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Thread: Help me understand device whitelisting in the 4G VoLTE era (Verizon vs ATT vs T-Mo)

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    Help me understand device whitelisting in the 4G VoLTE era (Verizon vs ATT vs T-Mo)

    I admit, I'm behind times. In the old days any GSM network (ATT, T-Mo) you could use any unlocked phone as long as it has the right band. The CDMA networks (Verizon, Sprint) required phones to be whitelisted. However, things have changed. From what I can figure out.

    - ATT: Now whitelist GSM phones, so even if it has the right bands may not work properly for VoLTE calls. This was the *****how with ATT prepaid and many MVNOs. SIM activation now tied to IMEI.
    - T-Mo: As far as I can tell, SIM activation is not tied to IMEI. No change from the past
    - Verizon: SIM activation still requires IMEI, but getting inconsistent reports if you can move the activated SIM to another phone that has the right band and it will work? So do phones need to be whitelisted on Verizon anymore? Or is the whitelisting for SIM activation the only restriction now?

    Thanks. Discussion for both prepaid and MVNOs. Is this info correct?

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    Quote Originally Posted by AndroAsc View Post
    I admit, I'm behind times. In the old days any GSM network (ATT, T-Mo) you could use any unlocked phone as long as it has the right band. The CDMA networks (Verizon, Sprint) required phones to be whitelisted. However, things have changed. From what I can figure out.
    VoLTE is not a standard in the USA. Every phone now must be certified to be VoLTE capable for the respective networks, because each carrier is using a slightly different implementation that's not compatible with each other.

    Currently, AT&T pre/post-paid and Cricket will enforce the whitelist. You are free to SIM swap as much as you like, as long as the phones are in the whitelist.

    If your phone's IMEI is not in the whitelist, it will get kicked off and your account will be suspended. This is checked every time the phone connects to the network, so if you SIM swap from a whitelisted phone to non-whitelisted phone, it will detected that and suspend the line. This also causes problems with phones that are VoLTE capable but not in the whitelist, like Canadian/International iPhones.

    The AT&T MVNOs have not been kicking off incompatible phones as far as I know, but require a whitelisted IMEI to activate. I have a single line on TracFone AT&T still working even though the phone isn't whitelisted.

    T-Mobile actual only seems to check the IMEI at activation, so theoretically, you could swap it into an unlocked phone after actvation. You are free to swap as you like. This might change in the future. They seem to be the most open to the International VoLTE standard as some China phones are VoLTE capable only with T-Mobile.

    T-Mobile MVNOs might or might not need an IMEI activation. I recently activated a Red Pocket/FreedomPop line (T-Mobile). No IMEI was required. Using it in an old phone, not Tmo VoLTE capable, with text/data only. Haven't heard of people getting kicked off.

    Verizon/Visible always had a whitelist and will pair the SIM with the phone's IMEI. Sometimes you can sim swap. Sometimes the system will auto re-pair, reports from PagePlus. Some Visible users reported using phones not whitelisted for Visible by swapping. Other times, the system detects it and request you to put the SIM back in the phone it was paired with.

    Not sure about other smaller Verizon MVNOs. The biggest is Tracfone which follows Verizon policy with the effects listed above.

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    Very well explained .

    I'll add that I have a free FreeUP SIM which uses AT&T. In Feb 2022, with AT&T dropping 3G support, I started using that SIM in a Tracfone-unlocked Samsung A51 which has the required bands, but it's not on AT&T whitelist. Initially, FreeUP's IMEI checker said it was compatible and it was working fine with VoLTE. But in June or so the account started getting the warning message below. Although the phone was still working, I didn't want them to shut off my line, so I switched the SIM into an unlocked Moto G Pure which is on AT&T whitelist. Eventually, I'll switch that SIM into a TF-branded Alcatel My Flip 2 (A406DL) flip-phone after it is unlocked by TF. The My Flip 2 is on AT&T whitelist.

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    I am sure there are exceptions, but:
    • FreedomPop GSMA (AT&T network) and GSMT (T-Mobile network) SIM cards are NOT tied to IMEI. I have been able to move the SIM cards around phones.
    • All three networks have some kind of whitelist, at least if a plan is to provide voice service.


    For myself, an LG Phoenix 2 (unlocked AT&T Prepaid) worked great with Mint (T-Mobile network) in early 2020. But with FreedomPop GSMT, it only worked briefly (had data service), then quickly lost service.
    https://www.howardforums.com/showthr...3#post17220623

    Additional data points / exceptions:


    Whitelists:
    Last edited by andyk88; 09-10-2022 at 01:39 PM.

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    I have 2 phone numbers on Airvoice (AT&T GSM) and 3 phones, can move SIM cards no problem. They never asked for IMEI.

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    Quote Originally Posted by hpham View Post
    Very well explained .

    I'll add that I have a free FreeUP SIM which uses AT&T. In Feb 2022, with AT&T dropping 3G support, I started using that SIM in a Tracfone-unlocked Samsung A51 which has the required bands, but it's not on AT&T whitelist. Initially, FreeUP's IMEI checker said it was compatible and it was working fine with VoLTE. But in June or so the account started getting the warning message below. Although the phone was still working, I didn't want them to shut off my line, so I switched the SIM into an unlocked Moto G Pure which is on AT&T whitelist. Eventually, I'll switch that SIM into a TF-branded Alcatel My Flip 2 (A406DL) flip-phone after it is unlocked by TF. The My Flip 2 is on AT&T whitelist.

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    My freeup line quit working so I had to activate it into an Alcatel flip phone. Now that it’s working I’ll try putting it back in the old 4G phone just to see if it’ll work again…
    Mourning the loss of my Nextel i325

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    Quote Originally Posted by andyk88 View Post

    For myself, an LG Phoenix 2 (unlocked AT&T Prepaid) worked great with Mint (T-Mobile network) in early 2020. But with FreedomPop GSMT, it only worked briefly (had data service), then quickly lost service.
    I think you lost service when 3G calling stopped working in your area. I found a fix for my Phoenix 2 on T-Mobile, which is to add an APN called ims, with APN set to ims and the type being ims. Note the lower case used in all three of these entries (though the first can be anything you want — just the APN itself and the type need to be “ims” in lower case. Do not select this APN, it just needs to be in the list of APNs and Android will use it for the IMS routing which is the backbone of VoLTE. When I make calls my LTE indicator stayed on — make sure you have Advanced Calling turned on in your settings, which is the switch to enable VoLTE.

    Note I don't use the Phoenix 2 regularly, I only did this as an experiment but it worked for 2 test calls. So I can’t say for sure this will stick, but t-Mobile has always been the carrier that followed all of the GSM/ITU standards the closest.

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    Thanks for the tip, high technology.

    A few references I found:
    https://blog.tello.com/news/3g-shutd...android-volte/
    https://www.howardforums.com/showthr...r-logo-missing

    It seems the "ims" APN may help if a phone is allowed on the network, but cannot make a call over LTE because the phone does not know what gateway to use.

    Unfortunately, I think my problem is that the T-Mobile network does not want my LG Phoenix 2 on the network at all. Specifying a gateway does not help, because the root of the problem is that the phone cannot even be on the network.

    The phone again had LTE connection initially. It again received text messages to install APN. However, by the time I checked that the Plinton APN was the same as last time, the data connection was already lost. I added a new APN ("ims" for Name, APN, APN type) as you suggested, power cycled, and still got "Emergency calls only".

    Under WIRELESS NETWORKS: More, Enhanced LTE Services is ON by default.

    I do not know if this patent is the basis for the "ims" APN. It seems the general idea is that "ims" is a special name that, among others, gets resolved to the correct gateway.
    https://patents.google.com/patent/WO2012095197A1/en
    Last edited by andyk88; 09-11-2022 at 01:36 AM.

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    Quote Originally Posted by Slepy View Post
    VoLTE is not a standard in the USA. Every phone now must be certified to be VoLTE capable for the respective networks, because each carrier is using a slightly different implementation that's not compatible with each other.
    I'm sure that either that's what they want you to think, or that at least they don't mind if people happen to think that...

    But it's also absolutely not true. Each of the big three carriers are running completely standards-compliant IR.92 implementations of VoLTE. Verizon was kind of the odd man out in the very very early days of their roll-out, but even they have been running a standards-compliant implementation for quite some time now. And AT&T's has been standards-based from the beginning.

    Which makes the whole whitelisting business even more frustrating, because it's complete crap.

    I talk a lot about this in detail in some past posts of mine here, like this one and this one.

    Quote Originally Posted by Slepy View Post
    The AT&T MVNOs have not been kicking off incompatible phones as far as I know,
    This is still true, as was your description of how native ATT pre/postpaid works with their whitelisting.

    I can confirm that I still have an ATT MVNO SIM in a completely unsupported / non-whitelisted model of phone, and that not only have I not been blocked, but I managed to enable both VoLTE and WiFi Calling on this phone after rooting it. Both features continue to work fine for me today, well after the AT&T "3G Sunset" date of February 2022.

    The most ornery ATT MVNO in my experience was TracFone (& subsidiaries) from back before the Verizon acquisition. They would actively IMEI-sweep their ATT accounts at some interval, and if any of the associated SIMs had previously been in phones that they deemed "supported" for VoLTE and then were later moved over to phones that weren't, VoLTE would work on the unsupported phone (provided it had been modded to enable VoLTE) for a short time (anywhere from hours to days) before eventually getting blocked on the carrier side. I'm not personally aware of other ATT MVNOs that went to that much trouble, and ATT themselves doesn't seem to care to IMEI-sweep ATT MVNO subs (just their own direct subs), instead apparently leaving that dirty work up to the MVNOs who (for whatever reason) happen to care about that.

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    I would agree in principle that this whole whitelist compliance thing is complete bunk, as far as the technical aspect goes. The phone makers make their devices to comply with things of a certain standard, described by that standard. You can be sure that when they offer a device direct that's spec'd as factory unlocked containing all U. S. frequency bands for LTE or 5G, as well as VoLTE features (for instance), they expect it to be able to be used on all carriers. Only by virtue of the device having an identifying IMEI is the carrier able to discriminate the device's "newness" or other characteristics that to them would reveal it hasn't paid its "special dues" to that carrier to be "compliant" on the network. It's just backdoor nonsense and the FCC should call it out and put an end to it. And the CTIA (cell industry lobby group) should denounce it too. There was a time when it looked like the U. S. industry was moving toward the idea of universal devices and bring-your-own-phone freedom, especially with the advent of LTE, which used a SIM card (physical). Everyone wanted to do what the GSM users had been doing for years: pick a phone and use it with whatever carrier was desired. But now this. This non-compliance thing exists only because the carriers have the technical capabilities to put up another roadblock to phone freedom. And the incentive can only be money, some payoff for them at some level.

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    Maybe we should all write/complain to the FCC?

    Quote Originally Posted by NathanA View Post
    Which makes the whole whitelisting business even more frustrating, because it's complete crap.

    I talk a lot about this in detail in some past posts of mine here, like this one and this one.
    Quote Originally Posted by whacker View Post
    It's just backdoor nonsense and the FCC should call it out and put an end to it. And the CTIA (cell industry lobby group) should denounce it too. There was a time when it looked like the U. S. industry was moving toward the idea of universal devices and bring-your-own-phone freedom, especially with the advent of LTE, which used a SIM card (physical). Everyone wanted to do what the GSM users had been doing for years: pick a phone and use it with whatever carrier was desired. But now this. This non-compliance thing exists only because the carriers have the technical capabilities to put up another roadblock to phone freedom. And the incentive can only be money, some payoff for them at some level.
    Maybe we should all write/complain to the FCC about all this whitelist nonsense?

    I myself wouldn't know what exactly to write, but the knowledgeable people here on HoFo can maybe draft a letter that will convince the FCC to do something about these whitelisting roadblocks. I know I'd be more than willing to send that letter to the FCC (like the letters we used to write in middle school!).

    I think if one of the experts here could just draft a "template" or "form letter", many other people too here on HoFo would be willing to send it over to the FCC. Let's start a letter-writing campaign! Maybe we can get rid of this whitelisting nonsense!

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    I am not discouraging anyone from contacting the FCC over this, but I am realistic about the odds of winning that fight which are slim to none. Until we can organize a PAC (Political Action Committee) with several $$ million in reserves there is little chance of making any changes.
    Just another day in paradise.....

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    Quote Originally Posted by sillyette View Post
    Maybe we should all write/complain to the FCC about all this whitelist nonsense?
    Unfortunately, AT&T will easily use as a defense that is a matter of life-safety, that they have to prevent people from using devices on their network that can't make phone calls to emergency services.

    Yes, there are devices that AT&T isn't whitelisting that would work and would make calls. But AT&T can likely tell the FCC there's some technical reason where the device may not make calls in every location...and that's really enough for the FCC to take AT&T's side.

    As Serial Port said, no need to discourage anyone from contacting the FCC. Here's the link and it's easy enough to report the issue:

    https://consumercomplaints.fcc.gov/hc/en-us

    AT&T is required to respond to you in 30 days....but I will assume that the responses will not be very satisfying.

    If you do complain, please post the results.

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    Quote Originally Posted by jet1000 View Post
    ............ But AT&T can likely tell the FCC there's some technical reason where the device may not make calls in every location...and that's really enough for the FCC to take AT&T's side.
    There in lies the issue with anything communication/FCC related. And as Serial Port said "I am realistic about the odds of winning that fight which are slim to none". The FCC is at the mercy of what the networks tell them, even landline companies. And our representatives in DC are totally clueless on anything likewise related to services yet alone whitelists. JMHO.

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