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I want to purchase an LTE phone for use with T-Mobile. According to Wikipedia model XT1053 is what I need... however it uses LTE bands that many of the other phones don't use.

  • What is an LTE band?

  • If I purchase model XT1055 and use it on TMobile will I only use LTE band 4, and the other ones are unused?

  • Is there an impact on battery life if using a phone that has a different LTE band then expected by the network?

  • Is it correct to say that these LTE bands are hard coded into the phone and can't be changed?

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  1. LTE bands are the bands of radio spectrum that the cellular networks run on. There are 44 defined bands and different carriers in different areas use different bands to provide service. Wikipedia has a fairly extensive list of who uses what bands.

  2. Yes, T-Mobile operates on band 4 (aka AWS), so any other band capability on the device would go unused.

  3. If you don't have the same band available on the phone as on the network, you won't be able to use the network period. It would be like trying to pick up an AM radio station on an FM-only radio.

  4. Yes. Band availability is determined by the hardware radio set the phone was built with.

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An "LTE band", or any other type of "band" that you read about with relation to a phone, is referring to the radio frequencies that the phone picks up. Each cellular provider builds their network on a specific set of radio frequencies which are divided up into chunks that are assigned band numbers. So, using your T-Mobile example, band 4 is specifically comprised of two frequency ranges:

  1. Upload bandwidth uses radio frequencies between 1710 and 1755 MHz
  2. Download bandwidth uses frequencies between 2110 and 2155 MHz

A phone's spec sheet effectively lists the frequencies that its antennas (and cellular radio) are designed to support. You cannot change the antenna's supported bands because this is not something that is set in software - the supported bands listed in a spec sheet are, generally, a statement about the phone's hardware support for different networks*. Therefore, your phone must support the carrier's LTE network bands in order for you to have LTE coverage. Otherwise the LTE radio will be unusable.

Cellular antennas these days are pretty much always multi-band pieces of hardware (that is, one antenna picks up several bands). The difference between powering a 5 band radio and a 2 band one is probably measurable with very precise instrumentation, but it's certainly not going to be an amount that would be perceptible when actually using the device. Further, having support for additional bands is generally considered a net benefit because you have the ability to use the phone on multiple carriers (assuming a SIM unlocked device).

Per your specific example of the XT1053 vs the XT1055: you could use the either on T-Mobile USA's LTE network, because both support band 4 LTE, which is what T-Mobile is using. However, the XT1055 will not work on T-Mobile's current HSPA+ network because it lacks support for the UMTS 1700 band. In places where LTE is too weak or not available, you would drop all the way back to EDGE (2G) speeds, whereas the XT1053 would be able pick up HSPA+42 speeds (if available).

*There are some exceptions to this rule, where a device may actually use a radio chipset/antenna combination that provides hardware support for a band that is effectively "locked out" by the software layer. One example of this is the Nexus 4, which does not list LTE support in its specs but does, in fact, have an LTE band 4 chip installed that can be enabled on older baseband versions. However, you could not force the N4 to work on, say, LTE band 17.

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    Some phones can have extra bands enabled via software. For example, the AT&T Galaxy S4 doesn't support the 1700 band, but QPST can enable it (since the underlying hardware actually has the capability). While this phone may not have that option, it isn't always accurate to say that a phone cannot have extra bands enabled. galaxys4root.com/galaxy-s4-tutorials/… – Stephen Schrauger Oct 8 '13 at 20:10
  • @StephenSchrauger: I would argue that's splitting hairs a bit, though. You couldn't force it to support some other arbitrary band without disassembling the phone and finding a way to attach a new antenna. The point I was intending to make is that you cannot change the hardware's supported bands via software means. Perhaps this wasn't clear enough. Incidentally, I would wager the number of phones with software band lockouts like that are pretty small (though perhaps increasing; the N4 has an LTE band 4 chip that is software-disabled by the baseband as well). – eldarerathis Oct 8 '13 at 20:18

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