In this paper we consider Orthogonal Time Frequency Space (OTFS) modulation based multiple-access (MA). We specifically consider Orthogonal MA methods (OMA) where the user terminals (UTs) are allocated non-overlapping physical resource in the delay-Doppler (DD) and/or time-frequency (TF) domain. To the best of our knowledge, in prior literature, the performance of OMA methods have been reported only for ideal transmit and receive pulses. In [20] and [21], OMA methods were proposed which were shown to achieve multi-user interference (MUI) free communication with ideal pulses. Since ideal pulses are not realizable, in this paper we study the spectral efficiency (SE) performance of these OMA methods with practical rectangular pulses. For these OMA methods, we derive the expression for the received DD domain symbols at the base station (BS) receiver and the effective DD domain channel matrix when rectangular pulses are used. We then derive the expression for the achievable sum SE. These expressions are also derived for another well known OMA method where guard bands (GB) are used to reduce MUI (called as the GB based MA methods) [19]. Through simulations, we observe that with rectangular pulses the sum SE achieved by the method in [21] is almost invariant of the Doppler shift and is higher than that achieved by the methods in [19], [20] at practical values of the received signal-to-noise ratio.

翻译：在本文中,我们考虑了基于Orthogon 时间频率空间(OTFS) 调制基于多存(MA) 的调制法。 我们特别考虑了 Orthogonal MA 方法(OMA), 即用户终端(UTs) 在延迟- Doppler (DD) 和/或时频(TF) 域中分配不重叠的物理资源。 根据我们的知识, 在以前的文献中, OMA 方法的性能仅用于理想的传输和接收脉冲。 在 [20] 和 [21] 中, 提出了显示可实现多用户干扰(MUI) 与理想脉冲的自由信号通信的方法。 由于理想脉冲无法实现, 理想脉冲(OMA) 理想脉冲(OMA) 方法(OMA) 的光谱效率(SE) 性能(SESE) 性能(SOD) 性能(SOD) 性能(MI) 方法(MUI) 和MI(MI) (MBI) 的变压方法(MGB) 实现的MU) 。