Lately, the deployment of heterogeneous wireless networks has emerged, as part of the 5G vision, to cope with the users’ exaggerated service demands. In this context, the application of Non-Orthogonal Multiple Access (NOMA) technique constitutes a promising solution to facilitate a balance between spectral efficiency and system complexity. In this article, we consider the problem of joint user association and uplink power allocation, in heterogeneous 5G wireless networks, employing NOMA technology. The coupled problem is treated under an incomplete information scenario, where the Base Stations (BSs) have statistical only knowledge of the users’ channel conditions. To deal with the incompleteness of Channel State Information (CSI), a Contract Theory (CT) based approach is introduced. A Reinforcement Learning (RL) based methodology, capitalizing on the provided feedback from the communication environment is initially adopted, in order to achieve the users to BS association in an iterative and distributed manner. The problem of uplink power allocation is subsequently formulated as a contract between each BS and its corresponding users. The optimal power is thus obtained as the solution of the optimization of each BS’s utility function, while ensuring the optimality of the utility function of each associated user, given the unique communications characteristics and type of each user. Detailed numerical evaluation of the performance of the proposed unified user association and power allocation framework is provided, via modeling and simulation, illustrating its operation, features and benefits, under densely deployed heterogeneous environments.

中文翻译：

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NOMA异构无线网络中的统一用户协会和合同理论资源编排

最近，作为5G愿景的一部分，已经出现了异构无线网络的部署，以应对用户夸大的服务需求。在这种情况下，非正交多址访问（NOMA）技术的应用构成了一种有希望的解决方案，可促进频谱效率与系统复杂性之间的平衡。在本文中，我们考虑了采用NOMA技术的异构5G无线网络中联合用户关联和上行链路功率分配的问题。在信息不完整的情况下处理耦合问题，其中基站（BS）仅统计用户的信道状况。为了处理信道状态信息（CSI）的不完整性，引入了一种基于合同理论（CT）的方法。基于强化学习（RL）的方法，最初采用从通信环境提供的反馈来利用，以便以迭代和分布式的方式实现用户到BS的关联。随后将上行链路功率分配问题表述为每个BS与其对应用户之间的合同。因此，在给定每个用户的独特通信特性和类型的情况下，在确保每个相关用户的实用功能的最优性的同时，获得最优功率作为优化每个BS的实用功能的解决方案。通过建模和仿真，对提议的统一用户关联和功率分配框架的性能进行了详细的数字评估，以说明其在密集部署的异构环境下的操作，功能和优势。