS control including assignment/modification of SPS configuration and DL/UL configured grant con- figuration, assignment/modification of parameters for uplink rate-control in the UE, that is, allocation of a priority and a prioritized bit rate for each resource block. The RRC sublayer also handles recovery from RLF condition; inter-RAT mobility including security activa- tion, transfer of RRC context information; measurement configuration and reporting which includes establishment/modification/release of measurement configuration (e.g., intra- frequency, inter-frequency, and inter-RAT measurements); setup and release of measure- ment gaps; and measurement reporting [14]. The RRC messages are sent to the UEs using SRBs, based on the same set of protocol layers that are used for user-plane packet processing except the SDAP sublayer. The SRBs are mapped to the CCCH during connection setup and to the DCCH once the connection is established. The control-plane and user-plane data can be multiplexed in the MAC sublayer and transmitted to the device within the same TTI. The MAC CEs can be used for control of radio resources in some specific cases where low latency is more important than cipher- ing, integrity protection, and reliable transport of data. New Radio Access Layer 2/3 Aspects and System Operation 237 Table 2.1: Radio resource