Patent ID: 8264982

Claim:
A method for forming Time Division Duplex (TDD) Multi-Input Multi-Output (MIMO) downlink beams, the method comprising: receiving an index of a codebook element from a mobile terminal at a Base Station (BS), wherein the codebook element refers to a codebook element whose correlation value has a greatest modulus value among correlation values that are calculated by the mobile terminal and are about correlation between the codebook element and a downlink channel corresponding to a non-transmitting antenna of the mobile terminal; calculating a downlink channel vector corresponding to the non-transmitting antenna of the mobile terminal according to the index of the codebook element whose correlation value has the greatest modulus value; measuring an uplink channel vector of a transmitting antenna of the mobile terminal, and regarding the uplink channel vector as the downlink channel vector corresponding to the transmitting antenna of the mobile terminal according to uplink-downlink channel symmetry of a TDD system; and performing Singular Value Decomposition (SVD) by using downlink channel vectors of antennas of the mobile terminal to determine a best transmitting precoding matrix, wherein the downlink channel vectors of the antennas of the mobile terminal are composed of the downlink channel vector corresponding to the non-transmitting antenna of the mobile terminal and the downlink channel vector corresponding to the transmitting antenna of the mobile terminal.