Multiuser Beam Allocation for Millimeter Wave Massive MIMO Systems

Abstract

In this paper multiuser beam allocation for millimeter wave (mmWave) massive MIMO systems is investigated, based on an improved hybrid precoding design framework. The framework includes two stages. In the first stage, an orthogonal pilot (OP) based beam training scheme is proposed, where all users can simultaneously perform the beam training with the base station (BS) and all the RF chains at the BS are fully utilized. In the second stage, a channel estimation method based on the results from the beam training is presented without transmitting any pilot sequences. Note that users close in geographical may share the same beam from the base station (BS) and cause the beam conflict. To mitigate the multiuser interference caused by beam conflicts, a quality of service (QoS) constrained beam allocation scheme is proposed, with the objective to maximize the equivalent channel gain for the users satisfying QoS constraints as well as maximizing the number of users satisfying QoS constraints on the premise of no beam conflict for all users. Simulation results verify the effectiveness of the proposed schemes and show that the QoS constrained beam allocation scheme can achieve higher spectral efficiency than existing schemes.