Channel Phase Nonreciprocity Compensation for Space-Frequency Line Coded OFDM Systems

This paper investigates the impact of phase nonreciprocity in space-frequency line code-orthogonal frequency-division multiplexing (SFLC-OFDM) systems, leading to significant performance degradation due to non-ideal multi-channel radio-frequency transceivers. A novel demodulation reference signal (DMRS) structure with phase rotation is proposed to address this challenge, enabling effective phase nonreciprocity compensation. To compensate for the channel phase nonreciprocity, the user equipment, as the uplink (UL) transmitter, estimates the downlink (DL) phase offset (PO) and then embeds this offset information into the phase of UL DMRS sequences. The base station, as the UL receiver, extracts the embedded DL PO and estimates the UL PO from the received DMRS sequences. The DL and UL PO values are then used at the base station to compensate for phase discrepancies between the UL and DL channels during the UL channel estimation process. Extensive numerical simulations across various system parameters validate the effectiveness of the proposed method in mitigating phase nonreciprocity and ensuring reliable SFLC-OFDM performance.