Multi-carrier modulation with source information allocated over variable quality communication channel

A multi-carrier communication system ( 400 ) groups subchannels ( 802 ) into different quality-of-signal (QoS) regions ( 804 ). An unconstrained optimization process ( 1200 ) is performed independently for the subchannels ( 802 ) of the different QoS regions ( 804 ) to allocate bit rates and power to the individual subchannels ( 802 ) so that the indicated QoS will result. Coders ( 504, 508, 512, 516 ) partition and error-correction encode source information using encoding schemes matched to the different QoS regions ( 804 ). A set ( 1100 ) of only a few directed QoS partition vectors ( 1102 ) direct the unconstrained optimization process ( 1200 ) to attempt bit-rate and power allocations on only a few promising groupings of subchannels ( 802 ) and QoS regions ( 804 ). An iterative process may take place between bit-rate and power allocation on one side and source information coding on the other for different directed QoS partition vectors ( 1102 ) to identify the best solution.