When folks are experiencing weak indoor signals, we often get the question on how much a user can boost the output signal of their LTE device. User equipment (UEs), which includes customer premise equipment (CPE), can only transmit power up to a limit specified by the LTE standard. Most LTE UEs are specified for operation in Power Class 3 which has a maximum power of 23 dBm (or 200 mW). The specification typically allows for a +/- 2dBm tolerance.

There are a few LTE bands that are spec'd to operate in Power Class 2 (with 26 dBm or ~400mW), for example LTE Band 41. Recall that B41 is the TDD 2.6 GHz band that mainly owned by Sprint (now T-Mobile) (old Wimax band - we have a bunch of popular Band 41 antennas here).

You can use our LTE amplifier filter to find the best amplifiers for different LTE bands here: https://shop.rfwel.com/amplifiers-repeaters/
Learn more about 4G LTE frequency bands (e.g., best antennas): here
Finally, you can find devices compatible with different LTE frequency bands and with various input/output power options here

If interested here is the LTE spec that includes this information: 3GPP TS 36.101 (e.g., see table 6.2.2-1 in ETSI version of revision 14.3.0 here)

Power classes for Rel 14 LTE UEs

Remember for 5G NR the 3GPP spec is TS 38.101. Because 5G NR has two quite different frequency operating regions requiring different specs, the 38.101 spec has been divided into two specs TS 38.101-1 covering frequencies below 6 GHz called (i.e., frequency range 1 (FR1)) and TS 38.101-2 covering millimeter wave bands above 20 GHz (i.e., FR2).