Comment Re:They need to free up low frequency (Score 1) 57
It is probably more likely that the phone modems have become less sensitive. In the old days you had maybe a 4 band phone, and now is well north of 20 bands (sorry I left the cell industry almost a decade ago, and at that time it was at 20 bands). A lot of those bands never get used by a given phone, but the Apple's and Samsung's of the world want a single model to work in every country for every carrier, so you pack in every possible band into the phone. Front end loss has steadily grown, requiring more power from the transmitting power amplifier, but the LNA's are already ~1 dB noise figure, and adding 6-8 dB of loss can't be overcome other than just letting the phone be less sensitive.
The antenna's signal has to pass through more switches, duplexers, and other complexity to get to the modem, so you have a lot worse noise figure. The rule of thumb a decade ago was about 0.1 dB of frontend loss for each additional channel. I would guess this is the issue more than 3G/4G/5G differences. 4G and 5G are slightly more, not less efficient with their encoding and efficient use of spectrum. Basically better DSP power with better CMOS nodes in the modems has allowed less wasted spectral space between channels, and more flexibility in packing channels together to handle both very low speed data (like voice) and huge bandwidths compared to 3G. Basically Moore's law has been employed to squeeze better efficiency and flexibility out of the existing spectrum.