Embodiments herein relate to a method, performed by a network node, for reducing a higher layer signaling overhead in multi antenna wireless communication systems. The network node operates in a communication network, which communication network is adapted to wirelessly serve a network device via a Radio Access, RA, node. The network node obtains information from the network device, which information comprises a category of the network device and a number of layers supported by the network device. The network node determines a length of a codebook subset restriction based on the information obtained from the network device. The network node further sends a codebook subset restriction bit map to the network device, according to the determined length of the codebook subset restriction.