By Adam Friedman
T-Mobile made an incredibly smart decision a few years ago. Unlike Verizon and AT&T, T-Mobile decided to build its 5G network from the bottom up. So while the others were focusing on mmWave 5G (which delivers the fastest 5G download data speeds), T-Mobile was buying nearly $8 billion worth of low-band 600MHz spectrum. It also spent $26 billion to buy Sprint so it could take control of the latter's mid-band 2.5GHz airwaves.