Generalized Hybrid Beamforming for Vehicular Connectivity Using THz Massive MIMO

Hybrid beamforming (HBF) array structure has been extensively demonstrated as the practically feasible architecture for massive multiple-input multiple-output (MIMO). From the perspectives of spectral efficiency (SE), energy efficiency (EE), cost, and hardware complexity, HBF strikes a balanced performance tradeoff when compared with the fully analog and the fully digital implementations. Using the HBF architecture, it is possible to realize three different subarray structures, specifically the fully connected, the subconnected and the overlapped subarray structures. This paper presents a novel generalized framework for the design and performance analysis of the HBF architecture. A parameter, known as the subarray spacing, is introduced such that varying its value leads to the different subarray configurations and the consequent changes in the system performance. Using a realistic power consumption model, we investigate the performance of the generalized HBF array structure in a cellular infrastructure-to-everything application scenario (involving pedestrian and vehicular users) using the single-path terahertz (THz) channel model. Simulation results are provided for the comparative performance analysis of the different subarray structures. The results show that the overlapped subarray implementation maintains a balanced tradeoff in terms of SE, EE, and hardware cost when compared with the popular fully connected and the subconnected structures. The overlapped subarray structure, therefore, offers promising potentials for the beyond-5G networks employing THz massive MIMO to deliver ultrahigh data rates whilst maintaining a balance in the EE of the network.