LTE Tutorial Long-Term Evolution 

Voice Codec Options for VoLTE Services

The quality of Voice service plays and will play an important role in the evolution of the telecommunication system. Voice subscribers are becoming habitual of Voice over IP (VoIP) services that provide extended audio bandwidth be it Skype or Whatsapp Calling. They also expect the same high quality from mobile voice services. With the maturity of LTE networks, devices and IMS services now operators are able to provide the VoIP like service quality and experience with HD Voice services over a mobile network.

HD voice allows subscribers to communicate by using the wider audio bandwidth. This makes conversion more intelligible and natural, transparent and easy. It doubles the audio bandwidth compared to traditional telephony. Ever wonder what goes behind Quality of Voice?  The answer is Codec/s.

A Codec converts an analog voice signal to digitally encoded signal at a transmitter and later decode digital version to analog at receiver. Codecs are designed for high quality and efficient coding of voice and enhanced packet-loss concealment for challenging radio channel conditions. Different codecs have the different sound quality, required bandwidth and computation requirements.

Available Voice Codec and Data rate

Following codec are available for voice mobile services. Also to mention Enhanced Voice Service (EVS) codec is the latest one that has been introduced in 3GPP release 12.

  • Enhanced Full-Rate (EFR)
  • AMR Narrowband (AMR-NB)
  • AMR Wideband (AMR-WB)
  • Extended AMR-WB (AMR-WB+)
  • Enhanced Voice Service (EVS)
Codec Name Year of  Launch Audio Bandwidth Technology Bitrates
Enhanced Full-Rate (EFR) 1996 Narrow Band 2G  12.2 Kbps
AMR Narrowband (AMR-NB)  1999 Narrow Band 3G/4G  4.72- 12.2 Kbps
AMR Wideband (AMR-WB)  2001 Wide Band HD Voice in 3G/4G 6.6 – 23.85 Kbps
Extended AMR-WB (AMR-WB+)  2004 Full Band  Full HD Voice in 3G/4G  6-48 Kbps
Enhanced Voice Service (EVS)  2014  Super Wide Band and
including all Above
Super HD Voice in 4G  5.9-128 Kbps

The human audible frequency range is from 0 Hz to 20 KHz and an audible band can be divided into different bands namely narrow band, Wideband etc. The picture below shows the theoretical bandwidths for Narrowband, Wideband, super wideband and Full Band.
The actual bandwidths in practical may be narrower e.g. bandwidth is typically 300–3400 Hz for Narrow Band. The lower band is for natural sound, presence, and comfort. The bandwidth in middle about 5000KHz is for natural voice, better understanding and voice recognition and high frequency for high-quality music.

Article Submitted By Vijay Sharma

About Vijay Sharma
Vijay is a IMS, Virtualization testing professional. He has many years of experience in working with VoLTE,LTE/4G, IMS node with major OEMs and ODMs  in various roles
(Testing Engineer, Customer support, network dimensioning). 
you may reach out him at LinkedIn: