  This work investigates the temporal dispersion of a wireless terahertz
communication signal caused by reflection from a rough (diffuse) surface, and
its subsequent impact on symbol error rate versus data rate. Broadband
measurements of diffuse reflectors using terahertz time-domain spectroscopy
were used to establish and validate a scattering model that uses stochastic
methods to describe the effects of surface roughness on the phase and amplitude
of a reflected terahertz signal, expressed as a communication channel transfer
function. The modeled channel was used to simulate a quadrature phase shift
keying (QPSK)- modulated wireless communication link to determine the
relationships between symbol error rate and data rate as a function of surface
roughness. The simulations reveal that surface roughness from wall texturing
results in group delay dispersion that limits achievable data rate with low
errors. A distinct dispersion limit in surface roughness is discovered beyond
which unacceptable numbers of symbol errors begin to accrue for a given data
rate.
