strated in Figures 3.17 and 3.18. 3.4.12 Connected Inactive State 5G requires new structures for the Radio Resource Control (RRC) protocols in order to minimize setup time and signaling. LTE RRC is designed with two RRC states: idle and connected. The LTE UE sits normally in the idle state to minimize UE power con- sumption. When there is a need to transmit any data, the UE is first transferred to the RRC-connected state, data transmission is completed, and the UE returns to the idle after state the inactivity timer expires. The LTE approach is not optimal for the frequent transmission of low data volumes, which is typical from smartphones or IoT devices. 5G Table 3.6 Channel coding complexity benchmarking [1]. Turbo Polar Silicon area efficiency 10 Gbps/mm2 <5 Gbps/mm² <5 Gbps/mm2 Energy efficiency > 100 bit/nJ <1 bit/nJ <100 bit/nJ 3 Technology Components Control Reference signals and data Control Data Data Data Data Data Complete sub-frame reception Low latency data decoding required symbol-by-symbol Low power consumption with micro-sleep during data symbols if no reception Figure 3.17 Pipeline processing in 5G. PDCCH Figure 3.18 Front-loaded demodulation reference signals. LTE reference signals distributed inside the slot Cell Reference Signals (CRSs) PDCCH PDSCH 5G front-loaded reference signals Front-loaded DMRS specifications include the RRC-connected inactive state, where the target is to maintain the RRC connection for a long time and minimize the RRC setup signaling. The UE can send data even after long inactivity without any RRC setup signaling, which also min- imizes latency. Minimized signaling is beneficial for the UE, radio network, and core network. The high-level RRC structure is illustrated in Figure 3.19. We note that the Connected Inactive State has similarities with the 3G Cell_PCH (Paging Channel) state, RRC signaling RRC idle connected Minimized signaling RRC connected RRC idle inactive connected Figure 3.19 Always-on RRC protocol in 5G. 3.4 Flexible Physical Layer and Protocols where the R