 channels like PRACH, PUSCH, PUCCH and downlink like PBCH, PDSCH, PDCCH). The reference signals are also explained: CSI-RS, DM-RS, Preface PT-RS, RIM-RS. Chapter 4 also details the mapping of physical channels and physical signals on resource elements. Chapter 5 presents the physical layer mechanisms to improve throughput and coverage. It describes the SUL mode, the carrier aggregation mechanism, dual connectivity and spectrum sharing for 4G/5G coexistence. Chapter 6 presents MIMO mechanisms used to improve the robustness of the transmission (diversity), the bit rate (SU-MIMO, MU-MIMO) and the reduction of interference (beamforming). It describes the evolution of antenna capabilities from MIMO to massive-MIMO and single-panel or multi-panel transmission mechanisms. The procedure for managing the beams and improving data rate is described with the use of the code book for the uplink and downlink transmissions. Chapter 7 presents the partitioning of the 5G band. It describes initial band partitioning and BWP band switching, allowing the mobile to camp on a cell and, under the control of the base station, to adapt its radio capabilities to the traffic load. It also describes the search area and CORESET control resource elements. Chapter 8 introduces the data link layer. It describes the different SDAP, PDCP, RLC and MAC sublayers by presenting their functional role and the services between the different sublayers. For each of the sublayers, the structure of the protocol is detailed. Chapter 9 presents the messages sent by the RRC layer: broadcasting information, connection management, measurement configuration. It details the MIB and SIB messages, the procedures for establishing the radio link and the mobility of the mobile, as well as the elements to be measured. A summary of the content of these nine chapters is provided in the following table. Chapter Designation Content Functional architecture NSA/SA Identities NG-RAN network architecture UE context gNB-CU/DU QoS and network slicing Protocol architecture eCPRI f