Hello There, I am using mi 4c & openwrt version 21.02. I use this router as a range extender. Main host router is like 2 room away, and i am connected to main router wirelessly with a link speed around 300mbps(from -52dBm to -60dBm). when i first setup everything i was surprised as my speed was like reaching peak 60-70mbps. as like main router.( i was connected via lan cable to my laptop). Then i setup wireless network to that Mi 4c and speed was downgrade to like 7-11mbps☹️. Try resetting all didn't help me. Still getting 50-70mbps via lan cable but via wireless only 6-10mbps. Why? note: i have no problem with mobile device. as I connected lan cable to my laptop and then create a wifi hotspot using connectify me, via connectify me my speed was like 20-30mbps. What can i do now?
Another note: Stock OEM Was a little bit unstable, Stock oem was providing around 20+mbps via wirelessly. but that was not stable like sometimes 30mbps, sometime 15 mbps, but was definitely higher than openwrt. I am hopping that i may have massed up some setting. can any one help me around? also is there anything i can do to improve range? although range is not my main issue.
I assume this is your device? - https://openwrt.org/toh/xiaomi/xiaomi_mi_router_4c
It's 802.11n capable, which means 300 Mbps with 40 Mhz channel bandwidth in 2.4 Ghz band configured as client. There comes the first hurdle. If your device detects neighbouring devices sending on the same channel in the 2.4 Ghz band, it will automatically switch from 40 MHz to 20 MHz channel bandwidth, unless you force 40 MHz. --> 20 MHz channel bandwidth equals 150 Mbps.
=> Try to force 40 MHz, just to have a look if it gets better, but if you are in a contested environment (city), forcing 40 MHz is not advised, as it will lead to lots of interference and make the internet worse for everybody for yourself and everybody around you. Best is to talk to all your neighbours and negotiate who is allowed to use which channels.
Since you use the mi 4c as repeater, i guess you use relayd to accomplish that? Relayd out of necessity (as you need to repeat the original signal from the main router) cuts your throughput in half.
--> 150 Mbps / 2 = 75 Mbps.
Add interference and walls and throughput may dwindle even more.
You report
- main router > wifi > mi 4c > lan > laptop = 50 - 70 Mbps
=> Not the best throughput ever, but looks ok, under the assumption you dropped to 20 MHz channel bandwidth:-) - main router > wifi > mi 4c > wifi > laptop = 7 - 11 Mbps
=> it could be that your laptops wifi card is also not very performant
hey, I solved the problem by myself! ( can be said as luck🫡) any ways after the post, i upgrade my openwrt version from 21to 22. and boom everything solved ! i just literally did nothing, no option changed, just upgraded the version. now the network speed bellows.
1.Main router>wifi>mi4c(openwrt22) >lan>laptop =40-50mbps
2.Main router>wifi>mi4c(openwrt)>wifi>laptop/mobile device= 30-40mbps.
Although Lan speed decreased like 10% from pervious version but it makes WiFi speed feels like rocket. Another 10% loss compare to lan cable is ok i guess. Any ways now my overall performance compare to stock oem firmware is like literally Double! Was getting around 5-15mbps avarage on stock oem(max was like 20-25) Even signal getting dropped+ Router hanged, Devices getting auto disconnected. Now every problem solved, Thanks to the Team for that amazing Firmware.
Awesome! 
Consider marking this topic solved 
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