THz Communications: A Key Enabler for Future Cellular Networks

Future cellular networks are expected to benefit from terahertz (THz) frequency bands, which enable high-speed and low-latency wireless connectivity, but several challenges have arisen in utilizing THz bands. In this paper, we first investigate channel characteristics and their modeling for THz bands, highlighting new opportunities and emerging challenges. In this context, we discuss the channel characteristics that become more prominent at THz frequencies than at lower microwave frequencies, such as atmospheric attenuation, scattering, and frequency selectivity. We also review various path-loss and scattering models for THz communications. We further survey the radio frequency front-end nonlinearities that affect THz communications and their modeling for multiple-input multiple-output (MIMO) systems. We then review massive MIMO and hybrid beamforming techniques, and their applicability for THz communications. We identify the challenges that arise from operating at ultra-high frequencies, such as beam blockage, power consumption of large-scale arrays, and beam squint. Finally, we provide an overview of emerging intelligent reflecting surface (IRS) technologies and their potential for enhancing THz wireless networks. We investigate how IRS and massive MIMO technologies can be integrated into THz wireless networks and discuss possible solutions to overcome the limitations that affect the throughput and efficiency of such systems.