Max-min fairness in compact MU-MIMO systems: Can the matching network play a role?

With the two conflicting demands of increasing the number of antennas in terminals and decreasing the devices sizes, considering compact MIMO systems became inevitable. Such systems suffer from both antenna coupling and noise correlation. This has led to the observation that the impedance matching network fundamentally affects the performance of such MIMO enabled communications systems. In this paper we consider a multi-user MIMO system, for which we design the matching network at the receiver given that it uses the optimal successive interference cancellation receiver. For the two cases of time sharing and no time sharing we design the matching network to alter the capacity region in order to maximize the minimum user rate. We compare to both the conventional matching, which ignores antenna coupling, and to the case of choosing the matching network such that the achievable rate is maximized. In both cases we observe a performance enhancement. We view our results as a new step in connecting the two worlds of information theory and circuit theory. Such results are of very relevant practical interest to wireless communication systems that adopt a large number of antennas while maintaining a small size.