 the implementation of the DU is split over multiple physical components with limited bandwidth interconnect. Refer to Fig. 3-8 below showing the Physical Layer flow which is the key component for discussion of bandwidths internal to the system given that we're dealing with IQ samples: Various Physical Layer internal bandwidths can be calculated in a similar fashion as the eCPRI bandwidth. In fact, we can use the eCPRI calculations as a starting point for band- width allocation. We assume a FR1/ <6 GHz (30 KHz Subcarrier Spacing (SCS)) 4-antenna (2-layer) system with 100 MHz carrier bandwidth (single carrier) and 64QAM support. Use the uplink processing chain as an example, where Baseband time domain sample bandwidth: 4 (carriers) X 4096 (subcarrier/Fast Fourier Transform (FFT)) X 14 (symbol/slot) X 2000 (slots/second) X 32 (16b I + 16b Q) = 14.7 Gbps. Baseband frequency domain sample bandwidth: 4 (carriers) X 3276 (subcarrier/FFT) X 14 (symbol/slot) X 2000 (slots/second) X 32 (16b I + 16b Q) = 11.7 Gbps. This is the eCPRI bandwidth discussed previously (2.93 Gbps/carrier). Beamforming and precoding reduce the decoded bandwidth from 4 to 2 layers or 5.9 Gbps. 116 Open Radio Access Network (O-RAN) Systems Architecture and Design DL From MAC UL To MAC CRC Attachment Code Block Concatenation Code Block Segmentation CRC validation Forward Error Correction Forward Error Correction Rate Matching Rate De-Matching Code Block Concatenation Scrambling De-Scrambling Modulation De-Modulation Option 7-3 (DL Only) Layer Mapping Layer De-Mapping Precoding Channel Estimate, Equalize Option 7-2 Resource Element Mapping Resource Element De-Map Beam Forming Beam Forming Option 7-1 iFFT + Cyclic Prefix FFT + Cyclic Prefix Option 8 Digital Front End Digital Front End To RF From RF FIGURE 3-8 Physical layer functional components. De-modulation generates an 8-bit Log Likelihood Ratio (LLR) for each bit that is input to the decoder. We calculate this bandwidth as 2 (layers) X 3276 (subcarrier/FFT) X (symbol/slot) X 2000 (slots/second) X