Optimal resource allocation for OFDM multiuser channels

In this paper, a unifying framework for orthogonal frequency division multiplexing (OFDM) multiuser resource allocation is presented. The isolated seeming problems of maximizing a weighted sum of rates for a given power budget P̄ and minimizing sum power for given rate requirements R̄ can be interpreted jointly in this framework. To this end we embed the problems in a higher dimensional space. Based on these results, we subsequently consider the combined problem of maximizing a weighted sum of rates under given rate requirements R̄ and a fixed power budget P̄ . This new problem is challenging, since the additional constraints do not allow to use the hitherto existing approaches. Interestingly, the optimal decoding orders turn out to be the ordering of the Lagrangian factors in all problems. Index Terms Broadcast Channel, Multiple-Access Channel, Orthogonal Frequency Division Multiplexing (OFDM), Power Control, Water-Filling