A communication device has an inner coder and an outer coder and transmits digital data over frequency channels. A method involves obtaining a characteristic of the frequency channels, and selecting performance parameters of the inner and outer coders for each channel based in part on the obtained characteristic of the channel. The performance parameter selecting step includes storing, for each of a plurality of combinations of inner and outer coder performance parameters, a corresponding transmission power requirement, and selecting a combination of inner and outer coder performance parameters by selecting a transmission power requirement, based on a multi-channel efficiency over respective data rates. Data is allocated to be transmitted to each channel.