Massive Wi-Fi throttling on Samsung Galaxy S20 FE 5G purchased from Amazon India (September 2021 unit)

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Samsung Galaxy S20 FE 5G for Rs. 36999 (33999 including HDFC Offer)


TL;DR from this thread

Amazon India sale is delivering units manufactured in India in September 2021 in this sale. This batch seems to have a lot of units that have a very unreliable Wi-Fi. It would connect fine and would stay fine for a while but after a while, it slows down considerably. Turning it off and on again would fix the issue temporarily. Resetting the phone does not fix it. If you have such a unit, you should instantly apply for a replacement or refund. XDA has a thread that has 2-3 other folks who got a unit with the same problem. There is also supposedly a Telegram group but I am not a member. There is also discussions on the official Samsung Community. One such thread.

Important stuff: For replacement, do not apply for it through the order page. It would force you to deal with a tech visit from an outsourced company which delays the process. In my case, the tech guy did not bother visiting me. Called me up on the phone and asked me to reset the phone and go through the entire process again and see if that fixed the issue and ping him later so that he can process a replacement. He ended up closing my complaint without confirming me first. Amazon chat support initiated another tech visit which added another two-day delay. Phone support told me that they cannot help me because of this active request in their system and I should contact them once it is over, and I am not satisfied with the resolution. So, use the phone support option. This seems to be a safe and the fastest way to get a replacement and maybe even a refund if replacement units are also affected by this problem.

One member of the forum has confirmed that the unit he got from an earlier stock does not suffer from this issue. XDA and a few other outlets do confirm that there have been a few isolated cases of this issue affecting the entire S20 series. It is just too hard to tell if this is a hardware based issue or a firmware based one.

I ended up applying for a refund. If you are not sure how to test out wi-fi stability, install an app like WiFiMan which continuously monitor wi-fi connection speed. Or just download a very large file (10GB File) and see if it stays at similar speed levels consistently. On my S10 Lite, it is stable while on Fe, it keeps on changing while placed at the same place at same distance from the wireless router. Upload connection speeds actually drop down to 6mbps regularly. In my opinion, this should not happen when power savings are disabled, screen is on, and the app accessing Wi-Fi modem is in foreground.
 
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A youtube comment said that this issue started from August update. Another comment on Samsung Community said October update doesn't fix this. It's crazy without an official statement from the company.
 
@Sushubh This is most likely just a software issue.

Someone in a s20 fe telegram group enabled Wifi Verbose logging, Ran logcat while connecting to a wifi and downloaded something and this is what they captured in the process.

Something in the phone's networking stack throttles the speed to 30mbps.


Source
 
@Sushubh In wifiman, You were seeing the theoretical maximum speeds fluctuate. That's different.

In the logs I shared here, Something else applies rate limits on the wifi connection and these are the rate limits you are actually running into.

The phone may say the theoretical maximum speeds are 200mbps but because of this other rate limit, It'll never reach those speeds.
 
you are right about that. but wifiman showed me that upload connection speed regularly dropped down significantly. even down to 6mbps regularly. so actual speeds were going to be pretty crappy when the throttling actually happens.

also, the phone in my case almost always connected to Wi-Fi 4 (802.11 n) before connecting to Wi-Fi 5 few seconds later. This almost never happens with S10 Lite for me.

someone mentioned on samsung forum that even moto's new phones have similar problems. geekyranjit even noticed it in his recent video. this could become a widespread problem in coming months on newer phones if this is being done intentionally to do what? preserve battery life? crazy.
 


I am still trying to get some sense of what's happening here but so far I think it may have something to do with the wifi driver.

I see this a bunch in the logs.


Source
 
I hope there could be a way to downgrade the software to older versions maybe untill this issue is resolved. If it's a software problem.
 
@Sushubh, Are you Connecting to WiFi using Device WiFi MAC or Randomised WiFi MAC ?? Can You Try Vice-Versa ??

If It doesn't Solve the Problem, Can you Send Screenshot of Networking Settings in Developer Options ??
 
No longer have the device. Changing to static mac didn't fix the issue for me as suggested by reddit threads.
 
I hope there could be a way to downgrade the software to older versions maybe untill this issue is resolved. If it's a software problem.

Can only downgrade till aug patch coz you shud have same binary number to downgrade. Aug and sep have binary 4
 
I have used it for 2 full days now and this issue doesn't happen anymore. I ran iperf3 tests for 2 hours today(the phone was charging for around 30 minutes) and it consistently gave ~550-600mbps down and ~250-350mbps up speeds.

With that said, This was 99% a thermal issue. There are two cwlan temperature sensors. I believe it monitors those sensors and applies rate limits if the temps gets too high. (The threshold is likely around ~40.5/41C)

Samsung has an app called Good Lock(previously known as Galaxy Labs, and a third party launcher called Fine Lock) which has quite a few nifty little apps to control various aspects of the phone.

One of these apps is called thermal guardian which is a very barebones and easy way to underclock/overclock the "system". In this app, You can increase the thermal threshold by +/- 2C. Increasing this threshold fixed the issue for some people. (This app also lists all the times it throttled something and why it did that).

In my case, Even with a -2C threshold everything works fine. A friend had to increase this to +1C(they also lives in a even hotter climate)

I guess one thing Samsung can do now is to not rate limit so aggressively when the temperature exceeds the thresholds. Other OEMs also reduce speeds but not so aggressively so it's not noticeable.

This was the only real problem for me and with this gone, I have no more complaints with this phone. 🙂
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October update didn't change this behavior.
 

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