Rate Balancing Based Linear Transceiver Design for Multiuser MIMO System with Multiple Linear Transmit Covariance Constraints

We solve the rate balancing problem in the downlink for a multiuser multiple-input-multiple-output (MIMO) system with multiple linear transmit covariance constraints. In particular, we adopt a linear transceiver structure to maximize the worst-case rate of the user while satisfying multiple linear transmit covariance constraints. The original rate balancing problem in the downlink is more complicated due to the coupled structure of the transmit filters. Hence, this optimization problem is solved in an alternating manner by switching between the virtual uplink and the downlink and exploiting the stream-wise mean square error (MSE) duality. An iterative algorithm has been proposed based on stream-wise MSE duality to obtain transceiver filters. In each iteration, the virtual uplink receiver filter design is formulated into a quadratically constrained quadratic programming (QCQP) by incorporating the multiple linear constraints, where the downlink receiver filters are obtained by minimizing each layer MSE. A geometric programming (GP) is solved to obtain the power allocation in the virtual uplink where the product of layer MSEs of each user is balanced with total transmit power constraint. Simulation results have been provided to validate the performance of the proposed algorithm.