1. drscientist's Avatar
    I have an AT&T Z10 that's unlocked and runs on T-Mobile. Every time I make a call, it's been switching from 4G LTE to Edge/2G. Why is that? Maybe the radios are bad? Calls also drop frequently.

    Mods, please don't close this thread. I've posted this a few times in the finding/fixes thread but it gets buried, and I've seen several other people with this issue.
    11-22-14 11:48 AM
  2. toobs623's Avatar
    Is it possible that there is a tower degraded in your area? Calls won't go over LTE, they would either run over HSPA, or if unavailable, EDGE.

    It's certainly worth trying a radio reload... or even just turning the device off, removing the sim for a couple of minutes and trying again.

    Posted via CB10
    drscientist likes this.
    11-22-14 11:55 AM
  3. FrankIAm's Avatar
    I'm thinking your RFF91LW Z10 doesn't support TMO's 1700MHz for 3G, and since you don't have VoLTE and TMO hasn't implemented 1900MHz in your area, it falls back to 2G.
    drscientist likes this.
    11-22-14 11:57 AM
  4. Superfly_FR's Avatar
    In France, you cannot have voice on 4G, even if the status of your connexion states otherwise.
    4G is data only and your device self-skip to the first available voice (Edge, 3G+, dual Carrier, 2G/GSM) mode (i.e antenna non 4G).
    Sorry I'm not sure about T-Mo, but it could be the same ...

    Call drops (and unpresented calls) are also frequent here, because the switch to the proper antena can take a while, especially if you are in a 2G/GSM area.
    The cascade ... Blame (like I do) you carrier every day.
    TIP: disable 4G when you really need a stable phone situation and you"re moving around. I know, it's a pain.

    P.S: for voice, you really don't care what frequency is used.

    Hope it helps,
    SF
    Last edited by Superfly_FR; 11-22-14 at 12:01 PM. Reason: Added some more infos.
    drscientist and cukierkas like this.
    11-22-14 11:58 AM
  5. joeldf's Avatar
    I'm thinking your RFF91LW Z10 doesn't support TMO's 1700MHz for 3G, and since you don't have VoLTE it falls back to 2G.
    I agree. On AT&T, while on a call, the phone drops from LTE to the UMTS bands - some of which AT&T calls "4G" - in reality, that's AT&T's HSPA+ bands. But, the AT&T branded phones don't cover the all the frequencies that T-Mobile uses for its 3G/HSPA+/fake 4G.

    T-Mobile and AT&T have some crossovers in the frequencies they use, but T-Mobile uses one other UMTS band - the 1700 Mhz band mentioned above, and that could be what they are using in your area for 3G/4G. So, it drops to the next available band, which happens to be one of the EDGE frequency bands -all of which are shared between AT&T and T-Mobile.

    This is actually an old issue of using AT&T branded BlackBerry phones on T-Mobile that goes back to when both carriers upgraded to 3G. When BlackBerry finally got 3G on their phones, there was always that gap in the bands used between the two. For example, people would get the Torch 9800 from AT&T which was a 3G phone, unlock it, and put a T-Mobile sim in it and get only 2G/EDGE.

    Posted via CB10
    drscientist likes this.
    11-22-14 12:15 PM
  6. drscientist's Avatar
    Interesting... thanks for all of the detailed replies guys! I noticed this wasn't happening on 10.2.1 but that may have been due to WiFi calling. It goes straight back to 4G LTE as soon as I hang up. What's been bothering me is the poor call quality and the constant call dropping, albeit this release is the most stable yet.

    Is there anyway I can check to see if T-Mobile has started 1900MHz in my area?
    11-22-14 12:19 PM
  7. homer1475's Avatar
    This has happened to me every since LTE was turned on in my area, even with an AT&T branded phone on the AT&T network. No degradation in call quality, I can just see it happening by the icons on the screen. Happens to my wife's iphone 5s also.

    When I'm in a stronger LTE area, my icons stay on LTE.
    drscientist likes this.
    11-22-14 05:14 PM
  8. cukierkas's Avatar
    Super fly explained all.

    Posted via the CrackBerry App
    drscientist likes this.
    11-22-14 05:17 PM
  9. drscientist's Avatar
    I'm thinking that it may be radio related now, actually. I've been noticing that every time I make a call, it switches to Edge and half the time the call drops and it says "No service available." I then have to wait about a minute for it to come back. It's really strange. I never had the issue before on 10.2.1, and I'm considering maybe switching back to it.

    Or it could just be that service has been bad and I never noticed?
    11-22-14 07:19 PM
  10. drscientist's Avatar
    Super fly explained all.

    Posted via the CrackBerry App
    Yeah, you're right. I just reread their comment and it all makes sense given what I just noticed. Thanks!
    Superfly_FR likes this.
    11-22-14 07:20 PM
  11. Superfly_FR's Avatar
    I'm thinking that it may be radio related now, actually. I've been noticing that every time I make a call, it switches to Edge and half the time the call drops and it says "No service available." I then have to wait about a minute for it to come back. It's really strange. I never had the issue before on 10.2.1, and I'm considering maybe switching back to it.

    Or it could just be that service has been bad and I never noticed?
    My experience with 4G deployment in my area has been is terrible. The more they activated it (for a very slight performance benfit against 3G+ / Dual carrier) the worst my experience was. I spent more than 4 hours with technical services and finally escalated to a greater competence level (thanks to my BBElite status) where explanations were clearer.

    Since I'm not tech, I'll try to keep it at a reasonable level of comprehension :
    1. It's not (really) your device fault, thus experience may vary depending on both hardware and software versions.
    2. There are two main concerns here : the antenas and the back-end but both have the same problem: they tried to build a new service (4G) on a old infrastructure. In many cases, both couldn't handle it due to "overload".
    The problem is particulary sensitive when you basically have only access to 4G/LTE and EDGE/2G/GSM, because the switch of frequencies is in fact handled by the back-end in a cascade mode.
    (simplified =>) 4G data - DC/3G+/3G data + voice - EDGE data + voice - 2G/GSM voice (and deprecated data).
    Yet, this cascading requires time, especially if your 3G (and the likes) connection if poor or lacking. In this typical case, the latency is too long and you fail into error ("No service available."). Note it is also the case when you receive a call (you may have friends stating either 'direct to answering machine' or 'it rang but finally goes to answering machine').

    So, until I find it's safe I only use 3G/2G mode in locations (home/office) where I know this is likely to happen and turn 4G on when I really need data ...
    Again, thanks the "discounters" that have made 4G "free" and sold it as a commercial competitive argument ... when IRL, the metrics are wayyyy under what they advertise, even often lower than what I had previously in 3G+/Dual Carrier modes.
    cukierkas likes this.
    11-24-14 04:56 AM
  12. jhirizarry's Avatar
    AT&T doesn't make voice calls over LTE, never been, only over 4G or less. This is a limitation of their network, will see if HD calls gets adopted, then it will go over LTE. But for now, no LTE for voice calls, only data.

    PassportSQW100-1/10.3.0.1418 on AT&T
    11-24-14 09:05 AM
  13. joekavorski's Avatar
    The radio from this release was garbage for me on my Z30 personally.

    Hoping I can downgrade the radio file!

    EDIT: Just sideloaded 1017 radio to my Z30. Since you have a Z10, you could try the radio posted on the 1133 leak thread. I would have used that one but theres no radio for anything but Passport and STL2/3/4.

    Superfly is likely 100% correct, but I thought I'd add my experiences with the radio from this release as well.
    Last edited by joekavorski; 11-24-14 at 09:34 AM.
    11-24-14 09:24 AM

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