Spectral Efficiency of Multiuser Massive MIMO-OFDM THz Wireless Systems with Hybrid Beamforming under Inter-carrier Interference

We address a hybrid beamforming design problem for a massive multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) terahertz (THz) system with multiple users to improve spectral efficiency, considering inter-carrier interference (ICI). Although numerous studies introduced hybrid beamforming for spectral efficiency analysis for single-user massive MIMO-OFDM THz communication systems considering ICI, the same has not yet been done for multiuser massive MIMO-OFDM systems. We model the signal-to-interference-plus-noise (SINR) ratio for each user, including ICI, in terms of beamforming parameters and formulate the optimization problem. The problem is solved with the existing Riemannian Manifold optimization (MO) and Zero-Forcing (ZF) algorithm. However, the computation time is found to be significantly high. To reduce the computational complexity, we reformulate the optimization problem and propose a new beamforming computation algorithm. We numerically solve the problem for several scenarios and find that the proposed algorithm significantly reduces the computation. Moreover, our findings indicate that ICI can considerably impact spectral efficiency, and this effect is more significant in high SNR regions.