Yes, I am trying to use a router. But the guy who is helping me on this matter said that only increase wifi range (he modified the router to increase its range) is not enough, the receiving end (Rover) must also change ACK_timeout and CTS setting. Otherwise, it will cutoff the connection over a certain distance by default.
I have tried a 4G dongle but it didn’t work. However, it may be because I used wrong type of dongle.