In this work we study the capacity of interference-limited channels with memory. These channels model non-orthogonal communications scenarios, such as the non-orthogonal multiple access (NOMA) scenario and underlay cognitive communications, in which the interference from other communications signals is much stronger than the thermal noise. Interference-limited communications is expected to become a very common scenario in future wireless communications systems, such as 5G, WiFi6, and beyond. As communications signals are inherently cyclostationary in continuous time (CT), then after sampling at the receiver, the discrete-time (DT) received signal model contains the sampled desired information signal with additive sampled CT cyclostationary noise. The sampled noise can be modeled as either a DT cyclostationary process or a DT almost-cyclostationary process, where in the latter case the resulting channel is not information-stable. In a previous work we characterized the capacity of this model for the case in which the DT noise is memoryless. In the current work we come closer to practical scenarios by modelling the resulting DT noise as a finite-memory random process. The presence of memory requires the development of a new set of tools for analyzing the capacity of channels with additive non-stationary noise which has memory. Our results show, for the first time, the relationship between memory, sampling frequency synchronization and capacity, for interference-limited communications. The insights from our work provide a link between the analog and the digital time domains, which has been missing in most previous works on capacity analysis. Thus, our results can help improving spectral efficiency and suggest optimal transceiver designs for future communications paradigms.

翻译：本文研究具有记忆的干扰受限信道容量问题。此类信道建模了非正交通信场景，如非正交多址接入（NOMA）与底层认知通信，其中其他通信信号产生的干扰远强于热噪声。干扰受限通信有望成为未来无线通信系统（如5G、WiFi6及后续演进）中的常见场景。由于通信信号在连续时间（CT）域具有固有循环平稳性，接收端采样后得到的离散时间（DT）接收信号模型包含期望信号与加性采样CT循环平稳噪声。该采样噪声可建模为DT循环平稳过程或DT近似循环平稳过程——后者将导致信道不具有信息稳定性。此前工作已刻画了DT噪声为无记忆情形下的信道容量。本文通过将生成DT噪声建模为有限记忆随机过程，更贴近实际场景。记忆效应的存在要求发展一套新工具来分析具有记忆的加性非平稳噪声信道容量。研究结果首次揭示了干扰受限通信中记忆、采样频率同步与容量三者间的关系。本文工作提供了模拟域与数字域时间尺度间的桥梁，填补了以往绝大多数容量分析研究的空白。相关结论可提升频谱效率，并为未来通信范式的最优收发机设计提供指导。