Employing massively distributed antennas brings radio access points (RAPs) closer to users, enabling aggressive spectrum reuse that can bridge gaps between the scarce spectrum resource and extremely high connection densities in future wireless systems. Examples include the cloud radio access network (C-RAN), ultradense network (UDN), and cell-free massive multiple-input, multiple-output (CF-mMIMO) systems. These systems are usually designed in the form of fiber wireless communications (FWC), where distributed antennas or RAPs are connected to a central unit (CU) through optical fronthauls. A large number of densely deployed antennas or RAPs require an extensive infrastructure of optical fronthauls. Consequently, the cost, complexity, and power consumption of the network of optical fronthauls may dominate the performance of the entire system. This article provides an overview and outlook on the architecture, modeling, design, and performance of massively distributed antenna systems (DAS) with nonideal optical fronthauls. Complex interactions between optical fronthauls and wireless access links require optimum designs across the optical and wireless domains by jointly exploiting their unique characteristics. It is demonstrated that systems with analog radio-frequency-overfiber (RFoF) links outperform their baseband-overfiber (BBoF) or intermediate-frequency-overfiber (IFoF) counterparts for systems with shorte fiber length and more RAPs, which are all desired properties for future wireless communication systems.

中文翻译：

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具有非理想光纤前传的大规模分布式天线系统：6G 无线通信系统的一项有前途的技术


采用大规模分布式天线使无线接入点 (RAP) 更接近用户，从而实现积极的频谱重用，从而弥补未来无线系统中稀缺频谱资源与极高连接密度之间的差距。示例包括云无线接入网络 (C-RAN)、超密集网络 (UDN) 和无小区大规模多输入多输出 (CF-mMIMO) 系统。这些系统通常以光纤无线通信 (FWC) 的形式设计，其中分布式天线或 RAP 通过光学前传连接到中央单元 (CU)。大量密集部署的天线或 RAP 需要广泛的光前传基础设施。因此，光前传网络的成本、复杂性和功耗可能主导整个系统的性能。本文对具有非理想光学前传的大规模分布式天线系统 (DAS) 的架构、建模、设计和性能进行了概述和展望。光前传和无线接入链路之间的复杂交互需要通过共同利用光和无线领域的独特特性来进行跨光和无线领域的优化设计。事实证明，对于具有较短光纤长度和更多 RAP 的系统，具有模拟射频光纤 (RFoF) 链路的系统优于其基带光纤 (BBoF) 或中频光纤 (IFoF) 系统，这些都是光纤长度所需的属性。未来的无线通信系统。