ation of a TAG (Timing Advance Group) for each cell, required in particular in the case of heterogeneous networks for which the secondary cell is carried by a remote radio node RRH (Radio Remote Head); - simultaneous transmission of the SRS reference signal and the PUCCH and PUSCH physical channels on different CC radio channels (parallelTxSRS-PUCCH- PUSCH); - simultaneous transmission of the PRACH random access channel and SRS/PUCCH/PUSCH signals through different DC radio channels (parallelTxSRS- PUCCH-PUSCH); - simultaneous TDD-TDD and TDD-FDD inter-band communication (simultaneousRxTxInterBandCA); - the use of different numerologies on each CC radio channel (diffNumerologyAcrossPUCCH-Group). The carrier aggregation procedure is established by the RRC control message. The activation and deactivation of the SCell secondary cells is carried out by control messages on layer 1 (physical) and layer 2 (MAC) called L1/L2 Control Signaling and carried by the PDCCH/PDSCH channel (DCI information: Downlink Control Information). The DCI information is transmitted either only on the primary cell PCell (Cross Carrier Scheduling) or on each CC PCell and SCell (Self Carrier Scheduling): 1) the gNB entity sends the RRC Reconfiguration message to the mobile indicating the configuration of the radio resource; 2) the mobile applies the new configuration and responds to the gNB entity with the RRC ReconfigurationComplete message; 3) secondary cells can be quickly turned on or off through the MAC CE (Medium Access Control Control Element) layer. The activation and deactivation of the cell is carried out by the LCID index 111001 followed by a 4-byte message or the LCID index 111010 followed by a one-byte message. The LCID (Logical Channel Identifier) is performed at the MAC layer to reassemble PDCP frames from the same medium. 5G-NR Radio Interface - Operations on the Frequency Bands The message enables or disables a secondary cell by respectively setting the bit to 1 or 0. Channel PDCCH (CORESET) CC #0 PCell CC #1 SCell CC #2 SCel