A method and apparatus for feedback of channel information characterizing a wireless transmission between a base station and a mobile station over a communications channel. The method involves, at the base station, receiving a primary identifier identifying a cluster associated with a channel response generated by a mobile station, receiving a differential identifier identifying channel response member within the cluster identified by the primary identifier, and locating in a codebook of predetermined channel responses a predetermined channel response identified by the primary identifier and the differential identifier. The predetermined channel responses in the codebook are grouped in a plurality of clusters in accordance with a correlation criterion, each cluster including a plurality of predetermined channel response members. The method also involves generating a control signal for controlling transmissions to the mobile station in accordance with the located predetermined channel response. The method also involves, at the mobile station, determining a channel response for at least one carrier frequency received at the mobile station, and locating in a codebook of predetermined channel responses a predetermined channel response that is a closest match to the determined channel response, causing the mobile station to transmit a primary identifier identifying a cluster associated with the located predetermined channel response to the base station, and causing the mobile station to transmit a differential identifier identifying the located predetermined channel response member within the cluster identified by the primary identifier.