Source
r/tmobile•
derektm

Technical question about Band Selections

Question

So I was doing some speedtests today and noticed that the Phone was connected to B2 only. The speed was around 6 Mb/s.

Just for fun I disabled B2 and repeated the speedtest. Instantly the phone did CA with Bands 4 and 12 and my speeds were around 50 Mb/s.

The phone will not CA with other bands while it is on B2, nor will it switch over to B4 and B12.

What gives? Can someone explain? Is it possible the B2 is not configured to work with CA? Can the phone not see that and switch to the ones that do? Signal strengths were similar. Thanks

Screenshots https://imgur.com/gallery/HS9xg Galaxy S8.

u/Logvin

Posted Nov 12, 2017, 7:42 PM UTC

98
50atomic•

Different cell sites.

8
derektmOP4G LTE+•

Ah so CA only works with Bands from the same tower.

3
anonMLS•

I don't know if that's it. In some areas I aggregate Band 4 and Band 2, but there's one situation where I'm literally aiming the phone line-of-sight at a tower from 400 meters away, and it only aggregates Band 2/12 and Band 4/12, but never Band 2/4.

1
curtise35•

nor will it switch over to B4 and B12

Have you tried doing something data intensive like watching a 1080p@60 Twitch stream or 4k YouTube video when on band 2? Your phone doesn't want to do carrier aggregation unless it has to.

3
derektmOP4G LTE+•

No just a simple speedtest. I'll try that and report back.

1
derektmOP4G LTE+•

Ok just tested. Started a 4K YouTube video while downloading a 1GB file in the background. Wouldn't switch to the other 2 bands. I did notice B2 does have a little better signal but not by much. I have Tmobile One Plus btw.

1
curtise35•

Weird. If you want to verify that they are on two separate towers you can download cellmapper from the play store. When on band 2 you should see something like eNB 12345 Cell 11 - LTE. If the eNB 5-digit number is different after turning off band 2 then you got handed over to a different cell like 50atomic assumed.

Unfortunately the algorithm in the modem firmware isn't working in your favor here.

3
derektmOP4G LTE+•

Alright I'll def check that. I've had Cellmapper running all day. Trying to contribute since Tmo is new to my area. You're probably right about that modem firmware. Thanks again!

1