On the influence of the antenna pattern in noncoherent massive MIMO systems

Noncoherent multi-user detection schemes are attractive in multi-user massive MIMO uplink systems. In particular, sorted decision-feedback differential detection (DFDD) in combination with noncoherent decision-feedback equalization (nDFE) over the users has been shown to perform well though avoids the need for channel estimation. Up to now, in all studies a uniform linear receiver array employing omni-directional antennas has been assumed. In this paper, we assess the influence of the antennas´ radiation patterns on the performance of the noncoherent massive MIMO. Based on analytic expressions, we present an optimization approach for the array assuming that the individual antennas are electronically switchable to change the direction of the main radiation. The gains are assessed by means of numerical simulations. It is shown that in the noncoherent setting the antenna pattern has a much more pronounced influence and, thus, has to be designed more carefully than in the coherent case.