This is a bit of an advertisement from Verizon, for trials going on right now in various US locations. The service is scheduled to begin between the end of 2017 and beginning of 2018:

http://www.verizon.com/about/news/5g-trials-rapid-connectivity-enterprise/

The first deployments will be for fixed wireless broadband service, as opposed to mobile (which will come later).

And, of course, others are involved in similar trials, including AT&T and Google.

http://www.aglmediagroup.com/shentel-att-trials-feature-fdd-lte-massive-mimo/

Looks like 5G mobile trials are going on in Tokyo, but scheduled for service later than the above two fixed service examples.

http://www.fiercewireless.com/tech/ericsson-softbank-5g-trial-tokyo-to-include-mobility-at-28-ghz

The interesting part of the European trials is that massive MIMO is being tested initially on 4G systems? Also going on as we type.

https://www.thefastmode.com/technology-solutions/10387-swedens-telia-showcases-757mbps-in-massive-mimo-trial-on-commercial-4g-network