1. A method performed by a transmitter to provide a precoder subset to a receiver in a multi-antenna wireless communication system, the method comprising: determining the precoder subset comprising one or more precoder elements, each precoder element being a precoder element of a codebook, and the precoder subset including less than all precoder elements of the codebook wherein determining the precoder subset comprises for each rank, determining whether that rank is at or below a rank threshold; for each rank at or below the rank threshold, including all precoder elements of that rank of the codebook in the precoder subset; for each rank above the rank threshold, including less than all precoder elements of that rank of the codebook in the precoder subset; and providing the precoder subset to the receiver, wherein the codebook is defined for a plurality of ranks, and wherein for each rank, the codebook comprises a plurality of precoder elements corresponding to that rank.