Non-orthogonal multiple access (NOMA) has been a strong candidate to support massive connectivity in future wireless networks. In this regard, its implementation into cooperative relaying, named cooperative-NOMA (CNOMA), has received tremendous attention by researchers. However, most of the existing CNOMA studies have failed to address practical constraints since they assume ideal conditions. Particularly, error performance of CNOMA schemes with imperfections has not been investigated, yet. In this letter, we provide an analytical framework for error performance of CNOMA schemes under practical assumptions where we take into account imperfect successive interference canceler (SIC), imperfect channel estimation (ICSI), and hardware impairments (HWI) at the transceivers. We derive bit error rate (BER) expressions in CNOMA schemes whether the direct links between source and users exist or not which is, to the best of the authors' knowledge, the first study in the open literature. For comparisons, we also provide BER expression for downlink NOMA with practical constraints which has also not been given in literature, yet. The theoretical BER expressions are validated with computer simulations where the perfect-match is observed. Finally, we discuss the effects of the system parameters (e.g., power allocation, HWI level) on the performance of CNOMA schemes to reveal fruitful insights for the society.
翻译:非横向多重接入(NOMA)是支持未来无线网络大规模连通的有力候选者,在这方面,对合作转发(称为合作-NOMA(CNOMA))的实施受到研究人员的极大关注,然而,现有的CNOMA研究大多未能解决自它们假定理想条件以来的实际制约因素。特别是,CNOMA计划有缺陷的错误性能尚未得到调查,然而,在本信内,我们提供了一个分析框架,分析在实际假设下,CNOMA计划的错误性能表现,其中我们考虑到不完善的连续取消干扰者(SICI)、不完善的频道估计(ICSI)和收发器的硬件缺陷(HWI)等。我们在CNOMA计划中的误差率(BER)表示,不论源与用户之间的直接联系是否存在,是否因为根据作者所知,这是开放文献的首项研究。比较中,我们还提供了BER的表达方式,用于将NOMA计划与实际限制(在文献中也没有给出的)进行下调,然而,理论BER的表达方式得到验证,计算机模拟,在计算机模拟中观察到了HMACM的精确度分布。最后,我们讨论了CWI计划的业绩效果的效果。