Let me start by saying point-blank. Don’t stress about microwave latency. It’s not an issue, period. It’s good to ask about it, but don’t get talked into buying one radio over another because of some (supposed) latency advantage. Hear me out and tell me if I’m wrong…
My first brush with microwave latency was 1986, so I'm pretty familiar with the topic. My engineers were writing the industry’s first wireless Ethernet specs (typed up on my 128k MAC) and calculated round-trip propagation delay through the air, along with whatever delays were associated with the equipment. Those specs were confirmed by Cisco when we co-developed the first full-duplex Ethernet interface, and later by Motorola in a technology transfer deal.
Here’s what I know. Latency of a microwave transmission is (considerably) less than optical fiber, but only as the signal travels through air as opposed to glass. There’s also the fact of equipment latency, and that's where fiber wins. Yet microwave hardware (of the FCC licensed variety) introduces mere microseconds of delay, a minuscule figure when you consider that it takes 150 milliseconds before VoIP suffers.
So why all the fuss about latency?