Utility-based joint physical-MAC layer optimization in OFDM

In this paper, joint physical-MAC layer optimization in OFDM systems using adaptive modulation and subcarrier allocation is investigated based on utility theory. Since utility qualifies the level of users´ satisfaction derived from the radio resources they occupy, it is ideal for a network optimization metric. We formulate the cross-layer optimization problem as one that maximizes the sum of the utilities over all active users through rate adaptation and dynamic subcarrier allocation with the limited radio resource and time-varying wireless channel constraints. Two effective subcarrier allocation algorithms with low complexity are proposed to solve the constrained optimization problem. Simulation results demonstrate the significant improvement of utility-based cross-layer optimization in OFDM.