In this work, we consider the uplink of a scalable cell-free massive MIMO system where the users are served only by a subset of access points (APs) in the network. The APs are physically grouped into predetermined "cell-centric clusters", which are connected to different cooperative central processing units (CPUs). Given the cooperative nature of the considered communications network, we assume that each user is associated with a "virtual cluster", that, in general, involves some APs belonging to different cell-centric clusters. Assuming the maximum-ratio-combining at the APs, we propose a user-association procedure aimed at the maximization of the sum-rate of the users in the system. The proposed procedure is based on the Hungarian Algorithm and exploits only the knowledge of the position of the APs in the network. Numerical results reveal that the performance of the proposed approach is not always better than the alternatives but it offers a considerably lower backhaul load with a negligible performance loss compared to full-cell free approaches.
翻译:在这项工作中,我们考虑的是可扩缩的无细胞大型MIMO系统的升级,即用户只能通过网络中的一组接入点(APs)来服务。APs被物理地分组成预定的“以细胞为中心的集群 ”, 与不同的合作中央处理单位(CPUs)相连。考虑到考虑的通信网络的合作性质,我们假设每个用户都与“虚拟集群”有关,一般而言,它涉及属于不同细胞中心组群的一些APs。假设APs的最大连接,我们提议了一个用户联合程序,目的是尽量扩大系统中用户的总和率。拟议的程序以匈牙利阿尔哥里特姆为基础,只利用对APs在网络中的位置的了解。数字结果显示,拟议方法的性能并不总是比替代方法好,但是它提供了相当低的背部负载,与全细胞自由方法相比,其性能损失微不足道。