Concepts and solutions for link adaptation and inband signaling for the GSM AMR speech coding standard

The European Telecommunications Standards Institute (ETSI) has just defined an adaptive multi rate (AMR) speech codec standard for the GSM system with a multitude of source and channel coding rates. The standard aims to provide robust high quality speech together with the flexibility to deliver radio network capacity enhancements by means of low bit-rate operation. The codec rates are dynamically selected with respect to the rapidly changing radio conditions and to local capacity requirements. This paper describes various approaches for link adaptation with respect to varying radio channel conditions and puts a focus on the solution in the AMR standard. Moreover the method of inband signaling that is standardized is discussed and motivated.