  Mitigating channel fading and transceiver impairments are desirable for
high-speed terahertz (THz) wireless links. This paper analyzes the performance
of a multi-antenna THz wireless system by considering the combined effect of
pointing errors and fluctuating two-ray (FTR) fading model. We provide a
statistical characterization of the maximal ratio combining (MRC) receiver over
independent and nonidentical (i.ni.d.) channel conditions in terms of
multi-variate Fox's H by deriving density and distribution functions of the
signal-to-noise ratio (SNR) of a single-link THz link using incomplete Gamma
function. We develop exact analytical expressions of outage probability,
average bit-error-rate (BER), and ergodic capacity for both single-antenna and
MRC receivers. We also present the diversity order of the system by deriving
asymptotic expressions for outage probability and average BER at high SNR to
obtain insights into the system performance. We validate our derived analytical
expressions with Monte-Carlo simulations and demonstrate the effect of various
system and channel parameters on the performance of single and multi-antenna
THz wireless communications.
