Thanks for the answer.
I need to be more clear.
I need to use wi-fi as failover connection because the ethernet link between camera and NVR is via powerline. So if the powerline goes down for eletricity fault the camera should detect the ethernet link is down an should try to connect to the router via W-Fi.
Obviusly the camera is backed up with a battery and the router, DVR/NVR, VPN concentrator are backed up with an UPS