Wavemobile Struggles to Get Big UK Mobile Operators to Fix WiFi Calling
The Technical Director for rural connectivity provider Wavemobile, Anthony Timson, has complained that the “biggest issue” they face today is the interaction devices roamed onto their network face with respect to the popular WiFi Calling service. Users who roam on to Wave’s network find that the big mobile operators (EE, O2, Vodafone and Three UK) seem to block it.
Just for some context, it’s important to recognise that Wavemobile are a company that specialises in deploying both private and public 2G/4G/5G mobile network services. For example, the provider can deliver community mobile networks to serve remote UK villages (here) and they’ve also worked to extend their cells on to buses in rural parts of the Swansea Bay area (here). Not to mention indoor connectivity solutions.
“Wavemobile is realistically the fifth UK (MNO). I am happy to be corrected on this, but we are a licenced [Radio Access Network] operator with our own MNC, Core, Numbering resources, and DIAMETER/MAP peering into the GSM cloud. We have engineered a practical solution to not-spot coverage that actually works (not perfectly, but that is for another post),” said Anthony.
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The provider says they use British made cellXica Ltd M3Q radios for all operators, and can deliver coverage to a hamlet or small village in a “discrete rooftop package” that consumes less than 100 Watts. But the most annoying problem that they experience is the inability to get WiFi Calling to work with the big operators.
Anthony Timson said:
“Our biggest issue today is the interaction devices roamed onto our network face with WiFi Calling. For some reason known only to the big four, if a phone is roamed onto our network and you go inside a building to join WiFi Calling, you are blocked from using it.
This is made worse by the fact that our present solution for that is to deny access to customers affected by this, which means only Emergency Call access – but even denying access to our network still doesn’t allow WiFi Calling. This needs attention by the UK operators as we are lawfully allowed to transmit wherever Ofcom grants us a license. It is [the mobile operators] that [are] preventing use of WiFi calling, not us!
Our team loves solving coverage issues independently of any other operator control. We have had some support, but not where we need it which is on opening up the S6a/S8 or ePDG over cellular interfaces to support a better customer experience.”
ISPreview did ask the big mobile operators to respond to Wavemobile’s concern, but sadly none of them chose to comment. But we have since been informed that the provider may be making some progress, at least with respect to O2 (VMO2); an operator that Wave has worked with a few times before. Time will tell.
Mark is a professional technology writer, IT consultant and computer engineer from Dorset (England), he also founded ISPreview in 1999 and enjoys analysing the latest telecoms and broadband developments. Find me on X (Twitter), Mastodon, Facebook, BlueSky, Threads.net and Linkedin.
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What a shame. The 4 big MNOs should be ashamed. A company willing to put coverage where they can’t be bothered. Even if that means the life and death of someone. Yet, they can’t even simply email / reach out to wavemobile or ispreview to advise. I hope the regulator gets involved. I wonder if its worth reaching out to the competition and markets authority.
No, they should be punished by hefty fines.
In what way would this be the death of anybody? The emergency network (999) is totally independent of your MNO, with coverage reaching FAR wider than MNO networks. No matter your device, provider or account type (contract or PAYG), you’ll still be able to call 999 in an emergency. You can even use it without a SIM card.
This is just a new MNO trying to make something work, but realising they can’t without cooperation from the existing MNOs. Their business model likely hinges on charging roaming fees to the existing MNOs when users roam onto their network in rural areas.
If you’re an MNO being charged fees by some other network for areas that aren’t economically viable for you to build in, why on earth would you spend more time and resources to make their technology work??
@MNO employee
999 calls rely on coverage from at least one MNO via emergency call roaming, and phones must have a SIM inserted in order to make these calls.
You may be referring to the 4G Emergency Services Network (ESN) but this still works based on emergency call roaming for devices with 4G calling capabilities with a SIM from any network.
The software sometimes displays emergency calls only without a SIM inserted at times, but is unable to actually make them without a SIM inserted.
wavemobile has a built-in 2G layer and is in the process of integrating Emergency Call handling over IMS (VoLTE). We have integrated with BT and have compliant emergency call handling including cell position.
@MNO Employee, the areas where most of our sites are located are total not-spots. How do you propose these 999 calls would be able to connect from there? Pixie dust? To date there have been over 100 Emergency calls on our network and these have resulted in Coastguard, Ambulance and Mountain Rescue involvement. Your post reads like we do not serve a purpose, but I am sure the recipients of the emergency calls being serviced would beg to differ.
We have invested a considerable sum of money to make our network work, and the frustrations we face are due to us wishing to remain truly independent. We are also willing to pay for interconnect) we already do infact) but UK operators are generally unwilling to peer to another UK operator citing legal reasons why they can’t do National Roaming (something OFCOM has informed us is incorrect).
If WiFi calling over cellular worked, it would be an easy fix. The issue is that WiFi calling over WiFi doesn’t work and that is plainly wrong, and not supporting the customers of said operator.
I will add that VMO2 is speaking with us about a resolution to this issue and taking it seriously, so thank you to them.
I’m sure it has nothing to do with the lucrative roaming fees that networks generally charge if a customer makes a call while roaming (I appreciate that Wavemobike is somewhat the exception here!).
This isn’t about roaming in the sense that we think of when going on holiday.
In the UK, private companies are allowed to own and run mast sites. Your provider benefits because they don’t have to pay out to put in a mast but rather pay a small part of the call cost (although some have other agreements)
I think the difficulty with this article is the awkward way it is written and that Wavemobile aren’t good at communicating the problem.
What I think they are saying is that when someone uses one of their masts/sites, their phones won’t then hand over to WiFi Calling.
This would seem to be a technical problem related to how WiFi Calling is implemented.
I’ve a suspicion that VoWiFi might actually mean VoLTE in this article.
IMA-roaming issues make sense, but VoWiFi specifically replaces LTE/NR as your radio bearer, with WiFi.
There’s a technical issue in the ETSI specs that’s almost certainly at play here.
WiFi Calling works by connecting to an ePDG and transporting the same data that would have gone over the mobile network for calls over an IPSec tunnel to the ePDG. By design, you connect to the ePDG belonging to the network you most recently visited; if your last network was Wavemobile, then you must connect to Wavemobile’s ePDG for WiFi Calling, and then tunnel call traffic from there.
This is meant to avoid issues when you route over IP to your home network, and have problems with latency and buffering for voice calls. However, in this situation, it causes two issues:
1. Wavemobile need to run an ePDG that can authenticate roaming users (authentication is via the SIM card, using EAP-AKA’), with enough capacity for all users who’ve recently roamed on their RAN.
2. Every UK network needs a suitable roaming setup so that they trust traffic that comes through Wavemobile’s ePDG as-if it came from a Wavemobile 4G/5G network.
There’s a lot of moving parts to get right here; I’m not sure any UK network has done roaming WiFi Calling yet at all.
What about WiFi calling over a data only session on wavemobile. That way, I assume negates majority of any security concerns.
Weirdly, I stumbled across a wavemobile site in Scotland when on holiday, I got a welcome message, asking if I wanted to stay data only or allow wavemobile to use my number etc. All seemed pretty okay, but I guess if WiFi calling worked over their 4G, it would mean less hassle for both me as the end user and wave…
I suppose, ultimately, wavemobile and the networks need to get round a table and bash out some practical ideas. Because the idea of multiple networks on one radio surely benefits everyone!
The question is, how does any small operator, get an invite to the Big MNOs….
This is a very clear problem for wavemobile – WiFi calling on WiFi does not work in areas that we serve with our cellular network. We do not need an ePDG as *we* are not tunneling anything, a WiFi network that is out of our control is. This is also not VoLTE, it’s WiFi calling over a WiFi network that we do not control, that just happens to be within range of our cellular network!
This is a very specific scenario as we are an independent operator providing data coverage in not-spots. In an ideal world we would be able to offer VoLTE or WiFi calling over Cellular (yes, that exists although the GSMA isn’t keen on it). All the present options on the table require us to become a network extension of the big four vs being independent – but that’s a commercial problem, whereas the point of this post is a technical one.
WiFi calling over cellular is fairly common in the US, you normally see that when using dual SIM the network that isn’t providing the data can provide its WiFi calling service over the cellular network of the primary data SIM and that works fine.
It clearly seems that there’s poor implementation somewhere. It could be as simple as the rules that the MNOs have in place to artificially block WiFi calling when abroad (on other networks) so they can charge you roaming fees. Many worldwide operators allow their WiFi calling to work seamlessly anywhere in the world it can connect. The UK networks just like to restrict it.
I think what Simon is saying is that:
– A phone will always attempt WiFi calling to the ePDG owned by the RAN it was last in contact with (i.e. in this case Wavemobile) and that this is a feature of the standards for phones (i.e. can probably be considered immutable in the short term).
– To make WiFi calling work for users who connect to WiFi after connecting to Wavemobile’s RAN then Wavemobile has to provide an ePDG with suitable authentication and forwarding arrangements.
Wavemobile DO need an ePDG and MUST tunnel if they want this to work as the phone will always contact Wavemobile’s ePDG after having been on their network.
@JB The last RAN this subscription used is Wavemobile, therefore, by the spec, it’ll connect to Wavemobile’s ePDG. Wavemobile then need to provide an ePDG, and get the other networks (who, to the best of my knowledge, have never done this before) to accept traffic from Wavemobile’s ePDG.
@Tom With dual-SIM, the “trick” is that you have two independent phones from a network perspective, and the one that’s sending data over the other network’s cellular link has never accessed any other network’s RAN, so will contact its home ePDG. It doesn’t know that it’s doing so over a cellular data connection. With Wavemobile, you roam onto Wavemobile with your single subscription, and that triggers the use of Wavemobile’s ePDG instead of your home network’s ePDG.
@Dassa Exactly right. The other option is to set up MOCN or similar with other networks, so that the phone doesn’t roam to Wavemobile, but connects over Wavemobile’s RAN infrastructure to the home MNO’s core network.
Simon – the bit I am puzzled with is how the UE knows the epdg DNS entry to connect to. If wavemobile were a GSMA member (in progress) then it would be published on our IR.21. That would mean that the UE would need to go a DNS repo to recover the IP address to connect the tunnel to. This all stacks up if we publish an IPSEC endpoint on (pub.)epc.mnc004.mcc234.3gppnetwork.org. However, vodafone UK uses epdg.vodafone.co.uk – where does the phone get that from as that’s the first thing it tries connecting to (that *IS* the DNS lookup). Some networks prefix with the pub.epdg… others use a totally different scheme.
We actually do have a fair bit of Wifi calling over cellular that is working right now. Hundreds of megabytes a day, but it’s not consistent and it’s quite possible it’s being tunneled over a Dual-SIM fallback, or a MiFi type device.
Given your reasoning above, there is no solution for us in this situation other than to turn off our network. That is actual nonsense in reality as we have a licence (Ok Mr Pedant?) to transmit.
Let’s see what a week or two in the O2 labs gives us and go from there. In the meantime, residents in the areas where we are now turned off, I hope you don’t need an emergency call when away from your homes.
@wavemobile CTO
The spec for finding an ePDG is spread across several 3GPP TS documents (of course, because why would they make this easy?). I’d not looked in a while, and I didn’t pick up that this has changed since I last looked (so I don’t know which release changed it).
The core document that describes how ePDGs are meant to work is TS 23.402; in section 4.5.4, the requirements are set out. The details have varied by release; R18 now says you use your HPLMN ePDG if you’re in your home country (determined by means outside the spec), and your VPLMN otherwise, but older releases said to use the VPLMN.
There’s three ways for a UE to determine the ePDG DNS name, in preference order:
1. By configuration on the SIM, via H-ANDSF or similar that tells it the name of the HPLMN ePDG. If this is supplied, and you’re connecting to the HPLMN ePDG, you don’t try alternative names for it.
2. By generating names based on the TAC or LAC; see TS 23.003 for the gory details here.
3. By generating the name from MNC and MCC – this is always of the form epdg.epc.mncXXX.mccYYY.pub.3gppnetwork.org where XXX and YYY are your 3 digit MNC and MCC.
So, fixes are:
1. Wait for everyone’s handset to be updated to versions that always use the HPLMN ePDG when in-country. Then, it just works as long as networks do the needed things to convince phones that they’re in-country (sounds like you have this in progress with O2).
2. Deal with the GSMA bureaucracy, stand up your own ePDG on epdg.epc.mnc004.mcc234.pub.3gppnetwork.org, and then fight mobile network bureaucracy so that they accept call data via your ePDG, not just via your 4G/5G networks.
Thank you Simon – that’s really quite helpful (and appreciated), and a pointer in the right direction. I am really not sure what the GSMA were thinking of with this unless it’s an LI requirement to have home routed voice. In the 3G days and early internet maybe local routing would keep the packets flowing, but now OTT voice messaging has shown the robustness of even peer-to-peer. The first thing we really need to figure out is why we are not being presented as “GB” when both our IP range, and MCC shows we are. We are using CGNAT local addresses though, so maybe that’s worth a first look.
Also to add that we do occasionally see requests for epdg.epc.mnc004.mcc234.3gppnetwork.org come across the cellular data interface (although it’s mostly the other UK MNO’s who we do support IPSEC routing to). Given that we have no 23404XXXX IMSI’s active this at least explains why devices are trying to reach our non-existent ePDG.
Would be good if he learnt to spell (licensed).
I’m on EE mobile with BT FTTP, when I’m on a phone call outside and come in doors my phone switches to WiFi and drops the call. So it’s not just wave mobile with the issue when EE and BT can’t roam from cell to WiFi Calling and they are supposed to be using the same hardware.
And that is the issue
wIFI calling and transitions to and from VoLTE is a complex thing the forum is full of WIFI Calling compatibility issues of devices and networks.
There will be a limited resource of individuals that understand the subject in detail.
There is now VoNR complexities
So why would the providers divert resource and cost to resolve niche technology which probably now could be replaced simply by IP networks including Wavemobile and their partners.
WIFI calling is a major step forward and though dropped calls is annoying it is probably affecting a small percentage and WIFI Calling is really best endeavours because they do not control the quality of the IP network.