A.1 Scope

26.1933GPPAdaptive Multi-Rate - Wideband (AMR-WB) speech codecRelease 17Source controlled rate operationSpeech codec speech processing functionsTS

The present document gives a description of the general baseband operation of Adaptive Multi-Rate Wideband speech traffic channels in the transmitter and in the receiver of GSM Mobile Stations (MS)s and Base Station Systems (BSS)s during Discontinuous Transmission (DTX).

For clarity, the description is structured according to the block diagrams in Figures 1 and 3. Except in the case described next, this structure of distributing the various functions between system entities is not mandatory for implementation, as long as the operation on the air interface and on the speech decoder output remains the same.

In the case of BSSs where the speech transcoder is located remote from the Base Transceiver Station (BTS), the implementation of the interfaces between the DTX handlers and the Radio Sub System (RSS) as described in the present document together with all their flags is mandatory, being part of the A‑bis interface as described in GSM 08.60 and GSM 08.61.

The DTX functions described in this technical specification are mandatory for implementation in the GSM MSs implementing the AMR-WB speech codec. The receiver requirements are mandatory for implementation in all GSM BSSs implementing the AMR-WB speech codec, the transmitter requirements only for those BSSs where downlink DTX or Tandem Free Operation will be used.