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Router can no longer connect to EE b20 lte mast
#1
Hello - I'm a new poster, definitely out in the sticks, the Isle of Skye.

Until about 2 months ago I was receiving 4G internet via an EE sim in a Huawei 535-333 router. This setup had worked for about 18 months and had been great because before the EE mast at Tarskavaig was erected I had only satellite broadband. However, my router can no longer connect and says "registration failed". The same sim inserted in an iPhone connects to 4G no problem. The same sim in the Huawei router when driven 200 miles away, connects fine. I have tried a total of 3 routers - no joy.

EE tech support admit that something has changed at the Tarskavaig mast, but they don't know what. EE carried out a software upgrade at the mast in September (about the time the problem arose) but insist that that couldn't be the cause! They don't know which router would work for me. Not enough people are affected (me and my neighbour) to send out engineers to investigate.

I suggested to EE tech support that the problem might arise in either voLTE or IMS software differences between the iPhone and router. They agree that is possible, but were not able to offer any solutions.

The Tarskavaig mast is 800MHz (B20) LTE only.

The other router I tried was a ZTE MF286D.

I would be very grateful to hear if anyone else has similar experience, and to receive any advice or suggestions.

Thanks very much.
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#2
Based on having a similar experience connecting to masts 50+km away across Donegal bay here, it seems like the mast is outside the maximum distance for the modem to synchronise the LTE Timing advance. The software upgrade on the mast may have affected how its eNodeB determines this value. The upper bands such as 1, 3 and 7 are even more sensitive where some modems can only connect on the lower frequency bands, but not the upper bands after a certain distance from the mast operating those bands.

One router worth trying is the Zyxel NR5103E as its MediaTek modem is able to connect with masts further out than what the Snapdragon and Balong modems are capable of. Huawei routers mainly use Balong chipsets and that ZTE model is Qualcomm based. The Shannon modems in some Samsung and Google Pixel phones are also able to connect to masts further out, however, I'm not aware of any routers that use a Shannon modem.

If you mention which iPhone model you have, I will check if there's a router using the same modem / chipset.
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#3
(15/12/2023, 09:23 PM)Seán Wrote: Based on having a similar experience connecting to masts 50+km away across Donegal bay here, it seems like the mast is outside the maximum distance for the modem to synchronise the LTE Timing advance.  The software upgrade on the mast may have affected how its eNodeB determines this value.  The upper bands such as 1, 3 and 7 are even more sensitive where some modems can only connect on the lower frequency bands, but not the upper bands after a certain distance from the mast operating those bands. 

One router worth trying is the Zyxel NR5103E as its MediaTek modem is able to connect with masts further out than what the Snapdragon and Balong modems are capable of.  Huawei routers mainly use Balong chipsets and that ZTE model is Qualcomm based.  The Shannon modems in some Samsung and Google Pixel phones are also able to connect to masts further out, however, I'm not aware of any routers that use a Shannon modem. 

If you mention which iPhone model you have, I will check if there's a router using the same modem / chipset.

That is a very interesting line of attack - thanks!

The same EE sim from the router, when inserted in an iPhone SE (2nd gen. 2020) works fine.

I am approximately 8km from the Tarskavaig mast.

I could check this theory by driving nearer to the Tarskavaig mast (fortunately my car has a regular UK plug socket).
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#4
At 8km it may not be a distance issue, especially with the low 800MHz band and it being 4G.  Usually devices devices start having problems synchronising with the LTE carrier beyond around 35km. 

The "Registration failed" indicates the that router is not registering with the network, so it is worth testing your router closer to the mast to rule out the distance anyway, They could have set a shorter range limit to avoid mainland users connecting where you could be right at the limit where some modems are still able to synchronise.  If there was an APN issue I would expect to see a message like "Disconnected" or "Failed to connect".

The iPhone SE 2020 model has an Intel modem, which I'm not aware of any routers using.  Surprisingly from the info I found, the iPhones with Intel modems also have issues connecting to distant masts in rural ares which the newer iPhones with Snapdragon modems would connect fine with, e.g. the iPhone SE 2022 model has a Snapdragon X60.
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#5
Some interesting results from testing.

I drove for a few miles until I was looking straight across the water at the Tarskavaig mast, I estimate 5km distant. Plugged in the Huawei 535-333 and it connected straightaway, 3 signal bars illuminated (maximum).

I drove back home with the router still plugged in and observed the signal bars. The router remained connected the whole way back, showing 2 signal bars as I drove past my house, and then 3 signal bars about 200m meters past my house at the shore, again looking straight towards Tarskavaig, but this time approximately 8km distant.

I then parked at home, unplugged the router, took it to the upstairs room with window looking towards Tarskavaig where it always used to work (with 3 signal bars) and plugged it in. Nothing. No connection. No signal bars.

I then unplugged the router and drove back the 200m to the shore just outside our house and plugged in. To my surprise it connected straightaway and after a slight pause, showed 3 signal bars (initially it seemed to have connected but with no signal bars showing). I was not expecting connection to succeed here, so I repeated the experiment, unplugging and plugging in. On the next 9 occasions the router did not connect.

My working theory, is that Sean is right about LTE Timing Advance being involved and that at a shorter range the router managed to register successfully and maintain the connection all the way home, but at 8km range the router cannot reliably (one out of ten times only) register successfully.

Sean, my question to you is "is this enough information to go back to EE and ask them to do something, and if so, what?".

I have the email of the last Level 2 tech support guy I spoke with.

Thanks
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#6
It would be worth getting back to EE mentioning this range limit and that you tested it in your car, i.e. that it connects fine when you drive closer to the mast, maintains the connection to your house, but once you power cycle the router, it will not reconnect until you drive closer to the mast again. Hopefully if the engineer has the ability to make changes to the mast that they can increase the range limit.

One possible workaround in the meantime would be to get a small UPS (or a 12v battery backup) that would let you drive closer to the mast for the router to connect and to keep it powered when you take it back home to try to maintain the connection.
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#7
8km should not be an issue - the attach boundaries are usually far in excess of this. Indeed people are connecting to the Tarskavaig site from Sgùrr Alasdair, circa 17km away.
Will have a consider though 800MHz only sites can be odd...
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#8
Thanks Sean. I've emailed the EE tech support guy and ordered a small UPS. I'll update the forum if I make any progress.
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#9
(19/12/2023, 04:49 PM)pedroc Wrote: 8km should not be an issue - the attach boundaries are usually far in excess of this. Indeed people are connecting to the Tarskavaig site from Sgùrr Alasdair, circa 17km away.
Will have a consider though 800MHz only sites can be odd...
Thanks pedroc - it does seem to be odd. I'm trying a different router today, TL-MR6500v, only because it says it's VoLTE-enabled which might make a difference. If not, it's going straight back!

I don't understand the phone vs router behaviour. And was very surprised when moving from 8km to 5km appeared to make a difference. I will probably drive back to the 5km site and check that successful connection is repeatable. I was so surprised when the router connected at 5km I just went with it instead of checking for repeatability.
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#10
Sorry to report that my previous observations were not valid. It turns out that there is another EE mast in the area (at Elgol) which is transmitting on B3 & B20. When I thought I was driving closer to the Tarskavaig mast and connecting on B20, I was in fact, driving within range of the Elgol transmitter and connecting on B3.

The TL MR6500v has better reporting and I was able to see to which band I had connected. It also displays which bands are available and allows manual selection. The bottom line is that I can connect on B3 but never connect on B20.

If I was in an area where both bands were available and I left the MR6500v on Auto, it would use B3 and an APN of EE(default:1), IPv4, everywhere, eesecure, secure, CHAP. If I then manually forced it to use B20, whilst leaving the APN unchanged, it would not connect.

At my house I can only receive B20 from Tarskavaig to which 3 different brands of router cannot connect (since September).

As stated before my iPhone SE (2020) connects to 4G on B20 from Tarskavaig (field test mode says CellID 6081036).

Today I could not reproduce connecting from 5km (now known to be on B3 Elgol) and driving home whilst maintaining connection. I tried three times and it just didn't happen today (which actually makes more sense).

So, I'm still mystified why my phone can connect & my router(s) cannot.
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#11
6081036 is Tarskavaig. Have you tried to make a VoLTE call using the MR6500v router on Tarskavaig site - "VoLTE enabled" does not mean it has configuration to work on all operators' VoLTE?
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#12
That is an interesting find where it can connect on band 3 but not band 20 from the Elgol mast. It also makes me wonder what happened the last day where it was able to hold on to the connection all the way back home, such as whether it managed to hand over to band 20 just that once off time or whether it still held on to the weak band 3 signal until you unplugged it to take inside.

The next time it's calm and dry outside, try testing your router outside manually locked to band 3 to see if it pick up and connect with even a weak signal on band 3. If it is able to connect at all on band 3, you can try getting a high gain directional antenna such as the Iskra P-58 or P-62 to aim at Elgol. The antenna has SMA connectors that attach in place of the pigtails on the TP-LINK. Another option would be to the MikroTik LHG LTE which is an outdoor parabolic dish router that has very high gain on band 3.
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#13
(21/12/2023, 08:13 PM)Seán Wrote: That is an interesting find where it can connect on band 3 but not band 20 from the Elgol mast.  It also makes me wonder what happened the last day where it was able to hold on to the connection all the way back home, such as whether it managed to hand over to band 20 just that once off time or whether it still held on to the weak band 3 signal until you unplugged it to take inside. 

The next time it's calm and dry outside, try testing your router outside manually locked to band 3 to see if it pick up and connect with even a weak signal on band 3.  If it is able to connect at all on band 3, you can try getting a high gain directional antenna such as the Iskra P-58 or P-62 to aim at Elgol.  The antenna has SMA connectors that attach in place of the pigtails on the TP-LINK.  Another option would be to the MikroTik LHG LTE which is an outdoor parabolic dish router that has very high gain on band 3.

I will investigate reception outside the house on a calm dry day, but I'm almost sure that there's no chance of my receiving from Elgol because of intervening hills. Which means that, if my observation from the other day of maintaining connection really happened (I'm beginning to doubt my own eyes!) then the router must have managed to switch from B3 Elgol to B20 Tarskavaig as I drove home. I'll probably try another hour or two talking to tech support, for my sins.

Tomorrow the ups arrives.

(21/12/2023, 07:49 PM)pedroc Wrote: 6081036 is Tarskavaig. Have you tried to make a VoLTE call using the MR6500v router on Tarskavaig site - "VoLTE enabled" does not mean it has configuration to work on all operators' VoLTE?
I haven't, because I just can't connect on B20 from Tarskavaig (or B20 from Elgol for that matter), the router just says "disconnected" and I can't do anything.

Yes, agree that the advertising may not reflect reality.
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#14
Apologies, I mistyped there. Have you tried VoLTE call with the MR6500v on B3 from one of the surrounding sites?
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#15
(22/12/2023, 08:53 AM)pedroc Wrote: Apologies, I mistyped there. Have you tried VoLTE call with the MR6500v on B3 from one of the surrounding sites?

No worries. I'll try to make a VoLtE on B3 today. Thanks
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#16
Well, on a clear, calm day I switched on the original Huawei 535 at home - no registration. I connected the UPS, drove it towards Elgol, wherupon it connected on B3. I then drove home. The signal strength varied on the way, nearly down to zero, but maintained connection until I was parked at home with full signal strength. Carried the router from car to usual upstairs room, maintaining connection. Plugged in UPS to mains. All set.

I am certain that the only frequency at home is B20. The router registered successfully on B3 and managed an inter-frequency handover to B20 on the way home.

EE still say there is no problem at Tarskavaig mast (I reported problem again just before Christmas).

Thanks Sean for UPS suggestion. It's not ideal, but far, far better than nothing!
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#17
Not quite a router issue, but just as an observation on similar symptoms - may or may not assist. At home I'm on cell edge of multiple sites, and can flip between ~4 B3 cells & a couple of B20 ones.. with VoWiFi picking up the slack.

I noticed quite a few months ago that my VoLTE phone would readily attach to B20 but would not initiate any voice or data traffic - it had to be on B3 or VoWiFi. Yet calls in-progress would hand to B20 happily, this muddied the troubleshooting waters for quite a while until I replicated the inability to initiate on B20 elsewhere. In all locations, another phone of the same model was fine.

I have since changed devices, and the symptoms totally cleared - suggesting a phone fault. Never could fathom the logic of it.
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#18
Long time, no signal ....... but now it's back.

After many, many denials from EE that they'd changed anything whilst I couldn't get a signal for months, they have clearly changed something back, because now I can connect on B20 without issue.

No idea what they did, but suppose I shouldn't complain too much.
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#19
Just a quick postscript. Whilst trying to set up 4G in a neighbouring cottage, I was expecting to need an external antenna to connect to Tarskavaig mast, but was surprised to find another. The eNB ID is 41408 according to LTE H-Monitor and transmits on bands 3 & 20. It's not present on CellMapper yet, and I coulldn't find a likely candidate in the S4GI list of sites. I suspect it's at Torrin on Skye. Can anyone locate this mast for me? My signal is pretty strong and stable, can't be far away - SINR 16dB. Thanks.
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#20
If you can get hold of an Android phone to run the NetMonster App, it will show the Timing Advance for the current cell it is on.  The modem uses this to calculate the timing offset so that its transmissions are synchronised within the 4G frame time slots by the time the signal reaches the 4G mast / site.  The timing advance is usually in increments of 78m for most modems, so in the following screenshot I was roughly 390m away from the mast operating eNB 3619:

   

With the phone on eNB ID 41408, note the TA reading in the NetMonster App and the GPS coordinates (e.g. with the GPS Test App).  Drive roughly 1km away or as far as you can get to this with the phone still on this eNode ID and take note of the new TA reading and GPS coordinates.  You can then use a map radius calculator such as the following to draw two circles from the two GPS coordinates, each the radius of its corresponding TA reading. If the TA reading within a few km, i.e. the site is nearby you can even try driving towards the site, watching the TA decrement to try to physically see the tower. Smile

https://www.calcmaps.com/map-radius/

One of the two spots that the circles intersect is where that 4G site is to within about +/-78m.  You can then drive a short distance (e.g. 0.5km) towards ether intersection point to see which one it is, i.e. whether the TA goes up / down as you start heading towards one of the intersection points.
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