In this letter, an orthogonal time frequency space (OTFS) based non-orthogonal multiple access (NOMA) scheme is investigated for the coordinated direct and relay transmission system, where a source directly communicates with a near user with high mobile speed, and it needs the relaying assistance to serve the far user also having high mobility. Due to the coexistence of signal superposition coding and multi-domain transformation, the performance of OTFS-based NOMA is usually challenging to be measured from a theoretical perspective. To accurately evaluate the system performance of the proposed scheme, we derive the closed-form expressions for the outage probability and the outage sum rate by using the Inversion formula and characteristic function. Numerical results verify the performance superiority and the effectiveness of the proposed scheme.

翻译：本文研究了一种基于正交时频空间（OTFS）的非正交多址接入（NOMA）方案，用于协调直传与中继传输系统。在该系统中，信源与具有高移动速度的近端用户直接通信，同时需要中继辅助以服务同样具有高移动性的远端用户。由于信号叠加编码与多域变换的共存，基于OTFS的NOMA性能通常难以从理论角度进行衡量。为准确评估所提方案的系统性能，我们利用反演公式和特征函数推导了中断概率和中断和速率的闭式表达式。数值结果验证了所提方案的性能优越性和有效性。