OTFS-Based Multiple-Access in High Doppler and Delay Spread Wireless Channels

We propose a multiple-access (MA) method in the uplink of a orthogonal time frequency space modulation-based wireless communication system where the channel has high Doppler and delay spread. Each user terminal (UT) is allocated delay-Doppler (DD) resource blocks which are spaced at equal intervals in the DD domain. This limits the corresponding time-frequency (TF) transmit signal to a sub-domain of the entire TF domain. By allocating non-overlapping portions to the TF transmit signal of different UTs, multi-user interference (MUI) is avoided. The proposed MA method is analytically shown to be MUI free and therefore has a significantly higher sum spectral efficiency when compared to other methods proposed in literature which utilize guard bands in the DD domain to reduce MUI.