Strange network connection quality problem with dual sim

[RaoulTeeuwen]

Hello.

My employer gave me a S21 5G phone. I use it with a physical SIM in slot 1 and an eSIM. People told me they had problems contacting me on my SIM1 number. I fiddled around with settings.

If i set 'Network mode' (Settings/Connections/Mobile Networks) for the eSIM to '3G only', network quality for SIM1 shows all bars. If i toggle the Network mode of the eSIM to anything else, the quality drops significantly, probably causing, in areas with less reception like in buildings, the SIM1 to have 1 bar or worse.

Roaming, VoLTE toggling etc doesn't seem to influence this. And the behaviour is repeatable (toggle Network mode influences connection quality bars of SIM1).

Anybody have any idea? Is this a design flaw, with 2 radio modules (one for every of the dual SIMs) that influence each other, leading to lower connection quality?

[osteidl]

Hi,

I have same problem and I have find out that problem is when I am connected to any wifi - during this time I am not "online" for calling people on SIM 1. When I disconnect wifi it is working as before. As per my opinion this is some mistake after update - before it it was working properly...

It was helped also, when I choose use 2G for the SIM 1 only. I am using SIM1 as personal for calling only, so 2G is sufficient.

[guifran]

1. Same problem here. I have 2 physical SIM cards. Samsung S21 256GB dual

I changed the SIM 1 to 3G and now works better, but this should not be the solution as I don´t use Wifi, so for that reason i need proper speed with 4G. Do you have any update from Samsung?

[RaoulTeeuwen]

I don't 😞

[osteidl]

After update to Android 12 situation is the same. 3G is NOT working also. Just only 2G is working without problems...hopefully samsung know about that...

[RaoulTeeuwen]

I have no idea how to report this to Samsung 😞 ; i can imagine this is a problem with a lot of these big companies: they get swamped with mentions, emails etc: hard to filter the stuff you need to pay attention to. Would be nice if a business customer that has contacts with a Samsung account manager or something would be able to have Samsung look into this.

[AnthonyP]

Hi, 

I'm from Belgium. And I have exactly the same issue. I just found it, after making 50different tests.

When I disable my second SIM, that I have very nice speed with the ping and jitter very low. When I enable the second SIM, then the speed decreased with 10x. Same for jitter and ping.

I think the s21 ultra is using the same antenna for the two SIM. And when you are using at the same time, it will just devide the signal

Gr, 

[osteidl]

Hi,

I am using e-sim + standard sim at slot No. 1. Still the same problem. 

There is a option to write on Samsung help desk...I will try it when I will have some time.

[Galxy s21]

Same how can i fix this issue

[Members_X23O6sU]

Hi. Is there any update to this issue? I am facing the same with my new Galaxy S22 Ultra.

[cheflaszlo]

noting will be improved by S22

2 sim sharing 1 antenna. what a big problem., unbelievable. 

my phone gets to an unbelievably difficult stage, map losing gps. i literally have to start up a gps application to get signal back.

took me months to realize,  i was blaming my network provider.  no, the issues are with the phone's antenna.