Joint fixed beamforming and eigenmode precoding for super high bit rate massive MIMO systems using higher frequency bands

In order to tackle rapidly increasing traffic, the 5th generation (5G) mobile communication system will introduce small cells using higher frequency bands with wider bandwidth to achieve super high bit rate transmission of several tens Gbps. Massive MIMO beamforming (BF) is one of promising technologies to compensate for larger path-loss in the higher frequency bands. Joint analog fixed BF and digital precoding has been proposed to reduce the cost of a Massive MIMO transceiver. However, the conventional scheme assumes the transmission of a few streams using well-known codebook-based precoding as the digital precoding, and both a selection method of the fixed BF weights and a digital precoder design, which are suitable for the super high bit rate transmission using multiple streams, have not been studied. This paper proposes a joint fixed BF and CSI-based precoding (called FBCP) scheme for the 5G Massive MIMO systems. FBCP first selects the analog fixed BF weights based on maximum total received power criterion, and then it calculates eigenmode (EM) precoding matrix exploiting CSI. This paper targets a 5G system achieving 20 Gbps in 20 GHz band as one example, and throughput performances of the proposed FBCP are evaluated by link level simulation and compared with those of the fixed BF and those of the EM precoding.