Integrated Sensing and Communications (ISAC) surpasses the conventional frequency-division sensing and communications (FDSAC) in terms of spectrum, energy, and hardware efficiency, with potential for greater enhancement through integration of NOMA and signal alignment techniques. Leveraging these advantages, this paper proposes a multiple-input multiple-output-NOMA-ISAC framework with signal alignment and thoroughly analyzes its performance for both downlink and uplink. 1) The downlink ISAC is investigated under three different precoding designs: sensing-centric (S-C) design, communications-centric (C-C) design, and Pareto optimal design. 2) For the uplink case, two scenarios are investigated: S-C design and C-C design, based on the interference cancellation order of the communication signal and the sensing signal. In each of these scenarios, key performance metrics including sensing rate (SR), communication rate (CR), and outage probability are investigated. For a deeper understanding, the asymptotic performance of the system in the high signal-to-noise ratio (SNR) region is also explored, with a focus on the high-SNR slope and diversity order. Finally, the SR-CR rate regions achieved by ISAC and FDSAC are studied. Numerical results reveal that in both downlink and uplink cases, ISAC outperforms FDSAC in terms of sensing and communications performance and is capable of achieving a broader rate region, clearly showcasing its superiority over the conventional FDSAC.

翻译：集成感知与通信（ISAC）在频谱、能量和硬件效率方面超越了传统的频分感知与通信（FDSAC），通过结合非正交多址接入（NOMA）与信号对齐技术可进一步提升其性能潜力。基于这些优势，本文提出了一种集成信号对齐的多输入多输出-NOMA-ISAC框架，并对其在下行与上行场景中的性能进行了全面分析。1）针对下行ISAC，研究了三种不同的预编码设计：感知中心（S-C）设计、通信中心（C-C）设计以及帕累托最优设计。2）针对上行场景，基于通信信号与感知信号的干扰消除顺序，研究了两种情形：S-C设计与C-C设计。在每种情形中，深入分析了感知速率（SR）、通信速率（CR）以及中断概率等关键性能指标。为深化理解，还探讨了系统在高信噪比（SNR）区域的渐近性能，重点关注高SNR斜率与分集阶数。最后，研究了ISAC与FDSAC的SR-CR速率域。数值结果表明，在下行与上行场景中，ISAC在感知与通信性能方面均优于FDSAC，且能够实现更广阔的速率域，充分展现了其相较于传统FDSAC的优越性。