Wireless Functions -- 5G Priority

Function overview
1. How a phone or computer finds a Wi-Fi?
The phone or computer broadcasts probe requests to all the channels on the bands it uses. The request contains information about the wireless access rate supported by the terminal.
A router providing WLAN connection services receives the request and sends a probe response to the terminal which contains the WLAN information.
The terminal aggregates the received probe responses and displays the list of available WLANs to the user for selection. These are the Wi-Fi signals we see when turning on the Wi-Fi function.
2. Which band to use if a dual-band terminal finds a dual-band router?
The user cannot distinguish between the two bands under the same WLAN name whose BSSIDs (signal MAC addresses) are discovered by the terminal. In this case, the wireless driver the user uses decides which band to use when the user selects the WLAN. For the user and router, the results of the selection are uncontrollable. (Dual-band means support for both the 2.4 and 5 GHz bands.)

Mechanism

Change the actions of the router in the process of the terminal discovering the WLAN (instructing the router not to send the 2.4GHz band probe response to the terminal) to lead the terminal to the 5 GHz band.
1. Dual-band router's identification of the terminal
The router needs to check whether the terminal supports dual-band before leading it to the 5 GHz band.
(1) If the router receives both 2.4 and 5 GHz band probe requests from the terminal, the terminal supports dual-band.
(2) If the router receives only a 5 GHz band probe request from the terminal, the terminal supports only the 5 GHz band.
(3) If the router receives only a 2.4 GHz band probe request from the terminal, the terminal supports only the 2.4 GHz band.
The identification process is time-consuming because it takes some time to check whether the terminal sends 2.4 and 5 GHz band probe requests. There exist multiple probe requests broadcast by different terminals, so the router has to rely on the terminal RSSI (signal strength) threshold to decide whether to save the information about an identified terminal, which then serves as the basis for subsequent responses.
2. Router's actions after 5G Priority is enabled.
(1) Before identification of a terminal
    (a) Not responding to probe requests from the 2.4 GHz band
    (b) Responding to probe requests from the 5 GHz band
Note:
Side effect:
Terminals that support only the 2.4 GHz band cannot discover the WLAN before it is identified by the router because the router does not respond to probe requests from the 2.4 GHz band. The gap is 2s. That means terminals supporting only the 2.4 GHz band may be unable to discover and connect to the WLAN within 2s.
After the router identifies the terminal, 2.4 GHz band probe requests of a dual-band terminal are not responded. But the terminal can still discover the WLAN passively. Therefore, some dual-band terminals can still discover 2.4 GHz band WLANs.\
(2) After identification of a terminal
(a) Terminals supporting only the 2.4 GHz band: The router sends a response after receiving multiple probe requests and only ensures that terminals can access it.
(b) Terminals supporting only the 5 GHz band: The router sends a response upon receiving a probe request and ensures that terminals can access it.
(c) Dual-band terminals: The router responds to probe requests from the 5 GHz band but does not respond to probe requests from the 2.4 GHz band, leading terminals to the 5 GHz band WLAN.
Note:
5G priority is functional only on dual-band routers.