Angle Domain Massive MIMO-OFDMA Using a Scalar Channel Estimate

Massive Multiple-Input Multiple-Output (MIMO) technology has the potential to deliver high spectral efficiencies by leveraging the ability to form narrow beams that can be resolve users based on location. Complexity is a significant barrier, particularly for massive MIMO systems employing orthogonal frequency division multiplexing (OFDM). This paper presents a simple technique for employing multiple-beamforming on the downlink of massive MIMO-OFDM systems. With a focus on practicability, the channel state information (CSI) is specified with only two scalar parameters, namely, beam angle and average channel signal to noise ratio. A novel channel estimation procedure is described, wherein, all mobile users will acquire CSI simultaneously using circularly-shifted pseudo-noise training sequences. The base station then performs an optimization task to identify suitable spectrum (or subcarriers) for each user. We have shown an iterative algorithm for orthogonal multiple access in this paper. Extension to non-orthogonal multiple access is straightforward. Simulation results are presented to show the behavior of our multiple-beam OFDM technique. We have considered only the cellular downlink in this paper.