3G camera

Reolink camera with a 48 network sim works for me. That’s 4g.

Came with solar but I don’t use it. I just bring it in and charge it ever 2-3 weeks depending on usage for me.

Is it for security (as in you want to record) or calving (just view live)?

If your current setup is working well except for the router I'd look at replacing the router. 2 issues I find with the all in ones is nightvision is not as good, due to the energy saving required for small battery/panel, also the panel mounting is too flimsy for any kind of exposed area I've had to go looking for mine a few times after wind, must gunter up a better one .

If the issue with your router is signal/mobile network related a 3G/4G camera is unlikely to be any better.

To be fair they work well for that purpose, I set mine to email still images to me on alarm. Just be careful mounting the solar panel, preferably sheltered from the wind as much as possible. Would be great if night vision was a bit better, if setup beside a light or covering a gate or doorway at short distance it's not so bad, but across open yard won't pickup a lot after dark.

I've cheap wired cameras here too and while not perfect the IR range is multiples of the battery Reolinks. Yes absolutely setup with with a PIR light could improve them significantly.

Obviously the Reolinks have poor IR in order to conserve battery. I just think it's worth pointing out to someone especially if they are considering replacing another camera system with them as there will likely be a significant difference.