Known is a communication system such as a cellular mobile radio system comprising a cellar network and a plurality of terminals. The system can have multi-rate codecs. These days, apart from a basic service such as full duplex or semi-duplex speech communication, such systems offer services as voice mail, voice messaging, or the like. In order to make more efficient use of system resources, in particular radio resources, for one-way voice communication, it is proposed to set the multi-rate codecs at a lower bit rate than for a two-way voice communication. Establishing whether a communication is a one-way voice communication can either be done a priori or dynamically. Use is made of the insight that a longer terminal-to-terminal delay can be applied for such a one-way communication because no echo cancelling has to be done in that case. For full flexibility, an asymmetric encoding and decoding can be applied.