Disclosed is a method performed by a first radio unit, RU, of a distributed base station system. The distributed base station system further comprises a Baseband Unit, BBU, connected to the first RU over a fronthaul link and a second RU connected to the first RU over an RU link. The first RU determines first part of beamforming weights that it uses for performing a first part of the beamforming of uplink signals received at its antennas into intermediate signals. The first RU further determines intermediate beamforming weights to be used for a second part of beamforming at the BBU. The first RU further receives, from the second RU, intermediate signals and intermediate beamforming weights determined by the second RU. The first RU combines the intermediate signals and sends them to the BBU. The first RU further combines the intermediate beamforming weights and sends them to the BBU.