The present paper investigates the trade-offs between the energy efficiency (EE) and spectral efficiency (SE) in the full-duplex (FD) multiuser multi-input multioutput (MU-MIMO) cloud radio access networks (CRANs) with simultaneous wireless information and power transfer (SWIPT). In the considered network, the central unit (CU) intends to concurrently not only transfer both energy and information toward downlink (DL) users using power splitting structures but also receive signals from uplink (UL) users. This communication is executed via FD radio units (RUs) which are distributed nearby users and connected to the CU through limited capacity fronthaul (FH) links. In order to unveil interesting trade-offs between the EE and SE metrics, we first introduce three conventional single-objective optimization problems (SOOPs) including (i) system sum rate maximization, (ii) total power minimization, and (iii) fractional energy efficiency maximization. Then, by making use of the multiobjective optimization (MOO) framework, the MOO problem (MOOP) with the objective vector of the achievable rate and power consumption is addressed. All considered problems are nonconvex with respect to designing variables comprising precoding matrices, compression matrices, and DL power splitting factors; thus, it is extremely intractable to solve these problems directly. To overcome these issues, we develop iterative algorithms by utilizing the sequential convex approximation (SCA) approach for the first two SOO problems and the SCA-based Dinkelbach method for the fractional EE problem. Regarding the MOOP, we first rewrite it as an SOOP by applying the modified weighted Tchebycheff method and, then, propose the iterative algorithm-based SCA to find its optimal Pareto set. Various numerical simulations are conducted to study the system performance and appealing EE-SE trade-offs in the considered system.

中文翻译：

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带有SWIPT的全双工MU-MIMO Cloud-RAN中的能量频谱效率权衡

本文研究了同时具有无线信息的全双工（FD）多用户多输入多输出（MU-MIMO）云无线电接入网络（CRAN）中的能效（EE）和频谱效率（SE）之间的权衡和功率传输（SWIPT）。在所考虑的网络中，中央单元（CU）不仅打算同时使用功率分配结构向下行链路（DL）用户传输能量和信息，而且还打算从上行链路（UL）用户接收信号。该通信通过分布在用户附近并通过有限容量前传（FH）链路连接到CU的FD无线电单元（RU）执行。为了揭示EE和SE指标之间有趣的取舍，我们首先介绍三个常规的单目标优化问题（SOOP），包括（i）系统总和率最大化，（ii）总功率最小化和（iii）分数能效最大化。然后，通过使用多目标优化（MOO）框架，解决了具有可实现速率和功耗的目标向量的MOO问题（MOOP）。就设计变量（包括预编码矩阵，压缩矩阵和DL功率分配因子）而言，所有考虑的问题都不是凸的。因此，直接解决这些问题非常棘手。为了克服这些问题，我们通过针对前两个SOO问题利用顺序凸逼近（SCA）方法以及针对分数EE问题使用基于SCA的Dinkelbach方法来开发迭代算法。关于MOOP，我们首先通过应用改进的加权Tchebycheff方法将其重写为SOOP，然后提出基于迭代算法的SCA来找到其最佳Pareto集。进行了各种数值模拟，以研究系统性能以及所考虑系统中的EE-SE折衷方案。