Exploiting user diversity in OTFS transmission for beyond 5G wireless systems

Orthogonal time frequency space (OTFS) modulation is a recent technology that offers a significant advantage on link reliability due to its strong delay-Doppler resilience. In classical cellular technology, overall system performance is limited by the fading and interference experienced by particular user equipment (UE) over its radio resources (RR). Besides, OTFS performance depends on the channel diversity of the UEs. Therefore, this letter examines the potential of multi-user diversity for OTFS systems considering practical scenarios. Specifically, we introduce a novel scheduling algorithm that proposes the assignment of the available RR of OTFS frame to the UE with the largest number of channel taps, resulting in enhanced channel diversity. It is shown via both mathematical analysis and simulation results that the proposed scheduling technique outperforms the scheme with random access to delay-Doppler RR in terms of system bit error rate (BER) with maximum likelihood (ML) receiver. The BER results validate the accuracy of the proposed technique for OTFS transmission with minimum mean square error (MMSE) detector considering various system configurations.