26.2023GPPAdaptive Multi-Rate - Wideband (AMR-WB) speech codecInterface to Iu, Uu and NbRelease 17Speech codec speech processing functionsTS
The interface between the UE AMR-WB speech codec (see 3GPP TS 26.201) and the Radio Access Network is an internal UE interface and is not detailed. The mapping is corresponding to the mapping described in clause 6 for the Iu interface.
NOTE: In case of modification of the maximum rate (e.g. by the RNC), it takes a short time period until the speech frames sent by the UE to the Radio Access Network comply with the modified maximum rate. To facilitate optimization of performance (for instance avoiding problems like audio gaps due to discarded packets) in sending direction from the UE to the network when changing mode as requested, it is a good implementation practice to allow adaptation of the UE Encoder to take effect, and to maintain currently used rate for the next few frames after the information about the rate adaptation has been sent to the UE Encoder.