o2 LTE configuration

I'm in cardiff and I'm getting very variable performance from o2 in my house. Signal isn't great, but it seems to be cycling through so many LTE configurations...

Sometimes get 5G @ 3500MHz. If this is actually connected (phone shows 5G but in reality it isn't always connected - not sure why it sometimes connects and sometimes doesn't, even in the exact same spot)., it works well, on downstream at least - even at peak times.

Also get incredibly random configurations of LTE. Various CA bonding of LTE800, 900, 1800, 2100 and 2300. Running a speedtest I can see it reconfiguring multiple times in the background, typically starting at 2 or 3 higher frequency carriers and then steadily moving down frequencies like it hasn't got enough signal?

Pure LTE performance at peak times (by which I mean 7am-midnight!) is extremely poor. Rarely more than 10mbit/sec, often struggling to get 1mbit/sec. If 5G is connected it's much better - 50-100mbit/sec.

Regardless of configuration though, even with 5G, upstream speeds are terrible. 1mbit/sec max really.

This brings me on to a few questions...

1) Why would it switch LTE config so often? Is it because it's trying each frequency but they are too congested so the mast is telling it to try other frequencies, but they are all bad? Clearly 5G works @ 3500MHz most of the time, so I'm not sure if it is a signal problem - if 5G can work at such a high frequency, 2300MHz should be able to work?

2) Why is upstream so poor, even with 5G? My guess is that the transmit from the phone to the mast is worse than the other way round, so downstream can work ok on 5G but upstream not?

3) Related - does VoLTE use the 5G carrier? Call performance is extremely bad even with 5G enabled. I assume this is because of upstream performance causing massive latency? My phone (pixel 7a) is terrible at using WiFi calling, it seems to think the WiFi is weak (it's not) and constantly switches back to cellular mid call. I can get round this by putting the phone in airplane mode but then I forget to turn it off when I leave the house.

FWIW I tried switching to EE but it was even worse, often showing 6CA, but really poor throughput downstairs, worse than o2 - with absolutely no data flowing.

In reply to a post by mr_mojo:

I'm in cardiff and I'm getting very variable performance from o2 in my house. Signal isn't great, but it seems to be cycling through so many LTE configurations...

Is this a phone or a router with LTE/5G support? Does it cycle when actively transmitting/receiving or only when idle? What tools are you using to determine the frequency connected? Ahh, I see its a Pixel 7a phone - so its ‘camping’ when idle on the LTE carrier to save its own battery, it will drop complex radio and use the lowest power settings so that your battery lasts as long as possible.

Sometimes get 5G @ 3500MHz. If this is actually connected (phone shows 5G but in reality it isn't always connected - not sure why it sometimes connects and sometimes doesn't, even in the exact same spot)., it works well, on downstream at least - even at peak times.

The UK is today using Non Standalone architecture for 5G, this means the phone is always connected to LTE and uses 5G NR bearers for data transmission when not idle.

Also get incredibly random configurations of LTE. Various CA bonding of LTE800, 900, 1800, 2100 and 2300. Running a speedtest I can see it reconfiguring multiple times in the background, typically starting at 2 or 3 higher frequency carriers and then steadily moving down frequencies like it hasn't got enough signal?

The mast/cell site will tell the phone to move to different frequencies based on load. The lower frequency generally will have a larger area so more customers, so in load user equipment (UE) is asked to move to the other layers which have less range.

Pure LTE performance at peak times (by which I mean 7am-midnight!) is extremely poor. Rarely more than 10mbit/sec, often struggling to get 1mbit/sec. If 5G is connected it's much better - 50-100mbit/sec.

That does sound like congestion, and O2 is not the best equipped network in the UK, they have a lot of customers and lower amount of spectrum, perhaps due to Telefonica having banking issues for years.

O2’s total customers on Wikipedia from annual reports, doesn’t necessarily include the MVNOs like GiffGaff, Tesco mobile, and Sky. Radio spectrum by operator in a nice table here by David W:
https://mastdatabase.co.uk/gb/spectrum/

Regardless of configuration though, even with 5G, upstream speeds are terrible. 1mbit/sec max really.

Is this in a window, or deep in a home? Is it a new built with foil backed insulation, or older? Does it do the same outside?

1) Why would it switch LTE config so often? Is it because it's trying each frequency but they are too congested so the mast is telling it to try other frequencies, but they are all bad? Clearly 5G works @ 3500MHz most of the time, so I'm not sure if it is a signal problem - if 5G can work at such a high frequency, 2300MHz should be able to work?

Mast decides, and tells the phone/device. The 2300 spectrum (Band 40) may have users on whom don’t have 5G capable hardware, or on a price plan that doesn’t support 5G (e.g. some MVNOs).

2) Why is upstream so poor, even with 5G? My guess is that the transmit from the phone to the mast is worse than the other way round, so downstream can work ok on 5G but upstream not?

The mast is £1m worth of equipment tuned with trained engineers in a fixed place. Your handset is at worst a £2000 unit that is mostly in a human hand (good blocker of radio) and moves around a lot…

3) Related - does VoLTE use the 5G carrier? Call performance is extremely bad even with 5G enabled. I assume this is because of upstream performance causing massive latency? My phone (pixel 7a) is terrible at using WiFi calling, it seems to think the WiFi is weak (it's not) and constantly switches back to cellular mid call. I can get round this by putting the phone in airplane mode but then I forget to turn it off when I leave the house.

No the clue is in the name, Voice over LTE. The equivalent would be Voice over NR (VoNR) but this isn’t available yet and will require Standalone Architecture of 5G NR. Maybe your phone is faulty.

FWIW I tried switching to EE but it was even worse, often showing 6CA, but really poor throughput downstairs, worse than o2 - with absolutely no data flowing.

Might be on a co-located structure with the O2 mast. In cities masts are often on buildings.

You can use the cellmapper.net website to try and locate the nearest to yourself, and if you have Android (obviously) you can use the Cellmapper app to even contribute back.

My guess is you have poor uplink signal, very common indoors, and why WiFi calling was created.

Many more technical types and you may get better diagnostics on this on the Digital Spy mobile phones forum.

Edited by jchamier (Sat 01-Jul-23 22:29:12)

The mast/cell site will tell the phone to move to different frequencies based on load. The lower frequency generally will have a larger area so more customers, so in load user equipment (UE) is asked to move to the other layers which have less range.

Yes, but what I can't understand is when running a speedtest it moves from 2300+2100 (say) down to 1800, then down to 900, then down to 800. Surely you'd want the load to stay on the higher frequencies?

Is this in a window, or deep in a home? Is it a new built with foil backed insulation, or older? Does it do the same outside?

It's absolutely awful everywhere in the city I've been, indoors and outdoors.

No the clue is in the name, Voice over LTE. The equivalent would be Voice over NR (VoNR) but this isn’t available yet and will require Standalone Architecture of 5G NR. Maybe your phone is faulty.

I thought VoNR was just for SA operation. What I'm asking is when the phone is in VoLTE config on NSA, does the VoLTE connection just use the LTE carriers, or will it use the LTE+NR carriers, given they are all bonded - my guess would be the latter since it is just IP and it would be hard to tell it just to use the LTE carriers, but it doesn't really explain the dire voice calling. Phone definitely isn't faulty; exact same problem on Pixel 4a 5G I had before this.

Strangely, I can actually do a video conference call on google meet that works mostly fine, but a simple VoLTE phone call doesn't work at all, in the exact same spot.

My guess is you have poor uplink signal, very common indoors, and why WiFi calling was created.

The problem is the 5ghz wifi signal isn't that strong in many areas of the house (though actually works perfectly fine - 100mbit+ symmetrical with very low latency. I think Android does something like if wifi signal quality < cellular signal quality then switch back to network. It's hugely frustrating as the phone calls go fine then after a few minutes it switches back to cellular which means the call keeps cutting in and out.

In reply to a post by mr_mojo:

Yes, but what I can't understand is when running a speedtest it moves from 2300+2100 (say) down to 1800, then down to 900, then down to 800. Surely you'd want the load to stay on the higher frequencies?

I wonder if the tool you're using to identify the bands is not tuned to the latest modem/chipset in the 7a. It is easy for phones/masts to move around the bands, this happens as you move anyway, so the technology allows for it.

It's absolutely awful everywhere in the city I've been, indoors and outdoors.

It does make me wonder if its a combination of the phone and network together, or perhaps the reporting tool is buggy on that relatively new chipset.

I thought VoNR was just for SA operation. What I'm asking is when the phone is in VoLTE config on NSA, does the VoLTE connection just use the LTE carriers,

From what I was told on the other forum in the last month, it will only work on SA, so when you make a call on NSA 5G, the existing LTE connection is used for the call. Phone calls don't use much data at all.

or will it use the LTE+NR carriers, given they are all bonded - my guess would be the latter since it is just IP and it would be hard to tell it just to use the LTE carriers, but it doesn't really explain the dire voice calling. Phone definitely isn't faulty; exact same problem on Pixel 4a 5G I had before this.

Probably only uses the LTE carrier. Awful voice has been a feature of O2 for decades; but it is worth trying another manufacturer device if you can borrow a friends etc in the same area, as perhaps your mobile operator has an issue with Google phones.

Strangely, I can actually do a video conference call on google meet that works mostly fine, but a simple VoLTE phone call doesn't work at all, in the exact same spot.

The first is just internet access, the second uses VoLTE and connects to the IMS gateway at the operator.

The problem is the 5ghz wifi signal isn't that strong in many areas of the house (though actually works perfectly fine - 100mbit+ symmetrical with very low latency. I think Android does something like if wifi signal quality < cellular signal quality then switch back to network. It's hugely frustrating as the phone calls go fine then after a few minutes it switches back to cellular which means the call keeps cutting in and out.

That would be a reason to use 2.4 Ghz for a phone, or have one of those setups that have both 2.4 and 5 on the same SSID - but WiFi topics are really for another channel.

I wonder if the tool you're using to identify the bands is not tuned to the latest modem/chipset in the 7a. It is easy for phones/masts to move around the bands, this happens as you move anyway, so the technology allows for it.

When I'm in London, where the O2 network is much better (common knowledge), it doesn't do this and the performance is great.

To be really clear this is 100% not a phone issue. It also happens on my partner's iPhone (the terrible performance), but j can't see network data. Neighbours also have perpetual problems with O2.

I can't use 2.4GHz because it is way more congested and performance is awful. It's just frustrating you can't tell Android to always use WiFi Calling if WiFi is enabled, regardless of signal strength.

And re Google meet, it makes no sense that a data internet application would work better than a VoLTE call, given I assume there is very heavy QoS applied to it.

In reply to a post by mr_mojo:

When I'm in London, where the O2 network is much better (common knowledge), it doesn't do this and the performance is great.

Useful additional data, so you've confirmed its the O2 capacity in Cardiff that's causing the problems. O2 is well known to be the weakest of the 4 physical networks, assumed due to Telefonica's financial situation.

To be really clear this is 100% not a phone issue. It also happens on my partner's iPhone (the terrible performance), but j can't see network data. Neighbours also have perpetual problems with O2.

On iPhone use the Field Test mode from the phone dialler, *3001#12345#* and it works quite well in iOS 16.x

I can't use 2.4GHz because it is way more congested and performance is awful. It's just frustrating you can't tell Android to always use WiFi Calling if WiFi is enabled, regardless of signal strength.

The option to 'always use' is up to the mobile network and some phones respect, some phones do not.

And re Google meet, it makes no sense that a data internet application would work better than a VoLTE call, given I assume there is very heavy QoS applied to it.

Very different server, may be an IMS issue, rather than the TCP/IP network link where the QoS is applied. Yes it should be better as its wholly under O2's control.

Perhaps a reason to move to another network, try the others, Vodafone, Three, or EE.

Edited by jchamier (Sun 02-Jul-23 11:34:40)

It's just frustrating you can't tell Android to always use WiFi Calling if WiFi is enabled, regardless of signal strength.

I also have poor mobile signal at home and I had problems with phone switching between WiFi Calling and 4G. My solution to this is to use a couple of macros in MacroDroid that says
"If connected to Home WiFi turn on airplane mode" and
"If not connected to Home WiFi turn off airplane mode"

Setup Airplane mode to leave WiFi on.

Works very well for me.

In reply to a post by TimJ:

It's just frustrating you can't tell Android to always use WiFi Calling if WiFi is enabled, regardless of signal strength.

I also have poor mobile signal at home and I had problems with phone switching between WiFi Calling and 4G. My solution to this is to use a couple of macros in MacroDroid that says
"If connected to Home WiFi turn on airplane mode" and
"If not connected to Home WiFi turn off airplane mode"

Setup Airplane mode to leave WiFi on.

Works very well for me.

Also enhances battery life if there is no signal or an erratic signal as the system does not waste time and energy scanning continually for a signal.