[SvenL]

There was a standard called Wi-Fi Direct for such a use case. I remember evaluating it for a automotive project (where cars would pass object only for a short time). Maybe it’s fits your use case.

https://en.m.wikipedia.org/wiki/Wi-Fi_Direct

[swiatlo]

wifi direct have transmiter and receiver too ;) In my opinion sending message like walkie-talkie radio protocol is different. (for example https://github.com/ntoivola/uvk5-chirp-driver-nunu )