Beam Training with Limited Feedback for Multiuser mmWave Massive MIMO

Abstract

Different from the existing hierarchical beam training schemes which typically require a feedback in each layer of the codebook to indicate the best codeword for the base station (BS), beam training in this work only needs two feedbacks in total. The proposed beam training scheme includes two stages and requires only one feedback in each stage by using the designed hierarchical codebook. In the first stage, beam training for the top layer of our designed codebook is performed to narrow the search range of the channel angle of departure (AoD). In the second stage, based on the feedback information from the first stage, beam training for the other layers of our designed codebook is performed, where the BS can obtain an estimate of the channel AoD. Simulation results show that the performance of the proposed beam training scheme with limited feedback can approach that of time-division multiple access (TDMA) hierarchical beam training scheme with much fewer feedbacks.