  Recent research investigates the decode-and-forward (DF) relaying for mixed
radio frequency (RF) and terahertz (THz) wireless links with zero-boresight
pointing errors. In this letter, we analyze the performance of a fixed-gain
amplify-and-forward (AF) relaying for the RF-THz link to interface the access
network on the RF technology with wireless THz transmissions. We develop
probability density function (PDF) and cumulative distribution function (CDF)
of the end-to-end SNR for the relay-assisted system in terms of bivariate Fox's
H function considering $\alpha$-$\mu$ fading for the THz system with non-zero
boresight pointing errors and $\alpha$-$\kappa$-$\mu$ shadowed ($\alpha$-KMS)
fading model for the RF link. Using the derived PDF and CDF, we present exact
analytical expressions of the outage probability, average bit-error-rate (BER),
and ergodic capacity of the considered system. We also analyze the outage
probability and average BER asymptotically for a better insight into the system
behavior at high SNR. We use simulations to compare the performance of the AF
relaying having a semi-blind gain factor with the recently proposed DF relaying
for THz-RF transmissions.
