Since the OP compared Internet latencies to the speed of light in glass...look up 802.1CM/IEEE1904.3 or "CPRI over Ethernet"/"Radio over Ethernet"! Those describe techniques for conveying LTE baseband signals (digital I/Q-samples) over Ethernet -- so the radios can live far away from the equipment that speaks the physical / MAC / radio-resource-control layers of LTE. There are strict latency/jitter requirements invol…
BBR is a sender-only modification to TCP that basically solves the problem of large buffers.