ge. 7.4. References All standards can be downloaded from the ETSI website: https://www. etsi.org/standards. 3GPP TS 38.211 NR - Physical Channels and Modulation; Version 16.1.0 Release 16 3GPP TS 38.213 NR - Physical layer procedures for control; Version 16.2.0 Release 16 3GPP TS 38.306 NR - User Equipment (UE) radio access capabilities; Version 16.1.0 Release 16 3GPP TS 38.331 NR - Radio Resource Control (RRC); Version 15.2.1 Release 15 5G-NR Radio Interface - Data Link Layer The data link layer is made up of four sublayers: - SDAP (Service Data Adaptation Protocol); - PDCP (Packet Data Convergence Protocol); - RLC (Radio Link Control); - MAC (Medium Access Control). A level n sublayer provides services to the n + 1 layer. Each level n layer receives data from the upper layer which it transfers to the lower layer by inserting control information in a header H. Packet IP n Packets IP n+1 Packet IP Flow (PDU session) SDAP SDU SDAP SDU SDAP sublayer SDAP frame Data Radio Bearer: SDAP SDU PDCP SDU PDCP sublayer PDCP frame RLC SDU RLC SDU RLC sublayer RLC frame MAC SDU MAC SDU MAC sublayer MAC frame Figure 8.1. Data link layer protocol. For a color version of this figure, see www.iste.co.uk/launay/5g.zip NG-RAN and 5G-NR: 5G Radio Access Network and Radio Interface, First Edition. Frédéric Launay. C ISTE Ltd 2021. Published by ISTE Ltd and John Wiley & Sons, Inc. NG-RAN and 5G-NR The data received by the upper sublayer is referred to as Service Data Unit (SDU). The frame transmitted to the lower sublayer comprises the SDU data to which control information is added. 8.1. SDAP protocol Connectivity to a data network through 5G-NR radio access and the 5G Core network (5GC) is provided by a PDU (Packet Data Unit) session. NG-RAN Packet Data Network PDU session Non 3GPP Figure 8.2. PDU session. For a color version of this figure, see www.iste.co.uk/launay/5g.zip The PDU session is defined by: - the format of the data to be transported (Ethernet, IP, unstructured); - the SMF (Session Management Function) involved in the es