Optimal Subcarrier-Chunk Scheduling for Wireless OFDMA Systems

In practical orthogonal frequency division multiple-access (OFDMA) systems, subcarriers are grouped into chunks and a chunk of subcarriers is regarded as the minimum unit for subcarrier allocation. Given that the number of chunks and the number of subcarriers in each chunk are predefined, we consider the optimal chunk allocation that maximizes a utility function of average user rates for a wireless OFDMA system under different power control policies. The relevant optimization problems are formulated as non-convex mixed-integer programs; yet it is shown that the optimal schemes can be obtained through Lagrange dual-based gradient iterations with fast convergence and low computational complexity under conditions. Furthermore, novel low-complexity algorithms are developed to approach the optimal strategies without a-priori knowledge of statistics of the intended wireless channels. Numerical results are provided to gauge the performance of the proposed schemes.