iPhone 11 WiFi Slow on 2.4GHz Channel

Hi,

I have also been having the same issue and have been in contact with Apple's Senior Tech Advisers.

I have tried all the below steps but they were not helpful. Some of these were recommended by the tech advisers or from Apple knowledge base articles.

The only thing left to do is to do a factory reset of the iPhone using iTunes and testing on a fresh copy of iOS 13.3 (without restoring a backup).

I did notify the advisers that other users have experienced this issue and pointed them to this discussion.

I am also noticing this issue on a new Apple Watch Series 4.

I think it might be some incompatibility between the network and Apple's handling of 2.4 GHz connectivity.

1. Issue

iPhone 11 and Apple Watch S4 have poor speeds on 2.4 GHz WiFi.

Critical issue: The poor network connectivity causes calls to fail/drop on the Apple Watch.

2. Internet, Router and Device specs

2.1. Xfinity cable

Download: 200Mbps

Upload: 10 Mbps

2.2. WiFi router 

Model: TP-Link Archer C7 (V2) AC1750

5 GHz: 1300 Mbps

2.4 GHz: 450 Mbps

Security: WPA2-PSK (AES)

Clients connected to 2.4 GHz network: 4 smart plugs

2.3. iPhone 11 128 GB

iOS 13.3

2.4. Apple Watch Series 4 - Aluminium (GPS)

watchOS 6.1.1

3. Testing details

3.1. Websites/Apps used

Google Speed Test

Netflix Fast.com

Ookla Speedtest (iPhone App)

Speedcheck (iPhone and Apple Watch Apps)

3.2. Performance on 5 GHz 

Android/PC/Mac/iPhone (in various rooms): 150-200 Mbps

3.3. Performance on 2.4 GHz

Android/PC/Mac (in various rooms): 60-80 Mbps

iPhone (10 ft. away & clear line of sight from router): 10-15 Mbps

Apple Watch (10 ft. away & clear line of sight from router): 1-2 Mbps

4. Troubleshooting methods

4.1. Method-1 

Turn off/on WiFi on iPhone

Reset iPhone Network Settings

Restart iPhone

Retest speed on iPhone and Watch

4.2. Method-2

Power off all devices on 2.4 GHz network including Apple Watch

Turn off all bluetooth devices

Followed Apple recommended settings: https://support.apple.com/en-us/HT202068

Restart WiFi router

Retest on all devices

4.3. Method-3

Factory reset WiFi router

Retest on all devices

4.4. Method-4

Applied two recent firmware updates to WiFi router

Retest on all devices

4.5. Method-5

Connected to public WiFi networks

But no way to verify if the network if 5GHz or 2.4GHz (SSID does not have 5G in name and tried to use a network analyzer app but there was no information)

Speed test results: 15-25 Mbps

5. Troubleshooting result

None of the methods (1-4) improved the 2.4 GHz performance on the iPhone and Apple Watch.

On retesting, all other devices continued to perform as previously observed.

I’m using Speedtest by Ookla, but that’s beside the point since all the measurements were done side by side the same way. The 6 is clearly fast on both frequencies, while the 11 is fast on 5 GHz and very slow on 2.4. I can really tell the difference on loading web pages as well, so I don’t doubt the relative difference. You can see the results on the 5 & 2.4 networks below on the iPhone 11 Any ideas about why?

I have an iPhone 6 and a new 11. On my 5 GHz Spectrum router WiFi, both get >100 mbps. On 2.4 GHz, the 6 gets 80+ mbps, but the new 11 only gets about 15 mbps. I’ve rebooted both phone and router and repeated the test multiple times. Could this be a software issue, or is it as I suspect a problem with the 2.4 GHz radio in my iPhone 11? Why else would the 11 be so slow on 2.4 Ghz but the old iPhone 6 be fine on 2.4? Guess I’ll just connect to the 5 GHz for now, but visit the Genius Bar when I can to have them troubleshoot it. Maybe my 11 just has a defective 2.4 radio.

Your measurement technique is suspect. 2.4 GHz Wi-Fi (802.11g, the fastest) is limited to 54 Mbps. And will only achieve that very close to the router. 802.11b (also 2.4 Ghz) is limited to 11 Mbps. So it is impossible for the 6 to get 80+ mbps on a 2.4 Ghz link.

If you are sure the problem is with your device an not with your understanding then choice is yours.