Why is my PC doing better with 802.11ac but not 802.11n?

I find this strange. My PC has the Intel dual-band 7265 module in it. I moved it upstairs the other day and noticed it was getting half the speed my cellphone was getting on 802.11n using a standard 20 mhz channel width on the 2.4 band. An older driver version seemed to be fine but I kept going backward to see how many versions were stored and then I had none left. Reinstalling the version or other versions including the newest did not resolve the problem, still half speed.

Now here is where it gets interesting, I decided to try turning on the ath10k radio for the first time and got full speed even using the 20 mhz width channel but on 802.11ac.

Why would my PC give me full speed on 5G but not on a 2.4 GHz channel which in theory should be easier for it because of greater signal penetration?

It's not the power level because I reduced the TX on the router to match the regular 2.4 power level.

My cellphone is still on the 2.4 band and still gets full speed upstairs while the PC cannot except on the 5 band.

I'd love some insight if anyone has any ideas as to what this could be. Thanks!

Which make model is your router?

Archer C7 v2 on 18.06.08

5GHz: Higher frequencies carry more data per quantum, with AC also much better modulation schemes. I'm not even going to start with spatial streams/STBC, beam forming and etc. Less pass-through of signals through walls means less neighbor AP interference.

In general, even the shittiest 5GHz signal will be better than 2,4GHz in a noisy environment.

Also, what is half speed for you? I'm getting around 4-6MB/s at 20dbm signal strength (-78/-98dBm) via 2,4GHz on a 20MHz channel with about 10-15 APs around me.

fwiw, did you check the wireless link speed reported in Windows?

ie. for 20 MHz bandwidth, it should report 144 Mbps (72 transmit + 72 receive = 144) for 2x2 wifi card such as the 7265 if there is a good 2.4 GHz signal, with maximum transfer speed around 72 Mbps.

Just anecdotally, all my devices get about a third of my contracted speed (about 70-80mbps on a 200mbps plan) on 2.4ghz while they all get full speed on 5ghz, I'm in an urban area so just put it down to a crowded spectrum, although I've never bothered to actually look into it, so not sure if that's actually the case.

ergamus: My internet connection is 50 mbit. On 2.4 using 802.11n the PC was getting 25 mbit while the cellphone next to it on the same connection was getting 50 mbit using the same fast.com speedtest.

bill808: I did and it was showing 144 in the status. I just now thought of something, I didn't test yet with Linux to see if it demonstrates the same behaviour or not. I will test that today.

mike: You are getting full speed for 802.11n on 2.4, you will never get faster unless you force a 40 mhz channel which is not a good practice and definitely not worth doing when you have the 5GHz option. For that package, keep using 5G.

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Update- I booted into Linux and tested. I had the same result as in Windows. So unless there is a common codebase between the two drivers I have the strange situation of my PC only liking 5 but not 2.4. It was never noticed before because the PC used to be on a lan cable downstairs. I suppose it is also possible that the router only likes the cellphone Snapdragon module but not the Intel module and the only way to know if this is a cause would be different routers to test with which isn't feasible because I don't have any other N or AC routers. Very strange.

Trying 19.07 is an option as well but not high priority because everything is stable for now with the current configuration.

I have archer c7v2 too and solved it in 19.07.x by changing over to non-ct wifi drivers and firmware.

Thanks Catfriend1, doesn't non-ct apply only to 5 GHz band though? So 2.4 may still be an issue as it is the stock generic radio.

I'm unsure. It should only apply to 5ghz but some reports came up by users it may side-affect 2.4ghz

What is make/model of your openwrt router?

fwiw, I had wifi compatibility issues with a Linksys EA6350 v3 (ipq4018, ath10k) on both 2.4 and 5 GHz used as a dumb Access Point. For 2.4 GHz, an old 802.11g internet radio was stuck with absurdly low downstream link speed (about 1.5 Mbps) despite being right next to the router which led to severe buffering. Upstream was fine at 54 Mbps.

On 5 GHz, intel 6300 wifi cards connected at full 300 Mbps wireless link speeds, but speed tests maxed out at 20 Mbps with Windows 10. I tested all drivers up to the last release in 2015.

This 5 GHz issue didn't happen with an earlier 19.07 snapshot for the EA6350v3. Non-CT drivers made no difference. Other wifi cards such as intel 6200, 7260 and Atheros AR5B22 were all fine.

I reverted to using Linksys OEM firmware to mainly fix the internet radio issue. Note I am not using the EA6350 as a router. It is wired to another openwrt modem router in another room.

I've also seen wifi issues with HH5A 2.4 GHz radio (I think it is ath9k) with intel 6205, 6300, 7260 wifi cards. Speeds tests collapse and cause wifi to fail on laptops in both Windows and Mint Linux. No issues with 5 GHz (ath10k) with these cards. Intel 6200 and Atheros AR5B22 work fine on 2.4 GHz.

fwiw, wifi compatibility is always going to be an issue with openwrt open source wifi drivers. General advice is use openwrt for your router, and offload wireless to dedicated access point running OEM firmware as the closed wifi drivers are generally better than open source drivers imho.