THz Communication for Non-terrestrial Networks

Beyond 5G (B5G), which is envisioned to have a user bit rate of 100 Gbps, will require a seamless backhaul to support it. The High-Altitude Platform System (hereafter referred to as HAPS), low earth orbit satellites, and NTN (Non-Terrestrial Network) communication platforms using aircraft are considered to be promising candidates as one of the use cases. NTN is expected to enable not only three-dimensional expansion of communication areas, but also various use cases with high data rates on a global scale. To realize such use cases, a high-speed, high-capacity link between the backhaul on the ground and the sky is indispensable. In particular, it is important to utilize HAPS that covers the stratosphere with stable climatic conditions. In this chapter, we discuss a communication scheme using the THz band (100 GHz band) as a new feeder link from the viewpoint of ensuring link performance even in relatively bad weather and achieving high speed and high capacity, taking into account free-space optical (FSO) communication and High-Altitude-Platform-Stations (HAPS) using existing frequencies, as well as the weather conditions required for a feeder link connecting ground stations to the stratosphere; the feasibility of 10 Gbps class THz-feeder link throughput in light rainfall will be discussed in terms of propagation characteristics, link budget, and main transmission signal processing.