On the Spectral Efficiency of MMSE-based MIMO OTFS Systems

Abstract

We investigate the spectral efficiency (SE) of an uplink multi-user multiple-input multiple-output (MIMO) system with orthogonal time frequency space (OTFS) modulation. Two multiple access schemes are considered hereafter, namely, delay division multiple access (DDMA) and Doppler division multiple access (DoDMA). To avoid multi-user interference (MUI), we separate the delay Doppler (DD) domain resource blocks assigned to different users by guard bands. We design a minimum-meansquare-error (MMSE) receiver to combine the received signals for the detection of different users. We analyze the SE for the considered MIMO-OTFS system and quantify the performance gains achieved over a MIMO system with orthogonal frequency-division multiple access (OFDMA). Our simulation results demonstrate a noticeable improvement in the performance of MIMO-OTFS over MIMO-OFDMA.

How to Combine OTFS and OFDM Modulations in Massive MIMO?

“…The equivalent DD domain received signal for the k h -th highmobility user, and the equivalent TF domain received signal for the k l -th low-mobility user are shown in (8) and (9), respectively, at the top of the next page. For notation simplicity, we further define…”

“…To serve a large number of users, employing different multiple access (MA) schemes for MIMO-OTFS systems has also become a popular topic [8], [9]. The coexistence of non-orthogonal MA and OTFS has been investigated in [8], while the performance of an orthogonal MA scheme was investigated in [9].…”

“…To serve a large number of users, employing different multiple access (MA) schemes for MIMO-OTFS systems has also become a popular topic [8], [9]. The coexistence of non-orthogonal MA and OTFS has been investigated in [8], while the performance of an orthogonal MA scheme was investigated in [9]. Moreover, the massive MIMO technology offers the potential for supporting multi-user scenarios with a substantial increase in the SE of OTFS systems [10]- [13].…”