Location-aware beamformed downlink control channel for ultra-dense networks

In this paper we consider transmit beamforming schemes for downlink control channel. In particular, we propose exploiting information on user location for selecting both the serving transmission/reception point (TRP) and transmit beam used for control channel transmissions. Moreover, a suppressed zero-forcing (SZF) scheme based on vertically and horizontally polarized transmit beams is proposed with multibeam transmissions in order to increase diversity and improve the reliability of the precoded control channel. Extensive numerical results are provided in a fifth generation new radio (5G-NR) ultradense network (UDN) context with a realistic system level simulator. Results show that control channel capacity can be increased significantly by means of multiuser multiple-input-multiple-output (MU-MIMO) techniques, without the need for accurate channel state information (CSI). Furthermore, it is shown that the proposed beamforming based scheme achieve the desirable >0.98 reliability of downlink control channel with different TRP array sizes. Further improvements in reliability are suggested in order to reach the challenging ultra-reliable low latency communication (URLLC) targets.