As far as I know, RRH/RRU and BBU is not new architecture. It might have you heard first time and working in LTE technology so you thought it is solely related to LTE network. RRH/RRU (Remote Radio Head/Remote Radio Unit) and BBU (Base band unit) are two components which are separated to each other and located at different places. In case of C-RAN (cloud RAN/centralized RAN), BBU would be running in data center environment while RRH will be located near to antennas.
RRH and BBU inter connect on optical fiber interface and both can be separated in km distance unit. RRH and BBU based network deployment will reduce CAPEX/OPEX for operator.
One more thing to remember is that when UE sends the data at 'n' the subframe, ACK-NACK should be received at 'n' + 4 subframe from eNodeB otherwise UE re-transmit the data. In other words, total delay from RRH to BBU + eNodeB processing should be less than or equal to 3. This constraint derives the distance between RRH and BBU.