 have flexibility with NR. We can deploy different bandwidths up to 400 MHz. Confinement of the spectrum with improved spectral efficiency The more bandwidth available, the more subcarriers can be allocated within a given spectrum allocation. This results in higher spectral efficiency. 20 MHz spectrum allocation Spectral efficiency: 90% Guard band 1,200 subcarriers (18MHz) Guard band >50 MHz spectrum allocation Spectral efficiency: 94-99% ~3,300 subcarriers (>49.5 MHz) Figure 4.4 - Enhanced spectral efficiency in NR In NR, due to the larger number of subcarriers available, the spectral efficiency is between 94-99%, while in LTE, it is 90%. NR channel structure Channel structure composes of logical channels, transport channels, and physical channels. Logical channels are composed of control and data channels. They are basically the service flow between Medium Access Control (MAC) and Radio Link Control (RLC) in the NR's protocol stack. Transport channels are the multiplexing of logical data in the logical channels, and this data is organized into transport blocks to be transported by the physical channels. Therefore, the physical channels carry these data blocks through the NR air interface. In a nutshell, logical channels create transport channels, and then transport channels create physical channels. We have also reference and synchronization signals. The left pane of the following figure shows the downlink channels, whereas the right pane of the figure shows the uplink channels: 5G Air Interface and Physical Layer Procedures - Part 1 CCCH DTCH DCCH CCCH DTCH DCCH Logical Channels Transport Channels DL-SCH UL-SCH Physical Channels PDSCH PDCCH PUSCH PUCCH PRACH Reference and Sync Signals CSI-RS/TRS PRACH Preamble Figure 4.5 - NR channel structure We will provide more details about these channels in the upcoming sections. The downlink reference and synchronization signals In the following figure, the downlink reference and synchronization signals for NR are listed. Physical Channels PDSCH PDCCH PUSCH PUCCH PRACH R