FSO-Based Backhauling for Airborne THz Base Stations

Airborne nodes in the form of high-altitude platform stations (HAPSs) or unmanned aerial vehicles (UAVs) can be used for backhauling and wireless access. In this paper, we investigate the cascaded free space optical (FSO)/terahertz (THz) link in which the FSO link serves as a backhaul between the gateway and the airborne node. In contrast, the THz link provides wireless communication between the airborne node and the user. We present channel models, including the atmospheric attenuation, geometrical loss, and fading effect. The FSO sub-system builds upon intensity-modulation direct-detection (IM/DD), while the THz sub-system employs coherent modulation and demodulation. Under the assumption of decode-and-forward relaying, we derive the end-to-end bit error rate (BER). We present numerical results to demonstrate the performance of cascaded airborne links.