Joint relay assignment and energy‐efficiency maximization in energy‐harvesting downlink/uplink clustered nonorthogonal multiple‐access networks,Transactions on Emerging Telecommunications Technologies

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Joint relay assignment and energy‐efficiency maximization in energy‐harvesting downlink/uplink clustered nonorthogonal multiple‐access networks
Transactions on Emerging Telecommunications Technologies ( IF 2.5 ) Pub Date : 2020-04-16 , DOI: 10.1002/ett.3962
Mohammed W. Baidas ₁

Affiliation

In this article, the problem of joint relay assignment and energy‐efficiency maximization (J‐RA‐EE‐MAX) in energy‐harvesting downlink (DL) and uplink (UL) clustered nonorthogonal multiple‐access (NOMA) networks is considered. Specifically, the aim is to perform relay assignment to user clusters in the DL and UL directions, while simultaneously maximizing energy efficiency (EE) over each relay via multiobjective optimization, and satisfying users' quality‐of‐service (QoS) constraints. However, problem J‐RA‐EE‐MAX happens to be nonconvex in each link direction, and thus is computationally prohibitive. Alternatively, a low‐complexity solution procedure is devised to solve problem J‐RA‐EE‐MAX in each link direction by: (i) optimally solving the energy‐efficiency maximizing power allocation (EE‐MAX‐PA) for each (user cluster, relay) combination to construct the relays' preference profile, and (ii) performing relay assignment via Gale's top trading cycles (TTC) matching mechanism. In particular, the optimal solution of the EE‐MAX‐PA problem is obtained by transforming it into a concave maximization problem, while the TTC mechanism is executed in linear time‐complexity so as to obtain a stable relay assignment. Simulation results are presented to validate the proposed solution procedure, which is shown to yield comparable user cluster sum‐rate and relay EE to the J‐RA‐EE‐MAX scheme, and superior to other schemes in both link directions, however, at lower computational complexity, while satisfying users' QoS constraints. Finally, this work sheds light on the importance of decoupling relay assignment in the DL/UL directions, which significantly improves user cluster sum‐rate and relay EE in comparison to coupled relay assignment schemes, and thus serves the requirements of 5G networks and beyond.

中文翻译：

能量收集下行/上行集群非正交多址网络中的联合中继分配和能量效率最大化

在本文中，考虑了能量收集下行链路（DL）和上行链路（UL）群集非正交多址（NOMA）网络中的联合中继分配和能量效率最大化（J‐RA‐EE‐MAX）问题。具体而言，目标是在DL和UL方向上对用户群集执行中继分配，同时通过多目标优化同时最大化每个中继上的能效（EE），并满足用户的服务质量（QoS）约束。但是，问题J‐RA‐EE‐MAX在每个链接方向上都是非凸的，因此在计算上是禁止的。或者，通过以下方式设计一种低复杂度的解决方案来解决每个链路方向上的问题J-RA-EE-MAX：（i）最佳地解决每个用户群的能量效率最大化功率分配（EE-MAX-PA），中继）组合以构建中继的偏好配置文件，以及（ii）通过Gale的最高交易周期（TTC）匹配机制执行中继分配。尤其是，通过将ETC-MAX-PA问题转化为凹最大化问题来获得最优解，而在线性时间复杂度下执行TTC机制以获得稳定的中继分配。给出了仿真结果以验证所提出的解决方案，该解决方案可产生可比的用户集群总和，并将EE中继到J-RA-EE-MAX方案，并且在两个链路方向上均优于其他方案，但在更低的链路上计算复杂度，同时满足用户的QoS约束。最后，这项工作阐明了DL / UL方向上去耦继电器分配的重要性，

更新日期：2020-04-16

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