Replying to myself here, but while browsing through the forum I found this post interesting, because the drawn map there explains the geographical location of my Deco X50-5G pretty well. It also seems like the red light issue mentioned earlier did have something to do with the device dropping to 4G and then coming back to 5G, as many others have reported on the forum. I can report it also happens with the 1.1.7 firmware.

I guess I could reformulate my question a bit better: What does the "Band" section in the internet settings actually mean, and how does it differ from the AT+QCAINFO output? If a NR5G band is consistently showing up in the AT+QCAINFO output and the router is showing a white 5G light, but it never shows up on the Band row, does the NR5G band actually get utilised?

  @juhovh 

My understanding is that when in NSA mode, it has to utilize the aggregate of LTE bands in order to get 5G.

So, in your screenshots I see that indeed this is the case. You are utilizing N28 band, just not in SA mode, but in NSA. This is why in the section "Band" you see B3, B8, but on at+qcainfo you also see N28.

I suppose that in order to see just N28 in the "band" section, it will need to be connected in SA mode.

  @madvinegar 

Yeah, it is my understanding as well that in NSA mode the 4G LTE core is used for control plane functions to authorise the 5G bands. However, if we look at screenshots from for example this post one can clearly see that other users have 4G and 5G bands (in this case B20 and N3) both shown concurrently. Another way to deploy 5G would be through DSS where 4G and 5G would be sharing bands, but according to details given by my ISP they have only deployed 5G on N28. And even in the DSS case I would expect some N bands to show up in the UI even if they overlap with B bands.

The only difference I can see compared to other users is that in all of their cases the 5G band has been of higher frequency than the LTE band (in the linked example B20 800MHz LTE and N3 1800MHz 5G). However, the way my ISP has decided to deploy 5G in the area is to maximise penetration by using the N28 band (700MHz) in combination with B1 (2100MHz), B3 (1800MHz), B8 (900MHz) and B20 (800MHz) with B3 apparently used as PCC for control plane functions. Their reported maximum speed for the 700MHz 5G band is 600Mbps and for the LTE bands 300Mbps, so according to them the 5G band should give better bandwidth even with the lower frequency.

My concern is that the X50-5G is not fully utilising the N28 band because it's lower frequency than all the rest (and therefore IF they were all LTE would also be lower bandwith, but that's not the case). If the Band row in the settings only shows the control plane bands, my question then is why does it show mixed 4G/5G bands for other users? Would be good to have a bit more documentation on what these fields actually mean.

  @juhovh 

As you said, it may have to do with how each ISP and each country deploy their 5G.

There's another situation where the internet view behaves a bit strangely. Whenever the PCC band changes, the app goes into an inconsistent state where the Network Type is 5G, but the PCI in 5G NR and NRARFCN are not defined, instead it shows PCI in 4G LTE and EARFCN.

I'm simply documenting this down, since I'm wondering if the red light problems might be related to these mixed states. The system usually does fix itself pretty soon after though, but it makes me wonder where these values are actually coming from.

On that note, at least some modems seem to support a command AT+QNWCFG=“lte_band_priority”,<bands>. I wonder if X50-5G could support this and give us access to it as well. It's not ideal to turn bands off completely, if it would be possible to order them based on priority, getting always the best working PCC band.

Just updating myself again on this investigation, I found this message on Reddit where someone was actually debugging 5G NSA network usage with an SDR, and according to the information there the 5G NSA setup would be able to do upload on both 4G PCC band and the additional 5G band. This would explain why I found the upload speed in particular more stable when enabling 5G (compared to only using 4G), but I wasn't sure if it was just my own imagination or related to the weather at the time of the measurement. Unfortunately I don't have an SDR setup nearby so can't see what's actually happening on the 5G band when transferring data.

Assuming the 5G band is actually used, the only reason I can think of why the 5G band doesn't show up on the Deco app, even though it shows up for some others, is that since there's just one 5G band it is implicitly included. In this case if there would be more 5G bands, the used one would be shown on the app alongside the 4G bands. I would like to get some official confirmation on this though, the app is not very clear on what different fields mean. Overall, it's quite unfortunate that X50-5G is not getting the same amount of features than some other Deco products (like X50 with its VPN support).

I just want to share the new iOS 18 FTM dashboard, which in my opinion is an excellent example of how to communicate the used 5G NSA band information, in this case it would show capabilities as SA+NSA. The 5G band information is there, the LTE PCC band information is there, and the other LTE bands that are used for download only are listed as well with the corresponding bandwidth.

Just in case you are looking for any inspiration on how to update the Deco app to communicate the used bands better.