Broadband Related > Mobile broadband

Three 5G Home Broadband annoyances - and workarounds

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re0:
So I picked up a 5G hub (ZTE MC801A) from the Three store the other day. I had to go to the store because the computer said "no" for ordering online, despite having coverage and good speeds (there are properties closer to the mast that have broadband availability, so it is available from the mast). I wanted to switch to 5G broadband and get rid of my G.fast connection to save a little bit while waiting for better options.

So far, it has not been without its problems. I have hopefully found decent workarounds for the annoyances I have experienced and thought I would share them to give my experience so far but also in case I can help someone in a similar situation.

The first issue - CGNAT

First issue I noticed is that, despite connecting using the 3internet Access Point Name (APN), I was frequently getting a shared Carrier-Grade Network Address Translation (CGNAT) Internet Protocol version 4 (IPv4) address. Toggling the connection on and off and even restarting the router would almost always result in a shared IPv4 address.

This was an issue because some websites and applications were responding very slowly even though transmissions speeds were normal, and there was the annoyance of CAPTCHAs due to the nature of having a shared IP. In addition, the update function on the router did not always work while using a shared IPv4 address for some reason, and using the device in bridge mode while in CGNAT appeared to make it impossible to access the world wide web normally (though, pinging externally appeared to work).

The workaround appears to be to create a new APN entry on the router using the usual "3internet" APN and DISABLING Internet Protocol version 6 (IPv6). This seems to force the device to pick up a normal, non-CGNAT IPv4 address. From my experience, it takes a few more attempts to connect to the internet, but I would rather wait an extra minute than experience issues. Another downside is the lack of IPv6, but, at least from what I have seen, 3internet does not give IPv6 addresses anyway.

I am not 100% sure why this happens. I believe it is trying to respect the APN settings, but it falls back on CGNAT instead of not having a connection. Unfortunate, annoying, but understandable if this is true.

The second issue - switching masts

I am (un)fortunate enough to have two sites broadcasting within a close range. One broadcasts B1+B3+B20+n78 while the other has B1+B3+B20+B28+B32+n28. The latter is inherently slower due to obstructions despite being closer, and because the 5G is only n28 instead of n78.

In spite of this, the modem loves to connect to B20 on the slower mast. Perhaps it is because the RSSI is lower, but RSRQ is about the same and the SINR is actually worse than B1 on the faster one. Even the n28 5G is a much lower SINR (~2 dB vs ~20 dB on n78). The result is that the speeds can be single figures in terms of Mbps. This ultimately meant that I had to position the router where I could get the best speeds without accidentally putting it where it would favour the other mast. It was a balancing act, and not always successful (probably a 50/50).

The workaround I have found useful, as opposed to just cell locking (which can only be unlocked with a factory reset), is to force B1 (and possibly B3). It appears reliable at keeping the slower mast out, which I imagine is due to the fact higher frequencies would be fairly attenuated by the obstructions, thus making it unfavourable to the modem. While there are no exposed options to do this in the web interface, this can be achieved using a script in the browser that executes commands.


So far, with the changes I have made, everything appears to be working fine now. No longer getting CGNAT addresses, so web browsing is now smooth. Forcing higher frequency bands appears to prevent the slower mast, getting between 100-300 Mbps down and 10-25 Mbps up depending on the time of day. I think even latency is slightly better on this mast, as low as 24ms (though the average is probably more like 30-40ms).

It is worth adding that contacting Three support did not prove to be that helpful in resolving the issue. The issues were initially blamed on the fact that the content filter was on (which is actually fairly logical in regards to web page issues if I was trying to load blocked content). Then there was the blame on maintenance in the area. But they were adamant that my IPv4 address was not being shared despite the fact I was telling them it was. I know it was CGNAT as the WAN address was a private IP address, and because I also tested it using a CGN test.

burakkucat:
Thank you for sharing your findings. It seems as if mobile broadband has many a pit (or snare) to trap those less experienced.  :-\

(I see that your signature block is now out of date and so requires a refresh!  ;)  )

re0:
It does make me wonder how many people tried 4G/5G broadband over the years and just cancelled due to such issues. Less experienced users would have no clue about these things, and support does not seem to provide good solutions either.

Regarding the signature, I technically still have the G.fast for now even though I am not using it. I want to iron out all the kinks before I can be confident enough to cancel. I have a legacy product with a good discount which is not subject to inflation that I would not be able to get again. :(

Alex Atkin UK:
I'd never want to switch to only 5G, the latency goes up dramatically under load and it takes months for them to fix contention issues.

Its great as a cheap backup connection, or to speed up my Steam downloads so it loads my main connection less, but I did a test using it as my primary connection before I got FTTP and it just wasn't reliable enough.

re0:
It's a lottery. Some areas are better than others. I think my latency is impacted more by the location of the modem rather than contention issues. If I place it somewhere with a higher SINR, it should encounter less errors in transmission and therefore not have to retransmit the data as frequently. This should, in theory, reduce spikes in the latency as long as the SINR is not impacted too much by other factors.

I have noticed that the single-thread downstream is not good at all so far. It does start off strong then just absolutely tanks it. There have been capacity issues reported nearby where I live, so perhaps I am connected to an impacted cell. I am not really sure, but I hope it can be rectified as it is poor regardless of whether I am located inside or outside (so it isn't an issue of poor signal).

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