Iterative Transceiver Optimization for Linear Multiuser MIMO Channels with Per-User MMSE Requirements

Authors: Martin Schubert, Shuying Shi, and Holger Boche

Affiliation: Heinrich Hertz Institut, Berlin.

e-mail: martin.schubert@hhi.fraunhofer.de

Abstract

We address the problem of jointly optimizing linear transmit and receive filters for a multi-user MIMO system, under the assumption that all users have individual Minimum-Mean-Square-Error (MMSE) requirements. Each user can perform spatial multiplexing with several data streams (layers). All users and layers are coupled by interference, so the choice of filters is intricately interwoven with the power allocation strategy. Design goals are max-min fairness under a total power constraint and power minimization under MMSE constraints.  This results in non-convex problem formulations, for which we propose computationally-efficient sub-optimal iterative algorithms. The iteration consists of alternating optimization of powers, transmit filters and receive filters. The convergence behavior of the iteration is analyzed and the performance of the algorithm is assessed by comparison with the global optimum, which is found by exhaustive search.