C.3.1 Rx_TRAU Process

28.0623GPPInband Tandem Free Operation (TFO) of speech codecsService descriptionStage 3TS

The Rx_TRAU Process receives Uplink TRAU Frames from the Abis/Ater Interface and synchronises to them, i.e. checks correct synchronisation and contents. It performs all actions of a conventional Uplink TRAU (see 3GPP TS 48.060 [3] and 3GPP TS 48.061 [4]). It extracts the data bits and calls, if appropriate, the Bad Frame Handler, the Uplink DTX functions and Comfort Noise Generator and finally the Speech Decoder. In case of AMR-WB a successive downsampling is performed before G.711 encoding.

The resulting speech samples are handled to the Tx_TFO Process for output to the A interface. In addition Rx_TRAU passes the Uplink TRAU Frames directly and unaltered to Tx_TFO.

It further extracts the control bits and commands from the Uplink TRAU Frames and sends corresponding Rx_TRAU Messages to the Tx_TRAU Process (see 3GPP TS 48.060 [3] and 3GPP TS 48.061 [4]) and the TFO_Protocol Process (see clause C.3.5).

In case of the AMR new Configuration parameters may be received via Config frames. They are always directly passed to Tx_TFO, although they are only sent in TFOul == ON (see Tx_TFO) to the distant TFO partner. The Configuration parameters are also sent to TFO_Protocol and Tx_TRAU.