During an initial part of a communication session, a transmitting node transmits digital data over a first air interface channel to a receiving node, using a first data rate and a first level of repetition. A degradation in quality of the communication session is detected. During a subsequent part of the communication session, the transmitting node transmits digital data over the first air interface channel as before but also transmits the digital data over a second air interface channel, using a second data rate and a second level of repetition. The second data rate is higher than the first data rate, and the second level of repetition is higher than the first level of repetition. Thus, during a given transmission period, the transmitting node may transmit a voice frame once over the first air interface channel and N times over the second air interface channel.