Radio network node comprises a plurality of antenna sub arrays, forming a multiple antenna array which is configured for beamforming, spatial multiplexing and Multiple Input Multiple Output, MIMO, transmission/reception, and further comprising an antenna base band processing unit and a central base band processing unit. The radio network node further comprises a plurality of antenna active modules, wherein each active antenna module is connected to one of the antenna sub arrays, comprised in the multiple antenna array, and wherein each active antenna module is configured for pre-processing of signals over the respective antenna sub array, before any forwarding of signals is made to the central base band processing unit.