It’s just one day since Droid Turbo has been on sale, but Verizon Wireless has pushed an OTA update with software version 21.21.15.en.US. So, in case your phone is still running the version 21.21.12.en.US, you might receive an update notification, right after you activate the phone.
If you’ve played with the device for a while, but have not got any software update notification, it’s not necessary to worry, you will surely get it in the near future, since the update rolled out gradually, but it never hurts to try to manually check for via phone settings.
There are no official changelogs regarding 21.21.15 update for Verizon Droid Turbo, but according some members experience over xda forums, the most noticeable change is the IMS registration. IMS stands for IP Multimedia Subsystem which related to VoLTE technology or Advanced Calling 1.0 services from Verizon Wireless.
Before installing the OTA or the device still running the initial software version (21.21.12), you may get “Not Registered” status on the IMS settings, it will be fixed with this OTA update.
The 21.21.15.en.US only a minor update for the Droid Turbo, as it only strengthens Advance Calling 1.0 services enabled by Verizon’s VoLTE technology, and some folks might not need it.
However, there’s many benefits of this service like HD Voice, 1-way and 2-way video calls (incl. Video calls over Wi-Fi), simultaneous voice and 4G LTE data and 6-way calls conference.