AT&T last month conducted a series of internal testing on its VoLTE service that the operator launched in May this year. According to AT&T,  the internal testing has proved that its VoLTE network performance is strong, showing an average of better than 99 percent in both accessibility and retainability. The internal testing covers how easily consumers can place a VoLTE call (accessibility) and how likely they are to stay connected to the VoLTE network during calls (retainability).

AT&T has rolled-out VoLTE and HD Voice since May this year in select areas in the District of Columbia, Georgia, Illinois, Indiana, Maryland, Michigan, Minnesota, Nevada, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Utah, Virginia, Washington and Wisconsin and will be expanding to more states. The carrier has also extended its VoLTE service by enabling roaming with Verizon 4G LTE network and said that it is working with other wireless carriers on the same.

AT&T added that the company will continue to optimize, test and expand its VoLTE coverage throughout 2015. AT&T predicts more VoLTE-capable devices to be introduced in the market place towards the end of this year and beginning next year. According to the service provider, its VoLTE service boasts the ability to allow users to simultaneously make HD calls and surf the web via the high speed 4G LTE network.