A software bug in Verizon Wireless' IP Multimedia Subsystem (IMS)
architecture caused the April 27 outage. The outage may have also caused the delay in releasing the Samsung Droid Charge.
Chief technology officer, Tony Melone, said that an element in the IMS core had a software problem, which escalated, affecting the core's back-up systems and shut
off all access to both mobile data networks.
Verizon implemented IMS as a way to support voice-over-LTE (VoLTE) on
its 4G LTE network. The IMS vendor identified the problem and programmed
a fix for the bug.
Melone explained the cause to reporters during a press conference at TIA 2011 after his keynote address.
Verizon's 4G network was rated 5Gs in our Review of Reviews. Currently, Verizon offers two 4G LTE smartphones: the Samsung Droid Charge and HTC ThunderBolt. The LG Revolution with VoLTE may have a May 26 release date.