  Recent research has focused on single antenna radio-frequency (RF) and
terahertz (THz) wireless systems to mix the access link with the backhaul. In
this paper, we evaluate the performance of a mixed RF-THz system employing
multiple antenna-assisted access point (AP) for the RF link and single-antenna
THz transmissions. We employ an equal gain combining (EGC) receiver at the AP
and use the fixed-gain amplify and forward (AF) relaying protocol to interface
the RF and THz links. We derive analytical expressions for probability density
function (PDF) and cumulative distribution function (CDF) of the end-to-end SNR
for the considered system assuming independent and non-identically distributed
(i.ni.d.) $\alpha$-$\mu$ distribution to model for both RF and THz channels and
pointing errors in the THz link. We analyze the system performance using the
outage probability, average bit error rate (BER), and ergodic capacity
involving bivariate Fox's H-function. We use the residue method to develop
asymptotic analysis using Gamma functions to show the impact of the various
channel and system parameters on the outage probability and average BER in the
high SNR regime. We use computer simulations to depict the scaling of the
performance with an increase in the number of antennas at the AP for signal
reception in the access link.
