Transmitting: 
  • After being processed at the MAC layer, the downlink data is sent to the physical layer in
    the format of MAC PDU. The MAC PDU arranges the data block size according to the allocation results of radio resources at the MAC layer. 
  • After the data packets are  processed through the channel coding, modulation, and IFFT at the physical layer, the CP is added to form the integrated time domain OFDMA symbols, and then, the symbols are transmitted in the downlink sub-frame structure through the RF processing.
Receiving:  
  • After the signals received by the antenna are processed through the RF intermediate
    frequency, the baseband IQ data is sent to the baseband for processing. 
  • After the baseband receiving end performs FFT, channel estimation, channel equalization,  sub-carrier demapping, demodulation, and channel decoding, the data packets are sent to the MAC layer through the interfaces. The competitive codes of the Ranging and bandwidth request competitive slots in the uplink sub-frame must be detected.