Cell-free massive MIMO (CF-mMIMO) represent a deeply investigated evolution from the conventional multicell co-located massive MIMO (MC-mMIMO) network deployments. Anticipating a gradual integration of CF-mMIMO systems alongside pre-existing MC-mMIMO network elements, this paper considers a scenario where both deployments coexist, in order to serve a large number of users using a shared set of frequencies. The investigation explores the impact of this coexistence on the network's downlink performance, considering various degrees of mutual cooperation, precoder selection, and power control strategies. Moreover, to take into account the effect of the proposed cooperation scenarios on the fronthaul links, this paper also provides a fronthaul-aware heuristic association algorithm between users and network elements, which permits fulfilling the fronthaul requirement on each link. The research is finally completed by extensive simulations, shedding light on the performance outcomes associated with the diverse cooperation levels and several solutions delineated in the paper.

翻译：无小区大规模MIMO代表了一种从传统多小区共址大规模MIMO网络部署中深入研究的演进方向。考虑到无小区大规模MIMO系统将与现有多小区共址大规模MIMO网络元素逐步融合，本文考虑两者共存的场景，以利用共享频率资源服务大量用户。研究探讨了这种共存对网络下行性能的影响，考虑了不同程度的相互协作、预编码器选择以及功率控制策略。此外，为将所提出的协作场景对前传链路的影响纳入考量，本文还提出了一种基于前传感知的启发式用户与网络元素关联算法，该算法能够满足每条链路的前传需求。研究最终通过大量仿真完成，揭示了文中描述的多种协作等级及若干解决方案所带来的性能结果。