Today, there are two frequency ranges for signal transmission in Wi-Fi networks - 2.4 GHz and 5 GHz. 2.4 GHz.

The main difference between the 2.4 GHz and 5 GHz bands comes down to the difference in the speed of the WiFi wireless connection and the range (coverage area) of the WiFi network.

The 2.4 GHz band has increased stability over long distances up to 50 or 150 meters, which depends on the configuration of the room, the transmitter power and the technical characteristics of the router antennas. The signal in this frequency range is less susceptible to attenuation when passing through obstacles: walls, floors...

The 5 GHz range has a significantly higher signal transmission speed, but such a signal does not like obstacles, for example, a brick wall is a serious obstacle for it...

Question: Which WiFi router should I buy to pair with the ACA-20C9 WiFi gateway?

Answer: The 2.4 GHz frequency is supported in all WiFi routers by default.
All modern routers operate in two frequency bands: 2.4 GHz and 5 GHz.