 bands as well. The flexibility of the L1 structure, 6 5G Physical Layer including how frequently the gNB needs to transmit synchronization/reference signals, allows the network power consumption to scale much better as a function of the traffic compared to LTE. The use of pipeline processing together with a shorter slot duration or mini-slot allows low-latency communications to be supported. Some of the Release 15 defined features are tailored for the use of non-traditional use cases, for example, URLLC, and thus are not foreseen in the first-phase implementations but likely later when 5G has established itself outside the classical mobile broadband domain. References 1 Holma, H. and Toskala, A. LTE for UMTS, 2e. Wiley. 2 3GPP Technical Specification TS 38.211. NR; Physical hannels and Modulation. 3 3GPP Technical Specification TS 38.213. NR Physical Layer Procedures for Control. 4 3GPP Technical Specification TS 38.214. NR Physical Layer Procedures for Data. 5 3GPP Technical Specification TS 38.212. NR Multiplexing and Channel Coding. 6 3GPP Technical Specification TS 38.215. NR Physical Layer Measurements. 7 3GPP Tdoc RP-182866 (2018). RAN1 UE Feature List. December 2018. 5G Radio Protocols Tero Henttonen 1 Jarkko Koskela 1 , Benoist Sébire 2 , and Antti Toskala 1 1 Nokia Bell Labs, Finland 2 Nokia Bell Labs, Japan CHAPTER MENU Introduction, 149 5G Radio Protocol Layers, 150 SDAP, 151 PDCP, 156 RLC, 160 MAC Layer, 162 The RRC Protocol, 168 Radio Protocols in RAN Architecture, 185 Summary, 185 References, 186 Introduction The Long-Term Evolution (LTE) radio protocols were primarily designed for the provision of PS services through a flat architecture. They were a major improvement over the previous generations, eliminating the complexity inherent in the support circuit-switched (CS) services and in a convoluted architecture. Many of the original principles of LTE remained untouched since Release 8 and have proved to be a solid baseline for over a decade. Thus, in the early days of 5G standardization, it was agr