3 Definitions, symbols and abbreviations

06.923GPPComfort noise aspects for Adaptive Multi-Rate speech traffic channelsTS

3.1 Definitions

For the purpose of the present document, the following terms and definitions apply.

Frame: time interval of 20 ms corresponding to the time segmentation of the adaptive multi-rate speech transcoder, also used as a short term for traffic frame.

SID frames: special SID (Silence Descriptor) frames. It may convey information on the acoustic background noise or inform the decoder that it should start generating background noise.

Speech frame: traffic frame that cannot be classified as a SID frame.

VAD flag: voice Activity Detection flag.

TX_TYPE: one of SPEECH, SID_FIRST, SID_UPD, NO_DATA (defined in GSM 06.93).

RX_TYPE: classification of the received traffic frame (defined in GSM 06.93).

Other definitions of terms used in the present document can be found in GSM 06.90 [3] and GSM 06.93 [5]. The overall operation of DTX is described in GSM 06.93 [5].

3.2 Symbols

For the purpose of the present document, the following symbols apply. Boldface symbols are used for vector variables.

Unquantized LSF vector

Quantized LSF vector

Unquantized LSF vector of frame m

Quantized LSF vector of frame m

Averaged LSF parameter vector

Logarithmic frame energy

Averaged logarithmic frame energy

Reference vector for LSF quantization

Computed LSF parameter prediction residual

Quantized LSF parameter prediction residual

3.3 Abbreviations

For the purpose of the present document, the following abbreviations apply.

AMR Adaptive Multi-Rate

BSS Base Station Subsystem

DTX Discontinuous Transmission

MS Mobile Station

SID SIlence Descriptor

LP Linear Prediction

LSP Line Spectral Pair

LSF Line Spectral Frequency

RX Receive

TX Transmit

VAD Voice Activity Detector

For abbreviations not given in this subclause, see GSM 01.04 [1].