Sprint plans to launch its HD Voice service for the HTC EVO 4G LTE by the end of the year, according to reports. The feature, significantly improves call quality, but it requires both handsets to support the service in order to be used. To ensure the quality of HD Voice, Sprint says it needs to upgrade a large portion of its markets with various network improvements, and launch additional smartphones that are compatible with the new feature. HD Voice will initially launch in select markets in 2012 and won’t become widely available until 2013 and 2014.
For the HTC EVO 4G LTE, HD Voice consists of one part common mode noise rejection using two microphones, and one part 1x-Advanced. Part of the CDMA 1x-Advanced specification is inclusion of support for higher quality EVRC voice encoding. Currently, virtually all the CDMA2000 carriers in the USA use EVRC-B for their voice calls, which has adaptive bitrates of between 4 and 8 kbps and sampling of up to 8 KHz. Sprint has talked rather publicly in the past about upgrading its CDMA2000 1x network to 1x-Advanced.