Recently, orthogonal time sequency multiplexing (OTSM) waveform was proposed using Walsh Hadamard transform (WHT) for doubly-dispersive channels at a lower modulation/demodulation complexity than orthogonal time frequency space (OTFS) waveform. At high frequencies, hardware imperfections such as in-phase and quadrature (IQ) imbalance is prominent at the transceiver. In this letter, the input-output (I/O) relation in the delay-sequency domain is derived under these impairments at the receiver. The impairment parameters are estimated in the delay-time domain and are compensated in the time domain using proposed dual pilot approach. The normalized mean square error (NMSE) of the estimated imbalance parameters is evaluated and it is observed that NMSE reduces with increase in SNR and with reduction in mobility. The results are evaluated with OTFS system and it is observed that the NMSE performance of OTSM is similar to OTFS under high pilot power and high SNR at no excess pilot power. The bit error rate performance of the compensated system is evaluated and its performance is close to the ideal system.

中文翻译：

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OTSM系统的IQ失衡估计与补偿

最近，正交时间序列复用 (OTSM) 波形被提出使用沃尔什 Hadamard 变换 (WHT) 用于双色散信道，其调制/解调复杂度低于正交时频空间 (OTFS) 波形。在高频下，收发器的同相和正交 (IQ) 不平衡等硬件缺陷非常突出。在这封信中，延迟序列域中的输入-输出 (I/O) 关系是在接收器的这些损伤下得出的。损伤参数在延迟时域中估计，并使用提出的双导频方法在时域中进行补偿。评估估计的不平衡参数的归一化均方误差 (NMSE)，观察到 NMSE 随着 SNR 的增加和移动性的降低而降低。使用 OTFS 系统对结果进行评估，观察到 OTSM 的 NMSE 性能在高导​​频功率和高 SNR 下在没有多余导频功率的情况下与 OTFS 相似。对补偿后系统的误码率性能进行了评价，其性能接近理想系统。