C-UM and RLC-AM); error correction through ARQ function (AM mode); segmentation (in RLC-AM and RLC-UM modes) and re-segmentation (in RLC-AM mode) of RLC SDUs; reassembly of SDU (in RLC- AM and RLC-UM modes); duplicate detection (in RLC-AM mode); RLC SDU discarding (in RLC-AM and RLC-UM modes); RLC re-establishment; and protocol error detection (in RLC- AM mode). The ARQ function within the RLC sublayer performs ARQ retransmission of RLC SDUs or SDU segments based on the RLC status reports. It further sends requests for RLC sta- tus reports when needed, and triggers an RLC status report after detecting a missing RLC SDU or SDU segment [8]. The RLC protocol performs segmentation of the PDCP PDUs, if neces- sary, and adds an RLC header containing a sequence number used for handling retransmissions. Unlike LTE, the NR RLC is not providing in-sequence delivery of data to higher layers due to the additional delay incurred by the reordering mechanism. In-sequence delivery can be pro- vided by the PDCP layer, if necessary. The services and functions of the MAC sublayer include mapping between logical and transport channels, as well as multiplexing/demultiplexing of MAC SDUs belonging to one or different logical channels on the transport blocks, which are mapped to the transport channels depending on the required physical layer processing. The MAC sublayer also per- forms scheduling of measurement reporting; error correction through HARQ [one HARQ entity per cell when carrier aggregation is utilized]; priority handling between user equip- ments through dynamic scheduling; and priority handling between logical channels of one UE through logical channel prioritization. A single MAC instantiation can support multiple numerologies, transmission timings, and cells. The mapping restrictions in logical channel prioritization can control which numerology(ies), cell(s). and transmission timing(s) a logi- cal channel can use. The main difference between MAC and RRC control lies in the signal- ing reliability. The signaling correspo