OTFS Channel Estimator based on Embedded Pilot Sequence Similarity

Traditional orthogonal time-frequency space (OTFS) channel estimation schemes place guard symbols around pilots to avoid interference from data symbols, thereby reducing spectrum efficiency (SE). To address this issue, this paper proposes an OTFS channel estimator based on the similarity of embedded pilot sequences (EPSS). Firstly, according to prior channel information, multiple pilots are sparsely embedded into an OTFS data frame, preventing mutual interference between pilots while fully utilizing the channel diversity gain, and the guard symbols of the pilots at the transmitter are revoked to improve SE. Secondly, at the receiver, a shift sequence with strong correlation to the embedded pilot sequence at the transmitter is designed. Through linear search, when the autocorrelation value of the shift sequence with the pilot sequence is greater than a threshold, the delay-Doppler taps of the channel can be estimated. Finally, an inverse gain matrix is designed to eliminate interference from data symbols to the pilots, thereby obtaining the channel gain. Through the design of an OTFS communication system, simulation results verify that the EPSS scheme significantly improves SE with a slight reduction in reliable communication performance.