enhanced voice service (EVS)
The voice quality of mobile devices was initially based on the historically defined telephone bandwidth of 3.1 kHz. The resulting voice quality is considered moderate and corresponds to an MOS value of about 2. The voice transmission is only sufficient for voice recognition and speech intelligibility.
HD Voice was the first quality improvement for voice telephony with mobile devices. HD-Voice works with Adaptive Multirate Wideband( AMR- WB) with a bandwidth of 7 kHz and is used in UMTS networks. A further improvement is achieved with Full-HD-Voice, which was developed by the Fraunhofer Institute for Integrated Circuits( IIS) under the name Enhanced Voice Service (EVS). Enhanced Voice Service is based on a voice bandwidth of 20 kHz.
Enhanced Voice Service is intended to transmit telephone calls with improved voice quality over the LTE network as Voice over LTE( VoLTE). However, the technology would have to be implemented for this.