The AMR (Adaptive Multi-Rate) standard is a speech coding algorithm operating at eight-bit rates in the range of 4.75 to 12.2 kbps and was specifically designed to improve link robustness. This technology was initially developed for GSM systems, the single most deployed 2G mobile telecommunication standard worldwide. The AMR narrowband codec was standardized by the European Telecommunications Standards Institute (ETSI) and adopted by the 3GPP as the mandatory codec for 2.5G and 3G wireless systems based on the evolved GSM core network (WCDMA, EDGE, GPRS).