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Comment by mod50ack | Hacker News Reader

VoLTE is so damn frustrating. LTE works via plug and play with any phone that supports the correct bands, but VoLTE doesn't. I have a Sony Xperia phone here in Canada and it's just not possible to use it on VoLTE without rooting to install specific provisioning files and whatnot.

And that's not even counting how you can't just go from country to country without changing firmware.

I've always used a local SIM whenever I go on a trip to another country. But with VoLTE, you're incentized to roam with the carrier that has whitelisted and provisioned your phone, because your phone will be fed that home VoLTE provisioning information when roaming.

There's the irony: I can VoLTE call with a Verizon SIM roaming on Bell, but not with a Bell Canada SIM on its own network.

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I understand why you feel that is ironic, but the VoLTE call on Bell uses only the Bell LTE data bearer and not any other resources that are VoLTE specific from the Bell network. Everything relating to VoLTE is coming from Verizon. In many roaming situations VoLTE roamers are downgraded to CS in order to comply with lawful intercept.

Oh, I know all that --- it's just funny to me.

My luck with both WifiCalling and VoLTE has been so touch and go between different devices and even within multiple devices of the same model... that i just gave up and started doing everything exclusively within Google Voice.

Nuking the Messages app also had a nice little benefit: No more text spam that the carriers refuse to do anything about.

I recently found myself without any LTE signal the other day and was told by support that I needed to contact a certain department by… calling them.

I did have WiFi so my first thought was WiFi calling. Unfortunately, it appears on iOS that WiFi calling for some reason depends on hotspot, which I couldn’t enable without and LTE connection. Kinda deflated the purpose.

Thankfully, I had completely forgotten about Google voice, which someone reminded me about.

I remember a few years back though, a phone I had on I forget which carrier could fall back on 2g networks when LTE wasn’t available for whatever reason. It seems that ability is disappearing as old generation networks are shut down.

VoLTE has been "broken" (from a standards perspective) since before it even launched in most markets - it is just too "finicky" and configuration-specific. LTE/4G demonstrated the success of standards in that it "just works" as long as you have the right bands in place. Since most (modern) phones have the bands needed for the main global markets, you can pop in a SIM card and get connected anywhere.

VoLTE is far more complex, and there's network-specific configurations "hard-coded" into the (usually) Qualcomm modem firmware, including IPSec parameters for communicating with the IPsec endpoint in front of the IMS SIP server.

An example of one of these configurations (in JSON-ish format): https://github.com/JohnBel/QualcommMBNs/blob/master/extracte... - even including things like a "user agent":

``` "ImsUserAgent": { "ValueString": "Vodafone VOLTE Qualcomm" }, ```

VoLTE roaming can work, but it's complex and requires specific roaming agreements between carriers. These arrangements need negotiated individually (for now) between operators, and have a number of considerations including technical and legal - since there's IPSec in use, local laws (in the country you roam in) might restrict the ability to do this, as local lawful intercept wouldn't work. The home network needs to set up rules for which networks won't permit IPsec to be used (I believe AT&T will do this, but only where there's a legal requirement to permit local interception of calls).

The long and short of it is that, as you say, VoLTE is a load more complex than it ought to be. Throw in delivery of SMS-over-IP (settings also in the above MBN example) for extra complexity - many operators rolled out VoLTE/VoWiFi without SMS support, and some still don't properly do SMS over IP as far as I recall.

5G more generally is starting to head this direction too though - with the complexity of EN-DC supported configurations for 4G, and the very limited support for 5G standalone, even among devices advertising it, I fear with 5G we will have another few years to go before you can buy a "5G" phone and have any confidence it will work. VoNR (the successor to VoLTE) will likely have all the same issues replay as we saw with 4G.

I really wish we could get carriers and standards bodies to bash heads together and set up a "baseline" standardised IMS profile for VoLTE/VoWiFi - there's nothing inherently preventing this from working, as you can easily use VoLTE on a private network if you follow the standards, but operators love to meddle, tweak, and add custom useragent strings etc.

> LTE/4G demonstrated the success of standards in that it "just works" as long as you have the right bands in place. Since most (modern) phones have the bands needed for the main global markets, you can pop in a SIM card and get connected anywhere. VoLTE is far more complex, and there's network-specific configurations "hard-coded" into the (usually) Qualcomm modem firmware, including IPSec parameters for communicating with the IPsec endpoint in front of the IMS SIP server.

I sort of get the feeling this is by design.

The success of standardization predates LTE by a lot if you look beyond the US which had competing technologies until LTE. GSM networks (2G) allowed roaming and switching between phones by swapping SIMs in all of Europe in the mid nineties, and most of the rest of the world a few years later. Just the US use of a unique 1900Mhz band kept roaming mostly unavailable.

Indeed, I was using LTE as an example of the peak standards benefit, but in Europe this simply hasn't been a factor for decades. 2G and 3G were similarly uneventful and straightforward (for the most part).

This was all standardized correctly in IR.92, but a bunch of software was essentially baked prior to standardization, which means you need a bunch of config to say "do the standards defined thing".

> local laws (in the country you roam in) might restrict the ability to do [IPSec]

Is there a way to find out which countries do this?

I don't even think my carrier Lucky Mobile supports it. I don't really get why? Does this actually save them money or is it because the people who care/need it are incentivized to upgrade to Virgin/Bell?

EDIT: Apparently it does automatically but they disable the toggle to turn it off.

Bell supports VoLTE on Lucky, but not WiFi Calling. They only offer it on the Bell and Virgin brands.

It’s likely done purposefully so that customers in rural areas cannot use the flanker brand, and must instead stay with the more expensive alternative.

My very old rooted huawei maimang 5 somehow manages to even get VoLTE roaming without problems, and it automatically got VoLTE settings on every network I tried.

I still have to see how my new Xiaomi will fare.

Lots of networks blocks VoLTE on the network end if the device is not on their whitelist. Both two of my Xiaomi phones fails to get VoLTE on both networks in my country that offers it. Mea while my S21 has no trouble since it is whitelisted with the same two networks that refuse to provide VoLTE to the Xiaomis. Sadly it's a case of making sure you have (1) a VoLTE capable network, (2) a VoLTE capable phone and most importantly (3) a network that whitelists your phone. One network in my country started out only whitelisting only the specific phones they sold (and rejecting phones sold elsewhere even if it's the exact same model, firmware, etc) but I believe they have since loosened up by accepting phones sold by others as long as it's the same model as what they sell themselves. It's a absolute mess and to be honest the only reliable choices are Apple and the last few generations of Samsung phones (as that's what all carriers here sell) but if you stray to other brands it's very hit and miss whether your carrier will support it and worse whether you have the choice of changing carriers to another that also supports your phone. Makes me pine for the good old days of GSM.

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