A method of operating a base station comprising a plurality of transmit antennas, each of the antennas transmitting on one or more carriers selected from a set of co-located carriers and serving each of one or more non-MIMO users by only one of the antennas and each of one or more MIMO users by two or more of the antennas, said method for allocating a maximum transmission power budget to each of the antennas comprising: allocating, for serving each of the MIMO users, one or more carriers selected from the set of co-located carriers; allocating, for serving each of the non-MIMO users, one or more carriers selected from the set of co-located carriers; deriving a set of coefficients by using, for each carrier of the set of co-located carriers, information about an amount of allocated MIMO user resources associated with the carrier and an amount of allocated non-MIMO user resources associated with the carrier, wherein each coefficient corresponds to a unique one of the antennas and represents a proportion of a maximum power budget for the carrier, and wherein for each carrier of the set of co-located carriers, one of the antennas is a primary antenna that serves one or more MIMO users and one or more non-MIMO users, and remaining ones of the antennas are secondary antennas that serve one or more MIMO users; deriving a maximum transmission power budget for each of the antennas by using for each carrier of the set of co-located carriers said coefficients and the maximum transmission power budget for the carrier; deriving for each antenna of the plurality of transmit antennas a total maximum transmission power budget for the antenna by combining the derived maximum transmission power budgets of the carriers transmitted on the antenna; determining whether the total maximum transmission power budget of the antenna exceeds a transmission power limit for the antenna; and, if the total maximum transmission power budget of a primary antenna of a carrier exceeds ist transmission power limit, determining whether radio conditions for a non-MIMO user satisfy one or more predefined criteria; and causing one of the secondary antennas of the carrier to be used to serve the non-MIMO user if the radio conditions of the non-MIMO user satisfy the one or more predefined criteria. allocating, for serving each of the MIMO users, one or more carriers selected from the set of co-located carriers; allocating, for serving each of the non-MIMO users, one or more carriers selected from the set of co-located carriers; deriving a set of coefficients by using, for each carrier of the set of co-located carriers, information about an amount of allocated MIMO user resources associated with the carrier and an amount of allocated non-MIMO user resources associated with the carrier, wherein each coefficient corresponds to a unique one of the antennas and represents a proportion of a maximum power budget for the carrier, and wherein for each carrier of the set of co-located carriers, one of the antennas is a primary antenna that serves one or more MIMO users and one or more non-MIMO users, and remaining ones of the antennas are secondary antennas that serve one or more MIMO users; deriving a maximum transmission power budget for each of the antennas by using for each carrier of the set of co-located carriers said coefficients and the maximum transmission power budget for the carrier; deriving for each antenna of the plurality of transmit antennas a total maximum transmission power budget for the antenna by combining the derived maximum transmission power budgets of the carriers transmitted on the antenna; determining whether the total maximum transmission power budget of the antenna exceeds a transmission power limit for the antenna; and, if the total maximum transmission power budget of a primary antenna of a carrier exceeds ist transmission power limit, determining whether radio conditions for a non-MIMO user satisfy one or more predefined criteria; and causing one of the secondary antennas of the carrier to be used to serve the non-MIMO user if the radio conditions of the non-MIMO user satisfy the one or more predefined criteria.