 access control (MAC) Control/configuration Transport channels Physical layer (PHY) Control/configuration/ Physical layer measurements Physical channels Figure 2.1 The layer 2/3 protocols in NR protocol stack [8]. transmission that enables the UE to request when specific system information is required instead of NG-RAN consuming radio resources to periodically broadcast system informa- tion, and the extension of the measurement reporting framework to support beam measure- ments for handover in a beamformed operation [8]. In NR layer 2 protocol structure, each sublayer provides certain services to the immediately adjacent layers by processing the incoming service data units (SDUs) and generating the proper protocol data units (PDUs). The functional processing of the protocol layers is further classified into user-plane and control-plane protocols (Fig. 2.2), where the reliability requirement of the control-plane information is much higher than that of the user-plane data. New Radio Access Layer 2/3 Aspects and System Operation User-plane Control-plane IP packets (user data) NAS messages QoS flows System QoS management information Paging RRC messages Radio bearers Header Encryption and compression, integrity encryption protection RLC channels Logical channels Transport channels Channel coding Channel coding Channel coding Channel coding Physical channels Figure 2.2 NR layer 2 user-plane and control-plane functional mapping and processing. The service data adaptation protocol is a new sublayer in layer 2 which immediately inter- faces with the network layer and provides a mapping between the QoS flows and data radio bearers (DRBs). It also marks the QoS flow identifiers (QFIs) in the downlink and uplink packets. A single-protocolo entity of SDAP is configured for each individual PDU Session. The services and functions of the PDCP sublayer on the user-plane include sequence num- bering; header compression and decompression [only supports Robust Header Compression (ROHC) protocol]; transfer of user data; reordering an