 or in software on a multicore CPU is shown below in Figs. 6-11 and 6-12: The O-RAN fronthaul specification defines different IQ compression types to reduce the fronthaul bandwidth: Block Floating Point compression Block Scaling compression u-Law compression Beamspace compression and decompression Modulation compression Selective RE sending compression Low physical layer The Low Physical Layer (PHY) is responsible for the conversion of frequency to time domain and antenna preprocessing to prepare the samples for transmission over the air. These steps are the most compute-intensive and therefor typically implemented in Field Programmable Gate Array (FPGA)/Application Specific Integrated Circuit (ASIC) or vector Digital Signal Processor (DSP) centric systems that excel in computational efficiency rather than simplicity of code or other aspects. Beamforming and time/frequency domain conversion These components are part of the Physical Layer processing chain and discussed in broad terms elsewhere in this book. One important aspect on beamforming is the cen- tralized nature of the beamforming operation: given that this involves a matrix Chapter 6 User-plane application components 229 multiplication between all layers (which are carried over a single eCPRI link to/from the DU) and all antennas (which are egress from the RU), beamforming is an operation that is difficult to split over multiple components. On the other hand, the remainder opera- tions (Fast Fourtier Transform (FFT), Digital Front-End (DFE)) are unique per antenna and hence scale in a manner that allows them to be implemented in a scalable fashion using multiple devices, each of which is allocated to a subset of the RU antenna count. Especially in Massive MIMO systems, this topic becomes an architectural challenge given the contrary directional "pull" between centralized beamforming and distributed remainder processing. PRACH extraction and filtering As we said before, the reason for partial offload of PRACH processing to the RU is both to reduce compute 