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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).

[Alex Atkin UK]

Its what you'd expect really, everyone jamming onto the same tower.  Although I have two sims at the moment while waiting for my Smarty Social Tariff to kick-in.  As I already have two routers, I had them both live (until I ran out of Smarty credit) and they seem to latch on different cells from the same tower, which is interesting.

I guess it makes sense, 5G is supposed to handle MIMO much better I believe so having two SIMs with the same carrier you're not necessarily contending with yourself as much as on 4G, if the backhual isn't overloaded.  I'm fairly sure they laid fresh fibre a few weeks back due to roadworks and the speed immediately jumping up afterwards (its often as fast as my FTTP), though oddly latency under load seemed to get worse.

I will probably do a bit more testing on that before I cancel Three, given last time it was a nightmare getting through to their call centre to actually cancel.

[re0]

It looks like the poor single-thread download speeds are persistent during peak hours, and it's a deal breaker. I can deal with the slightly higher and jittery ping (which doesn't increase much at peak, and I have no issues gaming with it) and I can even deal with the drop to around 100 Mbps (multi-thread download) at peak time. But I can't accept single-thread downloads dropping to ADSL speeds as it makes downloading from websites and using certain applications a nightmare when it's going to be as low as about 3-5% of my G.fast speeds (so around 10 Mbps, though off-peak speeds are only about half or a third, which is good).

I really, really want to give this a fair chance as it could save me a bit of money and give me more flexibility. Sadly, it seems like I've finally reached something that I cannot resolve myself, and I think it is something that cannot easily or quickly be resolved. I should have focused more on single-thread speeds at different times of day on my phone prior to making a decision to taking 5G broadband, but this is in hindsight. I was too focused on multi-thread speeds and the position where the service is best.

I will keep trying it and see if support has anything to offer, but I think it will be fruitless. In the end, I think I will just have to cancel the service and look to stay on G.fast or find a cheaper alternative for a landline connection.

[Chrysalis]

Tried EE?

[meritez]

I use this:
https://www.scancom.co.uk/products/ee-enhanced-technology-data-sim-data-only-pre-paid-1

Absolutely no issues.

[re0]

I want to try EE, but their PAYG does not include 5G and their contracts are prohibitively expensive for the sake of testing (though, I technically could cancel within 14 days and just pay for what I've used). Using an EE MVNO with 5G access like 1pMobile would be cheaper for a bit of testing without needing a credit check.

I have looked at Scan Com SIMs (on various networks) a few times and they do appear to be very good value, but I would not commit and pay so much in a single go unless I was confident enough following testing of the service.

With all that said, I would have to conduct the testing on my smartphone as the modem I have is locked to Three. And the implication here is that I would have to buy a new 5G modem out of pocket, which would negate any savings made if this is ultimately utilised on a short-term basis.

I have tried Vodafone 5G through Lebara just because I happened to have a SIM with data, but the 5G was almost non-existent despite the coverage checker saying "good" signal. The mast is likely taller than the elevation difference, but it appears that there are significant man-made obstructions (buildings).

[meritez]

Strange that your ZTE MC801a is locked, mine is not, have they started locking them again?

[DaveC]

I use this:
https://www.scancom.co.uk/products/ee-enhanced-technology-data-sim-data-only-pre-paid-1

Absolutely no issues.

What's your monthly usage?  Have you gone beyond the 600GB fair usage limit?  scancom did use to sell a "truely unlimited" EE sim, but that looks like it has disappeared from their site now.

Thanks.

[meritez]

What's your monthly usage?  Have you gone beyond the 600GB fair usage limit?  scancom did use to sell a "truely unlimited" EE sim, but that looks like it has disappeared from their site now.

Thanks.

Around 800GB a month, still works.

[re0]

Strange that your ZTE MC801a is locked, mine is not, have they started locking them again?

You're right, it's not locked. I made an assumption based on the fact the Huawei 5G CPE Pro 2 was locked.

I threw in the Lebara (Vodafone) SIM and it worked fine, just needed to change the APN. I didn't do much testing, but it can aggregate B1(15 MHz)+B7(20 MHz)+B8(10 MHz)+n78 when choosing bands manually (otherwise it'll just lock B20). The signal is a bit weaker despite being closer than Three, but I imagine the massive amounts of 4G bandwidth (55 vs 15 MHz) give it a slight edge as I believe both Three and Vodafone have deployed 40 MHz n78 locally (unconfirmed). Or at least in theory, since speeds start off near 300 Mbps and drop to below 200 Mbps like some kind of artificial limit, and this also happened when I tried it a few months ago while on my smartphone despite being in locations nearer the mast.

Speeds aside, Vodafone uses CGNAT. This rules it out as being a viable option just due to the inherent nature of such a NAT. I think the only operator that doesn't use CGNAT is Three (on a specific APN).

[tickmike]

It would be nice to get 2G  signal   even any signal in the house.