S21 5G isn't working in Standalone network

[amir_ra]

Hi, 

I'm using an S21 5G and want to attach it to a private 5G SA network. First, the phone can detect the network and attach but after a while(some minutes) is dropped off. I already used this phone in a public None-SA network and there is no problem but it's not working in SA mode. we tested another phone from other brands and it also working in our private network without any problem.

I'll appreciate it if you support and let me know your comments.

[nowdeleted]

Do you have WiFi calling set up ?? As my s21 is connected to my own network ( netgear) and when at work it automatically connects to BT. No signal issues at all
You can reset the network on your phone, then it should show available networks and connect to your own network.

[amir_ra]

No, I mean private 5G cellular network, not WiFi, band N78.

[nowdeleted]

Go to settings and choose WiFi

Click on the three dots in the corner and the advanced, choose WiFi frequency band

Select 5ghz so that all networks using that band show up. You can now click on the preferred network.

[Bradleigh]

No 3 dots then advanced? What are you on about?

[Chise]

A few months back I have encountered a similar issue as you when travelling to China, but it was with a commercial deployment of nation-wide SA-only 5G network (they have removed their NSA deployment), on N78. My phone was Fold 3 5G.

Inserting my SIM card to another device will allow 5G SA connection on that device, but having a working 5G SIM inserted into my device will not. I have consulted the carrier I was using, and they can see from their end that the device is SA-capable, and the network allows my device to connect to its network.

It appears that there is a switch under Developer Settings of devices sold in regions that have SA network deployed (e.g. China and RoK) called '5G Service Mode' that would allow the device to use the SA networks when it is available, and otherwise the device will not connect to any 5G SA network, with the only 5G option being NSA.

I believe there was a workaround if the device is One UI 3 or earlier, as there are some instructions and guides out there. Sadly, this is already a dead end starting from One UI 4. I have checked my Fold 4 and there is a property in the device that I cannot modify: "ril.supportSA", has value "0".

So, it is up to Samsung, to see if they are 'kind enough' to have 5G SA capability enabled in a future OTA, like they did to phones sold in Korea, providing that what they say is true - the device itself is SA capable.