  Orthogonal time sequency multiplexing (OTSM) has been recently proposed as a
single-carrier waveform offering similar bit error rate to orthogonal time
frequency space (OTFS) and outperforms orthogonal frequency division
multiplexing (OFDM) in doubly-spread channels (DSCs); however, with a much
lower complexity making it a potential candidate for 6G wireless networks. In
this paper, the performance of OTSM is explored by considering the joint
effects of multiple hardware impairments (HWIs) such as in-phase and quadrature
imbalance (IQI), direct current offset (DCO), phase noise, power amplifier
non-linearity, carrier frequency offset, and synchronization timing offset for
the first time in the area. First, the discrete-time baseband signal model is
obtained in vector form under all mentioned HWIs. Second, the system
input-output relations are derived in time, delay-time, and delay-sequency (DS)
domains in which the parameters of all mentioned HWIs are incorporated. Third,
analytical expressions are derived for the pairwise and average bit error
probability under imperfect channel state information (CSI) as a function of
the parameters of all mentioned HWIs. Analytical results demonstrate that under
all mentioned HWIs, noise stays additive white Gaussian, effective channel
matrix is sparse, DCO appears as a DC signal at the receiver interfering with
only the zero sequency, and IQI redounds to self-conjugated sequency
interference in the DS domain. Simulation results reveal the fact that by
considering the joint effects of all mentioned HWIs and imperfect CSI not only
OTSM outperforms OFDM by 29% in terms of energy of bit per noise but it
performs same as OTFS in high mobility DSCs.
