There is provided beam forming using an antenna array configured to transmit across an angular sector. A first set of virtual antenna ports is determined by a mapping of physical antenna ports of the antenna array, the first set of virtual antenna ports defining a beam pattern. A first set of reference signals for acquiring channel state information is transmitted over the first set of virtual antenna ports. Angular information about a wireless transceiver device receiving the transmitted first set of reference signals is acquired. The beam pattern is adapted based on an accuracy of the angular information and/or the angular information itself.