US carrier AT&T plans to introduce High Definition (HD) Voice on an all-IP, Voice Over LTE (VoLTE) network in select markets beginning May 23. 

Initially, HD Voice from AT&T will be available in select areas in Illinois, Indiana, Minnesota and Wisconsin, and will continue to expand on a market-by-market basis.

HD Voice customers can simultaneously talk while surfing the Web at 4G LTE speeds. HD Voice will be enabled on the Samsung Galaxy S®4 mini with more devices to come.