A wireless device (12) is configured to transmit a signal simultaneously from a group (104) of physical antenna ports (106), based on associating disjoint frequency sub-bands with respective ones of the physical antenna ports (106). The frequency sub-bands collectively span a frequency bandwidth and each physical antenna port (106) supports transmission over the frequency bandwidth and has a per-port transmit power associated therewith. The wireless device (12) is configured to transmit the signal further based on allocating the per-port transmit power of each physical antenna port (106) in the group (104) only to frequency elements of the signal that fall within the frequency sub-band associated with the physical antenna port (106). A radio network node (10) in a network (16) is configured to perform channel estimation based on receiving a reference signal from the wireless device (12) and its channel estimation accounts for channel changes that may appear at the border between two frequency sub-bands.