Hybrid non-orthogonal multiple access (H-NOMA) has recently received significant attention as a general framework of multiple access, where both conventional orthogonal multiple access (OMA) and pure NOMA are its special cases. This paper focuses on the application of H-NOMA to ambient Internet of Things (IoT) with energy-constrained devices, where a new backscatter communication (BackCom) assisted H-NOMA uplink scheme is developed. Resource allocation for H-NOMA uplink transmission is also considered, where an overall power minimization problem is formulated. Insightful understandings for the key features of BackCom assisted H-NOMA and its difference from conventional H-NOMA are illustrated by developing analytical results for the two-user special case. For the general multi-user scenario, two algorithms, one based on the branch-bound (BB) principle and the other based on successive convex approximation (SCA), are developed to realize different tradeoffs between the system performance and complexity. The numerical results are also provided to verify the accuracy of the developed analytical results and demonstrate the performance gain of H-NOMA over OMA.

翻译：混合非正交多址接入（H-NOMA）作为一种普适的多址接入框架近年来受到广泛关注，其中传统正交多址接入（OMA）与纯NOMA均为其特例。本文重点研究H-NOMA在设备能量受限的环境物联网（IoT）中的应用，提出了一种新型背向散射通信（BackCom）辅助的H-NOMA上行方案。同时，本文考虑了H-NOMA上行传输的资源分配问题，建立了一个总功率最小化问题。通过分析两用户特殊场景的解析结果，阐释了BackCom辅助H-NOMA的关键特性及其与传统H-NOMA的区别。针对通用多用户场景，分别基于分支定界（BB）原理和逐次凸近似（SCA）方法开发了两种算法，以实现系统性能与复杂度之间的不同权衡。数值结果验证了所提解析结果的准确性，并展示了H-NOMA相比OMA的性能增益。