Optimal discrete bit loading for DMT based constrained multicarrier systems

We present the solution for the optimal discrete bit loading in multicarrier systems employing discrete multitone (DMT) modulation, when additional constraints on either the maximum allowable energy for each subchannel or the maximal cardinality of the QAM constellations to be used are given. Conditions for the optimality of greedy algorithms in this context are also provided. The solution is based on some results in matroid theory about combinatorial optimization.