Proper coordination is needed to guarantee the performance of wireless networks in dense deployments. Contention-based systems suffer badly in terms of latency when multiple devices compete for the same resources. Coordinated Orthogonal Frequency Division Multiple Access (Co-OFDMA) is proposed for Wi-Fi 8 to remedy this, as it enables multiple Access Points (APs) to share spectrum more efficiently. However, fine-grained resource allocation, namely within 20MHz bandwidth, is argued to be impractical due to the over-the-air scheduling overhead and complexity in terms of physical layer signaling. A wired backhaul mitigates the need for over-the-air scheduling and synchronization, and it allows for coordination even if APs are not in each others' range. Furthermore, it forms the basis for more advanced multi-AP coordination schemes like coordinated beamforming and joint transmission. In this work we demonstrate the realization of Wi-Fi 6 compliant fine-grained Co-OFDMA using a fiber backhaul, enabled by the open-source platforms openwifi and White Rabbit. We show that the performance in terms of carrier frequency offset pre-compensation and time synchronization between two APs exceeds related wireless standard requirements. Furthermore, the quality of the received constellation of the Co-OFDMA frame as reported by a wireless connectivity tester is better than individual frames sent by the APs.

翻译：在密集部署场景中，需要适当的协调机制来保障无线网络性能。当多个设备竞争相同资源时，基于竞争的系统在时延方面表现严重恶化。为改善此问题，Wi-Fi 8提出了协调正交频分多址接入方案，该方案能使多个接入点更高效地共享频谱资源。然而，细粒度资源分配（即在20MHz带宽内）因空中调度开销及物理层信令复杂度而被认为难以实现。有线回程可消除对空中调度与同步的需求，即使接入点不在彼此覆盖范围内仍可实现协调。此外，有线回程为更先进的多接入点协调方案（如协调波束赋形与联合传输）奠定了基础。本研究通过开源平台openwifi与White Rabbit，演示了基于光纤回程的、符合Wi-Fi 6标准的细粒度协调正交频分多址接入系统实现。实验表明，两个接入点间的载波频率偏移预补偿与时间同步性能均超越相关无线标准要求。此外，根据无线连接测试仪报告的数据，协调正交频分多址接入帧的接收星座图质量优于各接入点单独发送的帧。