Just to underline what was
mentioned upthread, the signal you typically receive from the cell tower at your handset (-30 to -120 dBm) is around 10 microwatts or less (more typically is picowatts and can be femtowatts). The signal your handset is pumping out (5-25 dBm, say) is typically around 10 to a few hundred milliwatts. So the cell tower signal is around a thousand times weaker than that from the handset you are carrying around, at least (though more typically something in the range of a million to billion times).
Massive MIMO is just a phased array technique for improving S/N; it's actually going to reduce RF energy in directions where active handsets aren't.