Verizon and Nokia are ready to test. Nokia CTO Hossein Moiin intends to test Antonio Forenza's pCell technology early next year. Last year, I wrote extremely skeptically about Artemis/pCell informed by three very respected engineers. CEO Steve Perlman made wildly implausible claims, including that they would deploy across 350 San Francisco rooftops by the end of last year. They haven't been seen.
Moiin is a respected, independent engineer. I have to look again. USC Prof Giuseppe Caire now says "The early trials showed pCell achieving far higher concurrent user capacity than any wireless technology I am aware of." That's very different from his earlier comments (below) and I assume he's been shown something newer. Peter White at Faultline has an important article about semi-secret trials in U.S. sports stadiums. (Paywall.)
Verizon in a startling move Monday told analysts they would soon test Massive MIMO and beamforming. (pCell is very similar.) These are key "5G" tools that weren't expected until about 2020.