Optimizing Receive Combining Vectors for Multiantenna Users in Multiuser MIMO Precoding

Methods to design combining vectors at the receiver for multiantenna users in the multiuser multiple-input multiple-output downlink channel are presented. The proposed methods are applicable for linear and nonlinear precoding. A fast user ordering algorithm is provided to reduce computational complexity. Furthermore, an adaptive codebook for combining vectors is presented to decrease the precoding complexity and the amount of overhead information in the downlink. Simulation results show significant gains compared with other methods such as receive antenna selection or dominant eigenmode combining.