QUOTE(duckaton @ May 20 2017, 01:41 PM)
I have a 100Mbps connection but
I can never reach that kind of speed by wifi 2.4ghz.
max I can get is around 20-30Mbps only.
I can reach 100Mbps using lan and 5ghz
but many of my devices not compatible.
If you all can get that speed by wifi 2.4ghz
please guide me. Thank you

u cant get 100Mbps with 2.4ghz single stream wifi adapter. Mojority devices only come with single stream wifi. All my smartphone and tablet max can get 80++Mbps on 2.4ghz
.
you need atleast 2 or 3 stream 2.4ghz wifi apdater to get 100Mbps. But be noted even if you have more than 1 stream 2.4ghz wifi adpater, if it's far always from the router u cant get the speed u wanted too.
For laptop and PC, u can buy a 2 or 3 or even 4 stream wifi adapter. For smartphone and tablet, than u cant do anything about it as it's the hardware limitation, just stick with 5ghz.
1 have an old 3 stream 2.4ghz wifi usb dongle, and it can get full 100Mbps
This is the speedtest result with 3 streams 2.4ghz wifi usb dongle.