Patent ID: 7330701

Claim:
A method of forming a beam of a signal to be transmitted, the method comprising: providing a codebook (C) of parameters that modify a transmitted signal: providing a channel matrix (H) of parameters representing the properties of a channel; transmitting a signal from a base station along the channel using an antenna comprising at least two elements; receiving said transmitted signal in a mobile station and estimating a parameter in the channel matrix characteristic of the channel by selecting the value of a parameter in the codebook that minimizes a criterion; transmitting an indication of the selected parameter over the return channel; and applying the codebook entry associated with the selected parameter to subsequent transmissions from the base station, wherein when 2 R/r /t<1, where R is a rate of transmission in bits/sec/Hz, r is a number of receive antennas, and t is a number of transmit antennas, a unit rank beamforming scheme is used, otherwise a higher rank beam forming scheme is used.