Orthogonal time sequency multiplexing (OTSM) has been recently proposed as a single-carrier (SC) waveform offering similar bit error rate (BER) to multi-carrier orthogonal time frequency space (OTFS) modulation in doubly-spread channels under high mobilities; however, with much lower complexity making OTSM a promising candidate for low-power millimeter-wave (mmWave) vehicular communications in 6G wireless networks. In this paper, the performance of OTSM-based homodyne transceiver is explored under hardware impairments (HIs) including in-phase and quadrature imbalance (IQI), direct current offset (DCO), phase noise, power amplifier non-linearity, carrier frequency offset, and synchronization timing offset. First, the discrete-time baseband signal model is obtained in vector form under the mentioned HIs. Then, the system input-output relations are derived in time, delay-time, and delay-sequency (DS) domains in which the parameters of HIs are incorporated. Analytical studies demonstrate that noise stays white Gaussian and effective channel matrix is sparse in the DS domain under HIs. Also, DCO appears as a DC signal at receiver interfering with only the zero sequency over all delay taps in the DS domain; however, IQI redounds to self-conjugated fully-overlapping sequency interference. Simulation results reveal the fact that with no HI compensation (HIC), not only OTSM outperforms plain SC waveform but it performs close to uncompensated OTFS system; however, HIC is essentially needed for OTSM systems operating in mmWave and beyond frequency bands.

翻译：正交时间序列复用（OTSM）近期被提出作为一种单载波（SC）波形，在高移动性下的双弥散信道中，其误码率（BER）性能与多载波正交时频空间（OTFS）调制相当，但复杂度显著降低，这使OTSM成为6G无线网络中低功耗毫米波（mmWave）车载通信的候选方案。本文研究了基于OTSM的零差收发器在硬件损伤（HIs）下的性能，这些损伤包括同相正交不平衡（IQI）、直流偏移（DCO）、相位噪声、功率放大器非线性、载波频率偏移和同步定时偏移。首先，在所提及的HIs条件下，以向量形式推导了离散时间基带信号模型。随后，在时间域、延迟-时间域和延迟序列（DS）域中建立了系统输入输出关系，并将HIs参数纳入其中。理论分析表明，在HIs条件下，DS域中的噪声仍保持高斯白噪声特性，且有效信道矩阵具有稀疏性。此外，DCO在接收端表现为直流信号，仅在DS域的所有延迟抽头上干扰零序列；然而，IQI导致了自共轭完全重叠的序列干扰。仿真结果揭示，在没有HIs补偿（HIC）的情况下，OTSM不仅优于普通SC波形，且性能接近未补偿的OTFS系统；然而，对于工作在毫米波及更高频段的OTSM系统，HIC是必不可少的。