Standardisation of the adaptive multi-rate codec

European Telecommunication Standards Institute (ETSI) initiated a standardisation program in October 1997 to develop an Adaptive Multi-Rate (AMR) codec for GSM. After two competitive selection phases, ETSI chose in October 1998 a codec developed in collaboration between Ericsson, Nokia, and Siemens. The codec standard was finalised, characterised, and formally approved in ETSI during early 1999. The AMR codec provides the next step of speech quality improvement in GSM after the introduction of Enhanced Full-Rate (EFR) codec in 1996. AMR offers substantial improvement in error robustness by adapting speech and channel coding depending on channel conditions. By switching to operate in the GSM half-rate channel during good channel conditions, AMR provides also channel capacity gain over the EFR codec. In April 1999, the Third Generation Partnership Project (3GPP) adopted the AMR codec as the mandatory speech codec for the third generation WCDMA system.