Decomposition of uplink multi-user OTFS channel with partial CSI feedback

Abstract

This work studies system design methods for the uplink multi-user orthogonal time–frequency space (OTFS) channel which forms a virtual multiple-input multiple-output (MIMO) communication system. For such system, the received signal contains interferences in the space, frequency, and time domain at the same time. To reduce the computational complexity, this work proposes to decompose the original large MIMO channel into parallel small sub-channels in the following order: first to decompose in the space domain, then to decompose in the time domain, thereby reducing the computational complexity. To help achieve channel decomposition, the proposed method requires the transmitter to perform precoding that needs channel state information (CSI) feedback. However, the proposed method only needs partial CSI feedback including delay and Doppler shift, so the feedback burden is small. Simulation results of the bit error rate (BER) performance verify that the proposed channel decomposition method is effective.