With the imminent arrival of 6G communication, the relevance of advanced technologies, such as multi-input-multioutput (MIMO), nonorthogonal multiple access (NOMA), reconfigurable intelligent surfaces (RISs), and integrated sensing and communication (ISAC), has become prominent for plethora of Internet of Things (IoT) applications. However, integrating ISAC into a MIMO heterogeneous network (HetNets) necessitates reevaluating network performance in terms of outage probability and ergodic rates. This article introduces a novel analytical framework for evaluating downlink transmissions in MIMO HetNets. The proposed framework considers independent homogeneous Poisson point processes (PPP) for spatial arrangement of the NOMA-enabled base stations (BSs) and users. BS in the tth tier exploits superimposed NOMA signal for target sensing. Active RISs are considered to be distributed with homogeneous PPP and are used to mitigate blockage for user equipments when the direct link from the BSs does not exist. The approximated and asymptotic outage probability expressions are derived for two distinct scenarios: one involving direct transmission from the BS to the typical blocked user and the other entailing transmission via active RIS. Moreover, a practical case of imperfect successive interference cancelation (i-SIC) is considered. The analysis emphasizes the benefits of the proposed active RIS-NOMA compared to conventional orthogonal multiple access HetNets, and valuable insights are drawn by varying the number of RIS elements. Additionally, an increase in the RIS elements significantly improves the proposed active RIS-NOMA outage performance. The approximated expressions of ergodic rates, system throughput and beampattern for the sensing performance are also derived.

中文翻译：

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具有集成传感和通信功能的 NOMA 主动 RIS 辅助 MIMO 异构物联网网络的性能分析


随着6G通信的即将到来，多输入多输出（MIMO）、非正交多址（NOMA）、可重构智能表面（RIS）以及集成传感与通信（ISAC）等先进技术的相关性已变得越来越重要。以大量物联网 (IoT) 应用而闻名。然而，将 ISAC 集成到 MIMO 异构网络 (HetNet) 中需要根据中断概率和遍历率重新评估网络性能。本文介绍了一种用于评估 MIMO HetNet 中下行链路传输的新颖分析框架。所提出的框架考虑了支持 NOMA 的基站 (BS) 和用户的空间布置的独立同质泊松点过程 (PPP)。第 t 层中的 BS 利用叠加的 NOMA 信号进行目标感知。主动 RIS 被认为是通过同质 PPP 进行分布的，并且用于在不存在来自 BS 的直接链路时减轻用户设备的阻塞。近似和渐近的中断概率表达式是针对两种不同的场景得出的：一种涉及从 BS 到典型阻塞用户的直接传输，另一种需要通过主动 RIS 进行传输。此外，还考虑了不完美连续干扰消除（i-SIC）的实际情况。该分析强调了所提出的主动 RIS-NOMA 与传统正交多路访问 HetNet 相比的优势，并且通过改变 RIS 元素的数量得出了有价值的见解。此外，RIS 元件的增加显着提高了拟议的主动 RIS-NOMA 中断性能。还推导了传感性能的遍历速率、系统吞吐量和波束方向图的近似表达式。