SSH EN 301 248 V4.1.1:2000

Digital cellular telecommunications system (Phase 2) (GSM); Discontinuous Transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels (GSM 06.81 version 4.1.1)

Scope

The present document gives a description of the general baseband operation of Enhanced Full Rate 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 4. 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 remotely in the Base Station Controller (BSC), 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
(ETS 300 737) [13].
The DTX functions described in the present document are mandatory for implementation in the GSM MSs. The receiver
requirements are mandatory for implementation in all GSM BSSs, the transmitter requirements only for those where
downlink DTX will be used.