UAV-Assisted Mixed THz–RF Relaying Under Transceiver Fluctuations

This study investigates the performance of a relay-assisted dual-hop mixed terahertz-radio frequency (THz-RF) wireless communication system, where a dynamic source communicates with a static destination through a dynamic relay. Both source and relay are modeled as fluctuating UAVs (unmanned aerial vehicles) with uniform fluctuations in yaw and pitch directions. The Source-to-relay link operates in the THz band and incorporates the joint effects of path loss, small-scale fading modeled by$\alpha$-$\mu$distribution, and pointing errors modeled by a recently proposed model. The relay-to-destination link operates in the RF band and is modeled by considering the joint effects of path loss and small-scale fading (Rayleigh fading). For the proposed system, novel closed-form expressions for the probability density function, cumulative distribution function, moment-generating function, and$n$-th moment of the end-to-end signal-to-noise ratio are derived in terms of the uni-variate Fox's$H$-function (UFH). These statistical results are then used to obtain new closed-form expressions for key performance metrics, including outage probability (OP), average bit error rate (BER), and average channel capacity. Furthermore, asymptotic expressions for the OP and average BER are derived, and the diversity order of the system is determined. Finally, the impact of key design parameters on system performance is investigated.