Why is there such a huge difference in the speeds of a 3g and 4g modem?

Question

mobile connection

There are two modems, Beeline - 4g and 3g. Where they connect 4g does not catch. Both work on hspa+.
But at the same time, a 3g modem gives a maximum of 300 kb / s at any time of the day, and 4g - 1 mb / s. -75dbm both.
Why such a difference? 4g modem is not mine, so buying a second one is a little strangled by a toad. Perhaps in the firmware or something else?

Answer 1

Apparently, the 4g modem is simply more modern and technologically advanced with better stuffing, which is why it receives and transmits better with an equally weak signal.

Answer 2

As option 3g works on usb 1
Well, and most importantly, different versions of hspa
https://ru.wikipedia.org/wiki/HSDPA

Answer 3

Because the top of the development of 3G technology is HSDPA, and the bottom of 4G is DC+HSPA+. DC should be read as double client .
Thus, one channel for reception, the second for transmission, hence the difference.