  This work analyzes the discrete solution of Hughes-Hartogs (HH) for the
transmission rate maximization problem with power constraint in the OFDMA
systems and explores mechanisms to reduce the computational complexity of
greedy algorithms. In addition to the solution characterization, a
computational complexity analysis is developed, considering the number of
executed operations for running time purpose. Moreover, we have compared the
system capacity via the throughput obtained with the HH solution, and its
variants combined with three complexity reduction mechanisms. These tools
consist of an initial allocation bit vector calculated by rounding the results
of the water-filling (WF) solution, the multiple subchannels per iteration
updating, and the adoption of a subchannel grouping procedure. Our findings
indicate that the update of multiple subchannels and the subcarriers grouping
techniques reduce the number of iterations required for convergence of the
original HH, with some throughput degradation. Also, the bit-allocation
mechanism based on the WF is deployed as an alternative to overcome the HH
solution, increasing the computational complexity.
