Verizon: Their main network is in the 700MHz band (band 13) but for a couple of years they’ve been offering LTE in some areas on the AWS band (band 4- upload is 1700MHz and download is 2100MHz). They brand this as XLTE, Users with gear that supports both bands may find themselves automatically pushed into the XLTE band due to lower congestion. And while it’s currently less crowded, the higher frequencies result in less coverage and building penetration. Verizon is also now overlaying LTE into older 3G spectrum (Band 2, 1900MHz) in some areas.
AT&T is even more of a hodgepodge, since their legacy of buying other cellphone companies results in a patchwork of licensed frequencies. In most areas, you’ll be using AWS (Band 4, 1700/2100) or Band 17 (700MHz). In some areas, they’ve opened up 3G bands to LTE (Band 2, 1900MHz) and in others they’ve licensed Band 5 (850MHz). To be safe, you’ll need a modem or hotspot to cover all of these bands (like the Comrex Connect modem)
Sprint: They suffer from the legacy of introducing 4G service first, but in a non-LTE form that died away quickly. They now offer LTE in this band 41 (2500MHz) but the extremely high frequency leads to coverage difficulty. They’ve been promoting their “Vision” plan for the last few years which overlays LTE on all their available spectrum (1900MHz Band 2 and 850MHz Band 26) as well as backhaul upgrades, but our experience is still mixed in many areas.
T-Mobile: Their very late LTE deployment results in mostly urban coverage.LTE is provided mostly in the AWS band 4 (1700/2100MHz) but they’ve been overlaying on their 3G band 2 (1900MHz) and are starting to deploy LTE on Band 12 (700MHz) in some limited areas where they have spectrum.
So depending on your carrier or location, you may be experiencing LTE on Band 2, 4, 5, 12, 13, 17, 26, or 41. Compare this with most countries that have two choices for all carriers. The situation in the US has resulted in the inability to move a data modem or phone from one carrier to the other. Thankfully, higher-end smartphones and tablets now cover the majority of US bands, so they are portable.