A mobile terminal can receive N or less different data streams transmitted in parallel over N antennas. The number of different data streams actually transmitted in parallel to the mobile terminal corresponds to transmission rank. If the speed of the mobile terminal does not exceed a predetermined threshold, the mobile terminal utilizes a full-size codebook containing precoder elements for all N transmission ranks to determine a recommended transmission rank and precoder matrix for use in transmitting data to the mobile terminal. Otherwise, the mobile terminal utilizes a reduced-size codebook which excludes the precoder elements for at least transmission rank-N to determine the recommended transmission rank and precoder matrix where transmission rank-N corresponds to N different data streams being transmitted in parallel over the N antennas. The mobile terminal transmits an indication of the recommended transmission rank and precoder matrix to the network.