A maximum rate loading algorithm for discrete multitone modulation systems

A novel approach to loading for discrete multitone modulation (DMT) systems is proposed. This algorithm assigns energy to different subchannels in order to maximize the data rate for a given margin while previous algorithms proposed are aimed mainly at maximizing the margin at a target data rate. Two implementations are suggested, both with finite granularity: the first one leads to the optimal waterfilling solution, and the second results in a suboptimal but slightly less complex flat-energy distribution. The algorithm is extended to the case of a rate adaptive system with both a target guaranteed fixed data rate service and a variable one. Simulation results are presented for a Rayleigh fading channel with additive white Gaussian noise.