Contrary to orthogonal multiple-access (OMA), non-orthogonal multiple-access (NOMA) schemes can serve a pool of users without exploiting the scarce frequency or time domain resources. This is useful in meeting the sixth generation (6G) network requirements, such as, low latency, massive connectivity, users fairness, and high spectral efficiency. On the other hand, content caching restricts duplicate data transmission by storing popular contents in advance at the network edge which reduces 6G data traffic. In this survey, we focus on cache-aided NOMA-based wireless networks which can reap the benefits of both cache and NOMA; switching to NOMA from OMA enables cache-aided networks to push additional files to content servers in parallel and improve the cache hit probability. Beginning with fundamentals of cache-aided NOMA technology, we summarize the performance goals of cache-aided NOMA systems, present the associated design challenges, and categorize related recent literature based on their application verticals. Concomitant standardization activities and open research challenges are highlighted as well.
翻译:与正交多址接入(OMA)相反,非正交多址接入(NOMA)方案可以为用户池提供服务,而不需要利用稀缺的频率或时间域资源。这对于满足第六代(6G)网络要求非常有用,例如低延迟,大规模连通性,用户公平性和高光谱效率。另一方面,内容缓存通过在网络边缘预先存储流行内容来限制重复数据传输,从而减少6G数据流量。在本调查中,我们重点研究基于缓存的 NOMA 无线网络,这可以利用缓存和 NOMA 的好处;从 OMA 切换到 NOMA 使缓存辅助网络能够并行地向内容服务器推送其他文件,并提高缓存命中概率。从缓存辅助 NOMA 技术的基础开始,我们总结了缓存辅助 NOMA 系统的性能目标,介绍了相关的设计挑战,并根据其应用垂直类别对相关的最新文献进行分类。同时,突出标准化活动和开放的研究挑战。