 3.4.6 Summary This section provided a brief overview of the air interface protocols of the NG-RAN and some of the basic procedures. NR draws most of the protocol aspects from LTE with some enhancements to support new 5G services and functions. For example, a new protocol layer SDAP was introduced to support the 5G QoS concept. The PDCP, RLC, and MAC protocol layers were enhanced (compared with LTE) to support lower latency and higher throughput more efficiently. The NR MAC also supports beam failure recovery procedure. Finally, the NR RRC supports a new state, INACTIVE, to provide for quick and efficient transition to CONNECTED state. 3 5G System Overview References 3GPP Technical Specification 29.281 (2019). General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U). 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification 37.324 (2020). E-UTRA and NR; Service Data Protocol (SDAP) specification. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification 38.321 (2020). NR; Medium Access Control (MAC) protocol specification. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification 38.322 (2020). NR; Radio Link Control (RLC) protocol specification. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification 38.323 (2020). NR; Packet Data Convergence Protocol (PDCP) specification. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification 38.331 (2020). NR; Radio Resource Control (RRC); Protocol specification. 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3GPP Technical Specification 38.413 (2020). NG-RAN; NG Application Protocol (NGAP). 3GPP. Available at: www.3gpp.org (accessed May 22, 2020). 3.5 NR Physical Layer 3.5 NR Physical Layer Alexei Davydov Intel Corporation, Russia 3.5.1 Introduction In this section we focus on the NR physical layer, which is in large part designed to meet IMT-2020 requirements for 5G systems. In addition to improvin