In fifth generation (5G) networks, the densification of small base stations in the coverage region of macro base station (MBS) leads to significant inter-cell interference (ICI). Similarly, drones (a.k.a. unmanned aerial vehicles) have a diverse scope in multifarious 5G assisted applications and, therefore, cause considerable drones interference (DI) as a result of excessive drone usage. This paper investigates the bottleneck uplink (UL) coverage performance of the MBS edge users in the presence of ICI and DI. To mitigate both ICI and DI, we use an efficient resource allocation scheme known as reverse frequency allocation (RFA). Moreover, we use decoupled association (DeCA) in place of coupled association to further improve UL signal-to-interference ratio. The results depict that RFA in conjunction with DeCA overpass all other techniques in terms of improved UL coverage performance because of effective DI and ICI mitigation.

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.