tion MAC CE consists of either one or four octets that are identified by MAC PDU subheaders with LCID indices 58 or 57, respectively. It has a fixed size consisting of either a single octet or 4 octets and contains 7 or 31 C-fields (mapped to individual component carriers Cj) and one R-field. The DRX and long DRX command MAC CEs are identified by MAC PDU subhea- ders with LCID indices 60 and 59, respectively, both of which have a fixed size of zero bits. Timing advance command The timing advance command MAC CE is identified by a MAC PDU subheader with LCID index 61. It has a fixed size of one octet and includes timing advance group (TAG) identity (TAG ID) which indicates the TAG ID of the addressed TAG (2 bit); and timing advance command which indicates the index value TA = (0, 1, 2, , 63) that is used to control the amount of timing adjustment that MAC entity has to apply (6 bits). UE contention resolution identity The UE contention resolution identity MAC CE is identified by a MAC PDU sub- header with LCID index 62. It has a fixed 48 bit size and consists of a single field containing UE contention resolution identities. Semi-persistent (SP) CSI-RS/CSI-IM resource set activation/deactivation The network may activate and deactivate the configured SP CSI-RS/CSI-IM resource sets of a serving cell by sending the SP CSI-RS/CSI-IM resource set acti- vation/deactivation MAC CE. The configured SP CSI-RS/CSI-IM resource sets are initially deactivated upon configuration and after a handover. Aperiodic CSI trigger state sub-selection The network may select among the configured aperiodic CSI trigger states of a serv- ing cell by sending the aperiodic CSI trigger state sub-selection MAC CE. Transmission configuration indicator (TCI) states activation/deactivation UE-specific PDSCH The network may activate and deactivate the configured TCI states for physical downlink shared channel (PDSCH) of a serving cell by sending the TCI states acti- vation/deactivation for UE-specific PDSCH MAC CE. The configured TCI states for PDSCH a