To keep supporting next-generation requirements, the radio access infrastructure will increasingly densify. Cell-free (CF) network architectures are emerging, combining dense deployments with extreme flexibility in allocating resources to users. In parallel, the Open Radio Access Networks (O-RAN) paradigm is transforming RAN towards an open, intelligent, virtualized, and fully interoperable architecture. This paradigm brings the needed flexibility and intelligent control opportunities for CF networking. In this paper, we document the current O-RAN terminology and contrast it with some common CF processing approaches. We then discuss the main O-RAN innovations and research challenges that remain to be solved.

中文翻译：

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O-RAN 架构中的无蜂窝 mMIMO 支持：5G 及更高网络的 PHY 层视角

为了继续支持下一代要求，无线电接入基础设施将越来越密集。无小区 (CF) 网络架构正在出现，将密集部署与向用户分配资源的极大灵活性相结合。与此同时，开放无线电接入网络 (O-RAN) 范例正在将 RAN 转变为开放、智能、虚拟化和完全可互操作的架构。这种范例为 CF 网络带来了所需的灵活性和智能控制机会。在本文中，我们记录了当前的 O-RAN 术语并将其与一些常见的 CF 处理方法进行对比。然后，我们将讨论仍有待解决的主要 O-RAN 创新和研究挑战。