Low-complexity Data Detection Design for OTSM System with Doppler Squint Effect

Low Earth orbit (LEO) satellite communication, a key technology in the 6 G era, faces significant challenges due to severe Doppler shifts and multi-path propagation. The recently proposed Orthogonal Time Sequency Multiplexing (OTSM) modulation, which multiplexes information symbols in the delay-sequency (DS) domain, demonstrates promising performance in high-mobility LEO scenarios. Compared to Orthogonal Time Frequency Space (OTFS) modulation, OTSM offers lower transceiver complexity, as DS domain symbols can be efficiently transformed using the Walsh-Hadamard Transform (WHT), which involves only additions and subtractions. However, existing analyses often overlook the Doppler Squint Effect (DSE)-a prevalent phenomenon in wideband systems where the Doppler shift varies with frequency, causing timefrequency coupling. Ignoring DSE leads to severe performance degradation in high-mobility LEO satellite communications. This paper derives the input-output relationship for OTSM systems under DSE. We further examine the structural properties of the resulting channel matrix and, building on this structure, develop a low-complexity data detection algorithm based on successive interference cancellation (SIC). Simulation results show that the proposed algorithm effectively mitigates the performance loss caused by DSE, thereby offering a theoretical basis for the application of OTSM in 6 G LEO satellite communications.