Space-Time Coding and LMMSE Receiver in OTFS Modulation

. Orthogonal Time Frequency Space (OTFS) modulation is a two-dimensional modulation method that is developed in the delay-Doppler domain that is used in doubly-dispersive fading channels. At the transmitter, OTFS utilizes additional transform operations, and the receiver is used above the conventional multicarrier modulation operations, which attains greater performance rather than OFDM. In the delay-Doppler domain, OTFS along with phase rotation by utilizing transcendental numbers proved to attain entire diversity. The proposed work uses space-time coding (STC) in a MIMO configuration. Also, to attain complete transmit diversity in OTFS, the Alamouti code structure is used. Thus, the usage of STC-OTFS along with phase rotation will attain complete diversity in delay-Doppler and spatial domains. In addition, the low complexity LMMSE receiver is employed that uses Sparsity and the quasi-banded shape of the matrices which are included in the demodulation procedure. Hence, the proposed work achieves higher performance than the existing methods.