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Question 5GHz wifi issue - solved

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I have a new arrival, a new S21 Ultra 256 (SW-G998B). A dbrand black swarm grip case is on the way. (thanks for the recs). It replaces an ancient Nexus 6 whose battery was starting to swell. Now, I will have something current to hack on once I give it some time to make sure everything is settled. I'm curious how much control Flutter can exercise on the cameras, but that's another topic not related to this one. Nova Launcher 7 (prime) is working well as is DroidCamX from my Surface Book 2. Most things with the S21 Ultra seem to be working well.

The biggest issue at the moment is with the 5GHz wifi. It just doesn't appear in the list and manually trying to join doesn't work either. It's a ZTE router with both 2.4 and 5GHz active. Multiple devices are on both. The phones, ipads, and laptops are on the 5GHz while the Roomba and a Mi LED light are on 2.4. With the other devices using it okay, I'm guessing that's not the issue. I tried some solutions with the S21, wiped the cache partition, played with the hotspot band, and enable/disable wifi scanning for location. I set the hotspot to 5GHz preferred and was able to join it from my iPhone 11 Pro. The S21 can join the iPhones hotspot. It both cases, I don't know specifically what was used, 2.4 or 5. But, with all of this, the 5GHz SSID from the ZTE router still will not show in the list and cannot be used. I had seen mention of a WiFi band frequency selector, but that doesn't appear to exist any more. On the router, the channels for both are set to auto, but the status shows SSID1 (2.4) is on channel 1 and SSID5 (5) is on channel 100. From what I've read about how advanced the S21 Ultra wifi is supposed to be, in theory, the S21 should not be limited on which channels are supported. Any thoughts on why other devices can connect and use 5GHz wifi, but the S21 cannot? Any ideas on what I might check/test next?

Thanks

Tim
 
The issue is solved.

I did not test other routers. With the Covid/quarantine situation, I don't visit other homes and thus don't have easy access to other routers. I would have to stumble across one.

But, thanks for the impetus to check something. I pulled out my ancient Nexus 6 to test with. It did not see the 5GHz SSID either. But, it did have Wifi Analyzer installed. With that, I was able to filter for 5GHz only and saw another SSID appear. When I ran Wifi Analyzer on my S21, I saw that same 5GHz SSID. So, the phone was seeing 5GHz. Wifi Analyzer also provided a crucial bit of information to the puzzle. On the graph across the bottom, it was only showing channels 34 to 50. So, the channel 100 the router selected when on 'auto' was way outside of the range. I had even selected channel 100 in Wifi Analyzer, but that did not help it appear. I updated the router and changed the channel to one near the middle of that range that was not being used by other nearby SSID on either band. Now, the S21 was able to see my router's 5GHz SSID in the list and joined it with no problems.

As advanced as the S21 Ultra is, it does not appear to support channels in ranges as high as either the iPhones, iPads, or my laptops. Since the Nexus 6 had the same issue, it's possible this is an Android limitation and not specific to the S21.
 
The issue is solved.


As advanced as the S21 Ultra is, it does not appear to support channels in ranges as high as either the iPhones, iPads, or my laptops. Since the Nexus 6 had the same issue, it's possible this is an Android limitation and not specific to the S21.
Glad you got it sorted out. But my wifi is configured to auto select channels based on traffic, and it is currently running on Channel 149 without any issues. So assuming that the S21U cannot utlize channels that laptops or ios devices can may not be entirely correct. Also, this is not an android limitation. My wife's 3 year old OnePlus also uses the same 5GHz network without any issue.

My suggestion would be to look at your router settings again.
Screenshot 2021-07-31 073220.jpg
 
Glad you got it sorted out. But my wifi is configured to auto select channels based on traffic, and it is currently running on Channel 149 without any issues. So assuming that the S21U cannot utlize channels that laptops or ios devices can may not be entirely correct. Also, this is not an android limitation. My wife's 3 year old OnePlus also uses the same 5GHz network without any issue.

My suggestion would be to look at your router settings again.View attachment 5374593
Hmmm. Thanks for that info. That was the only setting changed. Perhaps I need to play with other channel values to be sure.
 
I played with the channels some more. This ZTE has a drop down selector for channel choice. There are steps of 4 from 100 to 128. If any of those is selected, that 5GHz SSID does appear in the list on the S21. There is a gap in the selection between 64 and 100. If manually set to 64 or lower or if a 64 or lower channel is chosen by auto, then that 5GHz SSID is listed and can be used on the S21.

I'm not quite sure what else to make of this yet. The only thing being changed is the channel and that seems to control the S21 working or not, though the other devices are fine. The router belongs with this rental apartment. So, I'm reluctant to hack too much on it.
 

blaacksheep

Senior Member
Jun 20, 2020
405
179
Buffalo
I think it's mostly due to FCC regulations (if you're in the US). I know that there are more 5 GHz channels available in other countries that are not available here because of previous allocations. Probably your router/hotspot isn't running US specific firmware and when set to auto it might use frequencies that your phone has locked out. Your doing the right thing by manually assigning an unused channel on the router/hotspot. Just check it occasionaly to see if someone else is using the same channel should your signal degrade.
 
I played with the channels some more. This ZTE has a drop down selector for channel choice. There are steps of 4 from 100 to 128. If any of those is selected, that 5GHz SSID does appear in the list on the S21. There is a gap in the selection between 64 and 100. If manually set to 64 or lower or if a 64 or lower channel is chosen by auto, then that 5GHz SSID is listed and can be used on the S21.

I'm not quite sure what else to make of this yet. The only thing being changed is the channel and that seems to control the S21 working or not, though the other devices are fine. The router belongs with this rental apartment. So, I'm reluctant to hack too much on it.
Seems to be an issue with the router then. We've established that older as well as newer phones can use higher channels successfully. The only variable here that needs changing is the router (or its settings). Without that, I'm not sure how we can investigate further.

But if you've found a temporary fix for your issue, I'd suggest leaving it at that for now, till you get access to a newer or more capable router. I'm using an Asus RT-AC86U btw, if it's any help.
 
I think it's mostly due to FCC regulations (if you're in the US). I know that there are more 5 GHz channels available in other countries that are not available here because of previous allocations. Probably your router/hotspot isn't running US specific firmware and when set to auto it might use frequencies that your phone has locked out. Your doing the right thing by manually assigning an unused channel on the router/hotspot. Just check it occasionaly to see if someone else is using the same channel should your signal degrade.
I have no knowledge of legal requirements for WiFi bands or channels on phones in the USA, so you might be right. In which case, I'd withdraw my conclusion about the router. But he mentioned that other devices are able to use the 5GHz including iPhones and iPads. So I'm not sure why a 2021 phone shouldn't be able to do the same.
 
Thanks for the ideas. I'm US, but this issue is not US related. The S21 Ultra is Exynos/SW-G998B/SER (Russia) and the router is in Belarus (2nd location on profile). So, no US limitations between these two. The iPhones, iPads, and laptops are US that I brought with me. If anything, it seems they would be the devices that would not work, but they work fine. It kind of makes me wish I had my Google wifi to test against. Since the ZTE is now working with the S21, finding a different solution is not required. It is an interesting puzzle, though.
 
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blaacksheep

Senior Member
Jun 20, 2020
405
179
Buffalo
Thanks for the ideas. I'm US, but this issue is not US related. The S21 Ultra is Exynos/SW-G998B/SER (Russia) and the router is in Belarus (2nd location on profile). So, no US limitations between these two. The iPhones, iPads, and laptops are US that I brought with me. If anything, it seems they would be the devices that would not work, but they work fine. It kind of makes me wish I had my Google wifi to test against. Since the ZTE is now working with the S21, finding a different solution is not required. It is an interesting puzzle, though.

You've done the easiest fix for the problem without flashing firmware onto your router or phone!
 

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    Thanks for the ideas. I'm US, but this issue is not US related. The S21 Ultra is Exynos/SW-G998B/SER (Russia) and the router is in Belarus (2nd location on profile). So, no US limitations between these two. The iPhones, iPads, and laptops are US that I brought with me. If anything, it seems they would be the devices that would not work, but they work fine. It kind of makes me wish I had my Google wifi to test against. Since the ZTE is now working with the S21, finding a different solution is not required. It is an interesting puzzle, though.