| 摘要 |
A multi-user MIMO downlink beamforming system with limited feed forward (200) is provided to enable precoding matrix information to be efficiently provided to a subset of user equipment devices (201.i), where zero-forcing transmit beamformers (wi) are computed at the base station (210) and assembled into a precoding matrix (W). The precoding matrix is encoded using a compact reference signal codebook (225, 207.i) for forward link signaling, either by sending bits indicating the index of the transmission matrix used, or by transmitting one or more precoded pilots or reference signals wherein the pilot signals are precoded using vectors uniquely representative of the transmission matrix used which includes candidate reference signal matrices which meet a predetermined condition number requirement, such as a condition number threshold. The precoding matrix information (227) is extracted at the user equipment devices (201.i) using the compact reference signal codebook (207.i) and used by the MMSE receiver (209.i) to generate receive beamformers (vi). |
