Iterated Water-Filling for OFDMA Rate and Power Allocation with Proportionality Constraints

The present correspondence deals with the rate and power allocation problem for multi-user orthogonal frequency division multiple access (OFDMA). Using directional derivatives we first derive an explicit solution of the single-user OFDM power allocation problem for a general class of rate-power functions. In a nested algorithm, this solution is used to determine the solution of the closely related rate allocation problem for both the single-user and multi-user case with proportionality constraints. The results are applied to a widely used class of rate-power function.