Joint Estimation and Compensation of CFO, IQ Imbalance and Channel Parameters for Zero Padded OTSM Systems

The Orthogonal Time Sequency Multiplexing (OTSM) waveform demonstrates superior performance compared to the Orthogonal Frequency Division Multiplexing (OFDM) waveform under linear time-varying (LTV) channels and multiple Doppler conditions. However, the direct conversion OTSM transceiver system is constrained by hardware impairments like carrier frequency offset (CFO) and IQ imbalance. In this Letter, we address these impairments by estimating and compensating for them using a dual pilot approach in the delay-time domain. Channel estimation is done at discrete pilot locations using two different methods. In high-mobility scenarios, the system employing phase compensation at periodic intervals exhibits better performance than the direct channel estimation method, which incorporates CFO into the channel. We evaluate the mean square error of the estimated LTV channel, which decreases with higher pilot power and reduced CFO. The performance analysis covers both uncoded and low-density parity-check (LDPC) coded systems.