论文标题
最佳的用户负载和以用户为中心的无单元无线网络的能源效率
Optimal User Load and Energy Efficiency in User-Centric Cell-Free Wireless Networks
论文作者
论文摘要
无细胞的大型MIMO是多源MIMO和大型MIMO的一种变体，其中天线$ LM $的总数分布在系统中的$ L $远程无线电单元（RUS）之间，从而启用了宏观的多样性和关节处理。由于试点污染和系统可伸缩性，每个RU只能为有限数量的用户服务。通过$ l $ rus在一个资源块（RB）上同时获得有关总和光谱效率（SE）的最佳用户数量并不是一个简单的挑战，因为许多系统参数都相互交织。例如，正交解调参考信号（DMRS）飞行员的尺寸$τ_p$限制了RU可以使用的用户数量。因此，根据$τ_p$，最佳用户负载产生的最大总和SE会有所不同。另一个关键参数是用户的上行链路传输功率$ p^{\ rm ue} _ {\ rm tx} $，其中存在中断，干扰和能源无效的用户之间的权衡。我们研究了多个参数在无细胞大量MIMO中对总和SE和用户中断的影响，以及不同水平的RU天线分布的性能。我们提供了广泛的数值研究，以阐明系统SE相对于各种参数的行为，包括系统负载的效果，即在任何RB上提供活跃用户的数量。结果表明，总的来说，一个具有许多RU和RU天线很少的系统产生了最大的SE，在该系统中，分布式天线的好处在非常密集的网络中降低。
Cell-free massive MIMO is a variant of multiuser MIMO and massive MIMO, in which the total number of antennas $LM$ is distributed among the $L$ remote radio units (RUs) in the system, enabling macrodiversity and joint processing. Due to pilot contamination and system scalability, each RU can only serve a limited number of users. Obtaining the optimal number of users simultaneously served on one resource block (RB) by the $L$ RUs regarding the sum spectral efficiency (SE) is not a simple challenge though, as many of the system parameters are intertwined. For example, the dimension $τ_p$ of orthogonal Demodulation Reference Signal (DMRS) pilots limits the number of users that an RU can serve. Thus, depending on $τ_p$, the optimal user load yielding the maximum sum SE will vary. Another key parameter is the users' uplink transmit power $P^{\rm ue}_{\rm tx}$, where a trade-off between users in outage, interference and energy inefficiency exists. We study the effect of multiple parameters in cell-free massive MIMO on the sum SE and user outage, as well as the performance of different levels of RU antenna distribution. We provide extensive numerical investigations to illuminate the behavior of the system SE with respect to the various parameters, including the effect of the system load, i.e., the number of active users to be served on any RB. The results show that in general a system with many RUs and few RU antennas yields the largest sum SE, where the benefits of distributed antennas reduce in very dense networks.
