Multiuser transmit beamforming for MIMO uplink with individual SINR targets

For multiuser multiple-input multiple-output (MIMO) uplink communications where the signal-to-interference-plus-noise ratio (SINR) of the k-th user, denoted as SINR_k, is expected to achieve the target value _gammak, we first consider the ideal scenario where multiuser channel matrices are perfectly known to every user and we solve the problem of maximizing min_k(SINR_k/_gammak) over all possible beamformers under individual transmit power constraints via alternating optimization strategies and the generalized eigenvalue problem (GEVP) programming. Then, we study a more realistic situation where only a few number of bits are allowed to feed back to users. We propose to integrate the genetic algorithm into the Lloyd´s vector quantization method to design the optimum codebook in terms of maximizing E(min_k(SINR_k/_gammak)) with expectation taken with respect to fading channels.