The two largest US operators, AT&T and Verizon, have been global frontrunners in 5G. This is not so much in terms of subscriber bases, since their lack of midband spectrum forced them to start roll-out in millimeter wave bands, which do not lend themselves to broad coverage. AT&T is now deploying in sub-GHz spectrum too, but in such a huge base, it will be hard to achieve the 10% penetration of the subscriber base that the South Korean operators are enjoying (see separate item). The two US giants are not reporting 5G numbers yet, but even if these are modest so far, they have been frontrunners in a more important way, by driving some of the broader architectural changes that…