In the example shown in FIG. 2, each baseband controller 204 comprises Layer-1 (L1) functionality, Layer-2 (L2) functionality, and Layer-3 (L3) functionality configured to perform at least some of the Layer-1 processing, Layer-2 processing, and Layer-3 processing, respectively, for the air interface implemented by the C-RAN system 200. Each radio point 206 includes Layer-1 functionality that implements any Layer-1 processing for the air interface that is not performed in the controllers 204 and one or more radio frequency (RF) circuits (not shown) that implement the RF front-end functions for the air interface and the one or more antennas 210 associated with that radio point 206.

Different splits in the air-interface processing between the controller 204 and the radio points 206 can be used. In one example, each baseband controller 204 can be configured to perform all of the digital Layer-1, Layer-2, and Layer-3 processing for the air interface, while the radio points 206 (specifically, the RF circuits) implement only the RF functions for the air interface and the antennas 208 associated with each radio point 206. In that case, in-phase and quadrature (IQ) data representing time-domain symbols for each antenna is communicated between the controller 204 and the radio points 206. Other splits can be used and data can be communicated between the controllers 204 and the radio points 206 in other formats. In the following description, the fronthaul data communicated between the controllers 204 and the radio points 206 for the air interface is generally referred to as “IQ data” even though such fronthaul data can take many forms, including forms that are not IQ data.