Cross-Pilot Superposition for Fractional Parameter Estimation in DoA-Aided OTFS Receivers

In this letter, a novel superimposed pilot scheme is proposed for channel estimation in multi-antenna orthogonal time frequency space (OTFS) receivers. Under the assumption of a large uniform linear array (ULA) size at the receiver, the multipath components are separated directly in the angular domain. It is then shown that the proposed superimposed pilot scheme enables the computation of integrated delay and Doppler profiles by averaging the received delay-Doppler matrix across the Doppler and delay axes, respectively. This procedure helps reduce data-to-pilot interference through data averaging. Moreover, it is demonstrated that fractional delays and Dopplers of the multipath components can be estimated by correlating the integrated delay and Doppler profiles with the corresponding delay/Doppler terms. Simulation results show that the proposed approach outperforms existing OTFS superimposed pilot schemes, achieving a lower bit error rate (BER) while exhibiting a trade-off between peak-to-average power ratio (PAPR) and communication performance.