5G‐NR Radio Interface – The Physical Layer

OFDM modulation consists of modulating orthogonal subcarriers. OFDM modulation offers good spectral efficiency and provides resilience to the frequency selective fading of the propagation channel. OFDM modulation has been implemented on the long‐term evolution radio interface. The 5G‐NR time division duplexing frame provides flexibility in the direction of radio resources per slot: OFDM symbols in a slot can be up, down or flexible. The dynamic configuration corresponds to the sequencing of the transmission of the mobile based on the control signal downlink control information. The physical primary synchronization signal ensures the synchronization of the OFDM signal and the time synchronization at the half‐frame level. The physical secondary synchronization signal provides time synchronization at the frame level. The physical random access channel contains a preamble used by the mobile to ask for the establishment of a radio bearer.