The promise of the USA’s multi-tiered CBRS spectrum band has been discussed for so long that it is easy to forget that there are still no commercial services in the 3.5 GHz band, either in its licensed or shared tiers; and still barriers to full deployment, though most of them are political rather than technical. And with the timing of 5G in shared spectrum uncertain, there is likely to be plenty of time for CBRS to make its mark on the mobile services landscape, even if impatience is rising for it to kick off its activities. So much is riding on the success of the FCC’s bold experiment with opening up a formerly federal band for mobile broadband, with three…