proposed in [19]. In [20], a channel estimation method was proposed where the entire OTFS block was utilized for pilot transmission. However, this method may not be effective if the channel estimates become outdated. In [21], a pilot-aided channel estimation method was presented for OTFS with the assumption of a channel causing integer Doppler shifts with respect to the delay-Doppler grid. This is while in reality, multipath channels not only cause integer but also fractional Doppler shifts. To address this issue, an embedded pilot-based channel estimation method was recently proposed in [22] where a single isolated pilot symbol in each OTFS block is deployed. This pilot symbol is surrounded by guard symbols in delay-Doppler grid to avoid interference due to the delay and Doppler spread of the channel between the pilot and data symbols. Starting from channel estimation in point-to-point single-input single-output (SISO) systems, the authors extend their solution to MIMO and multiuser uplink/downlink scenarios. However, a drawback of this approach is an increased training overhead due to the large number of guard symbols as the number of users increases. This is not favorable in vehicular channels with high density of users. In a massive MIMO setup, the aforementioned solutions are not effective in finding the channel estimates, since for a large number of antennas it requires a large number of orthogonal pilot sequences. This leads to a large amount of pilot overhead. To deal with this issue, in a recent work [23], the authors showed that the OTFS MIMO channel is sparse along the delay, Doppler, and 6 Orthogonal Time-Frequency Space Modulation: Principles and Implementation angle dimensions. This three-dimensional sparsity allows for formulating the channel estimation problem as a sparse signal recovery problem and channel estimation with a low pilot overhead. Apart from the abovementioned detection methods for OTFS, the authors in [24] propose an inter-symbol interference (ISI) cancellation method deploying soft