2 General

05.093GPPLink adaptationRelease 1999TS

The present document gives the detailed requirements for the correct operation of in call service specific link adaptation and control for GSM services implemented in GSM Mobile Stations (MS)s and Base Station Systems (BSS)s.

For the Adaptive Multi-Rate (AMR) speech service, the detailed description and requirements for the associated inband signaling, AMR codec mode adaptation, and AMR codec configuration are given.

An inband signaling channel is defined for AMR which enables the MS and the BTS to exchange messages on applied or requested speech and channel codec modes. Codec mode adaptation for AMR is based on received channel quality estimation in both MS and BTS, followed by a decision on the most appropriate speech and channel codec mode to apply at a given time.

The overall operation of AMR, in terms of used codec modes as well as general adaptation behaviour is controlled by the network.