Ce-Fi: Centralized Wi-Fi over Packet-Fronthaul

Cloud radio access network (C-RAN) in cellular systems offers improved coverage and efficiency due to statistical multiplexing. Applying centralization to Wi-Fi networks could yield similar benefits, particularly in dense deployments like campus networks. However, this is challenging due to the usage of unlicensed, shared spectrum and strict protocol timing constraints like carrier sensing, making such systems highly sensitive to C-RAN induced delays. Existing approaches typically rely on radio-over-fiber and either demand very low delay or neglect neighboring Wi-Fi networks. In this paper, we present Ce-Fi, a centralized Wi-Fi architecture operating over a packet-based fronthaul (FH) connecting the central unit with the remote radio heads. Ce-Fi employs a two-level design with two bands: the network discovery and user association is handled standard compliantly on one band while another band is used for the actual data transmission with the centralized Wi-Fi. To tolerate the FH-induced delay, we propose minor changes to the 802.11 medium access control protocol like NAV extension and the usage of a piggybacking mechanism enabling the C-RAN-AP to transmit without prior channel contention. We evaluate Ce-Fi through simulations, demonstrating that it supports high throughput even under high FH-delays and in the presence of neighboring legacy networks.