t reQuest (HARQ) mechanism. 8.4.1. Operations 8.4.1.1. gNB side operation The operations at the gNB entity level are demonstrated in Figure 8.17. Logical channel PCCH BCCH CCCH DCCH DTCH MCCH MTCH CCCH DCCH DTCH Mangement of the scheduling, of the HARQ mechanism, of the random Multiplexing Multiplexing Demultiplexing access, of the discontinuous reception, of the timing advance. PCH BCH DL-SCH UL-SCH Transport channel Figure 8.17. MAC operation gNB side The MAC layer transfers the Paging Control Channel (PCCH) to the Paging Channel (PCH). 5G-NR Radio Interface - Data Link Layer The MAC layer transfers the Master Information Block (MIB) messages from the Broadcast Control Channel (BCCH) to the Broadcast Channel (BCH). The MAC layer performs multiplexing, for the downlink direction, of different logical channels to the Downlink Shared Channel (DL-SCH). The different logical channels multiplexed for the downlink direction are the following: - the BCH logical channel containing System Information Block (SIB) messages; - the Common Control Channel (CCCH) containing Radio Resource Control (RRC) common control messages; - the Dedicated Control Channel (DCCH) containing the RRC dedicated control messages; - the Dedicated Traffic Channel (DTCH) containing Internet Protocol (IP) packets. The MAC layer performs demultiplexing, for the uplink direction, of the Uplink Shared Channel (UL-SCH) to restore the various logical channels. The different logical channels resulting from demultiplexing for the uplink direction are the following: - the CCCH logical channel containing the RRC common control messages; - the DCCH logical channel containing the RRC dedicated control messages; - the DTCH logical channel containing the IP packets. The MAC layer performs multiplexing, for the downlink direction, of the Multicast Control Channel (MCCH) and Multicast Traffic Channel (MTCH) to the Multicast Channel (MCH). The MAC layer control entity performs the following functions: - management of the scheduling of the different logical channels