whose frequency is over 275 GHz for ultrahigh-speed wireless links, since the frequency bands
from 275 GHz to 3000 GHz are not yet allocated for specific active services in the world, and there
is a possibility to employ extremely large bandwidths for ultra-broadband wireless communications
[4]–[9]. Even though existing microwave and millimeter-wave wireless technologies will enhance
their data rates by improving the spectral efficiency with use of multi-value modulation schemes
such as 16 QAM or MIMO (multiple input multiple output) techniques, the THz communications will
promise a data rate of 100 Gb/s using relatively simple modulation schemes like ASK and QPSK
because of their broad bandwidths.