All voice codecs include speech coding (source coding), channel coding (error protection and bad frame detection), concealment of erroneous or lost frames (bad frame handling), Voice Activity Detection (VAD), and a low bit rate source controlled mode for coding background noise. The codecs operate either in the GSM full-rate traffic channel at the gross bit rate of kbit/s (FR, EFR, AMR-WB), or in the half-rate channel at the gross bit rate of kbit/s (HR), or in both (AMR). AMR and AMR-WB have also been. | GSM and UMTS The Creation of Global Mobile Communication Edited by Friedhelm Hillebrand Copyright 2001 John Wiley Sons Ltd ISBNs 0-470-84322-5 Hardback 0-470-845546 Electronic Chapter 14 Voice Codecs Kari Jarvinen1 Overview Five voice codecs have been standardised for GSM. These are Full-Rate FR codec Half-Rate HR codec Enhanced Full-Rate EFR codec Adaptive Multi-Rate AMR codec Adaptive Multi-Rate Wideband AMR-WB codec All voice codecs include speech coding source coding channel coding error protection and bad frame detection concealment of erroneous or lost frames bad frame handling Voice Activity Detection VAD and a low bit rate source controlled mode for coding background noise. The codecs operate either in the GSM full-rate traffic channel at the gross bit rate of kbit s FR EFR AMR-WB or in the half-rate channel at the gross bit rate of kbit s HR or in both AMR . AMR and AMR-WB have also been specified for use in 3G WCDMA. The FR codec 1 was the first voice codec defined for GSM. The codec was standardised in 1989. Ituses kbit s for speech coding and kbit s for channel coding. FR is the default codec to provide speech service in GSM. The HR codec 2 was developed to bring channel capacity savings through operation in the half-rate channel. The codec was standardised in 1995. It operates at kbit s speech coding bit rate with kbit s used for channel coding. The codec provides the same level of speech quality as the FR codec except in background noise and in tandem two encodings in MS-to-MS calls where the performance is somewhat lower. The EFR codec 3 was the first codec to provide digital cellular systems with voice quality equivalent to that of a wireline telephony reference ITU ADPCM standard at 32 kbit s . The EFR codec brings substantial quality improvement over the previous GSM codecs. EFR was standardised first for the GSM based PCS 1900 system in the US during 1995 and was adopted to GSM in 1996. The EFR codec uses
